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Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Feb. 25, 2019	Jun. 30, 2018
Document And Entity Information
Entity Registrant Name	Retrophin, Inc.
Entity Central Index Key	0001438533
Trading Symbol	rtrx
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding		41,412,835
Entity Public Float			$ 912,685,763
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Small Business	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 102,873	$ 99,394
Marketable securities	368,668	201,236
Accounts receivable, net	14,490	13,872
Inventory, net	5,619	5,351
Prepaid expenses and other current assets	2,312	3,112
Prepaid taxes	1,716	2,842
Total current assets	495,678	325,807
Property and equipment, net	3,146	3,230
Other assets	7,709	5,556
Investment-equity	15,000	0
Intangible assets, net	186,691	184,817
Goodwill	936	936
Total assets	709,160	520,346
Current liabilities:
Accounts payable	6,954	18,938
Accrued expenses	49,695	36,018
Guaranteed minimum royalty, short term	2,100	2,000
Other current liabilities	4,065	3,902
Business combination-related contingent consideration	19,350	9,100
Convertible debt	22,457	0
Derivative financial instruments, warrants	0	15,710
Total current liabilities	104,621	85,668
Convertible debt	195,091	45,077
Other noncurrent liabilities	4,496	2,472
Guaranteed minimum royalty, long term	13,049	13,095
Business combination-related contingent consideration, less current portion	73,650	80,900
Total liabilities	390,907	227,212
Stockholders' Equity:
Preferred stock $0.0001 par value; 20,000,000 shares authorized; 0 issued and outstanding as of December 31, 2018 and 2017, respectively	0	0
Common stock $0.0001 par value; 100,000,000 shares authorized; 41,389,524 and 39,373,745 issued and outstanding as of December 31, 2018 and 2017, respectively	4	4
Additional paid-in capital	589,795	471,800
Accumulated deficit	(270,017)	(177,655)
Accumulated other comprehensive loss	(1,529)	(1,015)
Total stockholders' equity	318,253	293,134
Total liabilities and stockholders' equity	$ 709,160	$ 520,346

CONSOLIDATED BALANCE SHEETS (Parentheticals) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Preferred Stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	41,389,524	39,373,745
Common stock, shares outstanding (in shares)	41,389,524	39,373,745

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net product sales	$ 164,246	$ 154,937	$ 133,591
Operating expenses:
Cost of goods sold	5,527	3,605	4,554
Research and development	123,757	78,168	70,822
Selling, general and administrative	103,654	101,333	91,941
Change in fair value of contingent consideration	11,590	19,389	18,383
Restructuring	(242)	3,608	893
Legal fee settlement	0	2,625	5,212
Total operating expenses	244,286	208,728	191,805
Operating loss	(80,040)	(53,791)	(58,214)
Other Income (expense), net:
Other income (expense), net	(474)	1,107	(264)
Interest income	5,499	3,234	3,975
Interest expense	(9,810)	(4,422)	(4,734)
Loss on extinguishment of debt	(17,042)	0	0
Change in fair value of derivative instruments	0	(4,491)	1,655
Total other income (expense), net	(21,827)	(4,572)	632
Loss before benefit (provision) for income taxes	(101,867)	(58,363)	(57,582)
Income tax benefit (provision)	(811)	(1,368)	9,679
Net loss	$ (102,678)	$ (59,731)	$ (47,903)
Net loss per common share:
Basic (in USD per shares)	$ (2.54)	$ (1.54)	$ (1.29)
Diluted (in USD per shares)	$ (2.54)	$ (1.54)	$ (1.29)
Weighted average common shares outstanding:
Basic (in shares)	40,433,171	38,769,816	36,997,865
Diluted (in shares)	40,433,171	38,769,816	38,288,012
Comprehensive loss:
Net loss	$ (102,678)	$ (59,731)	$ (47,903)
Foreign currency translation gain (loss)	39	(339)	93
Unrealized gain (loss) on marketable securities	(553)	(186)	99
Comprehensive loss	$ (103,192)	$ (60,256)	$ (47,711)

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2015		36,465,853
Beginning balance at Dec. 31, 2015	$ 299,971	$ 4	$ 365,802	$ (682)	$ (65,153)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	29,102		29,102
Legal fee settlement-short swing profit recovery	2,025		2,025
Exercise of warrants and reclassification of derivative liability (in shares)		898,633
Exercise of warrants and reclassification of derivative liability	20,720		20,720
Unrealized gain/(loss) on marketable securities	99			99
Foreign currency translation adjustments	96		3	93
Issuance of common shares under the equity incentive plan and proceeds from exercise. (in shares)		542,183
Issuance of common shares under the equity incentive plan and proceeds from exercise.	4,016		4,016
Tax shortfall from stock option exercises	(359)		(359)
Net loss	(47,903)				(47,903)
Ending balance (in shares) at Dec. 31, 2016		37,906,669
Ending balance at Dec. 31, 2016	307,767	$ 4	421,309	(490)	(113,056)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	26,645		26,645
Legal fee settlement-short swing profit recovery	0
Exercise of warrants and reclassification of derivative liability (in shares)		607,481
Exercise of warrants and reclassification of derivative liability	14,866		14,866
Unrealized gain/(loss) on marketable securities	(186)			(186)
Foreign currency translation adjustments	(339)			(339)
Issuance of common shares under the equity incentive plan and proceeds from exercise. (in shares)		819,573
Issuance of common shares under the equity incentive plan and proceeds from exercise.	8,087		8,087
ESPP stock purchase and expense (in shares)		40,022
ESPP stock purchase and expense	893		893
Net loss	(59,731)				(59,731)
Ending balance (in shares) at Dec. 31, 2017		39,373,745
Ending balance at Dec. 31, 2017	293,134	$ 4	471,800	(1,015)	(177,655)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	19,494		19,494
Legal fee settlement-short swing profit recovery	0
Exercise of warrants and reclassification of derivative liability (in shares)		1,036,054
Exercise of warrants and reclassification of derivative liability	5,305		5,305
Unrealized gain/(loss) on marketable securities	(553)			(553)
Foreign currency translation adjustments	39			39
Issuance of common shares under the equity incentive plan and proceeds from exercise. (in shares)		892,713
Issuance of common shares under the equity incentive plan and proceeds from exercise.	10,588		10,588
ESPP stock purchase and expense (in shares)		87,012
ESPP stock purchase and expense	2,269		2,269
Convertible debt issue	74,945		74,945
Net loss	(102,678)				(102,678)
Ending balance (in shares) at Dec. 31, 2018		41,389,524
Ending balance at Dec. 31, 2018	$ 318,253	$ 4	$ 589,795	$ (1,529)	$ (270,017)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash Flows from Operating Activities:
Net loss	$ (102,678)	$ (59,731)	$ (47,903)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	18,668	17,804	16,135
Deferred income tax	0	(6,425)	(22,661)
Settlement expense	0	2,625	5,212
Loss on extinguishment of debt	17,042	0	0
Loss on allowance for inventory	2,457	609	262
Accretion on notes receivable	0	(651)	(1,927)
Accretion on contingent consideration	1,357	1,723	1,976
Amortization of debt discount and deferred financing costs	3,398	656	656
Amortization of premiums on investments	382	1,338	1,097
Share based compensation	19,774	26,874	29,102
Legal accrual reversal	0	0	(2,967)
Change in estimated fair value of contingent consideration	11,590	19,389	18,383
Payments from change in fair value of contingent consideration	(8,085)	(3,949)	(4,416)
Change in estimated fair value of liability classified warrants	0	4,491	(1,655)
Foreign currency transaction gain	464	(1,081)	0
Other operating activities	(396)	(83)	54
Changes in operating assets and liabilities, net of business acquisitions:
Accounts receivable	152	4,945	(6,090)
Inventory	(2,773)	(1,706)	(568)
Prepaid expenses and other current assets	(1,358)	(2,702)	(2,447)
Prepaid income taxes	1,126	621	4,644
Accounts payable	(2,708)	2,060	(2,916)
Accrued expenses and other current liabilities	16,630	596	12,588
Net cash provided by (used in) operating activities	(24,958)	7,403	(3,441)
Cash Flows from Investing Activities:
Purchase of fixed assets	(727)	(887)	(1,428)
Purchase of intangible assets	(18,974)	(13,122)	(10,496)
Investment - Equity	(15,000)	0	0
Proceeds from the sale/maturity of marketable securities	162,755	114,526	159,520
Purchase of marketable securities	(331,345)	(102,415)	(184,111)
Proceeds from the maturity of notes receivable	0	47,500	47,500
Cash paid upon acquisition, net of cash acquired	0	0	(615)
Net cash provided by (used in) investing activities	(203,291)	45,602	10,370
Cash Flows from Financing Activities:
Payment of acquisition-related contingent consideration	(9,721)	(4,099)	(10,511)
Payment of other liability	(1,000)	(852)	(1,000)
Payment of guaranteed minimum royalty	(2,000)	(2,000)	(2,000)
Proceeds from exercise of warrants	5,305	3,645	6,005
Proceeds from exercise of stock options	10,588	8,087	4,016
Proceeds from issuance of 2025 convertible senior notes	276,000	0	0
Repurchase of 2019 convertible senior notes including premium	(40,203)	0	0
Payment of debt issuance and financing costs	(8,820)	0	0
Other financing activities	1,714	664	(359)
Net cash provided by (used in) financing activities	231,863	5,445	(3,849)
Effect of exchange rate changes on cash	(135)	(58)	117
Net increase in cash and cash equivalents	3,479	58,392	3,197
Cash and cash equivalents, beginning of year	99,394	41,002	37,805
Cash and cash equivalents, end of year	102,873	99,394	41,002
Supplemental Disclosure of Cash Flow Information:
Cash paid for interest	1,880	2,070	2,070
Cash paid for income taxes	218	7,172	7,933
Non-cash Investing and financing activities:
Short swing profit judgment offset with settlement expense accrual	0	0	2,025
Reclassification of derivative liability to equity due to exercise of warrants	0	11,221	14,715
Accrued royalty in excess of minimum payable to the sellers of Thiola	14,572	13,247	11,206
Term extension of current Thiola agreement	0	5,885	0
Present value of contingent consideration payable upon acquisition related to L-UDCA	0	0	25,000
Adoption of ASU 2017-11 - reclassification of derivative liability of warrants with down round provisions	$ 15,710	$ 0	$ 0

DESCRIPTION OF BUSINESS

12 Months Ended

Dec. 31, 2018

Organization, Consolidation and Presentation of Financial Statements [Abstract]

DESCRIPTION OF BUSINESS

Organization and Description of Business

Retrophin, Inc. (“we”, “our”, “us”, “Retrophin” and the “Company”) refers to Retrophin, Inc., a Delaware corporation, as well as our direct and indirect subsidiaries. Retrophin is a fully integrated biopharmaceutical company headquartered in San Diego, California focused on identifying, developing and delivering life-changing therapies to people with rare diseases. We regularly evaluate and, where appropriate, act on opportunities to expand our product pipeline through licenses and acquisitions of products in areas that will serve patients with serious or rare diseases and that we believe offer attractive growth characteristics.

The Company is developing the following pipeline products:

The Company is developing fosmetpantotenate (RE-024), a novel small molecule, as a potential treatment for PKAN. PKAN is a genetic neurodegenerative disorder that is typically diagnosed in the first decade of life.

Sparsentan, also known as RE-021, is an investigational product candidate with a dual mechanism of action, a potent angiotensin receptor blocker (“ARB”) and selective endothelin receptor antagonist (“ERA”), with in vitro selectivity toward endothelin receptor type A. Sparsentan is currently being evaluated in two pivotal Phase 3 clinical studies in the following indications:


•	Focal segmental glomerulosclerosis ("FSGS") is a rare kidney disease characterized by proteinuria where the glomeruli become progressively scarred. FSGS is a leading cause of end-stage renal disease.


•	Immunoglobulin A nephropathy ("IgAN") is an immune-complex-mediated glomerulonephritis characterized by hematuria, proteinuria, and variable rates of progressive renal failure. IgAN is the most common primary glomerular disease.

The Company is a party to a joint development agreement with Censa Pharmaceuticals Inc., a privately held biotechnology company focused on developing therapies for orphan metabolic diseases, to evaluate sepiapterin ("CNSA-001") for the treatment of phenylketonuria (PKU).

In September 2017, the Company entered a three-way Cooperative Research and Development Agreement ("CRADA") with the National Institutes of Health’s National Center for Advancing Translational Sciences (NCATS) and patient advocacy foundation NGLY1.org to collaborate on research efforts aimed at the identification of potential small molecule therapeutics for NGLY1 deficiency.

Liquid ursodeoxycholic acid ("L-UDCA") is a liquid formulation of ursodeoxycholic acid being developed for the treatment of a rare liver disease called primary biliary cholangitis ("PBC"). The Company obtained the rights to L-UDCA in 2016 with the intention of making L-UDCA commercially available to the subset of PBC patients who have difficulty swallowing.

The Company sells the following three products:


•	Chenodal (chenodiol tablets) is approved in the United States for the treatment of patients suffering from gallstones in whom surgery poses an unacceptable health risk due to disease or advanced age. Chenodal has been the standard of care for cerebrotendinous xanthomatosis ("CTX") patients for more than three decades and the Company is currently pursuing adding this indication to the label.


•	Cholbam (cholic acid capsules) is approved in the United States for the treatment of bile acid synthesis disorders due to single enzyme defects and is further indicated for adjunctive treatment of patients with peroxisomal disorders.


•	Thiola (tiopronin tablets) is approved in the United States for the prevention of cystine (kidney) stone formation in patients with severe homozygous cystinuria.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

A summary of the significant accounting policies applied in the preparation of the accompanying consolidated financial statements follows:

Principles of Consolidation

The consolidated financial statements represent the consolidation of the accounts of the Company and its subsidiaries in conformity with accounting principles generally accepted in the United States ("U.S. GAAP"). All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

In preparing financial statements in conformity with U.S. GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of expenses during the reporting period. Due to inherent uncertainty involved in making estimates, actual results reported in future periods may be affected by changes in these estimates. On an ongoing basis, the Company evaluates its estimates and assumptions. These estimates and assumptions include revenue recognition, valuing equity securities in share-based payments, estimating expenses of contracted research organizations, estimating fair value of equity instruments recorded as derivative liabilities, estimating the fair value of net assets acquired in business combinations, estimating the useful lives of depreciable and amortizable assets, goodwill impairment, estimating the fair value of contingent consideration, estimating of valuation allowances and uncertain tax positions, and estimates associated with the assessment of impairment for long lived assets.

Revenue Recognition

Product sales for the years ended December 31, 2018, 2017 and 2016 consisted of sales of Chenodal, Cholbam and Thiola. Effective January 1, 2018, the Company adopted Accounting Standards Codification (" ASC"), Topic 606, Revenue from Contracts with Customers, using the full retrospective transition method. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect substantially all the consideration it is entitled to in exchange for the goods or services it transfers to the customer.

Revenue from product sales is recorded at delivery, net of applicable provisions for rebates under government (including medicaid) programs, commercial rebates, prompt pay discounts, and other sales-related deductions. We review our estimates of rebates and other applicable provisions each period and record any necessary adjustments in the current period.

See Note 3 for further discussion.

Research and Development Costs

Research and development includes expenses related to sparsentan, fosmetpantotenate and our other pipeline programs. We expense all research and development costs as they are incurred. Our research and development costs are comprised of salaries and bonuses, benefits, non-cash share-based compensation, license fees, milestones under license agreements, costs paid to third-party contractors to perform research, conduct clinical trials, and develop drug materials and delivery devices, and associated overhead expenses and facilities costs. We charge direct internal and external program costs to the respective development programs. We also incur indirect costs that are not allocated to specific programs because such costs benefit multiple development programs and allow us to increase our pharmaceutical development capabilities. These consist of internal shared resources related to the development and maintenance of systems and processes applicable to all of our programs.

Clinical Trial Expenses

We record expenses in connection with our clinical trials under contracts with contract research organizations (CROs) that support conducting and managing clinical trials. The financial terms and activities of these agreements vary from contract to contract and may result in uneven expense levels. Generally, these agreements set forth activities that drive the recording of expenses such as start-up and initiation activities, enrollment and treatment of patients, or the completion of other clinical trial activities.

Expenses related to clinical trials are accrued based on our estimates and/or representations from service providers regarding work performed, including actual level of patient enrollment, completion of patient studies and progress of the clinical trials. Other incidental costs related to patient enrollment or treatment are accrued when reasonably certain. If the amounts we are obligated to pay under our clinical trial agreements are modified (for instance, as a result of changes in the clinical trial protocol or scope of work to be performed), we adjust our accruals accordingly on a prospective basis. Revisions to our contractual payment obligations are charged to expense in the period in which the facts that give rise to the revision become reasonably certain.

We currently have three Phase 3 clinical trials in process that are in varying stages of activity, with ongoing non-clinical support trials. As such, clinical trial expenses will vary depending on the all the factors set forth above and may fluctuate significantly from quarter to quarter.

Employee Stock-Based Compensation

The Company recognizes all employee share-based compensation as a cost in the financial statements. Equity-classified awards principally related to stock options, restricted stock units (“RSUs”) and performance stock units ("PSUs"), are measured at the grant date fair value of the award. The Company determines grant date fair value of stock option awards using the Black-Scholes option-pricing model. The fair value of RSUs and PSUs are determined using the closing price of the Company’s common stock on the grant date. For service based vesting grants, expense is recognized over the requisite service period based on the number of options or shares expected to ultimately vest. For PSUs, expense is recognized over the implicit service period, assuming vesting is probable. No expense is recognized for PSUs if it is not probable the vesting criteria will be satisfied. Forfeitures are accounted for as they occur.



	Initial Vesting Term
Stock Options	3 to 4 years
Restricted Stock Units	2 to 4 years

Earnings (Loss) Per Share

We calculate our basic earnings per share by dividing net income by the weighted average number of shares outstanding during the period. The diluted earnings per share computation includes the effect, if any, of shares that would be issuable upon the exercise of outstanding stock options, derivative liability, convertible debt and RSUs, reduced by the number of shares which are assumed to be purchased by the Company from the resulting proceeds at the average market price during the year, when such amounts are dilutive to the earnings per share calculation.

Cash and Cash Equivalents

We consider all highly liquid marketable securities with an original maturity of three months or less to be cash equivalents. Due to the short-term maturity of such investments, the carrying amounts are a reasonable estimate of fair value.

Marketable Securities

The Company accounts for marketable securities held as “available-for-sale” in accordance with ASC 320, “Investments Debt and Equity Securities” (“ASC 320”). The Company classifies these investments as current assets and carries them at fair value. Unrealized gains and losses are recorded as a separate component of stockholders’ equity as accumulated other comprehensive loss. Realized gains or losses on marketable security transactions are reported in the Consolidated Statements of Operations and Comprehensive Income (Loss). Marketable securities are maintained at one financial institution and are governed by the Company’s investment policy as approved by the Company's Board of Directors.

Trade and Notes Receivable

Trade Receivables, Net

Trade accounts receivable are recorded net of allowances for prompt payment and doubtful accounts. Estimates for allowances for doubtful accounts are determined based on existing contractual obligations, historical payment patterns and individual customer circumstances. The allowance for doubtful accounts was zero and $0.2 million at December 31, 2018 and 2017, respectively. For the years ended December 31, 2018, 2017 and 2016, bad debt expense recorded in the Statement of Operations and Comprehensive Income (Loss) was approximately zero, $0.2 million and $0.2 million, respectively.

Notes Receivable

Notes receivable arose from the sale of a pediatric priority review voucher (the "PRV"). On July 2, 2015, the Company sold and transferred the PRV to Sanofi for $245.0 million. $150.0 million was received upon closing, and $47.5 million was due on each of the first and second anniversaries of the closing. In accordance with U.S. GAAP, the Company recorded the future short term and long term notes receivable at their present value of $46.2 million and $44.9 million, respectively, at the date of the sale using a discount rate of 2.8%. The accretion on the notes receivables totaled $0.7 million and $1.9 million for 2017 and 2016, respectively, and is recorded in interest expense, net, in the Consolidated Statements of Operations and Comprehensive Income (Loss). The first and second annual payments were received on July 1, 2016 and June 30, 2017 in accordance with the terms of the sale agreement. As of December 31, 2018, there are no outstanding notes receivable.

Inventory and Related Reserves

Inventory, which is recorded at the lower of cost or net realizable value, includes materials, labor, and other direct and indirect costs and are valued using the first-in, first-out method. The Company periodically analyzes its inventory levels to identify inventory that may expire prior to expected sale or has a cost basis in excess of its estimated realizable value, and writes down such inventory as appropriate. In addition, the Company's products are subject to strict quality control and monitoring which the Company’s manufacturers perform throughout their manufacturing process. The Company does not directly manufacture any product. The Company has single suppliers for products Chenodal and Thiola, and prospectively arranges for manufacture from contract service providers for its product Cholbam. The inventory reserve was $1.8 million and $0.7 million at December 31, 2018 and 2017, respectively.

Inventory, net of reserve, consisted of the following at December 31, 2018 and 2017 (in thousands):



	December 31, 2018		December 31, 2017
Raw material	$	4,689	$	3,435
Finished goods	930		1,916
Total inventory	$	5,619	$	5,351

Segment Information

The Company currently operates in one business segment focused on the development and commercialization of innovative therapies for people with serious and life threatening rare diseases and medical conditions. The Company is not organized by market and is managed and operated as one business. A single management team reports to the chief operating decision maker who comprehensively manages the entire business. The Company does not operate any separate lines of business or separate business entities with respect to its products. Accordingly, the Company does not accumulate discrete financial information with respect to separate products, other than revenues, and does not have separately reportable segments.

Property and Equipment, net

Property and equipment are stated at cost, net of accumulated depreciation. Depreciation is computed using the straight-line method over the related estimated useful lives as presented in the table below. Significant additions and improvements are capitalized, while repairs and maintenance are charged to expense as incurred. Property and equipment purchased for specific research and development projects with no alternative use is expensed as incurred.

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Intangible Assets, Net

Our intangible assets consist of licenses, purchased technology and acquired in-process research and development (IPR&D). Intangible assets with definite lives are amortized on a straight-line basis over their estimated useful lives and are reviewed periodically for impairment.

Intangible assets related to IPR&D projects are considered to be indefinite-lived until the completion or abandonment of the associated research and development efforts. During the period the assets are considered indefinite-lived, they will not be amortized but will be tested for impairment. If and when development is complete, which generally occurs when regulatory approval to market a product is obtained, the associated assets are deemed finite-lived and are amortized over a period that best reflects the economic benefits provided by these assets.

Goodwill

Goodwill represents the excess of purchase price over fair value of net assets acquired in a business combination and is not amortized. Goodwill is subject to impairment testing at least annually or when a triggering event occurs that could indicate a potential impairment. The Company has one segment and one reporting unit and as such reviews goodwill for impairment at the consolidated level.

For the years ended December 31, 2018, 2017 and 2016 there were no impairments to goodwill.

Impairment of Long-Lived Assets

Our long-lived assets are primarily comprised of intangible assets and property and equipment. We evaluate our finite-lived intangible assets, other than goodwill and property and equipment, for impairment whenever events or changes in circumstances indicate the carrying value of an asset or group of assets may not be recoverable. If these circumstances exist, recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset group to future undiscounted net cash flows expected to be generated by the use and eventual disposition of the asset group. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceeds the fair value of the assets.

In addition, indefinite-lived intangible assets, comprised of IPR&D, are reviewed for impairment annually and whenever events or changes in circumstances indicate that it is more likely than not that the asset is impaired by comparing the fair value to the carrying value of the asset. To determine the fair value of the asset, the Company used the multi-period excess earnings method of the income approach. The more significant assumptions inherent in the application of this method include: the amount and timing of projected future cash flows (including revenue, cost of sales, research and development costs, and sales and marketing expenses), and the discount rate selected to measure the risks inherent in the future cash flows.

There were no impairments related to intangible assets in the years ended December 31, 2018, 2017 and 2016.

Contingent Consideration

We record contingent consideration resulting from a business combination at its fair value on the acquisition date. On a quarterly basis, we revalue these obligations and record increases or decreases from their fair value as an adjustment to the consolidated statement of operations. Changes to contingent consideration obligations can result from changes to discount rates, accretion of the liability due to the passage of time, changes in revenue forecasts and changes in our estimates of the likelihood or timing of achieving commercial milestones.

Income Taxes

The Company follows ASC 740, Income Taxes, which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements or tax returns. Under this method, deferred tax assets and liabilities are based on the differences between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Deferred tax assets are reduced by a valuation allowance to the extent management concludes it is more likely than not that the asset will not be realized.

The standard addresses the determination of whether tax benefits claimed or expected to be claimed on a tax return should be recorded in the financial statements. Under ASC 740, the Company may recognize the tax benefit from an uncertain tax position only if it is more likely than not that the tax position will be sustained on examination by the tax authorities, based on the technical merits of the position. The tax benefits recognized in the financial statements from such a position should be measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. ASC 740 also provides guidance on de-recognition, classification, interest and penalties on income taxes, accounting in interim periods and requires increased disclosures. The Company’s policy is to record estimated interest and penalty related to the underpayment of income taxes or unrecognized tax benefits as a component of its income tax provision.

Reclassifications

Certain reclassifications have been made to the prior year financial statements in order to conform to the current year’s presentation.

Patents

The Company expenses external costs, such as filing fees and associated attorney fees, incurred to obtain issued patents and patent applications pending. The Company also expenses costs associated with maintaining and defending patents subsequent to their issuance in the period incurred.

Derivative Financial Instruments, Warrants

The Company does not use derivative instruments to hedge exposures to cash flow, market or foreign currency risks. However, since 2013, the Company has issued five tranches of common stock purchase warrants to secure financing, remediate covenant violations and provide consideration for amendments with respect to a credit facility extinguished in 2015.

Historically, the Company accounted for these instruments, which did not have fixed settlement provisions, as derivative instruments in accordance with FASB ASC 815-40, Derivative and Hedging - Contracts in Entity’s Own Equity. This was due to an anti-dilution provision for the warrants that provided for a reduction to the exercise price if the Company issued equity or equity linked instruments in the future at an effective price per share less than the exercise price then in effect for the warrant ("down round provision"). As such, the warrants were re-measured at each balance sheet date based on estimated fair value. Changes in estimated fair value were recorded as non-cash adjustments within other income (expenses), net, in the Company’s Consolidated Statements of Operations and Comprehensive Income (Loss).

As of January 1, 2018, the Company early adopted ASU 2017-11, which revised the guidance for instruments with down round provisions. As such the Company treats outstanding warrants as free-standing equity linked instruments that will be recorded to equity in the Consolidated Balance Sheet.

The fair value of the derivative liability balance as of December 31, 2017 of $15.7 million was reclassified by means of a cumulative-effect adjustment to equity as of January 1, 2018.

Recently Adopted Accounting Pronouncements

In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. Under the new standard, revenue is recognized at the time a good or service is transferred to a customer for the amount of consideration for which the entity expects to be entitled for that specific good or service. Entities may use a full retrospective approach or report the cumulative effect as of the date of adoption. The Company adopted the new standard on January 1, 2018 using the full retrospective approach and there was no impact on timing or recognition of revenue. See Note 3 for further discussion.

In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfers of Assets Other Than Inventory. The new guidance changes the accounting for income tax effects of intra-entity transfers of assets other than inventory. Under the new guidance, the selling (transferring) entity is required to recognize a current tax expense or benefit upon transfer of the asset. Similarly, the purchasing (receiving) entity is required to recognize a deferred tax asset or deferred tax liability, as well as the related deferred tax benefit or expense, upon receipt of the asset. As of January 1, 2017, the Company reversed the balance of $4.9 million in its prepaid tax asset account as a charge to retained earnings.

In July 2017, the FASB issued ASU No. 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features. These amendments simplify the accounting for certain financial instruments with down round features. The amendments require companies to disregard the down round feature when assessing whether the instrument is indexed to its own stock, for purposes of determining liability or equity classification. See Note 15 for further discussion.

In January 2017, the FASB issued ASU 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The new guidance dictates that, when substantially all of the fair value of the gross assets acquired (or disposed of) is concentrated in a single identifiable asset or a group of similar identifiable assets, it should be treated as an acquisition or disposal of an asset. The guidance was adopted as of January 1, 2018.

Recently Issued Accounting Pronouncements

From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on its consolidated financial position or results of operations upon adoption.

In February 2016, the FASB issued ASU No. 2016-02, Leases. The new standard establishes a right-of-use ("ROU") model that requires a lessee to record a ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. Subsequently, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, ASU No. 2018-11, Targeted Improvements, and ASU No. 2018-20, Narrow-Scope Improvements for Lessors, to clarify and amend the guidance in ASU No. 2016-02. The ASUs are effective for interim and annual periods beginning after December 15, 2018, with early adoption permitted. We will adopt the ASUs on January 1, 2019 on a modified retrospective basis through a cumulative adjustment to our beginning accumulated deficit balance. Prior comparative periods will not be restated under this method, and we will adopt all available practical expedients, as applicable. The Company has finished its search for leases and reviewed the related contacts and determined its impact to the consolidated balance sheet is less than 5% of total assets and liabilities as of January 1, 2019. No material cumulative-effect adjustment to equity is expected.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Topic 326 amends guidance on reporting credit losses for assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, Topic 326 eliminates the probable initial recognition threshold in current GAAP and, instead, requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial assets to present the net amount expected to be collected. For available for sale debt securities, credit losses should be measured in a manner similar to current GAAP, however Topic 326 will require that credit losses be presented as an allowance rather than as a write-down. This ASU update affects entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. The amendments affect loans, debt securities, trade receivables, net investments in leases, off balance sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. This update is effective for fiscal years beginning after December 15, 2019, including interim periods within those fiscal years. The Company is currently evaluating whether the adoption of the new standard will have a material effect on its consolidated financial statements and related disclosures.

REVENUE RECOGNITION

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

REVENUE RECOGNITION

Product Revenue, Net

The Company sells Chenodal and Cholbam (Kolbam), which are aggregated as bile acid products, and Thiola through direct-to-patient distributors. The Company sells its products worldwide, with more than 95% of the revenue generated in North America.

Revenues from product sales are recognized when the customer obtains control of the Company’s product, which occurs upon delivery to the customer. The Company receives payments from its product sales based on terms that generally are within 60 days of delivery of product to the patient.

Deductions from Revenue

Revenues from product sales are recorded at the net sales price, which includes provisions resulting from discounts, rebates and co-pay assistance that is offered to its customers, health care providers, payors and other indirect customers relating to the Company’s sales of its products. These provisions are based on the amounts earned or to be claimed on the related sales and are classified as a reduction of accounts receivable (if the amount is payable to the customer) or as a current liability (if the amount is payable to a party other than a customer). Where appropriate, these reserves take into consideration the Company’s historical experience, current contractual and statutory requirements and specific known market events and trends. Overall, these reserves reflect the Company’s best estimates of the amount of consideration to which it is entitled based on the terms of the contract. If actual results in the future vary from the Company’s provisions, the Company will adjust the provision, which would affect net product revenue and earnings in the period such variances become known. Our historical experience is that such adjustments have been immaterial.

Government Rebates: We calculate the rebates that we will be obligated to provide to government programs and deduct these estimated amounts from our gross product sales at the time the revenues are recognized. Allowances for government rebates and discounts are established based on actual payer information, which is reasonably estimated at the time of delivery, and the government-mandated discounts applicable to government-funded programs. Rebate discounts are included in other current liabilities in the accompanying consolidated balance sheets.

Commercial Rebates: We calculate the rebates that we incur due to contracts with certain commercial payors and deduct these amounts from our gross product sales at the time the revenues are recognized. Allowances for commercial rebates are established based on actual payer information, which is reasonably estimated at the time of delivery. Rebate discounts are included in other current liabilities in the accompanying consolidated balance sheets.

Prompt Pay Discounts: We offer discounts to certain customers for prompt payments. We accrue for the calculated prompt pay discount based on the gross amount of each invoice for those customers at the time of sale.

Product Returns: Consistent with industry practice, we offer our customers a limited right to return product purchased directly from the Company, which is principally based upon the product’s expiration date. Generally, shipments are only made upon a patient prescription thus returns are minimal.

Co-pay Assistance: We offer a co-pay assistance program, which is intended to provide financial assistance to qualified commercially insured patients with prescription drug co-payments required by payors. The calculation of the accrual for co-pay assistance is based on an identification of claims and the cost per claim associated with product that has been recognized as revenue.

The following table summarizes net product revenues for the twelve months ended December 31, 2018, 2017 and 2016 (in thousands):



	Twelve Months Ended December 31,
	2018	2017	2016
Thiola	89,176	82,311	71,199
Bile acid products	75,070	72,626	62,392
Total net product revenue	164,246	154,937	133,591

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT

12 Months Ended

Dec. 31, 2018

Future Acquisition Right And Joint Development Agreement [Abstract]

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT

Censa Pharmaceuticals Inc.

In December 2017, the Company entered into a Future Acquisition Right and Joint Development Agreement (the “Option Agreement”) with Censa, which became effective in January 2018. The Company has agreed to fund certain development activities of Censa’s CNSA-001 program, in an aggregate amount expected to be approximately $17 million through proof of concept, and has the right, but not the obligation, to acquire Censa (the “Option”) on the terms and subject to the conditions set forth in a separate Agreement and Plan of Merger. In exchange for the Option, the Company paid $10 million, and an additional $5 million upon Censa’s completion of a specified development milestone set forth in the Option Agreement.

If the Company exercises the Option, the Company will acquire Censa for $65 million in upfront consideration, subject to certain adjustments, paid as a combination of 20% in cash and 80% in shares of the Company’s common stock, valued at a fixed price of $21.40 per share; provided, however, that Censa may elect on behalf of its equity holders to receive the upfront consideration in 100% cash if the average price per share of the Company’s common stock for the ten trading days ending on the date the Company provides a notice of interest to exercise the Option is less than $19.26. In addition, if the Company exercises the Option and acquires Censa, the Company would be required to make further cash payments to Censa’s equity holders of up to an aggregate of $25 million if the CNSA-001 program achieves specified development and commercial milestones.

The Company determined that Censa is a variable interest entity ("VIE") and concluded that the Company is not the primary beneficiary of the VIE. As such, the Company did not consolidate Censa’s results into its consolidated financial statements. The Company will continue to monitor facts and circumstances for changes that could potentially result in the Company becoming the primary beneficiary.

Through December 31, 2018, the Company has paid Censa $10.0 million as an upfront payment, $16.8 million in development funding, and $5.0 million related to a development milestone. The Company capitalized the upfront and milestone payments and expensed the development funding paid to research and development expense in the Consolidated Statement of Operations and Comprehensive Income (Loss). The Company is treating the upfront payment and milestone payment, both of which are compensation for the Option, as a cost-method investment with a total carrying value of $15.0 million as of December 31, 2018.

BUSINESS COMBINATION AND ASSET TRANSACTIONS

Amendment to Trademark License and Supply Agreement

In November 2017, the Company amended their agreement with the manufacturer of Thiola to extend the term of the current exclusive U.S. and Canada licensing agreement by an additional five years, to 2029. The royalty rate and guaranteed minimum payment were also extended through the new agreement term. Upon execution of the amendment, the Company capitalized an additional $5.9 million in intangible assets and recorded a guaranteed minimum liability for the same amount.

In November 2018, the license agreement was amended to extend the territorial rights beyond the United States and Canada. As consideration for the expanded territory the Company paid an up-front fee of $0.3 million and will pay guaranteed minimum royalties equaling the greater of $0.1 million or 20% of our Thiola net sales generated from outside of the United States during each calendar year. Upon execution of the amendment, the Company capitalized an additional $1.0 million in intangible assets and recorded a guaranteed minimum liability of $0.7 million related to this amendment.

Acquisition of Liquid Ursodeoxycholic Acid (L-UDCA)

On June 20, 2016, the Company signed a definitive agreement to purchase the rights, titles, licenses and ownership of L-UDCA from Asklepion Pharmaceuticals, LLC ("Asklepion").

The acquisition was accounted for under the acquisition method of accounting in accordance with Accounting Standard Codification ("ASC") 805. The fair value of assets acquired and liabilities assumed was based upon an independent third-party valuation and the Company’s estimates. Critical estimates in valuing certain intangible assets include but are not limited to future expected cash flows from acquired product rights for L-UDCA, licenses, trade names and developed technologies, present value and discount rates. Management’s estimates of fair value are based upon assumptions believed to be reasonable, but which are inherently uncertain and unpredictable and, as a result, actual results may differ from estimates.

The purchase included $25.5 million for an intangible asset with a definite life related to product rights in the U.S. The useful life related to the acquired product rights is expected to be approximately 17 years once the NDA is approved by the FDA. Until approval, the asset is considered IPR&D with an indefinite life and is not amortized.

The contingent consideration of $25.0 million (present value) recorded during the period ended June 30, 2016, is related to an agreement to pay an additional cash amount in the form of milestones and sales royalties through 2035. The accrued contingent consideration was recorded as a liability at acquisition-date fair value using the income approach with an assumed discount rate of 12.0% over the applicable term. The undiscounted amount the Company could pay as contingent consideration under the agreement is up to $70.3 million.

The purchase price allocation of $25.5 million as of the acquisition completion date of June 16, 2016 was as follows (in thousands):



Cash paid upon consummation	$	500
Present value of contingent consideration	25,000
Total purchase price	$	25,500
Fair Value of Assets Acquired and Liabilities Assumed
Acquired product rights: L-UDCA (intangible asset)	$	25,500
Total purchase price	$	25,500

Unaudited pro forma information for the transaction is not presented, because the effects of such transaction are considered immaterial to the Company.

Divestiture of Assets:

Sale of Assets to Sanofi

The FDA granted Asklepion a Pediatric PRV, awarded to encourage development of new drugs and biologics for the prevention and treatment of rare pediatric diseases. A Pediatric PRV is transferable and provides the bearer with FDA priority review classification for a new drug application. The Pediatric PRV was transferred to the Company under the terms of the asset purchase agreement between the Company and Asklepion dated January 12, 2015, pursuant to which the Company acquired Cholbam.

On July 2, 2015, the Company sold and transferred the Pediatric PRV to Sanofi for $245.0 million. $150.0 million was received upon closing, and $47.5 million was due on each of the first and second anniversaries of the closing. In accordance with U.S. GAAP, the Company recorded the future short term and long term notes receivable at their present value of $46.2 million and $44.9 million, respectively, at the date of the sale using a discount rate of 2.8%. The gain from the sale of the asset was approximately $140.0 million, net of $4.9 million in fees contractually due as part of the Cholbam acquisition. The first and second annual payments were received on July 1, 2016 and June 30, 2017 in accordance with the terms of the sale agreement.

BUSINESS COMBINATION AND ASSET TRANSACTIONS

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

BUSINESS COMBINATION AND ASSET TRANSACTIONS

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT

Censa Pharmaceuticals Inc.

BUSINESS COMBINATION AND ASSET TRANSACTIONS

Amendment to Trademark License and Supply Agreement

Acquisition of Liquid Ursodeoxycholic Acid (L-UDCA)

On June 20, 2016, the Company signed a definitive agreement to purchase the rights, titles, licenses and ownership of L-UDCA from Asklepion Pharmaceuticals, LLC ("Asklepion").

The purchase price allocation of $25.5 million as of the acquisition completion date of June 16, 2016 was as follows (in thousands):



Cash paid upon consummation	$	500
Present value of contingent consideration	25,000
Total purchase price	$	25,500
Fair Value of Assets Acquired and Liabilities Assumed
Acquired product rights: L-UDCA (intangible asset)	$	25,500
Total purchase price	$	25,500

Unaudited pro forma information for the transaction is not presented, because the effects of such transaction are considered immaterial to the Company.

Divestiture of Assets:

Sale of Assets to Sanofi

MARKETABLE SECURITIES

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

MARKETABLE SECURITIES

The Company's marketable securities as of December 31, 2018 and 2017 were comprised of available-for-sale marketable securities which are carried at fair value, with the unrealized gains and losses reported in accumulated other comprehensive income (loss). The amortized cost of debt securities in this category are adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income (loss). Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. All available-for-sale securities are classified as current assets, even if the maturity when acquired by the Company is greater than one year due to the ability to liquidate within the next 12 months.

Marketable securities consist of the following (in thousands):



	As of December 31,
	2018		2017
Marketable Securities:
Commercial paper	59,255		6,897
Corporate debt securities	299,413		164,297
Securities of government sponsored entities	10,000		30,042
Total Marketable Securities:	$	368,668	$	201,236

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2018 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	59,313	$	—	$	(58	)	$	59,255
Corporate debt securities	Less than 1	149,824		—		(604		)	149,220
Total maturity less than 1 year		209,137		—		(662		)	208,475
Corporate debt securities	1 to 2	150,813		18		(638		)	150,193
Securities of government-sponsored entities	1 to 2	9,997		4		(1		)	10,000
Total maturity 1 to 2 years		160,810		22		(639		)	160,193
Total available-for-sale securities		$	369,947	$	22	$	(1,301	)	$	368,668

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2017 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	6,911	$	(14	)	$	6,897
Corporate debt securities	Less than 1	86,531		(198		)	86,333
Securities of government-sponsored entities		30,132		(90		)	30,042
Total maturity less than 1 year		123,574		(302		)	123,272
Corporate debt securities	1 to 2	78,388		(424		)	77,964
Total maturity 1 to 2 years		78,388		(424		)	77,964
Total available-for-sale securities		$	201,962	$	(726	)	$	201,236

During 2018 and 2017, the Company had no realized gains or losses on marketable securities. During 2016, the Company realized a gain of less than $0.1 million on marketable securities. The Company received proceeds from the sale or maturity of marketable securities of $162.8 million, $114.5 million and $159.5 million for 2018, 2017 and 2016, respectively.

The primary objective of the Company’s investment portfolio is to enhance overall returns while preserving capital and liquidity. The Company’s investment policy limits interest-bearing security investments to certain types of instruments issued by institutions with primarily investment grade credit ratings and places restrictions on maturities and concentration by asset class and issuer.

The Company reviews the available-for-sale investments for other-than-temporary declines in fair value below cost basis each quarter and whenever events or changes in circumstances indicate that the cost basis of an asset may not be recoverable. This evaluation is based on a number of factors, including the length of time and the extent to which the fair value has been below the cost basis and adverse conditions related specifically to the security, including any changes to the credit rating of the security, and the intent to sell, or whether the Company will more likely than not be required to sell the security before recovery of its amortized cost basis. The assessment of whether a security is other-than-temporarily impaired could change in the future due to new developments or changes in assumptions related to any particular security. As of December 31, 2018 and 2017, the Company believed the cost basis for available-for-sale investments were recoverable in all material respects. For both December 31, 2018 and 2017, any investments in an unrealized loss position for longer than 12 months were immaterial.

NOTES PAYABLE

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

NOTES PAYABLE

Convertible Senior Notes Due 2025

On September 10, 2018, the Company completed its registered underwritten public offering of $276 million aggregate principal amount of 2.50% Convertible Senior Notes due 2025 ("2025 Notes") and entered into a base indenture and supplemental indenture agreement ("2025 Indenture") with respect to the 2025 Notes. The 2025 Notes will mature on September 15, 2025 ("Maturity Date”), unless earlier repurchased, redeemed, or converted. The 2025 Notes are senior unsecured obligations of the Company and bear interest at an annual rate of 2.50%, payable semi-annually in arrears on March 15 and September 15 of each year, beginning on March 15, 2019.

The composition of the Company’s 2025 Notes are as follows (in thousands):



	December 31, 2018			December 31, 2017
2.50% convertible senior notes due 2025	$	276,000		$	—
Unamortized debt discount	(74,836		)	—
Unamortized debt issuance costs	(6,073		)	—
Total 2025 Notes, net of unamortized debt discount and debt issuance costs	$	195,091		$	—

The net proceeds from the issuance of the 2025 Notes were approximately $267.2 million, after deducting commissions and the offering expenses payable by the Company. A portion of the net proceeds from the 2025 Notes were used by the Company to repurchase $23.4 million aggregate principal amount of its 4.5% senior convertible notes due in 2019 in privately-negotiated transactions.

Holders may convert their 2025 Notes at their option only in the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2018 (and only during such calendar quarter), if the last reported sale price per share of the Company’s common stock for each of at least 20 trading days, whether or not consecutive, during the period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter exceeds 130% of the conversion price on the applicable trading day; (2) during the five consecutive business days immediately after any 10 consecutive trading day period (“measurement period”) if the trading price per $1,000 principal amount of 2025 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of the Company’s common stock on such trading day and the conversion rate on such trading day; (3) upon the occurrence of certain corporate events or distributions on the Company’s common stock; (4) if the Company calls the 2025 Notes for redemption; and (5) at any time from, and including, May 15, 2025 until the close of business on the scheduled trading day immediately before the Maturity Date. The Company will settle conversions by paying or delivering, as applicable, cash, shares of the Company’s common stock, or a combination of cash and shares of the Company’s common stock, at the Company’s election, based on the applicable conversion rate.

The initial conversion rate for the 2025 Notes is 25.7739 shares of the Company’s common stock per $1,000 principal amount of 2025 Notes, which represents an initial conversion price of approximately $38.80 per share. If a “make-whole fundamental change” (as defined in the 2025 Indenture) occurs, then the company will, in certain circumstances, increase the conversion rate for a specified period of time.

The 2025 Notes will be redeemable, in whole or in part, at the Company’s option at any time, and from time to time, on or after September 15, 2022 and, in the case of any partial redemption, on or before the 40th scheduled trading day before the Maturity Date, at a cash redemption price equal to the principal amount of the 2025 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date, but only if the last reported sale price per share of the Company’s common stock exceeds 130% of the conversion price on each of at least 20 trading days during the 30 consecutive trading days ending on, and including, the trading day immediately before the date the Company sends the related redemption notice. If a fundamental change (as defined in the 2025 Indenture) occurs, then, subject to certain exceptions, holders may require the Company to repurchase their 2025 Notes at a cash repurchase price equal to the principal amount of the 2025 Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date.

As of December 31, 2018, the 2025 Notes had a market price of $897 per $1,000 or $247.7 million principal amount. In the event of conversion, holders would forgo all future interest payments, any unpaid accrued interest and the possibility of further stock price appreciation. Upon the receipt of conversion requests, the settlement of the 2025 Notes will be paid pursuant to the terms of the 2025 Indenture. In the event that all of the 2025 Notes are converted, the Company would be required to repay the $276.0 million in principal value and any conversion premium in any combination of cash and shares of its common stock at the Company’s option. In addition, calling the 2025 Notes for redemption will constitute a “make whole fundamental change.”

The 2025 Notes are the Company’s general unsecured obligations that rank senior in right of payment to all of its indebtedness that is expressly subordinated in right of payment to the 2025 Notes, and equal in right of payment to the Company’s unsecured indebtedness.

The 2025 Notes are currently classified on the Company’s consolidated balance sheet at December 31, 2018 as long-term debt.

Under ASC 470-20, Debt with Conversion and Other Options, an entity must separately account for the liability and equity components of convertible debt instruments (such as the 2025 Notes) that may be settled entirely or partially in cash upon conversion, in a manner that reflects the issuer’s economic interest cost. The liability component of the instrument is valued in a manner that reflects the market interest rate for a similar nonconvertible instrument at the date of issuance. The initial carrying value of the liability component was $198.6 million. The equity component of $77.4 million, representing the conversion option, was determined by deducting the fair value of the liability component from the par value of the 2025 Notes and is recorded in additional paid-in capital on the consolidated balance sheet at the issuance date. That equity component is treated as a discount on the liability component of the 2025 Notes, which is amortized over the seven year term of the 2025 Notes using the effective interest rate method. The equity component is not re-measured as long as it continues to meet the conditions for equity classification. The Company allocated the total transaction costs of approximately $8.8 million related to the issuance of the 2025 Notes to the liability and equity components of the 2025 Notes based on their relative values. Transaction costs attributable to the liability component are amortized to interest expense over the seven-year term of the 2025 Notes, and transaction costs attributable to the equity component are netted with the equity component in stockholders’ equity.

The effective interest rate on the liability components of the 2025 Notes for the period from the date of issuance through December 31, 2018 was 7.7%. The following table sets forth total interest expense recognized related to the 2025 Notes (in thousands):



	Twelve Months Ended December 31,
	2018		2017
Contractual interest expense	$	2,108	$	—
Amortization of debt discount	2,582		—
Amortization of debt issuance costs	273		—
Total interest expense for the 2025 Notes	$	4,963	$	—

The 2025 Notes do not contain any financial or operating covenants or any restrictions on the payment of dividends, the issuance of other indebtedness or the issuance or repurchase of securities by the Company. The 2025 Indenture contains customary events of default with respect to the 2025 Notes, including that upon certain events of default, 100% of the principal and accrued and unpaid interest on the 2025 Notes will automatically become due and payable.

Convertible Senior Notes Due 2019

On May 29, 2014, the Company entered into a Note Purchase Agreement relating to a private placement by the Company of $46 million aggregate principal senior convertible notes due 2019 (the “2019 Notes”) which are convertible into shares of the Company’s common stock at an initial conversion price of $17.41 per share. The conversion price is subject to customary anti-dilution protection. The 2019 Notes bear interest at a rate of 4.5% per annum, payable semiannually in arrears on May 15 and November 15 of each year, beginning on November 15, 2014. The 2019 Notes mature on May 30, 2019 unless earlier converted or repurchased in accordance with the terms. The aggregate carrying value of the 2019 Notes on their issuance was $43 million, which was net of the $3 million debt discount.

In September 2018, the Company used part of the net proceeds from the issuance of the 2025 Notes discussed above to repurchase $23.4 million aggregate principal value of the 2019 Notes in privately-negotiated transactions for approximately $40.2 million in cash. The partial repurchase of the 2019 Notes resulted in a $17.0 million loss on early extinguishment of debt.

As of December 31, 2018 the fair value of a share of common stock was $22.63, exceeding the initial conversion price per share of the 2019 Notes. If the debt holders were to convert the Company would be required to issue 1,297,530 shares of common stock assuming that no fundamental change in the Company had occurred. The Company has reserved sufficient shares of its common stock to satisfy the conversion requirements related to the 2019 Notes. As of December 31, 2018, the convert value exceeded the carrying value by approximately $6.8 million.

In estimating the fair value of the Company’s convertible debt, the Company performed an analysis on the straight-debt portion and the conversion feature. To estimate the fair value of conversion feature, the Company used the Monte Carlo Simulation as of December 31, 2018. To estimate the fair value of straight-debt portion, excluding the conversion feature, the Company discounted to present value the scheduled coupon payments and principal repayment, using an appropriate fair market yield. As of December 31, 2018 the fair value of the debt was estimated at $30.0 million using level 2 inputs.

The net carrying amount of the Notes consists of the following (in thousands):



	December 31,
	2018			2017
Aggregate principle amount of Notes	$	22,590		$	46,000
Unamortized debt discount and debt issuance costs	(133		)	(923		)
	$	22,457		$	45,077

Interest Expense

Total interest expense recognized for the years ended December 31, 2018, 2017 and 2016 was $9.8 million, $4.4 million and $4.7 million, respectively.

FAIR VALUE MEASUREMENTS

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

The Company accounts for financial instruments in accordance with ASC 820, “Fair Value Measurements and Disclosures” (“ASC 820”). ASC 820 establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under ASC 820 are described below:

Level 1 – Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 2 – Quoted prices in markets that are not active or financial instruments for which all significant inputs are observable, either directly or indirectly; and

Level 3 – Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

In estimating the fair value of the Company’s contingent consideration, the Company used the Monte Carlo Simulation model as of December 31, 2018, a probability-based expected method as of December 31, 2017 and the comparable uncontrolled transaction (“CUT”) method in 2016 for royalty payments based on projected revenues. Based on the fair value hierarchy, the Company classified contingent consideration within Level 3 because valuation inputs are based on projected revenues discounted to a present value.

Financial instruments with carrying values approximating fair value include cash and cash equivalents, accounts receivable, notes receivable, deposits on lease agreements, and accounts payable, due to their short term nature.

The following table presents the Company’s asset and liabilities that are measured and recognized at fair value on a recurring basis, classified under the appropriate level of the fair value hierarchy as of December 31, 2018 (in thousands):



	As of December, 2018		Fair Value Hierarchy at December 31, 2018
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	102,873	$	62,978	$	39,895	$	—
Marketable securities, available-for-sale	368,668		—		368,668		—
Total	$	471,541	$	62,978	$	408,563	$	—
Liabilities:
Business combination-related contingent consideration	93,000		—		—		93,000
Total	$	93,000	$	—	$	—	$	93,000

The following table presents the Company’s assets and liabilities that are measured and recognized at fair value on a recurring basis, classified under the appropriate level of the fair value hierarchy as of December 31, 2017 (in thousands):



	As of December, 2017		Fair Value Hierarchy at December 31, 2017
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	99,394	$	92,726	$	6,668	$	—
Marketable securities, available-for-sale	201,236		—		201,236		—
Total	$	300,630	$	92,726	$	207,904	$	—
Liabilities:
Derivative liability related to warrants	$	15,710	$	—	$	—	$	15,710
Business combination-related contingent consideration	90,000		—		—		90,000
Total	$	105,710	$	—	$	—	$	105,710

The following table sets forth a summary of changes in the estimated fair value of the Company’s Level 3 derivative liability for the year ended December 31, 2017 (in thousands):



	Fair Value Measurements of Common Stock Warrants (Level 3)
	2017
Balance at January 1,	$	22,440
Reclassification of derivative liability to equity upon exercise of warrants	(11,221		)
Change in estimated fair value of liability classified warrants	4,491
Balance at December 31,	$	15,710

The following table sets forth a summary of changes in the estimated fair value of the Company's Level 3 business combination-related contingent consideration for the years ended December 31, 2018 and 2017 (in thousands):



	Fair Value Measurements of Acquisition-Related Contingent Consideration (Level 3)
	2018			2017
Balance at January 1,	$	90,000		$	87,478
Increase from revaluation of contingent consideration	11,590			19,389
Contractual Payments	(6,373		)	(6,006		)
Contractual Payments accrued at December 31	(2,171		)	(11,012		)
Foreign currency impact	(46		)	151
Balance at December 31,	$	93,000		$	90,000

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

INTANGIBLE ASSETS

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLE ASSETS

Ligand License Agreement

In 2013, the Company entered into a $2.5 million agreement with Ligand for a worldwide sublicense to develop, manufacture and commercialize a drug technology compound including sparsentan (the “Ligand License Agreement”). The cost of the Ligand License Agreement, which is presented net of amortization in the accompanying Consolidated Balance Sheet in intangible assets, net, is being amortized to research and development on a straight-line basis through September 30, 2023. As consideration for the license, we are required to make substantial payments upon the achievement of certain milestones, totaling up to $114.1 million. Through 2018, we have made milestone payments to Ligand of $7.2 million under the terms of the Ligand License Agreement. Should we commercialize sparsentan or any products containing related compounds, we will be obligated to pay to Ligand an escalating annual royalty between 15% and 17% of net sales of all such products.

In September 2015, the Ligand License Agreement was amended to facilitate sub-licensing in Asia-Pacific. As consideration for the amendment the Company paid $1.0 million.

In March 2018, the Ligand License Agreement was amended to update certain development milestones set forth in the Sublicense Agreement to comport with the current development timeline for sparsentan. As consideration, the Company paid Ligand $4.6 million, which replaced the amount that would have been due upon initiation of the first Phase 3 trial for sparsentan.

Manchester Pharmaceuticals LLC

In 2014, the Company acquired intangible assets with finite lives related to the Chenodal product rights, trade names, and customer relationships with the values of $67.8 million, $0.2 million, and $0.4 million, respectively. The useful lives related to the acquired product rights, trade names, and customer relationships are expected to be approximately 16, 1 and, 10 years, respectively. Amortization of product rights, trade names and customer relationships are being recorded in selling, general and administrative expense over their respective lives.

Thiola License Agreement

The Company entered into a license agreement with Mission Pharmacal in 2014, in which the Company obtained an exclusive, royalty-bearing license to market, sell and commercialize Thiola (tiopronin) in the United States and Canada, and a non-exclusive license to use know-how relating to Thiola to the extent necessary to market Thiola. The initial term of the license is 10 years and will automatically renew thereafter for periods of one year.

The Company paid Mission an up-front license fee of $3 million and will pay guaranteed minimum royalties during each calendar year the greater of $2 million or twenty percent (20%) of the Company’s net sales of Thiola through May 28, 2024.

In November 2017, the Company amended its agreement with Mission to extend the term of the current exclusive U.S. and Canada licensing agreement by an additional five years, to 2029. The royalty rate and guaranteed minimum payment were also extended through the new agreement term. Upon execution of the amendment, the Company capitalized an additional $5.9 million in intangible assets and recorded a guaranteed minimum liability for the same amount.

In November 2018, the Company amended its agreement with Mission to extend the territorial rights beyond the United States and Canada. As consideration for the expanded territory the Company paid an up-front fee of $0.3 million and will pay guaranteed minimum royalties equaling the greater of $0.1 million or 20% of our Thiola net sales generated from outside of the United States during each calendar year. Upon execution of the amendment, the Company capitalized an additional $1.0 million in intangible assets and recorded a guaranteed minimum liability of $0.7 million related to this amendment.

The present value of guaranteed minimum royalties payable using a discount rate of ranging from approximately 7% to 11% based on the Company’s then borrowing rate is $15.2 million and $15.1 million as of December 31, 2018 and 2017, respectively. As of December 31, 2018, the guaranteed minimum royalty current and long term liability was approximately $2.1 million and $13.1 million, respectively, and is recorded as guaranteed minimum royalty in the Consolidated Balance Sheet. As of December 31, 2017, the guaranteed minimum royalty current and long term liability was approximately $2.0 million and $13.1 million, respectively, and is recorded as guaranteed minimum royalty in the Consolidated Balance Sheet. The Company has capitalized $70.0 million related to the Thiola intangible asset which consists of the up-front license fee, professional fees, present value of the guaranteed minimum royalties and any additional payments through 2018 in excess of minimum royalties.

There are 10.4 years remaining in the term of the license agreement.

Cholbam (Kolbam) Asset Purchase

On March 31, 2015, the Company completed its acquisition from Asklepion of all worldwide rights, titles and ownership of Cholbam, including all related contracts, data assets, intellectual property, regulatory assets and the PRV. The Company capitalized $75.9 million and $7.3 million for the U.S. and international economic interest, respectively.

L-UDCA

On June 20, 2016, the Company signed a definitive agreement to purchase the rights, titles, and ownership of L-UDCA from Asklepion. The purchase included $25.5 million for an intangible asset with a definite life related to product rights for the U.S. The useful life related to the acquired product rights is expected to be approximately 17 years once the NDA is approved by the FDA. Until approval, the asset is considered IPR&D with an indefinite life and is not amortized.

Amortizable intangible assets as of December 31, 2018 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(20,213	)	$	47,636
Thiola License	15	70,009		(14,523		)	55,486
Economic Interest - U.S. revenue Cholbam	10	75,900		(28,487		)	47,413
Economic Interest - International revenue Cholbam	10	7,700		(2,890		)	4,810
Economic Interest - L-UDCA (acquired IPR&D)	Indefinite	25,500		—			25,500
Ligand License	11	7,900		(2,397		)	5,503
Manchester Customer Relationships	10	403		(192		)	211
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(75		)	132
Total		$	255,643	$	(68,952	)	$	186,691

Amortizable intangible assets as of December 31, 2017 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(15,976	)	$	51,873
Thiola License	10	54,471		(10,168		)	44,303
Economic Interest - U.S. revenue Cholbam	10	75,900		(20,903		)	54,997
Economic Interest - International revenue Cholbam	10	8,058		(2,219		)	5,839
Economic Interest - L-UDCA (acquired IPR&D)	Indefinite	25,500		—			25,500
Ligand License	11	3,300		(1,420		)	1,880
Manchester Customer Relationships	10	403		(152		)	251
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(33		)	174
Total		$	235,863	$	(51,046	)	$	184,817

The following table summarizes amortization expense for the twelve months ended December 31, 2018, 2017 and 2016 (in thousands):



	2018		2017		2016
Research and development	$	976	$	327	$	328
Selling, general and administrative	17,052		17,004		15,665
Total amortization expense	$	18,028	$	17,331	$	15,993

As of December 31, 2018, amortization expense (excluding infinite lived IPR&D) for the next five years is expected to be as follows (in thousands):



2019	$	19,166
2020	19,210
2021	19,158
2022	19,125
2023	18,825
Thereafter	65,707
Total	$	161,191

ACCRUED EXPENSES

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

ACCRUED EXPENSES

Accrued expenses consist of the following at December 31, 2018 and 2017 (in thousands):



	2018		2017
Compensation related costs	$	10,446	$	7,749
Research and development	16,515		6,989
Government rebate reserves	8,464		5,883
Selling, general and administrative	2,990		3,896
Royalty/contingent consideration	6,805		6,429
Restructuring expenses	—		3,549
Miscellaneous accrued expenses	4,475		1,523
Total accrued expenses	$	49,695	$	36,018

COMMITMENTS AND CONTINGENCIES

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Leases



Facilities	Base Rent	Lease Expiration
Corporate Headquarters San Diego, CA	$2.3 million	July 2024

In July 2016, the Company entered into an agreement to lease 23,107 square feet of office space, which commenced in December 2016, for a term of 7 years and 7 months. Under the terms of the lease, the Company will pay base annual rent (subject to an annual fixed percentage increase), plus property taxes, and other normal and necessary expenses, such as utilities, repairs, security and maintenance. Certain incentives were included in the lease, including approximately $1.5 million in tenant improvement allowances and seven months of rent abatement. The Company has the right to extend the lease for five years.

In July 2017, the Company amended the office lease to add an additional 22,339 square feet of office space in an adjacent building.

Following is a schedule of the future minimum rental commitments for our operating lease as of December 31, 2018 (in thousands):



	Rental Payments
2019	$	2,343
2020	2,414
2021	2,486
2022	2,560
2023	2,637
Thereafter	1,585
	$	14,025

Legal Proceedings

In August 2017, Martin Shkreli, the Company’s former Chief Executive Officer, was convicted on securities fraud charges following investigations by the U.S. Attorney for the Eastern District of New York and the U.S Securities and Exchange Commission. The Company was not a target of these investigations and cooperated with them fully. Mr. Shkreli has appealed his conviction to the United States Court of Appeals for the Second Circuit, and the appeal will likely not be decided until later in 2019. In connection with the trial and pending appeal proceedings, Mr. Shkreli sought advancement of his legal fees from the Company, and the Company has advanced a total of $5.4 million in legal fees, of which $3.8 million has been reimbursed by its directors’ and officers’ insurance carriers. Pending the outcome of Mr. Shkreli's appeal, the insurance carriers have reserved their rights to assert that certain of the advanced funds pertain to claims excluded from coverage under the relevant insurance policy and are therefore recoverable by the carriers. As a result, the final amount of the reimbursement from the insurance carriers is not currently estimable. In addition, a portion of these and the other legal fees the Company has advanced to Mr. Shkreli will be subject to reimbursement by Mr. Shkreli under Delaware law in the event it is ultimately determined that Mr. Shkreli is not entitled to be indemnified by the Company in these proceedings.

In August 2015, the Company filed a lawsuit in federal district court for the Southern District of New York against Mr. Shkreli, asserting that he breached his fiduciary duty of loyalty during his tenure as the Company’s Chief Executive Officer and a member of its Board of Directors. Mr. Shkreli served a demand for JAMS arbitration on Retrophin, claiming that Retrophin had breached his December 2013 employment agreement. In response to Mr. Shkreli’s arbitration demand, the Company asserted counterclaims in the arbitration that are substantially similar to the claims it previously asserted in the federal lawsuit against Mr. Shkreli. In October 2018, after the arbitration panel determined that Retrophin's counterclaims were arbitrable, the Company voluntarily dismissed the federal action without prejudice. The Company does not expect the claims and counterclaims in the arbitration to be heard by the arbitration panel before mid-2019. In connection with these proceedings, Mr. Shkreli sought advancement of his legal fees from the Company relating to his defense of the Company’s claims against him. The Company has advanced, and expects to continue to advance, certain of these legal fees to Mr. Shkreli.

For the years ended December 31, 2018 and 2017, the Company recorded zero and $2.6 million in expenses and paid zero and $3.6 million related to advancements for Mr. Shkreli, respectively. The Company received zero and $2.6 million in reimbursement from its directors’ and officers’ insurance carriers during the year ended December 31, 2018 and 2017, respectively. The reimbursement in 2017 is recorded as a liability on the Consolidated Balance Sheet pending the outcome of an appeal, if any.

From time to time the Company is involved in legal proceedings arising in the ordinary course of business. On October 23, 2018, Spring Pharmaceuticals, LLC (Spring) filed a lawsuit against the Company, Martin Shkreli, Mission Pharmacal Company and Alamo Pharma Services, Inc. in the United States District Court for the Eastern District of Pennsylvania alleging that the Company violated various federal and state antitrust and unfair competition laws by allegedly refusing to sell samples of the Thiola^® brand drug so that Spring can conduct the bioequivalence testing needed to submit an ANDA to the FDA for approval to market a generic version of the product. Spring is seeking injunctive relief and damages. The Company intends to vigorously defend against Spring’s claims. On January 15, 2019, the Company filed a motion to dismiss the lawsuit, which is in the process of being briefed.

The Company is not aware of any other proceedings or claims that could have, individually or in the aggregate, a material adverse effect on its results of operations or financial condition.

STOCKHOLDERS’ EQUITY / DEFICIT

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

STOCKHOLDERS’ EQUITY / DEFICIT

Common Stock

The Company is currently authorized to issue up to 100,000,000 shares of $0.0001 par value common stock. All issued shares of common stock are entitled to vote on a 1 share/1 vote basis.

Preferred Stock

The Company is currently authorized to issue up to 20,000,000 shares of $0.0001 par value preferred stock, of which 1,000 shares are designated Class "A" Preferred shares, $0.001 par value. Class A Preferred Shares are not entitled to interest, have certain liquidation preferences, special voting rights and other provisions. No preferred stock has been issued to date.

2015 Equity Incentive Plan

On June 8, 2015, the Company's stockholders approved the 2015 Equity Incentive Plan (the "2015 Plan"). The 2015 Plan is intended as the successor to and continuation of the Company’s 2014 Incentive Compensation Plan. Stockholders approved 1.4 million new shares to be issued under the 2015 Plan, in addition to 0.6 million unallocated shares remaining available for issuance under the 2014 Incentive Compensation Plan that were added to the 2015 Plan.

On May 18, 2016, the Company's stockholders approved an amendment to the 2015 Plan (the "Amended 2015 Plan"). The amendment provides for an additional 1.6 million new shares to be issued under the Amended 2015 Plan, in addition to 0.7 million unallocated shares remaining available for issuance. The amendment also includes a provision that on or after March 21, 2016, the number of shares available for issuance under the Amended 2015 Plan will be reduced by one share for each share subject to a stock option or stock appreciation right and by 2.0 shares for each share subject to any other type of stock award issued pursuant to the Amended 2015 Plan, and any such shares will return to the share reserve at the same rates upon cancellation or other forfeiture of such awards or shares.

On May 17, 2017, the Company's stockholders approved an amendment to the Amended 2015 Plan. The amendment provides for an additional 1.8 million new shares to be issued under the Amended 2015 Plan.

2018 Equity Incentive Plan

On May 9, 2018, the Company's stockholders approved the 2018 Equity Incentive Plan (the "2018 Plan"). The 2018 Plan is intended as the successor to and continuation of the Amended 2015 Plan. Stockholders approved 1.8 million new shares to be issued under the 2018 Plan, in addition to 1.6 million unallocated shares remaining available for issuance under the Amended 2015 Plan that were added to the 2018 Plan.

2017 Employee Stock Purchase Plan

The 2017 Employee Stock Purchase Plan ("2017 ESPP") originated with 380,000 shares of common stock available for issuance. Beginning on January 1, 2018, and ending on (and including) January 1, 2026, the number of shares of common stock available for issuance under the 2017 ESPP shall increase by an amount equal to the lesser of (i) one percent (1%) of the total number of shares of common stock outstanding on December 31st of the preceding calendar year and (ii) 300,000 shares of common stock.

Substantially all employees are eligible to participate and, through payroll deductions, can purchase shares on established dates semi-annually. The purchase price per share sold pursuant to the 2017 ESPP will be the lower of (i) 85% of the fair market value of common stock on the first day of the offering period or (ii) 85% of the fair market value on the purchase date. Each offering period will span up to six months. Purchases may be up to 15% of qualified compensation, with an annual limit of $25,000. The 2017 ESPP is intended to qualify as an “employee stock purchase plan” under Section 423 of the Internal Revenue Code.

As of December 31, 2018, there were approximately 680,000 shares authorized and 552,966 shares reserved for future issuance under the 2017 ESPP.

Stock Options

The fair values of stock option grants during the year ended December 31, 2018, 2017 and 2016 were calculated on the date of grant using the Black-Scholes option pricing model. Compensation expense is recognized over the period of service, generally the vesting period. During the year ended December 31, 2018, 1,349,250 stock options were granted by the Company. The following weighted average assumptions were used in the Black-Scholes options pricing model to estimate the fair value of stock options for the specified reporting periods:



	Twelve Months Ended December 31,
	2018		2017		2016
Risk free rate	2.80	%	2.10	%	1.20	%
Expected volatility	68	%	70	%	68	%
Expected life (in years)	6.2		6.1		5.8
Expected dividend yield	—		—		—

The risk-free interest rate was based on rates established by the Federal Reserve. The Company’s expected volatility was based on analysis of the Company’s volatility, as well as the volatilities of guideline companies. The expected life of the Company’s options was determined using the simplified method as a result of limited historical data regarding the Company’s exercise activity. The dividend yield is based upon the fact that the Company has not historically paid dividends, and does not expect to pay dividends in the foreseeable future.

The following table summarizes our stock option activity and related information for the years ended December 31, 2018:



			Weighted Average
	Shares Underlying Options		Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2017	7,153,668		$	17.16	6.95	$	39,010
Granted	1,349,250		25.56		—	—
Forfeited and expired	(476,369	)	24.50		—	—
Exercised	(749,212	)	14.13		—	9,325
Outstanding at December 31, 2018	7,277,337		$	18.55	6.94	$	40,650

The following table summarizes our stock options exercisable at December 31, 2018, 2017 and 2016:



		Weighted Average
	Shares Underlying Options	Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
2016	3,793,017	$	14.94	6.82	$	23,358
2017	4,610,233	$	15.97	5.85	$	31,991
2018	4,834,781	$	16.81	5.98	$	35,387

The weighted average grant date fair value of options granted was $16.21, $11.77, and $10.09 during the years ended December 31, 2018, 2017 and 2016, respectively. The aggregate intrinsic value for outstanding options is calculated as the difference between the exercise price of the underlying awards and the closing price of the Company’s common stock of $22.63, $21.07 and $18.93 as of December 31, 2018, 2017 and 2016, respectively. Unrecognized compensation cost associated with unvested stock options amounts to $30.0 million as of December 31, 2018, which will be expensed over a weighted average remaining vesting period of 2.7 years.

Restricted Stock Units

As of December 31, 2018, there was approximately $7.9 million of unrecognized compensation cost related to restricted stock units ("RSUs") granted. This amount is expected to be recognized over a weighted average period of 2.9 years.

The following table summarizes our restricted stock unit activity for the year ended December 31, 2018:



	Number of RSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2017	94,832		$	20.19
Granted	395,311		25.40
Vested	(58,251	)	20.08
Forfeited/cancelled	(31,466	)	25.20
Unvested December 31, 2018	400,426		$	24.95

Performance-based Stock Units

As of December 31, 2018, there was approximately $1.6 million of unrecognized compensation cost related to performance-based stock units ("PSUs") granted. This amount is expected to be recognized over a weighted average period of 1.3 years.

The following table summarizes our performance-based stock unit activity for the year ended December 31, 2018:



	Number of PSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2017	250,500		$	20.63
Granted	66,500		25.75
Vested	(85,250	)	22.33
Forfeited/cancelled	(5,000	)	18.46
Unvested December 31, 2018	226,750		$	21.54

Share Based Compensation

Total non-cash stock-based compensation expense consisted of the following for the years ended December 31, 2018, 2017 and 2016 (in thousands):



	Twelve Months Ended December 31,
	2018		2017		2016
Selling, general and administrative expenses	$	13,550	$	17,924	$	18,614
Research and development expenses	6,224		8,950		10,488
Total	$	19,774	$	26,874	$	29,102

Exercise of Warrants

During the twelve months ended December 31, 2018, 2017 and 2016, the Company issued the following shares of common stock upon the exercise of warrants for cash received by the Company: (in thousands except share amounts)



	Shares Issued	Cash Received		Derivative Liability Reclassified as Equity		Change in Fair Value Expense
2016	898,633	$	6,005	$	14,715	$	2,909
2017	607,481	$	3,645	$	11,221	$	3,033
2018	1,036,054	$	5,305	n/a		n/a

As of December 31, 2018 there are no warrants for common shares outstanding. See Note 15 for further discussion.

EARNINGS (LOSS) PER SHARE

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

EARNINGS (LOSS) PER SHARE

Basic earnings (loss) per share (“EPS”) represents net income (loss) attributable to common shareholders divided by the weighted average number of common shares outstanding during the measurement period. Diluted EPS represents net income attributable to common shareholders divided by the weighted average number of common shares outstanding during the measurement period while also giving effect to all potentially dilutive common shares that were outstanding during the period using the treasury stock method.

Basic and diluted EPS is calculated as follows (net income amounts are stated in thousands):



	For the year ended December 31,
	2018							2017							2016
	Shares	Net loss			EPS			Shares	Net loss			EPS			Shares	Net Income			EPS
Basic Earnings per Share	40,433,171	$	(102,678	)	$	(2.54	)	38,769,816	$	(59,731	)	$	(1.54	)	36,997,865	$	(47,903	)	$	(1.29	)
Dilutive shares related to warrants	—	—						—	—						1,290,147	—
Change in fair value of derivative instruments	—	—						—	—						—	(1,655		)
Dilutive Earnings per Share	40,433,171	$	(102,678	)	$	(2.54	)	38,769,816	$	(59,731	)	$	(1.54	)	38,288,012	$	(49,558	)	$	(1.29	)

For the years ended December 31, 2018, 2017 and 2016, the following shares were excluded because they were anti-dilutive:



	For the year ended December 31,
	2018	2017	2016
Convertible Debt	8,410,932	2,642,160	2,642,160
Restricted Stock	395,034	157,319	444,942
Options	7,210,576	7,080,998	6,286,584
Warrants	282,807	1,159,424	—
Total Anti-Dilutive Shares	16,299,349	11,039,901	9,373,686

INCOME TAXES

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

INCOME TAXES

For financial reporting purposes, net income (loss) before income taxes includes the following components (in thousands):



	Year Ended December 31,
	2018			2017			2016
United States	$	(87,573	)	$	(55,611	)	$	(52,750	)
Foreign	(14,294		)	(2,752		)	(4,832		)
Total	$	(101,867	)	$	(58,363	)	$	(57,582	)

The components of the provision (benefit) for income taxes, in the Consolidated Statement of Operations are as follows (in thousands):



	2018		2017			2016
Current
Federal	$	698	$	6,991		$	13,137
State	113		802			(155		)
	811		7,793			12,982
Deferred
Federal	—		(7,965		)	(18,814		)
State	—		1,540			(3,847		)
	—		(6,425		)	(22,661		)
Total tax provision (benefit)	$	811	$	1,368		$	(9,679	)

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate expressed as a percentage of income (loss) before income taxes:



	2018		2017		2016
Statutory rate - federal	(21.00	)%	(35.00	)%	(35.00	)%
State taxes, net of federal benefit	(4.44	)%	(3.30	)%	(3.16	)%
Change in FV of derivative liability (warrants)	—	%	2.82	%	1.10	%
Change in federal tax rate	—	%	23.29	%	—	%
Convertible Debt	21.77	%	—	%	—	%
Loss on extinguishment of debt	4.09	%	—	%	—	%
Other permanent differences	0.10	%	1.04	%	2.05	%
Tax credits	(11.86	)%	(5.79	)%	(1.58	)%
Return to provision adjustments and other true-ups	1.42	%	(3.48	)%	(1.15	)%
Other	1.06	%	1.25	%	3.09	%
Change in valuation allowance	9.79	%	21.62	%	16.30	%
Income tax provision (benefit)	0.93	%	2.45	%	(18.35	)%

The significant components of the Company’s deferred tax assets and liabilities as of December 31, 2018 and 2017 are as follows (in thousands):



	2018			2017
Deferred Tax Assets:
Net operating loss	$	9,700		$	1,099
Research and development and other tax credits	14,715			1,599
Contingent consideration	23,459			23,080
Other accrued expenses	3,710			2,603
Stock based compensation	16,761			15,695
Other	555			358
	68,900			44,434
Deferred Tax Liabilities:
Intangible assets	(14,288		)	(16,810		)
Convertible Debt	(18,419		)	—
Tax basis depreciation less than book depreciation	—			—
	(32,707		)	(16,810		)

Net deferred tax assets (liabilities) before valuation allowance	36,194			27,624
Valuation allowance	(36,194		)	(27,624		)
Total deferred tax liability	$	—		$	—

The Company has established a full valuation allowance against its U.S. federal and state deferred tax assets due to the uncertainty surrounding the realization of such assets in future periods. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which temporary differences become deductible. Management considers the scheduled reversal of deferred liabilities and tax planning strategies in making this assessment and evaluates the recoverability of the deferred tax assets as of each reporting date. At such time as it is determined that it is more likely than not that deferred assets are realizable, the valuation allowance will be reduced accordingly and recorded as a tax benefit.

The Company has recorded a valuation allowance of $36.2 million as of December 31, 2018 to reflect the estimated amount of deferred tax assets that may not be realized. The Company increased its valuation allowance by $8.6 million for the year ended December 31, 2018.

At December 31, 2018, the Company had available unused U.S. federal and state net operating loss (“NOL”) carryforwards of $36.5 million and $33.1 million, respectively, all of which are fully offset by a valuation allowance. The U.S. federal NOL carryforwards generated for tax years ending on or prior to December 31, 2017 and the state tax loss carryforwards will begin to expire in 2030 and 2022, respectively. In addition, at December 31, 2018, the Company had federal orphan drug tax credit carryforwards of $12.8 million that begin to expire in 2037 unless utilized, federal research and development tax credit carryforwards of $0.5 million that begin to expire in 2038 unless utilized and California Competes tax credit carryforwards of $2.0 million that begin to expire in 2022. The Company has international subsidiaries whose operations are not material for the year ended December 31, 2018.

The Company accounts for uncertain tax benefits in accordance with the provisions of ASC 740-10 of the Accounting for Uncertainty in Income Taxes. As of December 31, 2018 the Company had no unrecognized tax benefits.

The Company does not anticipate that the amount of unrecognized tax benefits as of December 31, 2018 will change materially within the following 12 months.

A reconciliation of the Company's unrecognized tax benefits for the years 2018 and 2017 is provided in the following table (in thousands):



	2018		2017
Balance as of January 1:	$	—	$	1,500
Increase in current period positions	—		—
Decrease in prior period positions	—		(1,500		)
Increase in prior period positions	—		—
Balance as of December 31:	$	—	$	—

The Company files income tax returns in the U.S. federal jurisdiction, various state and local, and foreign jurisdictions. The Company’s income tax returns are open to examination by federal, state and foreign tax authorities, generally for the years ended December 31, 2015 and later.

The Company’s policy is to record estimated interest and penalties related to the underpayment of income taxes or unrecognized tax benefits as a component of its income tax provision. During the years ended 2018, 2017 and 2016, the Company did not recognize any interest or penalties in its Consolidated Statements of Operations and Comprehensive Income (Loss) and there were no accruals recorded for interest or penalties at December 31, 2018 and 2017.

U.S. Tax Reform

The Tax Act of 2017 was enacted on December 22, 2017. The Tax Act of 2017 reduces the US federal corporate tax rate from 35% to 21%, as well as making several other significant changes to the tax law, effective January 1, 2018. Pursuant to the Securities and Exchange Commission Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118), given the amount and complexity of the changes in tax law resulting from the Tax Act of 2017, the Company had not finalized the accounting for the income tax effects of the Tax Act of 2017 as of December 31, 2017.

We completed our accounting for Tax Reform on December 22, 2018 and as of December 31, 2018, the Company's accounting for the following elements of the Tax Act of 2017 were completed and there were no changes to the provisional amounts previously recorded.

Revaluation of deferred tax assets and liabilities

We have remeasured our deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21% plus state and local tax. The Company recorded a decrease related to our deferred tax assets and liabilities of $13.0 million as a result of the tax rate decrease, with a corresponding adjustment to our valuation allowance for the year ended December 31, 2017.

Valuation allowances

The Company must assess whether its valuation allowance analyses for deferred tax assets are affected by various aspects of the Tax Act of 2017 (e.g., deemed repatriation of deferred foreign income, future GILTI inclusions, new categories of foreign tax credits). At December 31, 2017, the Company increased its valuation allowance by $12.0 million as a result of the Tax Act of 2017 and its effects on the realizability of our deferred tax assets.

DERIVATIVE FINANCIAL INSTRUMENTS

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVE FINANCIAL INSTRUMENTS

Since 2013, the Company has issued 5 tranches of common stock purchase warrants to secure financing, remediate covenant violations related to a credit facility and provide consideration for credit facility amendments.

Historically, the Company accounted for these instruments, which do not have fixed settlement provisions, as derivative instruments in accordance with FASB ASC 815-40, Derivative and Hedging - Contracts in Entity’s Own Equity. This was due to an anti-dilution provision for the warrants that provides for a reduction to the exercise price if the Company issues equity or equity linked instruments in the future at an effective price per share less than the exercise price then in effect for the warrant ("down round provision"). As such, the warrants were re-measured at each balance sheet date based on estimated fair value. Changes in estimated fair value were recorded as non-cash adjustments within other income (expenses), net, in the Company’s

The fair value of the derivative liability balance as of December 31, 2017 of $15.7 million was reclassified by means of a cumulative-effect adjustment to equity as of January 1, 2018.

The following table presents the Company’s derivative warrant issuances and balances outstanding during the years ended December 31, 2018 and 2017:



		Weighted Average
	Warrants	Exercise Price		Grant Date Fair Value
Outstanding at December 31, 2016	1,766,905	$	7.23	$	3.87
Issued	—	—		—
Canceled	—	—		—
Exercised	607,481	6.00		3.33
Outstanding at December 31, 2017	1,159,424	$	7.86	$	4.15
Issued	—	—		—
Canceled	554	5.99		3.33
Exercised	1,158,870	7.88		4.15
Outstanding at December 31, 2018	—	—		—

As of December 31, 2018 there are no outstanding warrants.

RETIREMENT PLAN	12 Months Ended
RETIREMENT PLAN	Dec. 31, 2018
Retirement Benefits [Abstract]
RETIREMENT PLAN	RETIREMENT PLAN The Company has a 401(k) defined contribution savings plan for the benefit of all eligible employees. Employer matching contributions were $0.9 million, $0.6 million, and $0.5 million for the years ended December 31, 2018, 2017 and 2016, respectively.

RESTRUCTURING

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Restructuring

RESTRUCTURING

On March 7, 2017, the Company initiated a plan to consolidate its operations to its corporate headquarters in San Diego, California. The Company adjusted employee related separation charges by $0.2 million in the current year as a result of this consolidation.

The following table presents a reconciliation of the restructuring liability recorded within accrued expenses on the Company's Condensed Consolidated Balance Sheets (in thousands):



	Twelve Months Ended December 31,
	2018			2017
Liability, beginning of period	$	3,549		$	893
Restructuring expenses	—			3,608
Cash settlements	(3,307		)	(897		)
Adjustments to previous estimates	(242		)	(55		)
Liability, end of period	$	—		$	3,549

PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT

Property, plant and equipment, net consisted of the following (in thousands):



	December 31,
	2018			2017
Computers and equipment	$	506		$	436
Furniture and fixtures	1,150			945
Leasehold improvements	2,628			2,071
Construction-in-progress	—			363
	4,284			3,815
Less: Accumulated depreciation	(1,138		)	(585		)
Total property and equipment, net	$	3,146		$	3,230

The construction-in-process balance consists of costs related to the Company’s leasehold improvements at its facilities in San Diego, California.

Depreciation expense for the years ended December 31, 2018, 2017 and 2016 was $0.6 million, $0.5 million and $0.1 million, respectively.

The Company has not capitalized interest related to the property and equipment purchases.

QUARTERLY FINANCIAL INFORMATION (UNAUDITED)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

QUARTERLY FINANCIAL INFORMATION (UNAUDITED)

The following table presents selected consolidated statements of operations data for each quarter for the fiscal years ended December 31, 2018 and 2017 (unaudited, in thousands, except for per share data):



	Fourth Quarter			Third Quarter				Second Quarter			First Quarter

For the year ended December 31, 2018:
Net product sales	$	43,771		$	40,706			$	41,337		$	38,432
Total operating expenses	48,756			76,289				62,897			56,344
Operating loss	(4,985		)	(35,583		)		(21,560		)	(17,912		)
Total other income (expense), net	(2,470		)	(18,518		)	¹	(602		)	(237		)
Loss before provision for income taxes	(7,455		)	(54,101		)		(22,162		)	(18,149		)
Income tax benefit (provision)	—			(415		)		(167		)	(229		)
Net income (loss)	$	(7,455	)	$	(54,516	)		$	(22,329	)	$	(18,378	)
Net Loss per common share
Basic	$	(0.18	)	$	(1.34	)		$	(0.56	)	$	(0.46	)
Diluted	$	(0.18	)	$	(1.34	)		$	(0.56	)	$	(0.46	)
For the year ended December 31, 2017:
Net product sales	$	42,177		$	40,340			$	38,800		$	33,620
Total operating expenses	57,354			50,948				52,398			48,028
Operating loss	(15,177		)	(10,608		)		(13,598		)	(14,408		)
Total other income (expense), net	4,139			(8,409		)		(1,556		)	1,254
Income (loss) before provision for income taxes	(11,038		)	(19,017		)		(15,154		)	(13,154		)
Income tax benefit (provision)	(6,580		)	1,223				1,925			2,064
Net income (loss)	$	(17,618	)	$	(17,794	)		$	(13,229	)	$	(11,090	)
Net income (loss) per common share
Basic	$	(0.45	)	$	(0.46	)		$	(0.34	)	$	(0.29	)
Diluted	$	(0.55	)	$	(0.46	)		$	(0.34	)	$	(0.32	)

¹In September 2018, the Company executed a partial repurchase of the 2019 Notes that resulted in a $17.0 million loss on early extinguishment of debt. See Note 7 for further discussion.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Principles of Consolidation

Use of Estimates

Revenue Recognition

Patents

Research and Development Costs

Clinical Trial Expenses

Employee Stock-Based Compensation



	Initial Vesting Term
Stock Options	3 to 4 years
Restricted Stock Units	2 to 4 years

Earnings (Loss) Per Share

Cash and Cash Equivalents

Marketable Securities

Trade and Notes Receivable

Trade Receivables, Net

Inventory and Related Reserves

Segment Information

Property and Equipment, net

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Intangible Assets, Net

Goodwill

Impairment of Long-Lived Assets

Contingent Consideration

Level 1 – Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities;

Level 2 – Quoted prices in markets that are not active or financial instruments for which all significant inputs are observable, either directly or indirectly; and

Level 3 – Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable.

Income Taxes

Reclassifications

Certain reclassifications have been made to the prior year financial statements in order to conform to the current year’s presentation.

Derivative Financial Instruments, Warrants

Recently Issued Accounting Pronouncements

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Schedule of Vesting Award Terms



	Initial Vesting Term
Stock Options	3 to 4 years
Restricted Stock Units	2 to 4 years

Schedule of inventory, net of reserve

Inventory, net of reserve, consisted of the following at December 31, 2018 and 2017 (in thousands):



	December 31, 2018		December 31, 2017
Raw material	$	4,689	$	3,435
Finished goods	930		1,916
Total inventory	$	5,619	$	5,351

Schedule of major classifications of property, equipment and software, including their respective expected useful lives

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Property, plant and equipment, net consisted of the following (in thousands):



	December 31,
	2018			2017
Computers and equipment	$	506		$	436
Furniture and fixtures	1,150			945
Leasehold improvements	2,628			2,071
Construction-in-progress	—			363
	4,284			3,815
Less: Accumulated depreciation	(1,138		)	(585		)
Total property and equipment, net	$	3,146		$	3,230

REVENUE RECOGNITION (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Summary of Net Product Revenue

The following table summarizes net product revenues for the twelve months ended December 31, 2018, 2017 and 2016 (in thousands):



	Twelve Months Ended December 31,
	2018	2017	2016
Thiola	89,176	82,311	71,199
Bile acid products	75,070	72,626	62,392
Total net product revenue	164,246	154,937	133,591

BUSINESS COMBINATION AND ASSET TRANSACTIONS (Tables)

12 Months Ended

Dec. 31, 2018

Business Combinations [Abstract]

Schedule of purchase price allocation

The purchase price allocation of $25.5 million as of the acquisition completion date of June 16, 2016 was as follows (in thousands):



Cash paid upon consummation	$	500
Present value of contingent consideration	25,000
Total purchase price	$	25,500
Fair Value of Assets Acquired and Liabilities Assumed
Acquired product rights: L-UDCA (intangible asset)	$	25,500
Total purchase price	$	25,500

MARKETABLE SECURITIES (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

Schedule of marketable securities

Marketable securities consist of the following (in thousands):



	As of December 31,
	2018		2017
Marketable Securities:
Commercial paper	59,255		6,897
Corporate debt securities	299,413		164,297
Securities of government sponsored entities	10,000		30,042
Total Marketable Securities:	$	368,668	$	201,236

Schedule of available for sale securities

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2018 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Gains		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	59,313	$	—	$	(58	)	$	59,255
Corporate debt securities	Less than 1	149,824		—		(604		)	149,220
Total maturity less than 1 year		209,137		—		(662		)	208,475
Corporate debt securities	1 to 2	150,813		18		(638		)	150,193
Securities of government-sponsored entities	1 to 2	9,997		4		(1		)	10,000
Total maturity 1 to 2 years		160,810		22		(639		)	160,193
Total available-for-sale securities		$	369,947	$	22	$	(1,301	)	$	368,668

The following is a summary of short-term marketable securities classified as available-for-sale as of December 31, 2017 (in thousands):



	Contractual Maturity (in years)	Amortized Cost		Unrealized Losses			Aggregate Estimated Fair Value
Marketable Securities:
Commercial paper	Less than 1	$	6,911	$	(14	)	$	6,897
Corporate debt securities	Less than 1	86,531		(198		)	86,333
Securities of government-sponsored entities		30,132		(90		)	30,042
Total maturity less than 1 year		123,574		(302		)	123,272
Corporate debt securities	1 to 2	78,388		(424		)	77,964
Total maturity 1 to 2 years		78,388		(424		)	77,964
Total available-for-sale securities		$	201,962	$	(726	)	$	201,236

NOTES PAYABLE (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of fair value of warrants

The composition of the Company’s 2025 Notes are as follows (in thousands):



	December 31, 2018			December 31, 2017
2.50% convertible senior notes due 2025	$	276,000		$	—
Unamortized debt discount	(74,836		)	—
Unamortized debt issuance costs	(6,073		)	—
Total 2025 Notes, net of unamortized debt discount and debt issuance costs	$	195,091		$	—



	Twelve Months Ended December 31,
	2018		2017
Contractual interest expense	$	2,108	$	—
Amortization of debt discount	2,582		—
Amortization of debt issuance costs	273		—
Total interest expense for the 2025 Notes	$	4,963	$	—

Schedule of net carrying amount of debt

The net carrying amount of the Notes consists of the following (in thousands):



	December 31,
	2018			2017
Aggregate principle amount of Notes	$	22,590		$	46,000
Unamortized debt discount and debt issuance costs	(133		)	(923		)
	$	22,457		$	45,077

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

FAIR VALUE MEASUREMENTS (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of fair value on a recurring basis



	As of December, 2018		Fair Value Hierarchy at December 31, 2018
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	102,873	$	62,978	$	39,895	$	—
Marketable securities, available-for-sale	368,668		—		368,668		—
Total	$	471,541	$	62,978	$	408,563	$	—
Liabilities:
Business combination-related contingent consideration	93,000		—		—		93,000
Total	$	93,000	$	—	$	—	$	93,000



	As of December, 2017		Fair Value Hierarchy at December 31, 2017
	Total carrying and estimated fair value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	$	99,394	$	92,726	$	6,668	$	—
Marketable securities, available-for-sale	201,236		—		201,236		—
Total	$	300,630	$	92,726	$	207,904	$	—
Liabilities:
Derivative liability related to warrants	$	15,710	$	—	$	—	$	15,710
Business combination-related contingent consideration	90,000		—		—		90,000
Total	$	105,710	$	—	$	—	$	105,710

Schedule of fair value measurements of common stock warrants using significant unobservable inputs (Level 3)

The following table sets forth a summary of changes in the estimated fair value of the Company’s Level 3 derivative liability for the year ended December 31, 2017 (in thousands):



	Fair Value Measurements of Common Stock Warrants (Level 3)
	2017
Balance at January 1,	$	22,440
Reclassification of derivative liability to equity upon exercise of warrants	(11,221		)
Change in estimated fair value of liability classified warrants	4,491
Balance at December 31,	$	15,710

Schedule of fair value measurements of acquisition-related contingent consideration



	Fair Value Measurements of Acquisition-Related Contingent Consideration (Level 3)
	2018			2017
Balance at January 1,	$	90,000		$	87,478
Increase from revaluation of contingent consideration	11,590			19,389
Contractual Payments	(6,373		)	(6,006		)
Contractual Payments accrued at December 31	(2,171		)	(11,012		)
Foreign currency impact	(46		)	151
Balance at December 31,	$	93,000		$	90,000

INTANGIBLE ASSETS (Tables)

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of amortizable intangible assets

Amortizable intangible assets as of December 31, 2018 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(20,213	)	$	47,636
Thiola License	15	70,009		(14,523		)	55,486
Economic Interest - U.S. revenue Cholbam	10	75,900		(28,487		)	47,413
Economic Interest - International revenue Cholbam	10	7,700		(2,890		)	4,810
Economic Interest - L-UDCA (acquired IPR&D)	Indefinite	25,500		—			25,500
Ligand License	11	7,900		(2,397		)	5,503
Manchester Customer Relationships	10	403		(192		)	211
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(75		)	132
Total		$	255,643	$	(68,952	)	$	186,691

Amortizable intangible assets as of December 31, 2017 (in thousands):



	Useful Life	Gross Carrying Amount		Accumulated Amortization			Net Book Value
Chenodal Product Rights	16	$	67,849	$	(15,976	)	$	51,873
Thiola License	10	54,471		(10,168		)	44,303
Economic Interest - U.S. revenue Cholbam	10	75,900		(20,903		)	54,997
Economic Interest - International revenue Cholbam	10	8,058		(2,219		)	5,839
Economic Interest - L-UDCA (acquired IPR&D)	Indefinite	25,500		—			25,500
Ligand License	11	3,300		(1,420		)	1,880
Manchester Customer Relationships	10	403		(152		)	251
Manchester Trade Name	1	175		(175		)	—
Internal use software	5	207		(33		)	174
Total		$	235,863	$	(51,046	)	$	184,817

Schedule of amortization expense for the next 5 years

The following table summarizes amortization expense for the twelve months ended December 31, 2018, 2017 and 2016 (in thousands):



	2018		2017		2016
Research and development	$	976	$	327	$	328
Selling, general and administrative	17,052		17,004		15,665
Total amortization expense	$	18,028	$	17,331	$	15,993

As of December 31, 2018, amortization expense (excluding infinite lived IPR&D) for the next five years is expected to be as follows (in thousands):



2019	$	19,166
2020	19,210
2021	19,158
2022	19,125
2023	18,825
Thereafter	65,707
Total	$	161,191

ACCRUED EXPENSES (Tables)

12 Months Ended

Dec. 31, 2018

Payables and Accruals [Abstract]

Schedule of accrued expenses

Accrued expenses consist of the following at December 31, 2018 and 2017 (in thousands):



	2018		2017
Compensation related costs	$	10,446	$	7,749
Research and development	16,515		6,989
Government rebate reserves	8,464		5,883
Selling, general and administrative	2,990		3,896
Royalty/contingent consideration	6,805		6,429
Restructuring expenses	—		3,549
Miscellaneous accrued expenses	4,475		1,523
Total accrued expenses	$	49,695	$	36,018

COMMITMENTS AND CONTINGENCIES (Tables)

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Lease and Sublease Agreements

Leases



Facilities	Base Rent	Lease Expiration
Corporate Headquarters San Diego, CA	$2.3 million	July 2024

Schedule of principal contractual commitments, excluding open orders

Following is a schedule of the future minimum rental commitments for our operating lease as of December 31, 2018 (in thousands):



	Rental Payments
2019	$	2,343
2020	2,414
2021	2,486
2022	2,560
2023	2,637
Thereafter	1,585
	$	14,025

STOCKHOLDERS’ EQUITY / DEFICIT (Tables)

12 Months Ended

Dec. 31, 2018

Equity [Abstract]

Assumptions used in Black-Scholes options pricing model

The following weighted average assumptions were used in the Black-Scholes options pricing model to estimate the fair value of stock options for the specified reporting periods:



	Twelve Months Ended December 31,
	2018		2017		2016
Risk free rate	2.80	%	2.10	%	1.20	%
Expected volatility	68	%	70	%	68	%
Expected life (in years)	6.2		6.1		5.8
Expected dividend yield	—		—		—

Share-based Compensation, Stock Options, Activity

The following table summarizes our stock option activity and related information for the years ended December 31, 2018:



			Weighted Average
	Shares Underlying Options		Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2017	7,153,668		$	17.16	6.95	$	39,010
Granted	1,349,250		25.56		—	—
Forfeited and expired	(476,369	)	24.50		—	—
Exercised	(749,212	)	14.13		—	9,325
Outstanding at December 31, 2018	7,277,337		$	18.55	6.94	$	40,650

The following table summarizes our stock options exercisable at December 31, 2018, 2017 and 2016:



		Weighted Average
	Shares Underlying Options	Exercise Price		Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
2016	3,793,017	$	14.94	6.82	$	23,358
2017	4,610,233	$	15.97	5.85	$	31,991
2018	4,834,781	$	16.81	5.98	$	35,387

Schedule of unvested restricted shares

The following table summarizes our restricted stock unit activity for the year ended December 31, 2018:



	Number of RSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2017	94,832		$	20.19
Granted	395,311		25.40
Vested	(58,251	)	20.08
Forfeited/cancelled	(31,466	)	25.20
Unvested December 31, 2018	400,426		$	24.95

Share-based Compensation, Performance Shares Award Nonvested Activity

The following table summarizes our performance-based stock unit activity for the year ended December 31, 2018:



	Number of PSUs		Weighted Average Grant Date Fair Value
Unvested December 31, 2017	250,500		$	20.63
Granted	66,500		25.75
Vested	(85,250	)	22.33
Forfeited/cancelled	(5,000	)	18.46
Unvested December 31, 2018	226,750		$	21.54

Schedule of share based compensation expenses

Total non-cash stock-based compensation expense consisted of the following for the years ended December 31, 2018, 2017 and 2016 (in thousands):



	Twelve Months Ended December 31,
	2018		2017		2016
Selling, general and administrative expenses	$	13,550	$	17,924	$	18,614
Research and development expenses	6,224		8,950		10,488
Total	$	19,774	$	26,874	$	29,102

Schedule of stock option activity



	Shares Issued	Cash Received		Derivative Liability Reclassified as Equity		Change in Fair Value Expense
2016	898,633	$	6,005	$	14,715	$	2,909
2017	607,481	$	3,645	$	11,221	$	3,033
2018	1,036,054	$	5,305	n/a		n/a

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

EARNINGS (LOSS) PER SHARE (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of basic and diluted net loss per share

Basic and diluted EPS is calculated as follows (net income amounts are stated in thousands):



	For the year ended December 31,
	2018							2017							2016
	Shares	Net loss			EPS			Shares	Net loss			EPS			Shares	Net Income			EPS
Basic Earnings per Share	40,433,171	$	(102,678	)	$	(2.54	)	38,769,816	$	(59,731	)	$	(1.54	)	36,997,865	$	(47,903	)	$	(1.29	)
Dilutive shares related to warrants	—	—						—	—						1,290,147	—
Change in fair value of derivative instruments	—	—						—	—						—	(1,655		)
Dilutive Earnings per Share	40,433,171	$	(102,678	)	$	(2.54	)	38,769,816	$	(59,731	)	$	(1.54	)	38,288,012	$	(49,558	)	$	(1.29	)

Schedule of common stock options, convertible debt and restricted stock units anti-dilutive

For the years ended December 31, 2018, 2017 and 2016, the following shares were excluded because they were anti-dilutive:



	For the year ended December 31,
	2018	2017	2016
Convertible Debt	8,410,932	2,642,160	2,642,160
Restricted Stock	395,034	157,319	444,942
Options	7,210,576	7,080,998	6,286,584
Warrants	282,807	1,159,424	—
Total Anti-Dilutive Shares	16,299,349	11,039,901	9,373,686

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of components of net income before incomes taxes

For financial reporting purposes, net income (loss) before income taxes includes the following components (in thousands):



	Year Ended December 31,
	2018			2017			2016
United States	$	(87,573	)	$	(55,611	)	$	(52,750	)
Foreign	(14,294		)	(2,752		)	(4,832		)
Total	$	(101,867	)	$	(58,363	)	$	(57,582	)

Schedule of income tax provision

The components of the provision (benefit) for income taxes, in the Consolidated Statement of Operations are as follows (in thousands):



	2018		2017			2016
Current
Federal	$	698	$	6,991		$	13,137
State	113		802			(155		)
	811		7,793			12,982
Deferred
Federal	—		(7,965		)	(18,814		)
State	—		1,540			(3,847		)
	—		(6,425		)	(22,661		)
Total tax provision (benefit)	$	811	$	1,368		$	(9,679	)

Schedule of reconciliation of the statutory federal income tax expense (benefit)

The following is a reconciliation of the statutory federal income tax rate to the Company’s effective tax rate expressed as a percentage of income (loss) before income taxes:



	2018		2017		2016
Statutory rate - federal	(21.00	)%	(35.00	)%	(35.00	)%
State taxes, net of federal benefit	(4.44	)%	(3.30	)%	(3.16	)%
Change in FV of derivative liability (warrants)	—	%	2.82	%	1.10	%
Change in federal tax rate	—	%	23.29	%	—	%
Convertible Debt	21.77	%	—	%	—	%
Loss on extinguishment of debt	4.09	%	—	%	—	%
Other permanent differences	0.10	%	1.04	%	2.05	%
Tax credits	(11.86	)%	(5.79	)%	(1.58	)%
Return to provision adjustments and other true-ups	1.42	%	(3.48	)%	(1.15	)%
Other	1.06	%	1.25	%	3.09	%
Change in valuation allowance	9.79	%	21.62	%	16.30	%
Income tax provision (benefit)	0.93	%	2.45	%	(18.35	)%

Schedule of deferred tax assets and liabilities

The significant components of the Company’s deferred tax assets and liabilities as of December 31, 2018 and 2017 are as follows (in thousands):



	2018			2017
Deferred Tax Assets:
Net operating loss	$	9,700		$	1,099
Research and development and other tax credits	14,715			1,599
Contingent consideration	23,459			23,080
Other accrued expenses	3,710			2,603
Stock based compensation	16,761			15,695
Other	555			358
	68,900			44,434
Deferred Tax Liabilities:
Intangible assets	(14,288		)	(16,810		)
Convertible Debt	(18,419		)	—
Tax basis depreciation less than book depreciation	—			—
	(32,707		)	(16,810		)

Net deferred tax assets (liabilities) before valuation allowance	36,194			27,624
Valuation allowance	(36,194		)	(27,624		)
Total deferred tax liability	$	—		$	—

Schedule of unrecognized tax benefits

A reconciliation of the Company's unrecognized tax benefits for the years 2018 and 2017 is provided in the following table (in thousands):



	2018		2017
Balance as of January 1:	$	—	$	1,500
Increase in current period positions	—		—
Decrease in prior period positions	—		(1,500		)
Increase in prior period positions	—		—
Balance as of December 31:	$	—	$	—

DERIVATIVE FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2018

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of derivative warrant issuances and balances outstanding

The following table presents the Company’s derivative warrant issuances and balances outstanding during the years ended December 31, 2018 and 2017:



		Weighted Average
	Warrants	Exercise Price		Grant Date Fair Value
Outstanding at December 31, 2016	1,766,905	$	7.23	$	3.87
Issued	—	—		—
Canceled	—	—		—
Exercised	607,481	6.00		3.33
Outstanding at December 31, 2017	1,159,424	$	7.86	$	4.15
Issued	—	—		—
Canceled	554	5.99		3.33
Exercised	1,158,870	7.88		4.15
Outstanding at December 31, 2018	—	—		—

RESTRUCTURING (Tables)

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Reserve by Type of Cost

The following table presents a reconciliation of the restructuring liability recorded within accrued expenses on the Company's Condensed Consolidated Balance Sheets (in thousands):



	Twelve Months Ended December 31,
	2018			2017
Liability, beginning of period	$	3,549		$	893
Restructuring expenses	—			3,608
Cash settlements	(3,307		)	(897		)
Adjustments to previous estimates	(242		)	(55		)
Liability, end of period	$	—		$	3,549

PROPERTY AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Summary of Property, Plant, and Equipment

The major classifications of property and equipment, including their respective expected useful lives, consists of the following:



Computers and equipment	3 years
Furniture and fixtures	7 years
Leasehold improvements	Shorter of length of lease or life of the asset

Property, plant and equipment, net consisted of the following (in thousands):



	December 31,
	2018			2017
Computers and equipment	$	506		$	436
Furniture and fixtures	1,150			945
Leasehold improvements	2,628			2,071
Construction-in-progress	—			363
	4,284			3,815
Less: Accumulated depreciation	(1,138		)	(585		)
Total property and equipment, net	$	3,146		$	3,230

QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Schedule of Consolidated Statements of Operations data for each quarter



	Fourth Quarter			Third Quarter				Second Quarter			First Quarter

For the year ended December 31, 2018:
Net product sales	$	43,771		$	40,706			$	41,337		$	38,432
Total operating expenses	48,756			76,289				62,897			56,344
Operating loss	(4,985		)	(35,583		)		(21,560		)	(17,912		)
Total other income (expense), net	(2,470		)	(18,518		)	¹	(602		)	(237		)
Loss before provision for income taxes	(7,455		)	(54,101		)		(22,162		)	(18,149		)
Income tax benefit (provision)	—			(415		)		(167		)	(229		)
Net income (loss)	$	(7,455	)	$	(54,516	)		$	(22,329	)	$	(18,378	)
Net Loss per common share
Basic	$	(0.18	)	$	(1.34	)		$	(0.56	)	$	(0.46	)
Diluted	$	(0.18	)	$	(1.34	)		$	(0.56	)	$	(0.46	)
For the year ended December 31, 2017:
Net product sales	$	42,177		$	40,340			$	38,800		$	33,620
Total operating expenses	57,354			50,948				52,398			48,028
Operating loss	(15,177		)	(10,608		)		(13,598		)	(14,408		)
Total other income (expense), net	4,139			(8,409		)		(1,556		)	1,254
Income (loss) before provision for income taxes	(11,038		)	(19,017		)		(15,154		)	(13,154		)
Income tax benefit (provision)	(6,580		)	1,223				1,925			2,064
Net income (loss)	$	(17,618	)	$	(17,794	)		$	(13,229	)	$	(11,090	)
Net income (loss) per common share
Basic	$	(0.45	)	$	(0.46	)		$	(0.34	)	$	(0.29	)
Diluted	$	(0.55	)	$	(0.46	)		$	(0.34	)	$	(0.32	)

¹In September 2018, the Company executed a partial repurchase of the 2019 Notes that resulted in a $17.0 million loss on early extinguishment of debt. See Note 7 for further discussion.

DESCRIPTION OF BUSINESS - Narrative (Details)	Dec. 31, 2018 product
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of products sold	3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Vesting Awards (Details)	12 Months Ended
	Dec. 31, 2018
Stock Options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years
Stock Options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	4 years
Restricted Stock Units \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	2 years
Restricted Stock Units \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	3 years

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)		12 Months Ended
	Jul. 02, 2015 USD ($)	Dec. 31, 2018 USD ($) tranche segment reporting_unit	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2018 USD ($)	Jan. 01, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Marketable securities		$ 368,668,000	$ 201,236,000
Allowance for doubtful accounts		0	200,000
Bad debt expense		0	200,000	$ 200,000
Inventory reserve		$ 1,800,000	700,000
Number of segments \| segment		1
Number of reporting units \| reporting_unit		1
Goodwill, impairment		$ 0	0	0
Impairment of intangible assets		$ 0	0	0
Number of tranches \| tranche		5
Cumulative effect of new accounting principle					$ 15,710,000	$ (4,868,000)
Marketable securities		$ 208,475,000	123,272,000
Asklepion Pharmaceuticals LLC \| Asset Purchase Agreement
Summary Of Significant Accounting Policies [Line Items]
Proceeds from sale of assets	$ 245,000,000
Discount rate of receivables	2.80%
Interest Expense \| Asklepion Pharmaceuticals LLC \| Asset Purchase Agreement
Summary Of Significant Accounting Policies [Line Items]
Accretion on the notes receivable			$ 700,000	$ 1,900,000
Accounting Standards Update 2016-16
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of new accounting principle						$ 4,900,000

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Inventory, Net of Reserve (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Raw material	$ 4,689	$ 3,435
Finished goods	930	1,916
Total inventory	$ 5,619	$ 5,351

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2018
Computers and equipment
Property, Plant and Equipment [Line Items]
Use life (in years)	3 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Use life (in years)	7 years

REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
REVENUE RECOGNITION (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Net product sales	$ 43,771	$ 40,706	$ 41,337	$ 38,432	$ 42,177	$ 40,340	$ 38,800	$ 33,620	$ 164,246	$ 154,937	$ 133,591
Thiola License
Disaggregation of Revenue [Line Items]
Net product sales									89,176	82,311	71,199
Bile acid products
Disaggregation of Revenue [Line Items]
Net product sales									$ 75,070	$ 72,626	$ 62,392
Geographic Concentration Risk \| Revenue from Contract with Customer \| United States
Disaggregation of Revenue [Line Items]
Concentration risk, percentage									95.00%

FUTURE ACQUISITION RIGHT AND JOINT DEVELOPMENT AGREEMENT - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Business combination, option agreement, purchase price		$ 65,000
Business combination, option agreement, purchase price, percent transferred in cash		20.00%
Business combination, option agreement, purchase price, percent transferred by issuance of equity		80.00%
Business combination, option agreement, share price			$ 21.40
Business combination, option agreement, percent of consideration paid in cash if share price falls below share price threshold		100.00%
Business combination, option agreement, weighted average ten day share price, which requires all cash payment		$ 19.26
Business combination, option agreement, contingent consideration	$ 25,000	$ 25,000
Investment-equity			$ 15,000	$ 0
Purchase Provision Terms \| CNSA-001 Program \| Censa Pharmaceuticals Inc.
Business Acquisition [Line Items]
Research and development arrangement, contract to perform for others, compensation earned	17,000
Censa Pharmaceuticals Inc.
Business Acquisition [Line Items]
Payments for the option to acquire business		10,000	10,000
Censa Pharmaceuticals, Inc, Equity Holders
Business Acquisition [Line Items]
Additional required payments for the option to acquire business, successful development milestones	$ 5,000	$ 5,000	5,000
Additional required payments for the option to acquire business, successful development funding			$ 16,800

BUSINESS COMBINATION AND ASSET TRANSACTIONS - Amendment to Trademark License and Supply Agreement (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Nov. 30, 2018	Nov. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense			$ 18,028	$ 17,331	$ 15,993
Thiola License
Acquired Finite-Lived Intangible Assets [Line Items]
Licensing agreement, extension term		5 years
Gross Carrying Amount		$ 5,900	$ 70,009	$ 54,471
Payments for the option to acquire business	$ 300
Payment of guaranteed minimum royalty	$ (100)
Minimum royalty, percentage	20.00%
Amortization expense	$ 1,000
Guaranteed minimum liability	$ 700

BUSINESS COMBINATION AND ASSET TRANSACTIONS - Acquisition of Liquid Ursodeoxycholic Acid (L-UDCA) Narrative (Details) $ in Thousands	Jun. 20, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 16, 2016 USD ($)
Business Acquisition [Line Items]
Acquisition related contingent consideration		$ 73,650	$ 80,900
Economic Interest - L-UDCA (acquired IPR&D)
Business Acquisition [Line Items]
Intangible assets acquired with definite lives	$ 25,500
Assets useful life (in years)	17 years
Present value of contingent consideration	$ 25,000			$ 25,000
Acquisition related contingent consideration	70,300
Total purchase price	$ 25,500			$ 25,500
Measurement Input, Discount Rate \| Economic Interest - L-UDCA (acquired IPR&D)
Business Acquisition [Line Items]
Business combination, contingent consideration, liability, measurement input (in percent)	0.120

BUSINESS COMBINATION AND ASSET TRANSACTIONS - Acquisition of Liquid Ursodeoxycholic Acid (L-UDCA) Assets Acquired (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 16, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 20, 2016
Business Acquisition [Line Items]
Cash paid upon consummation		$ 0	$ 0	$ 615
Economic Interest - L-UDCA (acquired IPR&D)
Business Acquisition [Line Items]
Cash paid upon consummation	$ 500
Present value of contingent consideration	25,000				$ 25,000
Total purchase price	25,500				$ 25,500
Intangible assets acquired	25,500
Total purchase price	$ 25,500

BUSINESS COMBINATION AND ASSET TRANSACTIONS - Divestiture of Assets (Details) - Asset Purchase Agreement $ in Millions	Jul. 02, 2015 USD ($)
Asklepion Pharmaceuticals LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets	$ 245.0
Discount rate of receivables	2.80%
Gain on sale of intangible assets	$ 140.0
Disposal fees	4.9
At Time Of Closing
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
PV of short term and long term receivables	46.2
At Time Of Closing \| Asklepion Pharmaceuticals LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets	150.0
Due On First And Second Anniversaries Of Closing
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets	47.5
PV of short term and long term receivables	44.9
Due On First And Second Anniversaries Of Closing \| Asklepion Pharmaceuticals LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets	$ 47.5

MARKETABLE SECURITIES (Details) - USD ($)	12 Months Ended
MARKETABLE SECURITIES (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Securities, Available-for-sale [Line Items]
Debt securities, realized gain (loss)	$ 0	$ 0
Marketable securities	368,668,000	201,236,000
Debt securities, available-for-sale, realized gain			$ 100,000
Proceeds from the sale/maturity of marketable securities	162,755,000	114,526,000	$ 159,520,000
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Marketable securities	59,255,000	6,897,000
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Marketable securities	299,413,000	164,297,000
Securities of government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Marketable securities	$ 10,000,000	$ 30,042,000

MARKETABLE SECURITIES - Available for Sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	$ 209,137	$ 123,574
Debt securities available for sale, unrealized gain, current	0
Debt securities available for sale unrealized loss, current	(662)	(302)
Marketable securities	208,475	123,272
Debt securities, available-for-sale, amortized cost basis, noncurrent	160,810	78,388
Debt securities, available for sale unrealized gain, noncurrent	22
Debt securities available for sale unrealized loss, noncurrent	(639)	(424)
Debt securities, available-for-sale, noncurrent	160,193	77,964
Debt securities, available-for-sale, amortized cost	369,947	201,962
Debt securities, available-for-sale, accumulated gross unrealized gain, before tax	22
Debt securities, available-for-sale, accumulated gross unrealized loss, before tax	(1,301)	(726)
Debt securities, available-for-sale	368,668	201,236
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	59,313	6,911
Debt securities available for sale, unrealized gain, current	0
Debt securities available for sale unrealized loss, current	(58)	(14)
Marketable securities	59,255	6,897
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current	149,824	86,531
Debt securities available for sale, unrealized gain, current	0
Debt securities available for sale unrealized loss, current	(604)	(198)
Marketable securities	149,220	86,333
Debt securities, available-for-sale, amortized cost basis, noncurrent	150,813	78,388
Debt securities, available for sale unrealized gain, noncurrent	18
Debt securities available for sale unrealized loss, noncurrent	(638)	(424)
Debt securities, available-for-sale, noncurrent	150,193	77,964
Securities of government sponsored entities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost basis, current		30,132
Debt securities available for sale unrealized loss, current		(90)
Marketable securities		$ 30,042
Debt securities, available-for-sale, amortized cost basis, noncurrent	9,997
Debt securities, available for sale unrealized gain, noncurrent	4
Debt securities available for sale unrealized loss, noncurrent	(1)
Debt securities, available-for-sale, noncurrent	$ 10,000

NOTES PAYABLE Narrative (Details)		1 Months Ended	9 Months Ended	12 Months Ended
NOTES PAYABLE Narrative (Details)	Sep. 10, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($) day $ / shares shares	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	May 29, 2014 USD ($) $ / shares
Debt Instrument [Line Items]
Debt instrument, repurchase amount	$ 23,400,000	$ 23,400,000	$ 23,400,000
Debt instrument, convertible, threshold percentage of stock price trigger				130.00%
Debt instrument, convertible note, market price, per $1,000				$ 897
Debt conversion, liability		198,600,000	198,600,000
Debt conversion, equity			77,400,000
Debt issuance costs, net		$ 8,800,000	$ 8,800,000
Debt instrument, interest rate, effective percentage		7.70%	7.70%
Loss on extinguishment of debt				(17,042,000)	$ 0	$ 0
Interest expense				$ 9,810,000	4,422,000	$ 4,734,000
Senior Notes \| Senior Notes Due 2025
Debt Instrument [Line Items]
Interest rate percentage	2.50%
Proceeds from issuance of debt	$ 267,200,000
Debt instrument, convertible, conversion price (in USD per share) \| $ / shares				$ 38.80
Long-term debt, excluding current maturities	$ 276,000,000
Long-term debt, excluding current maturities, repaid if converted				$ 276,000,000
Debt instrument, convertible, conversion ratio			0.0258
Long-term debt, term		7 years	7 years
Debt issuance costs, net				6,073,000	0
Credit agreement amount				247,700,000
Aggregate carrying value				276,000,000	0
Unamortized debt discount				$ 74,836,000	$ 0
Senior Notes \| Convertible Notes Due 2019
Debt Instrument [Line Items]
Interest rate percentage	4.50%
Debt instrument, repurchase amount		$ 40,200,000	$ 40,200,000
Debt instrument, convertible, threshold trading days \| day				20
Debt instrument, convertible, threshold consecutive trading days \| day				30
Debt instrument, convertible, threshold percentage of stock price trigger				130.00%
Debt instrument, convertible, threshold consecutive days measuring period \| day				10
Trading price per principal, percentage				98.00%
Loss on extinguishment of debt		$ (17,000,000)
Note Purchase Agreement \| Convertible Debt
Debt Instrument [Line Items]
Interest rate percentage							4.50%
Debt instrument, convertible, conversion price (in USD per share) \| $ / shares							$ 17.41
Credit agreement amount							$ 46,000,000
Aggregate carrying value							43,000,000
Unamortized debt discount							$ 3,000,000
Common stock, fair value \| $ / shares				$ 22.63
Incremental common shares attributable to dilutive effect of conversion of debt securities \| shares				1,297,530
Debt instrument, convertible, if-converted value in excess of principal				$ 6,800,000
Convertible debt, fair value disclosures				$ 30,000,000

NOTES PAYABLE - Schedule of Carrying Amount of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Sep. 30, 2018	Sep. 10, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Debt issuance costs, net		$ (8,800)
Senior Notes Due 2025 \| Senior Notes
Debt Instrument [Line Items]
Interest rate percentage			2.50%
Aggregate principle amount of Notes	$ 276,000			$ 0
Unamortized debt discount and debt issuance costs	(74,836)			0
Debt issuance costs, net	(6,073)			0
Net carrying amount	$ 195,091			$ 0

NOTES PAYABLE - Convertible Notes Payable (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Amortization of premiums on investments		$ 382	$ 1,338	$ 1,097
Senior Notes Due 2025
Debt Instrument [Line Items]
Interest expense, debt		4,963	$ 0
Senior Notes \| Senior Notes Due 2025
Debt Instrument [Line Items]
Interest expense, debt	$ 0	2,108
Amortization of premiums on investments	0	2,582
Amortization of debt discount	$ 0	$ 273

NOTES PAYABLE - Convertible Senior Notes Due 2019 (Details) - Convertible Debt - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Aggregate principle amount of Notes	$ 22,590	$ 46,000
Unamortized debt discount and debt issuance costs	(133)	(923)
Net carrying amount	$ 22,457	$ 45,077

FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset:
Marketable securities, available-for-sale	$ 368,668	$ 201,236
Liabilities:
Derivative liability related to warrants	0	15,710
Recurring basis
Asset:
Cash and Cash Equivalents	102,873	99,394
Marketable securities, available-for-sale	368,668	201,236
Total	471,541	300,630
Liabilities:
Derivative liability related to warrants		15,710
Business combination-related contingent consideration	93,000	90,000
Total	93,000	105,710
Recurring basis \| Quoted prices in active markets (Level 1)
Asset:
Cash and Cash Equivalents	62,978	92,726
Marketable securities, available-for-sale	0	0
Total	62,978	92,726
Liabilities:
Derivative liability related to warrants		0
Business combination-related contingent consideration	0	0
Total	0	0
Recurring basis \| Significant other observable inputs (Level 2)
Asset:
Cash and Cash Equivalents	39,895	6,668
Marketable securities, available-for-sale	368,668	201,236
Total	408,563	207,904
Liabilities:
Derivative liability related to warrants		0
Business combination-related contingent consideration	0	0
Total	0	0
Recurring basis \| Significant unobservable inputs (Level 3)
Asset:
Cash and Cash Equivalents	0	0
Marketable securities, available-for-sale	0	0
Total	0	0
Liabilities:
Derivative liability related to warrants		15,710	$ 22,440
Business combination-related contingent consideration	93,000	90,000	$ 87,478
Total	$ 93,000	$ 105,710

FAIR VALUE MEASUREMENTS - Changes in Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	$ 15,710
Reclassification of derivative liability to equity upon exercise of warrants	0	$ (11,221)	$ (14,715)
Change in estimated fair value of liability classified warrants	0	4,491	(1,655)
Balance, ending	0	15,710
Recurring basis
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	15,710
Balance, ending		15,710
Recurring basis \| Significant unobservable inputs (Level 3)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning	$ 15,710	22,440
Reclassification of derivative liability to equity upon exercise of warrants		(11,221)
Change in estimated fair value of liability classified warrants		4,491
Balance, ending		$ 15,710	$ 22,440

FAIR VALUE MEASUREMENTS - Fair Value of Level 3 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in estimated fair value of contingent consideration	$ (11,590)	$ (19,389)	$ (18,383)
Recurring basis
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1	90,000
Balance at December 31	93,000	90,000
Recurring basis \| Significant unobservable inputs (Level 3)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at January 1	90,000	87,478
Change in estimated fair value of contingent consideration	11,590	19,389
Contractual Payments	(6,373)	(6,006)
Contractual Payments accrued at December 31	(2,171)	(11,012)
Foreign currency impact	(46)	151
Balance at December 31	$ 93,000	$ 90,000	$ 87,478

INTANGIBLE ASSETS - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended				12 Months Ended
	Jun. 20, 2016	Nov. 30, 2018	Mar. 31, 2018	Nov. 30, 2017	Sep. 30, 2015	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2013	Jun. 16, 2016	Mar. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net						$ 161,191
Payments to date under terms of licensing agreement						18,974	$ 13,122	$ 10,496
Amortization expense						18,028	17,331	$ 15,993
Economic Interest - L-UDCA (acquired IPR&D)
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives	$ 25,500
Assets useful life (in years)	17 years
Total purchase price	$ 25,500										$ 25,500
Ligand License Agreement
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net										$ 2,500
Require to make substantial payments payable upon achievement of milestones										$ 114,100
Payments to date under terms of licensing agreement						7,200
Payment of amendment consideration					$ 1,000
Ligand License Agreement \| Minimum
Finite-Lived Intangible Assets [Line Items]
Annual royalty percentage										15.00%
Ligand License Agreement \| Maximum
Finite-Lived Intangible Assets [Line Items]
Annual royalty percentage										17.00%
Licensing Agreements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired			$ 4,600
Product rights
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net						$ 47,636	$ 51,873
Assets useful life (in years)						16 years	16 years
Finite-lived intangible asset						$ 67,849	$ 67,849
Product rights \| Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives									$ 67,800
Assets useful life (in years)									16 years
Trade Name
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net						$ 0	$ 0
Assets useful life (in years)						1 year	1 year
Finite-lived intangible asset						$ 175	$ 175
Trade Name \| Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives									$ 200
Assets useful life (in years)									1 year
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net						$ 211	$ 251
Assets useful life (in years)						10 years	10 years
Finite-lived intangible asset						$ 403	$ 403
Customer relationships \| Manchester Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Intangible assets with definite lives									$ 400
Assets useful life (in years)									10 years
Thiola License Agreement
Finite-Lived Intangible Assets [Line Items]
Assets useful life (in years)									10 years
Automatic renewal periods									1 year
Remaining weighed average period of amortization (in years)						10 years 4 months 28 days
Thiola License Agreement \| Mission Pharmacal Company
Finite-Lived Intangible Assets [Line Items]
Annual royalty percentage						20.00%
Mission an up-front license fee						$ 3,000
Guaranteed minimum royalties						2,000
Present value of guaranteed minimum royalties payable						15,200	15,100
Thiola License Agreement \| Mission Pharmacal Company \| Other Current Liabilities
Finite-Lived Intangible Assets [Line Items]
Guaranteed minimum royalties						2,100	2,000
Thiola License Agreement \| Mission Pharmacal Company \| Other Noncurrent Liabilities
Finite-Lived Intangible Assets [Line Items]
Guaranteed minimum royalties						$ 13,100	$ 13,100
Thiola License Agreement \| Mission Pharmacal Company \| Minimum
Finite-Lived Intangible Assets [Line Items]
Discount rate						7.00%	7.00%
Thiola License Agreement \| Mission Pharmacal Company \| Maximum
Finite-Lived Intangible Assets [Line Items]
Discount rate						11.00%	11.00%
Thiola
Finite-Lived Intangible Assets [Line Items]
Intangible assets finite-lived, net						$ 55,486	$ 44,303
Assets useful life (in years)							10 years
Licensing agreement, extension term				5 years
Finite-lived intangible asset				$ 5,900		$ 70,009	$ 54,471
Payments for the option to acquire business		$ 300
Payment of guaranteed minimum royalty		$ 100
Minimum royalty, percentage		20.00%
Amortization expense		$ 1,000
Guaranteed minimum liability		$ 700
United States \| Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Capitalized economic interest												$ 75,900
International \| Asklepion Pharmaceuticals LLC
Finite-Lived Intangible Assets [Line Items]
Capitalized economic interest												$ 7,300

INTANGIBLE ASSETS - Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Nov. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	$ (68,952)	$ (51,046)
Intangible assets finite-lived, net	161,191
Intangible assets, gross (excluding goodwill)	255,643	235,863
Intangible Assets, Net (Excluding Goodwill)	$ 186,691	$ 184,817
Chenodal Product Rights
Finite-Lived Intangible Assets [Line Items]
Useful Life	16 years	16 years
Gross Carrying Amount	$ 67,849	$ 67,849
Accumulated Amortization	(20,213)	(15,976)
Intangible assets finite-lived, net	47,636	$ 51,873
Thiola License
Finite-Lived Intangible Assets [Line Items]
Useful Life		10 years
Gross Carrying Amount	70,009	$ 54,471	$ 5,900
Accumulated Amortization	(14,523)	(10,168)
Intangible assets finite-lived, net	$ 55,486	$ 44,303
Economic Interest - U.S. revenue Cholbam
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Gross Carrying Amount	$ 75,900	$ 75,900
Accumulated Amortization	(28,487)	(20,903)
Intangible assets finite-lived, net	$ 47,413	$ 54,997
Economic Interest - Int'l revenue Cholbam
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Gross Carrying Amount	$ 7,700	$ 8,058
Accumulated Amortization	(2,890)	(2,219)
Intangible assets finite-lived, net	4,810	5,839
Economic Interest - L-UDCA (acquired IPR&D)
Finite-Lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 25,500	$ 25,500
Ligand License
Finite-Lived Intangible Assets [Line Items]
Useful Life	11 years	11 years
Gross Carrying Amount	$ 7,900	$ 3,300
Accumulated Amortization	(2,397)	(1,420)
Intangible assets finite-lived, net	$ 5,503	$ 1,880
Manchester Customer Relationships
Finite-Lived Intangible Assets [Line Items]
Useful Life	10 years	10 years
Gross Carrying Amount	$ 403	$ 403
Accumulated Amortization	(192)	(152)
Intangible assets finite-lived, net	$ 211	$ 251
Manchester Trade Name
Finite-Lived Intangible Assets [Line Items]
Useful Life	1 year	1 year
Gross Carrying Amount	$ 175	$ 175
Accumulated Amortization	(175)	(175)
Intangible assets finite-lived, net	$ 0	$ 0
Internal Use Software
Finite-Lived Intangible Assets [Line Items]
Useful Life	5 years	5 years
Gross Carrying Amount	$ 207	$ 207
Accumulated Amortization	(75)	(33)
Intangible assets finite-lived, net	$ 132	$ 174

INTANGIBLE ASSETS - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 18,028	$ 17,331	$ 15,993
Research and development
Finite-Lived Intangible Assets [Line Items]
Amortization expense	976	327	328
Selling, general and administrative
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 17,052	$ 17,004	$ 15,665

INTANGIBLE ASSETS - Amortization Expense Next Five Years (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
2019	$ 19,166
2020	19,210
2021	19,158
2022	19,125
2023	18,825
Thereafter	65,707
Intangible assets finite-lived, net	$ 161,191

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Compensation related costs	$ 10,446	$ 7,749
Research and development	16,515	6,989
Government rebate reserves	8,464	5,883
Selling, general and administrative	2,990	3,896
Royalty/contingent consideration	6,805	6,429
Restructuring expenses	0	3,549	$ 893
Miscellaneous accrued expenses	4,475	1,523
Total accrued expenses	$ 49,695	$ 36,018

COMMITMENTS AND CONTINGENCIES - Leases and Sublease Agreements (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Leases and Sublease Agreements \| Corporate Headquarters San Diego, CA
Other Commitments [Line Items]
Annual base rent	$ 2.3

COMMITMENTS AND CONTINGENCIES - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 2,343
2020	2,414
2021	2,486
2022	2,560
2023	2,637
Thereafter	1,585
Operating lease future minimum payments due, total	$ 14,025

COMMITMENTS AND CONTINGENCIES - Additional Information (Details) $ in Thousands	1 Months Ended			12 Months Ended			17 Months Ended
	Aug. 31, 2017 USD ($)	Jul. 31, 2017 ft²	Jul. 31, 2016 USD ($) ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)
Other Commitments [Line Items]
Legal fee settlement				$ 0	$ 2,625	$ 5,212
Martin Shkreli
Other Commitments [Line Items]
Contingent future legal fee advance payment							$ 5,400
Legal fees reimbursed from director and officer insurance carriers	$ 3,800			0	2,600
Legal fees paid				$ 0	$ 3,600
Operating lease for office space
Other Commitments [Line Items]
Square feet of leased office space \| ft²		22,339	23,107
Lessee, operating lease, term of contract			7 years 7 months
Lease incentive, tenant improvements			$ 1,500
Rent abatement, months			7 months
Right to extend lease			5 years

STOCKHOLDERS’ EQUITY / DEFICIT - Common Stock and Preferred Stock (Details)	12 Months Ended
	Dec. 31, 2018 vote $ / shares shares	Dec. 31, 2017 $ / shares shares
Class of Stock [Line Items]
Common stock, shares authorized (in shares) \| shares	100,000,000	100,000,000
Common stock, par value (in USD per share) \| $ / shares	$ 0.0001	$ 0.0001
Number of votes per common share owned \| vote	1
Preferred Stock, shares authorized (in shares) \| shares	20,000,000	20,000,000
Preferred stock, par value (in USD per share) \| $ / shares	$ 0.0001	$ 0.0001
Series A Preferred Stock
Class of Stock [Line Items]
Preferred Stock, shares authorized (in shares) \| shares	1,000
Preferred stock, par value (in USD per share) \| $ / shares	$ 0.001

STOCKHOLDERS’ EQUITY / DEFICIT - 2015 Equity Incentive Plan (Details) - shares	May 18, 2016	Dec. 31, 2018	Dec. 31, 2017	May 17, 2017	Jun. 08, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)		100,000,000	100,000,000
2015 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)					1,400,000
Shares remaining available for issuance under the plan (in shares)					600,000
2015 Equity Incentive Plan Amended
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	1,600,000			1,800,000
Shares remaining available for issuance under the plan (in shares)	700,000
Options \| 2015 Equity Incentive Plan Amended
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, reduction in number of shares available for grant	100.00%
Restricted Stock \| 2015 Equity Incentive Plan Amended
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment award, reduction in number of shares available for grant	200.00%

STOCKHOLDERS’ EQUITY / DEFICIT - 2017 Employee Stock Purchase Plan (Details) - 2017 ESPP - USD ($)	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares remaining available for issuance under the plan (in shares)	680,000	380,000
Potential increase in shares available for issuance, as a percent of total outstanding common stock	1.00%
Maximum number of additional shares authorized for issuance (in shares)	300,000
Purchase price of common stock, percent of fair market value	85.00%
Stock purchase offering period	6 months
Employee stock purchase plan, maximum compensation	15.00%
Employee stock purchase plan annual limit	$ 25,000
Shares reserved for future issuance (in shares)	$ 552,966

STOCKHOLDERS’ EQUITY / DEFICIT - Black Scholes Assumptions (Details) - Stock Options - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issued (in shares)	1,349,250
Risk free rate	2.80%	2.10%	1.20%
Expected volatility	68.00%	70.00%	68.00%
Expected life (in years)	6 years 2 months 12 days	6 years 1 month 6 days	5 years 9 months 22 days
Expected dividend yield	0.00%	0.00%	0.00%

STOCKHOLDERS’ EQUITY / DEFICIT - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Shares underlying options (in shares)	4,834,781	4,610,233	3,793,017
Exercise Price (in USD per share)	$ 16.81	$ 15.97	$ 14.94
Remaining contractual term, exercisable (in years)	5 years 11 months 23 days	5 years 10 months 6 days	6 years 9 months 26 days
Exercisable, aggregate intrinsic value	$ 35,387	$ 31,991	$ 23,358
Closing stock price of stock options outstanding and exercisable (in USD per share)	$ 22.63	$ 21.07	$ 18.93
Stock Options
Shares
Outstanding, beginning balance (in shares)	7,153,668
Granted (in shares)	1,349,250
Forfeited and expired (in shares)	(476,369)
Exercised (in shares)	(749,212)
Outstanding, ending balance (in shares)	7,277,337	7,153,668
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 17.16
Granted (in USD per share)	25.56
Forfeited and expired (in dollars per share)	24.50
Exercised (in USD per share)	14.13
Outstanding, ending balance (in USD per share)	$ 18.55	$ 17.16
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Remaining contractual term, outstanding (in years)	6 years 11 months 9 days	6 years 11 months 12 days
Exercised, Aggregate Intrinsic Value	$ 9,325
Outstanding, aggregate intrinsic value	$ 40,650	$ 39,010
Weighted average grant date fair value of options (in USD per share)	$ 16.21	$ 11.77	$ 10.09
Compensation expense not yet recognized, stock options	$ 30,000
Weighted average period for unrecognized costs (in years)	2 years 8 months 12 days

STOCKHOLDERS’ EQUITY / DEFICIT - Unvested Restricted Stock (Details) - Restricted shares $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to restricted shares granted \| $	$ 7.9
Weighted average period for unrecognized costs (in years)	2 years 10 months 24 days
Number of shares
Unvested beginning balance (in shares) \| shares	94,832
Granted (in shares) \| shares	395,311
Vested (in shares) \| shares	(58,251)
Forfeited/cancelled (in shares) \| shares	(31,466)
Unvested ending balance (in shares) \| shares	400,426
Weighted Average Grant Date Fair Value
Unvested beginning balance (in USD per share) \| $ / shares	$ 20.19
Granted (in USD per share) \| $ / shares	25.40
Vested (in USD per share) \| $ / shares	20.08
Forfeited/cancelled (in USD per share) \| $ / shares	25.20
Unvested ending balance (in USD per share) \| $ / shares	$ 24.95

STOCKHOLDERS’ EQUITY / DEFICIT - Performance-based Stock Options (Details) - Performance Shares $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to restricted shares granted \| $	$ 1.6
Weighted average period for unrecognized costs (in years)	1 year 3 months 18 days
Number of shares
Unvested beginning balance (in shares) \| shares	250,500
Granted (in shares) \| shares	66,500
Vested (in shares) \| shares	(85,250)
Forfeited/cancelled (in shares) \| shares	(5,000)
Unvested ending balance (in shares) \| shares	226,750
Weighted Average Grant Date Fair Value
Unvested beginning balance (in USD per share) \| $ / shares	$ 20.63
Granted (in USD per share) \| $ / shares	25.75
Vested (in USD per share) \| $ / shares	22.33
Forfeited/cancelled (in USD per share) \| $ / shares	18.46
Unvested ending balance (in USD per share) \| $ / shares	$ 21.54

STOCKHOLDERS’ EQUITY / DEFICIT - Share Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 19,774	$ 26,874	$ 29,102
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	13,550	17,924	18,614
Research and development expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total	$ 6,224	$ 8,950	$ 10,488

STOCKHOLDERS’ EQUITY / DEFICIT - Exercise of Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds exercise of warrants	$ 5,305	$ 3,645	$ 6,005
Class of warrant or right, title of security warrants or rights outstanding (in shares)	0
Warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock called by warrants (in shares)	1,036,054	607,481	898,633
Proceeds exercise of warrants	$ 5,305	$ 3,645	$ 6,005
Reclassification of derivative liability as equity		11,221	14,715
Change in fair value of warrants		$ 3,033	$ 2,909

EARNINGS (LOSS) PER SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares
Basic Earnings per Share (in shares)									40,433,171	38,769,816	36,997,865
Dilutive Earnings per Share (in shares)									40,433,171	38,769,816	38,288,012
Change in fair value of derivative instruments (in shares)									0	0	0
Net loss
Net loss	$ (7,455)	$ (54,516)	$ (22,329)	$ (18,378)	$ (17,618)	$ (17,794)	$ (13,229)	$ (11,090)	$ (102,678)	$ (59,731)	$ (47,903)
Change in fair value of derivative instruments									0	0	(1,655)
Dilutive Earnings per Share									$ (102,678)	$ (59,731)	$ (49,558)
Net income (loss) per common share, basic (in USD per shares)	$ (0.18)	$ (1.34)	$ (0.56)	$ (0.46)	$ (0.45)	$ (0.46)	$ (0.34)	$ (0.29)	$ (2.54)	$ (1.54)	$ (1.29)
Net income (loss) per common share, diluted (in USD per shares)	$ (0.18)	$ (1.34)	$ (0.56)	$ (0.46)	$ (0.55)	$ (0.46)	$ (0.34)	$ (0.32)	$ (2.54)	$ (1.54)	$ (1.29)
Warrants
Shares
Dilutive Earnings per Share (in shares)									0	0	1,290,147

EARNINGS (LOSS) PER SHARE - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	16,299,349	11,039,901	9,373,686
Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	8,410,932	2,642,160	2,642,160
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	395,034	157,319	444,942
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	7,210,576	7,080,998	6,286,584
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded from the calculation (in shares)	282,807	1,159,424	0

INCOME TAXES - Components of Net Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Loss before provision for income taxes	$ (7,455)	$ (54,101)	$ (22,162)	$ (18,149)	$ (11,038)	$ (19,017)	$ (15,154)	$ (13,154)	$ (101,867)	$ (58,363)	$ (57,582)
United States
Operating Loss Carryforwards [Line Items]
Loss before provision for income taxes									(87,573)	(55,611)	(52,750)
Foreign
Operating Loss Carryforwards [Line Items]
Loss before provision for income taxes									$ (14,294)	$ (2,752)	$ (4,832)

INCOME TAXES - Components of Income Tax Expense(Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current
Federal									$ 698	$ 6,991	$ 13,137
State									113	802	(155)
Total									811	7,793	12,982
Deferred
Federal									0	(7,965)	(18,814)
State									0	1,540	(3,847)
Total									0	(6,425)	(22,661)
Total tax provision (benefit)	$ 0	$ 415	$ 167	$ 229	$ 6,580	$ (1,223)	$ (1,925)	$ (2,064)	$ 811	$ 1,368	$ (9,679)

INCOME TAXES - Reconciliation of Federal Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Statutory rate - federal	(21.00%)	(35.00%)	(35.00%)
State taxes, net of federal benefit	(4.44%)	(3.30%)	(3.16%)
Change in FV of derivative liability (warrants)	(0.00%)	2.82%	1.10%
Change in federal tax rate	(0.00%)	23.29%	(0.00%)
Convertible Debt	21.77%	(0.00%)	(0.00%)
Loss on extinguishment of debt	4.09%	0.00%	0.00%
Other permanent differences	0.10%	1.04%	2.05%
Tax credits	(11.86%)	(5.79%)	(1.58%)
Return to provision adjustments and other true-ups	1.42%	(3.48%)	(1.15%)
Other	1.06%	1.25%	3.09%
Change in valuation allowance	9.79%	21.62%	16.30%
Income tax provision (benefit)	0.93%	2.45%	(18.35%)

INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred Tax Assets:
Net operating loss	$ 9,700	$ 1,099
Research and development and other tax credits	14,715	1,599
Contingent consideration	23,459	23,080
Other accrued expenses	3,710	2,603
Stock based compensation	16,761	15,695
Other	555	358
Deferred tax assets	68,900	44,434
Deferred Tax Liabilities:
Intangible assets	(14,288)	(16,810)
Convertible Debt	(18,419)	0
Tax basis depreciation less than book depreciation	0	0
Deferred tax liabilities	(32,707)	(16,810)
Net deferred tax assets (liabilities) before valuation allowance	36,194	27,624
Valuation allowance	(36,194)	(27,624)
Total deferred tax liability	$ 0	$ 0

INCOME TAXES - Narrative (Details) - USD ($)	12 Months Ended
INCOME TAXES - Narrative (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 36,194,000	$ 27,624,000
Increase in valuation allowance primarily attributable to Tax and Jobs Act of 2017	8,600,000	12,000,000
Income tax examination, penalties and interest expense	0	0	$ 0
Income tax examination, penalties and interest accrued	0	0
Tax Cuts and Jobs Act of 2017, income tax expense		$ 13,000,000
U.S. federal
Operating Loss Carryforwards [Line Items]
Available unused NOL carryforwards	36,500,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Available unused NOL carryforwards	33,100,000
Federal Orphan Drug Tax Credit
Operating Loss Carryforwards [Line Items]
Research and development tax credits	12,800,000
Research Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credits	500,000
Tax Competes Tax Credit Carryforward
Operating Loss Carryforwards [Line Items]
Research and development tax credits	$ 2,000,000

INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of January 1:	$ 0	$ 1,500
Increase in current period positions	0	0
Decrease in prior period positions	0	(1,500)
Increase in prior period positions	0	0
Balance as of December 31:	$ 0	$ 0

DERIVATIVE FINANCIAL INSTRUMENTS - Additional Information (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative liability related to warrants	$ 0	$ 15,710
Class of warrant or right, title of security warrants or rights outstanding (in shares)	0

DERIVATIVE FINANCIAL INSTRUMENTS - Derivative Warrant Issuances (Details) - Warrants - Derivative - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Shares
Outstanding, beginning balance (in shares)	1,159,424	1,766,905
Issued (in shares)	0	0
Canceled (in shares)	554	0
Exercised (in shares)	1,158,870	607,481
Outstanding, ending balance (in shares)	0	1,159,424
Weighted Average Exercise Price
Outstanding, beginning balance (in USD per share)	$ 7.86	$ 7.23
Issued (in USD per share)	0.00	0.00
Cancelled (in USD per share)	5.99	0.00
Exercised (in USD per share)	7.88	6.00
Outstanding, ending balance (in USD per share)	0.00	7.86
Weighted Average Grant Date Fair Value
Outstanding, Beginning Balance (in USD per share)	4.15	3.87
Issued (in USD per share)	0.00	0.00
Cancelled (in USD per share)	3.33	0.00
Exercised (in USD per share)	4.15	3.33
Outstanding, Ending Balance (in USD per share)	$ 0.00	$ 4.15

RETIREMENT PLAN (Details) - USD ($) $ in Millions	12 Months Ended
RETIREMENT PLAN (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Defined contribution plan, employer contributions	$ 0.9	$ 0.6	$ 0.5

RESTRUCTURING - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring adjustment	$ 242	$ 55

RESTRUCTURING - Schedule of Restructuring Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Restructuring Reserve [Roll Forward]
Liability, beginning of period	$ 3,549	$ 893
Restructuring expenses	0	3,608
Cash settlements	(3,307)	(897)
Adjustments to previous estimates	(242)	(55)
Liability, end of period	$ 0	$ 3,549

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 4,284	$ 3,815
Less: Accumulated depreciation	(1,138)	(585)
Total property and equipment, net	3,146	3,230
Depreciation	600	500	$ 100
Computers and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	506	436
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,150	945
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,628	2,071
Construction-in-progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 0	$ 363

QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net product sales	$ 43,771	$ 40,706	$ 41,337	$ 38,432	$ 42,177	$ 40,340	$ 38,800	$ 33,620	$ 164,246	$ 154,937	$ 133,591
Total operating expenses	48,756	76,289	62,897	56,344	57,354	50,948	52,398	48,028	244,286	208,728	191,805
Operating loss	(4,985)	(35,583)	(21,560)	(17,912)	(15,177)	(10,608)	(13,598)	(14,408)	(80,040)	(53,791)	(58,214)
Total other income (expense), net	(2,470)	(18,518)	(602)	(237)	4,139	(8,409)	(1,556)	1,254	(21,827)	(4,572)	632
Loss before benefit (provision) for income taxes	(7,455)	(54,101)	(22,162)	(18,149)	(11,038)	(19,017)	(15,154)	(13,154)	(101,867)	(58,363)	(57,582)
Income tax benefit (provision)	0	(415)	(167)	(229)	(6,580)	1,223	1,925	2,064	(811)	(1,368)	9,679
Net loss	$ (7,455)	$ (54,516)	$ (22,329)	$ (18,378)	$ (17,618)	$ (17,794)	$ (13,229)	$ (11,090)	$ (102,678)	$ (59,731)	$ (47,903)
Net Loss per common share
Basic (in USD per shares)	$ (0.18)	$ (1.34)	$ (0.56)	$ (0.46)	$ (0.45)	$ (0.46)	$ (0.34)	$ (0.29)	$ (2.54)	$ (1.54)	$ (1.29)
Diluted (in USD per shares)	$ (0.18)	$ (1.34)	$ (0.56)	$ (0.46)	$ (0.55)	$ (0.46)	$ (0.34)	$ (0.32)	$ (2.54)	$ (1.54)	$ (1.29)
Loss on extinguishment of debt									$ 17,042	$ 0	$ 0

Label	Element	Value
Additional Paid-in Capital [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 5,394,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(4,868,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 10,316,000