XenoPort (XNPT) 10-K 26 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 12, 2016	Jun. 30, 2015
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	XNPT
Entity Registrant Name	XENOPORT INC
Entity Central Index Key	1,130,591
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		63,456,081
Entity Public Float			$ 284,000,000

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 61,317	$ 11,958
Short-term investments	78,169	90,098
Accounts receivable	6,439	2,895
Inventories	2,068	1,458
Prepaids and other current assets	6,553	3,185
Total current assets	154,546	109,594
Property and equipment, net	1,792	2,422
Long-term inventories	7,581	9,098
Restricted investments and other assets	74	1,947
Total assets	163,993	123,061
Current liabilities:
Accounts payable	2,300	2,835
Accrued compensation	6,924	7,148
Accrued preclinical and clinical costs	1,316	1,554
Other accrued liabilities	7,610	5,117
Deferred revenue	1,134	1,134
Total current liabilities	19,284	17,788
Convertible senior notes, net	111,761
Deferred revenue	9,730	10,864
Other noncurrent liability	$ 2,918	$ 3,269
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000 shares authorized; no shares issued or outstanding
Common stock, $0.001 par value; 200,000 and 100,000 shares authorized at December 31, 2015 and 2014, respectively; 63,390 and 62,475 shares issued and outstanding, at December 31, 2015 and 2014, respectively	$ 63	$ 62
Additional paid-in capital	689,319	677,924
Accumulated other comprehensive income (loss)	47	(30)
Accumulated deficit	(669,129)	(586,816)
Total stockholders' equity	20,300	91,140
Total liabilities and stockholders' equity	$ 163,993	$ 123,061

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	100,000,000
Common stock, shares issued	63,390,000	62,475,000
Common stock, shares outstanding	63,390,000	62,475,000

STATEMENTS OF COMPREHENSIVE LOS

STATEMENTS OF COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Product sales, net	$ 39,459	$ 20,173	$ 6,414
Collaboration revenue	1,134	26,134	1,137
Royalty revenue	567	561	400
Total revenues	41,160	46,868	7,951
Operating expenses:
Cost of product sales	2,366	2,094	1,170
Research and development	22,715	23,679	33,325
Selling, general and administrative	95,301	70,194	59,084
Total operating expenses	120,382	95,967	93,579
Loss from operations	(79,222)	(49,099)	(85,628)
Interest income	518	253	213
Interest expense	(3,609)	(487)	(468)
Net loss	(82,313)	(49,333)	(85,883)
Other comprehensive loss:
Unrealized gains (losses) on available-for-sale securities	77	(30)	(22)
Comprehensive loss	$ (82,236)	$ (49,363)	$ (85,905)
Basic and diluted net loss per share	$ (1.30)	$ (0.81)	$ (1.81)
Shares used to compute basic and diluted net loss per share	63,193	60,856	47,545

STATEMENTS OF STOCKHOLDERS' EQU

STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2012	$ 130,210	$ 47	$ 581,741	$ 22	$ (451,600)
Beginning Balance (in shares) at Dec. 31, 2012		47,067,669
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)		590,242
Issuance of common stock upon exercise of options and vesting of restricted stock units	(1,875)	$ 1	(1,876)
Issuance of common stock in connection with Employee Stock Purchase Plan	719		719
Issuance of common stock in connection with Employee Stock Purchase Plan (in shares)		142,455
Stock-based compensation expense	10,544		10,544
Change in unrealized gains (losses) on investments	(22)			(22)
Net loss	(85,883)				(85,883)
Ending Balance at Dec. 31, 2013	53,693	$ 48	591,128		(537,483)
Ending Balance (in shares) at Dec. 31, 2013		47,800,366
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)		646,806
Issuance of common stock upon exercise of options and vesting of restricted stock units	(395)		(395)
Issuance of common stock in connection with Employee Stock Purchase Plan	714		714
Issuance of common stock in connection with Employee Stock Purchase Plan (in shares)		227,720
Stock-based compensation expense	9,041		9,041
Issuance of common stock (in shares)		13,800,000
Issuance of common stock	77,450	$ 14	77,436
Change in unrealized gains (losses) on investments	(30)			(30)
Net loss	(49,333)				(49,333)
Ending Balance at Dec. 31, 2014	$ 91,140	$ 62	677,924	(30)	(586,816)
Ending Balance (in shares) at Dec. 31, 2014	62,475,000	62,474,892
Issuance of common stock upon exercise of options and vesting of restricted stock units (in shares)		589,422
Issuance of common stock upon exercise of options and vesting of restricted stock units	$ (147)	$ 1	(148)
Issuance of common stock in connection with Employee Stock Purchase Plan	1,365		1,365
Issuance of common stock in connection with Employee Stock Purchase Plan (in shares)		325,911
Stock-based compensation expense	10,178		10,178
Change in unrealized gains (losses) on investments	77			77
Net loss	(82,313)				(82,313)
Ending Balance at Dec. 31, 2015	$ 20,300	$ 63	$ 689,319	$ 47	$ (669,129)
Ending Balance (in shares) at Dec. 31, 2015	63,390,000	63,390,225

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (82,313)	$ (49,333)	$ (85,883)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	711	623	1,199
Accretion of investment discounts and amortization of investment premiums, net	807	1,151	1,007
Amortization of discount and debt issuance costs on convertible senior notes	434
Stock-based compensation expense	10,178	9,041	10,544
Changes in assets and liabilities:
Accounts receivable	(3,544)	(1,956)	(939)
Prepaids and other current and noncurrent assets	(1,496)	(186)	16
Inventories	907	891	286
Accounts payable	(535)	1,403	865
Accrued compensation	(224)	4,407	(2,134)
Accrued restructuring charges			(993)
Accrued preclinical and clinical costs	(238)	730	(3,573)
Other accrued liabilities, current and noncurrent	2,144	1,666	2,839
Deferred revenue, current and noncurrent	(1,134)	(1,133)	(1,137)
Net cash used in operating activities	(74,303)	(32,696)	(77,903)
Investing activities
Purchases of investments	(198,870)	(155,885)	(91,000)
Proceeds from maturities of investments	210,067	102,679	154,765
Purchases of property and equipment	(80)	(493)	(256)
Net cash provided by (used in) investing activities	11,117	(53,699)	63,509
Financing activities
Proceeds from issuance of convertible senior notes, net of discount and debt issuance costs	111,327
Net cash proceeds provided by (used in) issuance of common stock and exercise of stock options	1,218	77,769	(1,156)
Net cash provided by (used in) financing activities	112,545	77,769	(1,156)
Net increase (decrease) in cash and cash equivalents	49,359	(8,626)	(15,550)
Cash and cash equivalents at beginning of period	11,958	20,584	36,134
Cash and cash equivalents at end of period	61,317	$ 11,958	20,584
Cash paid during the period for:
Interest expense	$ 1,422
Non-cash investing activity:
Inventories			11,733
Manufacturing property and equipment			$ 1,967

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Organization and Summary of Significant Accounting Policies	1. Organization and Summary of Significant Accounting Policies Nature of Operations XenoPort, Inc., or the Company, was incorporated in the state of Delaware on May 19, 1999. The Company is a biopharmaceutical company focused on commercializing HORIZANT ® In October 2015, following the completion of a Phase 2 study of XP23829 in patients with moderate-to-severe chronic plaque-type psoriasis, the Company announced that it would focus its resources on the continued commercialization of HORIZANT and seek partners for the further development and potential commercialization of XP23829 and XP21279. As such, the Company is seeking to maximize the value of these assets with potential partners whose expertise, resources and access to relevant markets will enable further development and potential commercialization of these assets. Given the Company’s focus on commercializing HORIZANT, it believes that the potential for HORIZANT may be enhanced through relationships that would enable further development and/or expanded commercialization efforts of HORIZANT. As such, the Company may enter into a relationship with a pharmaceutical company: for potential access to a primary care physician and/or expanded sales force to maximize the commercial potential of HORIZANT in the United States; for development and commercialization of HORIZANT outside the United States; and/or to develop and commercialize HORIZANT for indications that fall outside its core commercialization capabilities. Alternatively, the Company could enter into relationships that may enhance the efficiency of its sales force, such as co-promotion opportunities where potentially synergistic central nervous system products could be detailed to the current HORIZANT health care provider targets. On November 8, 2012, the Company executed a termination and transition agreement with Glaxo Group Limited, or GSK, that terminated its development and commercialization agreement with respect to HORIZANT, and also provided for a mutual release of claims and resolved all ongoing litigation between the parties. Pursuant to the termination and transition agreement, during a transition period that ended on April 30, 2013, GSK continued to exclusively commercialize, promote, manufacture and distribute HORIZANT in the United States. The Company did not receive any revenue nor incur any losses from GSK’s sales of HORIZANT during the transition period. On May 1, 2013, the Company assumed all responsibilities for further development, manufacturing and commercialization of HORIZANT in the United States. The results of operations of the acquired HORIZANT business, along with the fair values of the assets acquired in the transaction, have been included in its financial statements since May 1, 2013. In connection with the Company’s reacquisition of the HORIZANT business on May 1, 2013, GSK provided it with inventory of gabapentin enacarbil in GSK’s possession that was not required for use by GSK in the manufacture of HORIZANT and related manufacturing property and equipment. In exchange for such inventory, the Company agreed to make annual payments to GSK of $1,000,000 for six years beginning in 2016, which was recorded at its present value as “Other noncurrent liability” on its balance sheet and is being accreted to its contractual value over the repayment period. At December 31, 2015, the GSK liability comprised of a $923,000 current portion included in “Other accrued liabilities” and a $2,918,000 non-current portion included in “Other noncurrent liability.” The GSK liability of $3,269,000 as of December 31, 2014 comprised solely of a non-current portion included in “Other noncurrent liability.” Basis of Preparation The Company’s financial statements are prepared in accordance with the Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or the Codification, which is the single source of authoritative U.S. generally accepted accounting principles, or GAAP. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates. Fair Value of Financial Instruments The carrying amounts of certain of the Company’s financial instruments, including cash and cash equivalents and short-term investments, restricted investments, accounts receivables and accounts payables, approximate fair value due to their short-term maturities. The Company accounts for the fair value of its financial instruments in accordance with the provisions of the Fair Value Measurement Fair value is the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The Company applies the market approach valuation technique for fair value measurements on a recurring basis and attempts to maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. All of the Company’s cash equivalents and short-term investments are measured using inputs classified at Level 1 or Level 2 within the fair value hierarchy. Level 1 inputs are quoted prices in active markets for identical assets. Level 2 inputs are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Level 3 inputs are unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to, benchmark yields, interest rate curves, reported trades, broker/dealer quotes and market reference data. Cash Equivalents and Short-Term Investments The Company considers all highly liquid investments with original maturities of 90 days or less at the time of purchase to be cash equivalents, which primarily consist of money market funds, U.S. government-sponsored agencies and corporate debt securities. Management determines the appropriate classification of securities at the time of purchase. All investments have been designated as available-for-sale. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company has classified all investments as short-term, even though the stated maturity may be one year or more beyond the current balance sheet date. Available-for-sale securities are carried at estimated fair value with unrealized gains and losses reported as a component of other comprehensive loss in the statements of comprehensive loss. The cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities, if any, are recorded in interest income and expense. The cost of securities sold is based on the specific-identification method. Interest and dividends are included in interest income. Restricted Investments Under a facilities operating lease agreement, the Company is required to secure a letter of credit with cash or securities. At December 31, 2015 and 2014, the Company recorded $1,500,000 of restricted investments related to the letter of credit (see Note 8 for more information). The $1,500,000 was classified as “Prepaids and other current assets” as of December 31, 2015 and “Restricted investments and other assets” as of December 31, 2014. In connection with the Company’s license to use radioactive materials in its research facilities, it must maintain a $225,000 letter of credit with the Radiological Health Branch of the State of California. This requirement has been fulfilled through certificates of deposit with a financial institution. The fair value of the $225,000 secured amount was classified as “Prepaids and other current assets” as of December 31, 2015 and “Restricted investments and other assets” as of December 31, 2014. Segment Information The Company operates in one operating segment, which is the development and commercialization of product candidates for the treatment of neurological and other disorders, and has operations solely in the United States. To date, all of the Company’s revenues from product sales are related to sales of HORIZANT in the United States. The Company also has recognized upfront and milestone payments and royalty revenue from its partnership with Astellas Pharma Inc. and recognized upfront and additional payments from its partnership with Indivior (see Note 2 for more information on these arrangements). Concentrations of Risk The Company invests cash that is not being used for operational purposes. This exposes the Company to credit risk in the event of default by the institutions holding the cash and cash equivalents and available-for-sale securities to the extent of the amounts on its balance sheets. The credit risk is mitigated by the Company’s investment policy, which allows for the purchase of low risk debt securities issued by the U.S. government, U.S. government-sponsored agencies and highly rated banks and corporations, subject to certain concentration limits. The maturities of these securities are maintained at no longer than 16 months. The Company believes its established guidelines for investment of its excess cash enhances safety and liquidity through its policies on diversification and investment maturity. Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and available-for-sale investment securities in high-credit quality debt securities issued by the U.S. government, U.S. government-sponsored enterprises and highly rated banks and corporations. The carrying amounts of cash equivalents and available-for-sale investment securities are stated at fair value. The Company is subject to credit risk from its accounts receivable related to product sales. The Company’s trade accounts receivable arises from product sales in the United States. Three wholesale distributors represented 41%, 28% and 25%, respectively, of product sales for the year ended December 31, 2015. These three customers individually comprised 38%, 31% and 22%, respectively, of accounts receivable as of December 31, 2015. Three wholesale distributors represented 41%, 28% and 26%, respectively, of product sales for the year ended December 31, 2014. These three customers individually comprised 48%, 26% and 22%, respectively, of accounts receivable as of December 31, 2014. To date, the Company has not experienced any losses with respect to the collection of its accounts receivable and believes that its accounts receivable are collectible. The Company relies on a single third-party contract manufacturer organization to manufacture HORIZANT. Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, which is generally five to ten years for the Company’s laboratory equipment, furniture and fixtures and manufacturing property and equipment and generally three years for the Company’s computer equipment and software. Leasehold improvements are amortized over their estimated useful lives or the remaining lease term, whichever is shorter. Revenue Recognition Product Sales The Company began selling HORIZANT to wholesalers in May 2013 following the acquisition of the HORIZANT business from GSK. The Company recognizes revenue from HORIZANT drug product sales when there is persuasive evidence that an arrangement exists, delivery to the customer has occurred, the price is fixed or determinable and collectability is reasonably assured. Revenue from product sales is recorded net of estimated allowances for customer incentives such as cash discounts for prompt payment, distributor fees, expected returns, as appropriate (which are based on an analysis of historical return rates and deductions of HORIZANT, since its commercial launch by GSK in the second quarter of 2011), government rebates such as Medicaid reimbursements and patient assistance programs. Calculating certain of these items involves estimates and judgments based on contractual terms, historical utilization rates data for HORIZANT and new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future utilization rates for these programs and channel inventory data. If future actual results vary from the Company’s estimates, the Company may need to adjust these estimates, which could have an effect on net product sales and earnings in the period of adjustment. Items Deducted from Gross Product Sales Prompt Pay Discount The Company offers cash discounts to its customers, generally 2% of the sales price, as an incentive for prompt payment. Based on the Company’s commercialization experience, the Company expects customers to continue to comply with the prompt payment terms to earn the cash discount as the Company is selling HORIZANT to the same customers under similar prompt payment terms and conditions. The Company estimates cash discounts for prompt payment based on contractual terms and the Company’s historical customer utilization rates. The Company accounts for cash discounts by reducing accounts receivable by the full amount and recognizing the discount as a reduction of revenue in the same period the related revenue is recognized. Distributor Fees Under the Company’s inventory management agreements with significant wholesalers, the Company pays the wholesalers a fee primarily for distribution services as well as the maintenance of inventory levels. These distributor fees are based on a contractually determined fixed percentage of sales. The Company accrues the contractual amount and recognizes the discount as a reduction of revenue in the same period the related revenue is recognized. Product Returns The Company does not provide its customers with a general right of product return, but permits returns if the product is damaged or defective when received by the customer, or if the product has or is nearly expired. HORIZANT tablets currently have a shelf-life of 36 months from the date of manufacture. The Company will accept returns for products that will expire within six months or that have expired up to one year after their expiration dates. The Company obtained actual return history classified by the reasons for returns from GSK since GSK’s product launch in 2011, which provides a basis to reasonably estimate the Company’s future product returns. The Company estimates returns taking into consideration Company-specific adjustments to GSK’s returns history, the Company’s returns history, the shelf life of product, shipment and prescription trends and estimated distribution channel inventory levels. Government Rebates and Chargebacks The Company participates in a number of government rebate programs, such as the Medicaid Drug Rebate Program that provides assistance to eligible low-income patients based on each individual state’s guidelines regarding eligibility and services, Public Health Services or 340b programs, and the Medicare Part D Coverage Gap Discount Program, which provides rebates on prescriptions that fall within the “donut hole” coverage gap; and the Department of Veterans Affairs that offers discounts to authorized users of HORIZANT. HORIZANT is also listed on the Federal Supply Schedule, or FSS, of the General Services Administration which provides a discount to the Department of Defense, Department of Veterans Affairs, and TriCare. The Company estimates reductions to the Company’s revenues for government rebate programs based on product pricing, current rebates, GSK’s historical utilization rates, the Company’s actual utilization rates, new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future rebates for these programs and estimated levels of inventory in the distribution channel. Patient Assistance The Company offers a co-pay card program to assist commercially insured patients with the cost of their HORIZANT related co-payments. Participating retail pharmacies get reimbursed by the Company for the amount of the co-pay assistance provided to eligible patients. The Company estimates and accrues the cost of the co-pay program based on historical and current redemption activity for this program. The Company reimburses the participating pharmacies approximately one month after the prescriptions subject to co-pay assistance are filled. Multiple-Element Arrangements Revenue arrangements are accounted for in accordance with the provisions of the Revenue Recognition-Multiple-Element Arrangements In evaluating arrangements with multiple elements, the Company considers whether components of the arrangement represent separate units of accounting based upon whether certain criteria are met, including whether the delivered element has stand-alone value to the customer and whether there is objective and reliable evidence of the fair value of the undelivered items. This evaluation requires subjective determinations and requires management to make judgments about the fair value of individual elements and whether such elements are separable from other aspects of the contractual relationship. The consideration received in such arrangements is allocated among the separate units of accounting based on the relative selling price method under which the selling price for each deliverable is determined using vendor-specific objective evidence of selling price, if it exists; otherwise, third-party evidence of selling price. If vendor-specific objective evidence and third-party evidence of selling price are not available for a deliverable, the Company will use its best estimate of the selling price for that deliverable when applying the relative selling price method. The applicable revenue recognition criteria are applied to each of the separate units. Revenues from multiple deliverables combined as a single unit of accounting are deferred and recognized over the period during which the Company remains obligated to perform services. The specific methodology for the recognition of the revenue (e.g., straight-line or according to specific performance criteria) is determined on a case-by-case basis according to the facts and circumstances applicable to a given agreement. Payments received in excess of revenues recognized are recorded as deferred revenue until such time as the revenue recognition criteria have been met. Collaboration revenue consisted of the recognition of revenues from upfront and milestone payments from the Company’s partnership with Astellas Pharma Inc. and from upfront and additional payments from its license agreement with Indivior. The Company accounts for the revenue-related activities of these collaboration agreements as follows: • Up-front, licensing-type payments. • Milestones. The Company will assess the nature of contingent payments, and appropriate accounting for, these payments on a case-by-case basis in accordance with the provisions of the Revenue Recognition • Product royalties. Cost of Product Sales Cost of product sales includes direct and indirect costs to manufacture product sold, including tableting, packaging, storage, shipping and handling costs and inventory write-downs, if any, related to product sales of HORIZANT. Accounts Receivable Trade accounts receivable are recorded net of allowances for cash discounts for prompt payment, wholesaler discounts and chargebacks. The need for bad debt allowance is evaluated each reporting period based on the Company’s assessment of the credit worthiness of its customers. Inventories Inventories are stated at the lower of cost or market. Cost is determined on a first-in, first-out, or FIFO, basis. Inventories include active pharmaceutical ingredient, or API, contract manufacturing costs and overhead allocations. The Company regularly evaluates the Company’s inventories for excess quantities and obsolescence (expiration), taking into account such factors as historical and anticipated future sales compared to quantities on hand and the remaining shelf life of HORIZANT. Write-downs of inventories are considered to be permanent reductions in the cost basis of inventories. Inventories that are not expected to be consumed within 12 months following the balance sheet date are classified as long-term inventories. Inventories as of December 31, 2015 and 2014 are summarized as follows (in thousands): Year Ended 2015 2014 Raw materials $ 7,396 $ 9,273 Work in progress 134 517 Finished goods 2,119 766 Total inventory 9,649 10,556 Less: Long-term inventories 7,581 9,098 Total inventory classified as current $ 2,068 $ 1,458 Long-term inventories primarily consist of gabapentin enacarbil API used for production of HORIZANT. The Company evaluates demand for HORIZANT and expected consumption of the API based on projected sales of HORIZANT. Research and Development All research and development costs, including those funded by third parties, are expensed as incurred. Research and development expenses consist of costs associated with conducting preclinical studies and clinical trials, manufacturing development efforts for clinical trials and activities related to development-related regulatory filings. Clinical Trials The Company accrues and expenses the costs for clinical trial activities performed by third parties based upon estimates of the percentage of work completed over the life of the individual study in accordance with agreements established with contract research organizations and clinical trial sites. The Company determines the estimates through discussions with internal clinical personnel and external service providers as to progress or stage of completion of trials or services and the agreed upon fee to be paid for such services. Costs of setting up clinical trial sites for participation in the trials are expensed immediately as research and development expenses. Clinical trial site costs related to patient visits are accrued as patients’ progress through the trial and are reduced by any payments made to the clinical trial site. Non-refundable advance payments for research and development goods or services are recognized as expense as the related goods are delivered or the related services are provided in accordance with the provisions of the Research and Development Arrangements Stock-Based Compensation The Compensation — Stock Compensation The Company accounts for stock compensation arrangements to non-employees in accordance with the Equity-Based Payments to Non-Employees The effect of recording stock-based compensation under the Compensation — Stock Compensation Year Ended December 31, 2015 2014 2013 (In thousands, except per share amounts) Stock-based compensation by type of award: Stock options and awards $ 9,410 $ 8,531 $ 10,083 ESPP 768 510 461 Total stock-based compensation $ 10,178 $ 9,041 $ 10,544 Effect on basic and diluted net loss per share $ (0.16 ) $ (0.15 ) $ (0.22 ) The Company’s employee non-cash stock-based compensation was reported as follows: Year Ended December 31, 2015 2014 2013 (In thousands) Research and development $ 1,637 $ 2,062 $ 3,059 Selling, general and administrative 8,541 6,979 7,485 $ 10,178 $ 9,041 $ 10,544 Valuation Assumptions The Company estimates the fair value of its stock options without market conditions and stock purchase rights on the date of grant using a Black-Scholes valuation model that requires the input of highly subjective assumptions, including the option’s expected life and the price volatility of the underlying stock. The Company derived the expected life assumptions using data obtained from similar entities, taking into consideration factors such as industry, stage of life cycle, size and financial leverage. The Company has determined that its historical volatility can be used to derive the expected stock price volatility assumption. The Company expenses the resulting charge using the straight-line attribution method over the vesting period. Restricted stock units, or RSUs, without market conditions are measured at the fair value of the Company’s common stock on the date of grant and expensed over the period of vesting using the straight-line attribution approach. The calculation of the Black-Scholes valuations used the following weighted-average assumptions: Year Ended December 31, 2015 2014 2013 Dividend yield 0 % 0 % 0 % Volatility for options 0.76 0.81 0.82 Volatility for ESPP 0.50 0.55 0.59 Weighted-average expected life of options (years) 5.39 5.25 5.25 Weighted-average expected life of ESPP rights (years) 0.75 0.75 0.75 Risk-free interest rate for options 1.35-1.68 % 1.52-1.77 % 0.70-1.60 % Risk-free interest rate for ESPP rights 0.05-0.27 % 0.05-0.17 % 0.07-0.17 % The Company estimates the fair value of stock options and RSUs subject to market conditions using a Monte Carlo simulation model, which involves a series of random scenarios that may take different future price paths over the award’s contractual life. The grant date fair value is determined by taking the average of the grant date fair values under each of many Monte Carlo simulations. The determination of the fair value is affected by the Company’s stock price, as well as assumptions regarding a number of complex and subjective variables including its expected stock price volatility over the expected term of the awards, risk-free interest rates, and estimated forfeitures. Income Taxes Income taxes are accounted for in accordance with the Income Taxes The recognition, derecognition and measurement of a tax position is based on management’s best judgment given the facts, circumstances and information available at the reporting date. As of December 31, 2015, the Company had unrecognized tax benefits and expects no significant changes in unrecognized tax benefits in the next 12 months (see Note 11 for more information). The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense. To date, there have been no interest or penalties charged to the Company in relation to the underpayment of income taxes. Comprehensive Loss The Company presents all non-owner changes in stockholders’ equity in a single continuous statement of comprehensive loss and shows: (i) each component of net loss along with total net loss; (ii) each component of other comprehensive loss along with a total for other comprehensive loss; and (iii) a total amount for comprehensive loss. The Company’s other comprehensive loss is comprised of unrealized gains (losses) on available-for-sale securities. Advertising Costs Advertising costs, included in selling, general and administrative expenses, are charged to expense as incurred. Advertising expenses for the year ended December 31, 2015, 2014 and 2013, was $7,619,000, $9,568,000 and $8,244,000, respectively. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period without consideration for potential common shares. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period plus any dilutive potential common shares for the period determined using the treasury-stock method for restricted stock units and options to purchase stock and using the if-converted method for the convertible senior notes. For purposes of this calculation, restricted stock units, options to purchase stock and convertible senior notes are considered to be potential common shares and are only included in the calculation of diluted net loss per share when their effect is dilutive. Year Ended December 31, 2015 2014 2013 (In thousands, except per share amounts) Numerator: Net loss $ (82,313 ) $ (49,333 ) $ (85,883 ) Denominator: Weighted-average common shares outstanding 63,193 60,856 47,545 Basic and diluted net loss per share $ (1.30 ) $ (0.81 ) $ (1.81 ) Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect: Restricted stock units and options to purchase common stock 8,475 7,650 6,824 Warrants outstanding — — 283 Convertible senior notes 10,729 — — 19,204 7,650 7,107 On January 29, 2014, the Company completed an underwritten public offering of 12,000,000 shares of its common stock at a price to the public of $6.00 per share. On February 21, 2014, the underwriters exercised in full their option to purchase 1,800,000 additional shares. On February 3, 2015, the Company completed a private placement of $115,000,000 aggregate principal amount of 2.50% Convertible Senior Notes due 2022, or the 2022 Notes. The 2022 Notes are convertible at an initial conversion rate of 93.2945 shares of the Company’s common stock per $1,000 principal amount of the 2022 Notes, which is equal to an initial conversion price of approximately $10.72 per share of common stock. As of December 31, 2015, 10,728,867 shares of the Company’s common stock were issuable upon conversion of the 2022 Notes (see Note 7 for more information). Recent Accounting Pronouncements In May 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-09, Revenue from Contracts with Customers: Topic 606 Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements — Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In April 2015, the FASB issued ASU No. 2015-03, Interest — Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes In January 2016, the FASB issued ASU 2016-01, Financial Instruments — Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities

License and Collaboration Agree

License and Collaboration Agreements	12 Months Ended
	Dec. 31, 2015
License and Collaboration Agreements	2. License and Collaboration Agreements Indivior UK Ltd. In May 2014, the Company entered into an exclusive license agreement with Indivior, which became effective on June 19, 2014. Under the terms of this agreement, the Company granted to Indivior exclusive, world-wide rights to develop and commercialize pharmaceutical products containing AP Products for all indications, subject to its right of first negotiation with Indivior to collaborate to develop and commercialize AP Products for non-addiction indications. In exchange for these rights, the Company received an upfront, non-refundable cash payment of $20,000,000 in June 2014 and also received an additional $5,000,000 payment in July 2014 after delivery of specified materials to Indivior. The Company is also eligible to receive aggregate cash payments of up to $120,000,000 upon the achievement by Indivior of certain contingent event-based payments, of which $70,000,000 are regulatory and development-based and $50,000,000 are commercialization-based. In addition, the Company is entitled to receive tiered double-digit royalty payments of up to the mid-teens on a percentage basis on potential future net sales of the products in the United States, and high single-digit royalty payments on potential future net sales of the products outside the United States. The Company also agreed to transfer its existing AP Investigational New Drug applications, or INDs, and know-how to Indivior, and to provide supply transition assistance to facilitate the establishment of Indivior’s AP Product manufacturing capabilities pursuant to a mutually agreed supply transition plan. The Company assessed its transfer and assistance obligations under the Indivior agreement using the multiple-element arrangements revenue recognition guidance since those obligations involved more than one deliverable to Indivior. This analysis involved identification of the deliverables, determining if they qualify as separate units of accounting, arriving at fair value estimates for each separate unit of accounting, and allocating total consideration to each unit of accounting. The Company identified the following non-contingent deliverables under the license agreement: (1) grant of exclusive rights, or the license; (2) transfer of know-how necessary for the manufacture and development of AP Products; (3) transfer of INDs; (4) transfer of specified materials; and (5) supply of transition assistance to facilitate the establishment of Indivior’s AP Product manufacturing capabilities pursuant to a mutually agreed upon supply transition plan. The license, know-how, INDs and supply of transition assistance deliverables were combined into one unit of accounting since each of these deliverables was dependent on, and not separate from each other, and accordingly did not have stand-alone value. The transfer of specified materials represented the other unit of accounting. The total of the upfront cash payment of $20,000,000 and the additional cash payment of $5,000,000 were allocated into two units of accounting using the relative estimated selling price method. The Company developed its best estimate of selling prices for each deliverable in order to allocate the non-contingent arrangement consideration to the two units of accounting. For the license, know-how, INDs and supply of transition assistance, the Company used the discounted cash flow method to estimate the price at which it could sell them on a stand-alone basis. Embedded in the estimate were significant assumptions including: (1) probabilities of success during the development process; (2) potential customer market for the drug; (3) selling price for the drug; (4) costs to develop, maintain and manufacture the developed drug; and (5) discount rate. For the transfer of specified materials, the Company estimated the selling price based on the cost to purchase such materials from third party suppliers. Both the initial upfront cash payment of $20,000,000 and the additional cash payment of $5,000,000 were recognized as collaboration revenue upon the transfer of the deliverables to Indivior, which occurred in the third quarter of 2014. Astellas Pharma Inc. In December 2005, the Company entered into an agreement pursuant to which it licensed to Astellas Pharma Inc., exclusive rights to develop and commercialize gabapentin enacarbil in Japan, Korea, the Philippines, Indonesia, Thailand and Taiwan. Astellas commenced commercialization of gabapentin enacarbil in Japan, and began selling gabapentin enacarbil in July 2012 under the trade name of REGNITE ® The following table presents the Company’s total revenues that have been recognized during the year indicated pursuant to its current license agreements with Astellas and Indivior (in thousands): Year Ended December 31, 2015 2014 2013 Astellas $ 1,701 $ 1,695 $ 1,537 Indivior — 25,000 — $ 1,701 $ 26,695 $ 1,537

Cash and Cash Equivalents, Shor

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents, Short-Term Investments and Restricted Investments	3. Cash and Cash Equivalents, Short-Term Investments and Restricted Investments The following are summaries of cash and cash equivalents, short-term investments and restricted investments (in thousands): Cost Gross Gross Estimated As of December 31, 2015: Cash $ 5,311 $ — $ — $ 5,311 Money market funds 17,261 — — 17,261 U.S. government-sponsored agencies 12,249 1 — 12,250 Corporate debt securities 104,618 63 (17 ) 104,664 Certificates of deposit 1,725 — — 1,725 $ 141,164 $ 64 $ (17 ) $ 141,211 Reported as: Cash and cash equivalents $ 61,317 Short-term investments 78,169 Restricted investments(1) 1,725 $ 141,211 Cost Gross Gross Estimated As of December 31, 2014: Cash $ 3,383 $ — $ — $ 3,383 Money market funds 8,576 — — 8,576 U.S. government-sponsored agencies 2,000 — (2 ) 1,998 Corporate debt securities 88,127 12 (40 ) 88,099 Certificates of deposit 1,725 — — 1,725 $ 103,811 $ 12 $ (42 ) $ 103,781 Reported as: Cash and cash equivalents $ 11,958 Short-term investments 90,098 Restricted investments(1) 1,725 $ 103,781 (1) Included in “Prepaids and other current assets” as of December 31, 2015 and “Restricted investments and other assets” as of December 31, 2014. At December 31, 2015 and 2014, the contractual maturities of all investments held were less than 12 and 16 months, respectively. All investments have been designated as available-for-sale, and changes to unrealized gains and losses are reflected as the only component of accumulated other comprehensive loss. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company has classified all investments as short-term, even though the stated maturity may be one year or more beyond the current balance sheet date. No gross realized gains or losses were recognized in 2015, 2014 and 2013, and accordingly, there were no amounts reclassified out of accumulated other comprehensive loss to earnings in 2015, 2014 or 2013. The Company’s available-for-sale investments, which include cash equivalents and short-term investments, are measured at fair value on a recurring basis and are classified at the following fair value hierarchy (see Note 1 for the Company’s accounting policy on measuring fair value of financial instruments) (in thousands): Fair Value Measurements at Reporting Date Using Description Total As of 2015 Quoted Prices in Active Markets for Identical (Level 1) Significant Other (Level 2) Significant (Level 3) Money market funds $ 17,261 $ 17,261 $ — $ — U.S. government-sponsored agencies 12,250 — 12,250 — Corporate debt securities 104,664 — 104,664 — Certificates of deposit 1,725 — 1,725 — Total $ 135,900 $ 17,261 $ 118,639 $ — Fair Value Measurements at Reporting Date Using Description Total As of Quoted Prices in Active Markets for Identical (Level 1) Significant (Level 2) Significant (Level 3) Money market funds $ 8,576 $ 8,576 $ — $ — U.S. government-sponsored agencies 1,998 — 1,998 — Corporate debt securities 88,099 — 88,099 — Certificates of deposit 1,725 — 1,725 — Total $ 100,398 $ 8,576 $ 91,822 $ —

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2015
Property and Equipment, net	4. Property and Equipment, net Property and equipment at December 31, 2015 and 2014 consisted of the following (in thousands): December 31, 2015 2014 Laboratory equipment $ 9,878 $ 10,561 Manufacturing property and equipment 1,980 1,975 Furniture and fixtures 1,076 1,076 Computer equipment and software 5,482 5,656 Leasehold improvements 3,405 3,405 21,821 22,673 Less: Accumulated depreciation and amortization (20,029 ) (20,251 ) Property and equipment, net $ 1,792 $ 2,422

Other Accrued Liabilities

Other Accrued Liabilities	12 Months Ended
	Dec. 31, 2015
Other Accrued Liabilities	5. Other Accrued Liabilities Other accrued liabilities at December 31, 2015 and 2014 were as follows (in thousands): December 31, 2015 2014 Accrued product costs $ 446 $ 2,009 Accrued selling and marketing expenses 1,931 1,210 Accrued general and administrative expenses 643 466 Accrued rebates, allowances and returns 1,878 986 Interest payable — convertible senior notes 1,182 — GSK liability — current portion 923 — Other liabilities 607 446 Total other accrued liabilities $ 7,610 $ 5,117

Restructuring and Severance

Restructuring and Severance	12 Months Ended
	Dec. 31, 2015
Restructuring and Severance	6. Restructuring and Severance On May 31, 2012, the Company adopted the XenoPort Amended and Restated 2012 Severance Plan, or the 2012 Severance Plan, for the benefit of the Company’s non-executive employees. Under the terms of the 2012 Severance Plan, a non-executive employee terminated by the Company because of elimination of his or her position is eligible to receive continuation of medical insurance under COBRA and specified severance payments based on the employee’s level and years of service with the Company. The Company accounts for employee termination benefits in accordance with the provisions of the Compensation-Nonretirement Postemployment Benefits On June 14, 2013, the Company implemented a reduction in force that included the elimination of certain non-executive positions as the Company completed certain work projects on its AP development program. As a result, the Company recorded severance benefits charges of $703,000 in 2013, which were included in the “Research and development” line of the “Operating expenses” section of the Company’s statements of comprehensive loss. As of December 31, 2015 and 2014, there were no associated liability balances. On September 29, 2015, the Company implemented a restructuring plan in connection with its strategic shift to focus on the commercialization of HORIZANT and its decision to discontinue internal development of XP23829. This restructuring plan resulted in a reduction in force of approximately 25 employees and the recording of $1,671,000 in restructuring charges in the year ended December 31, 2015, of which $685,000 was recorded as “Research and development” expense and $986,000 was recorded as “Selling, general and administrative” expense. The restructuring charges related to severance benefits that were based upon existing severance agreements, including the 2012 Severance Plan. The Company paid or settled $767,000 in 2015, with the remaining $904,000 included within “Accrued compensation” on its balance sheet as of December 31, 2015 and estimated to be substantially paid by the first quarter of 2016. In connection with the strategic shift, Ronald W. Barrett, Ph.D., retired as Chief Executive Officer and as a Director of the Company, effective on September 29, 2015. Dr. Barrett’s retirement resulted in the recording of $1,225,000 in severance benefits in the year ended December 31, 2015, all of which was recorded as “Selling, general and administrative” expense and were based upon his existing Severance Rights Agreement. The Company paid or settled $147,000 in 2015, with the remaining $1,078,000 included within “Accrued compensation” on its balance sheet as of December 31, 2015 and estimated to be substantially paid by the first quarter of 2017.

Convertible Senior Notes

Convertible Senior Notes	12 Months Ended
	Dec. 31, 2015
Convertible Senior Notes	7. Convertible Senior Notes On February 3, 2015, the Company completed a private placement of $115,000,000 aggregate principal amount of the 2022 Notes. The net proceeds from the offering of the 2022 Notes were $111,327,000, after deducting the initial purchaser’s discount and debt issuance costs payable by the Company. Beginning on August 1, 2015, interest on the 2022 Notes is payable semi-annually in cash in arrears on February 1 and August 1 of each year, at a rate of 2.50% per year. The 2022 Notes mature on February 1, 2022, unless earlier converted or repurchased. The 2022 Notes are not redeemable prior to the maturity date. Holders may convert all or any portion of their 2022 Notes at their option at any time prior to the close of business on the business day immediately preceding the maturity date. The 2022 Notes are convertible at an initial conversion rate of 93.2945 shares of the Company’s common stock per $1,000 principal amount of the 2022 Notes, subject to adjustment, which is equal to an initial conversion price of approximately $10.72 per share of common stock. Upon conversion, the 2022 Notes may be settled in shares of the Company’s common stock, together with a cash payment in lieu of delivering any fractional share. The conversion rate will be subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that may occur prior to the maturity date, the Company will increase the conversion rate for a holder who elects to convert its 2022 Notes in connection with such a corporate event in certain circumstances. If the Company undergoes a fundamental change, which would include specified change of control transactions, or liquidation or dissolution or the Company’s common stock ceasing to be listed or quoted on specified national securities exchanges, and the fundamental change occurs prior to the maturity date of the 2022 Notes, holders of the 2022 Notes may require the Company to repurchase all or part of their 2022 Notes at a repurchase price equal to 100% of the principal amount of the 2022 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. As of December 31, 2015, the outstanding principal balance on the 2022 Notes was $115,000,000 and 10,728,867 shares of the Company’s common stock were issuable upon conversion of the 2022 Notes. The 2022 Notes are accounted for in accordance with ASC Subtopic 470-20, Debt with Conversion and Other Options The Company incurred $568,000 in debt issuance costs in connection with the issuance of the 2022 Notes, which are being amortized through the maturity date through the application of the interest method and reported as interest expense. In accordance with ASU No. 2015-03, the Company has presented debt issuance costs as a direct deduction from the carrying value of the 2022 Notes. As of December 31, 2015, the 2022 Notes were reported at their current carrying value of $111.8 million and which had a fair value of approximately $93.9 million based on Level 2 available market information.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies	8. Commitments and Contingencies Operating Leases The Company leases office space at 3410 Central Expressway, Santa Clara, California, the 3410 Lease, that commenced in December 2001 and will expire on May 31, 2016. In connection with the 3410 Lease, the Company entered into a letter of credit agreement of $1,500,000 in December 2006. The fair value of the certificate of deposit is presented in “Prepaids and other current assets” and “Restricted investments and other assets” on the balance sheet at $1,500,000 as of December 31, 2015 and 2014, respectively. This letter of credit is required until the termination of the lease. The Company recognized rent expense on a straight-line basis over the applicable lease terms. Rent expense was $2,495,000, $2,615,000 and $2,626,000 for the years ended December 31, 2015, 2014 and 2013, respectively. Deferred rent asset of $53,000 and $180,000 at December 31, 2015 and 2014, respectively, represented the difference between rent expense recognized and actual cash payments related to the Company’s operating leases. At December 31, 2015, deferred rent was comprised solely of a current deferred rent asset of $53,000. At December 31, 2014, deferred rent was comprised of a current deferred rent asset of $127,000 and a noncurrent deferred rent asset of $53,000. At December 31, 2015, future minimum payments under the Company’s non-cancelable facility operating lease were as follows (in thousands): Year ended December 31: 2016 $ 789 Total minimum lease payments $ 789 The Company began leasing fleet vehicles for its sales force in 2015. Each fleet vehicle is subject to an initial one year lease term, with a month-to-month renewal option thereafter. These leases are classified as operating leases. Rent expense for these leases was $649,000 for the year ended December 31, 2015. Future minimum payments are based on minimum amounts due during the initial one-year lease term. At December 31, 2015, future minimum payments under the Company’s non-cancelable fleet operating lease were as follows (in thousands): Year ended December 31: 2016 $ 489 2017 39 Total minimum lease payments $ 528 Guarantees and Indemnifications The Company, as permitted under Delaware law and in accordance with its bylaws, indemnifies its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company’s request in such capacity. The term of the indemnification period is for the officer’s or director’s lifetime. The Company may terminate the indemnification agreements with its officers and directors upon 90 days’ written notice, but termination will not affect claims for indemnification relating to events occurring prior to the effective date of termination. The maximum amount of potential future indemnification is unlimited; however, the Company has a director and officer insurance policy that limits its exposure and may enable it to recover a portion of any future amounts paid. The Company believes the fair value of these indemnification agreements is minimal. Accordingly, the Company had not recorded any liabilities for these agreements as of December 31, 2015.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity	9. Stockholders’ Equity Common Stock On May 19, 2015, the Company’s stockholders approved an amendment to the Company’s Amended and Restated Certificate of Incorporation to increase the number of authorized shares of the Company’s common stock from 100,000,000 shares to 200,000,000 shares. The increase in the number of authorized shares of the Company’s common stock was effected pursuant to a Certificate of Amendment of Amended and Restated Certificate of Incorporation filed with the Secretary of State of the State of Delaware on May 19, 2015 and was effective as of such date. On January 29, 2014, the Company completed an underwritten public offering of 12,000,000 shares of its common stock at a price to the public of $6.00 per share. Net cash proceeds from the public offering were $67,300,000, after deducting the underwriting discounts and commissions and offering expenses payable by the Company. On February 21, 2014, the underwriters exercised in full their option to purchase 1,800,000 additional shares resulting in additional net cash proceeds of $10,100,000, after deducting the underwriting discounts and commissions and offering expenses payable by the Company. Stockholders’ Rights Plan On December 16, 2005, the Company adopted a preferred stock rights plan, or the Rights Plan, pursuant to which each share of the Company’s common stock outstanding has attached to it a preferred stock purchase right, or a right, that confers the right to purchase one one-hundredth of a share of Series A junior participating preferred stock at an exercise price of $140.00 per right, subject to adjustment, and will be exercisable only if a person or group acquires beneficial ownership of 15% or more of the Company’s common stock or announces a tender offer for 15% or more of the Company’s common stock. If such a person acquires 15% or more of the Company’s common stock, all rights holders, except such person, will be entitled to acquire the Company’s common stock at a discount through the exercise of the right. The rights plan has been designed to discourage acquisitions of more than 15% of the Company’s common stock without negotiations with the board of directors. The rights expired on January 13, 2016. The rights trade with the Company’s common stock, unless and until they are separated upon the occurrence of certain future events. The board of directors may terminate the rights plan at any time or redeem the rights prior to the time the rights are triggered. On January 29, 2015, the Company entered into an amendment to the Rights Plan. The amendment was entered into in connection with the 2022 Notes offering (described in Note 7) and accommodates the structure of a blocker in the 2022 Notes such that no holder of the 2022 Notes will be entitled to receive shares of the Company’s common stock deliverable upon conversion of the Notes to the extent, that such receipt would cause the holder to become, directly or indirectly, the beneficial owner of more than 14.99% of the shares of the Company’s common stock outstanding at such time. Equity Incentive Plans On June 11, 2014, the Company’s stockholders approved the 2014 Equity Incentive Plan, or the 2014 Plan. The 2014 Plan is intended to be the successor to the 2005 Equity Incentive Plan, the 2005 Non-Employee Directors’ Stock Option Plan and the 2010 Inducement Award Plan, collectively referred to as the Prior Plans. All outstanding stock awards granted under the Prior Plans will continue to be subject to the terms and conditions as set forth in the agreements evidencing such stock awards. 2005 Equity Incentive Plan In January 2005, the Company’s board of directors adopted the 2005 Equity Incentive Plan, or the 2005 Plan. Under the terms of the 2005 Plan, options vest as determined by the board of directors, generally at the rate of 25% at the end of the first year, with the remaining balance vesting ratably over the next three years for initial employee grants and ratably over four years for subsequent grants. Options granted under the 2005 Plan expire no more than ten years after the date of grant. In January 2007, the Company’s board of directors approved the use of grants of restricted stock units to employees, directors or consultants under the 2005 Plan as part of the Company’s long-term incentive compensation program. Restricted stock units have no exercise price, are valued using the closing market price on the date of grant and vest as determined by the board of directors, typically either: (i) in annual tranches over a four-year period at the rate of 25% at the end of each year; (ii) in annual tranches over a three-year period at the rate of 25%, 25% and 50%, respectively, at the end of each year; (iii) in annual tranches over a three-year period at 50% on the second anniversary and 50% on the third year anniversary; or (iv) in one tranche on the one-year anniversary of the grant date. Employees can elect to have the Company withhold a portion of shares to pay for their payroll taxes in connection with the vesting of restricted stock units, where the Company would then make a cash payment for the associated payroll taxes on behalf of the employees, or employees can elect to make the cash payment for the associated payroll taxes. In May 2010, the Company granted performance stock unit awards to two executive employees under the 2005 Plan. Each performance stock unit award was scheduled to vest three years from the grant date, with the actual number of shares of common stock of the Company subject to issuance to be between 0% and 200% of the target amount, based on the performance of the Company’s total shareholder return as compared to the total shareholder returns of a group of pre-selected pharmaceutical companies over a performance period ending on the third anniversary of the grant date. The target amount of shares of common stock of the Company that were subject to issuance under the performance stock unit awards was 140,000, and the grant date fair value using a lattice valuation model of these performance stock unit awards was $2,675,000. In 2010, a performance stock unit award representing a target amount of 40,000 shares was cancelled due to the departure of one of the two executive employees. In 2013, 97,300 shares were cancelled based on the performance of the Company’s total shareholder return as compared to the total shareholder returns of a group of pre-selected pharmaceutical companies over the three year performance period. At December 31, 2015 and 2014, there were no shares subject to these performance stock unit awards, and the associated expense recognized in the years ended December 31, 2015, 2014 and 2013 was $0, $0 and $232,000, respectively. In February 2014, the Company granted performance stock options to its executive officers under the 2005 Plan. Each performance stock option is subject to two, equally weighted, performance conditions. One performance condition relates to the achievement of a pre-determined development criteria and the other relates to achievement of a pre-determined revenue criteria. Each performance stock option vests, if at all, upon achievement of the respective performance condition during a performance period ending on December 31, 2015. Shares associated with each performance condition vest 50% upon achievement of the performance condition, with the remaining 50% to vest on the one-year anniversary date of the initial vest date. The target amount of shares of common stock that are subject to issuance under these performance stock options was 316,000, and the grant date fair value using a Black-Scholes valuation model of these performance stock options was $1,334,000. Both performance conditions were achieved during 2015, resulting in the 50% vesting of each share. During the years ended December 31, 2015 and 2014, the Company recognized $547,000 and $445,000, respectively, in expense associated with these performance stock options. Under the terms of the 2005 Plan, the maximum number of shares that may be issued shall not exceed the total of 2,000,000, plus any shares issuable from options previously granted from the 1999 Plan at the date of the Company’s initial public offering, plus an annual increase equal to the lesser of (i) 2.5% of the total number of common shares outstanding at the end of the preceding calendar year and (ii) 2,000,000 common shares. In June 2014, in connection with the Company’s adoption of the 2014 Equity Incentive Plan, or the 2014 Plan, described below, no further awards may be granted under the 2005 Plan. Although the 2005 Plan has terminated, all outstanding options under the 2005 Plan will continue to be governed by their existing terms. 2005 Non-Employee Directors’ Stock Option Plan In January 2005, the Company’s board of directors adopted the 2005 Non-Employee Directors’ Stock Option Plan, or the 2005 Directors’ Plan, under which non-statutory options are automatically granted to non-employee directors. Before May 1, 2012, any individual who first became a non-employee director automatically received an option to purchase 25,000 shares subject to vesting in four equal successive annual installments. From May 1, 2012 to June 10, 2014, any individual who first became a non-employee director automatically received an option to purchase 30,000 shares subject to vesting in 24 successive equal monthly installments. Prior to May 1, 2012, non-employee directors serving on the date of each annual meeting of stockholders received an option to purchase 10,000 shares subject to vesting in 12 successive equal monthly installments measured from the grant date. From May 1, 2012 to June 10, 2014, non-employee directors serving on the date of each annual meeting of stockholders received an option to purchase 15,000 shares subject to vesting in 12 successive equal monthly installments measured from the grant date. Stock options were granted at exercise prices no less than the fair value on the grant date and expired no more than ten years after the date of grant. In addition, from May 1, 2012 to June 10, 2014, any individual who served as a non-employee director on the date of each annual meeting received a restricted stock unit award of 5,000 shares. These restricted stock unit awards vest in full on the one-year anniversary of the grant date. Under the terms of the 2005 Directors’ Plan, the maximum number of shares that may be issued shall not exceed the total of 150,000, plus an annual increase equal to the excess of (i) the number of shares subject to options granted in the preceding calendar year, over (ii) the number of shares added back to the share reserve from cancellations, provided that such increase shall not exceed 150,000 shares. In June 2014, in connection with the Company’s adoption of the 2014 Plan described below, no further awards may be granted under the 2005 Directors’ Plan. Although the 2005 Directors’ Plan has terminated, all outstanding options under the 2005 Directors’ Plan will continue to be governed by their existing terms. 2010 Inducement Award Plan In May 2010, the Company’s board of directors adopted the 2010 Inducement Award Plan, or the 2010 Inducement Plan. Under the terms of the 2010 Inducement Plan, options vest as determined by the board of directors or the compensation committee of the board of directors, generally at the rate of 25% at the end of the first year, with the remaining balance vesting ratably over the next three years. Options granted under the 2010 Inducement Plan expire no more than ten years after the date of grant. Restricted stock units have no exercise price, are valued using the closing market price on the date of grant and vest as determined by the board of directors or the compensation committee of the board of directors, typically in annual tranches over a four-year period at the rate of 25% at the end of each year. A total of 350,000 shares of common stock were initially authorized for issuance under the 2010 Inducement Plan, and an additional 625,000 shares were authorized for issuance in 2011. Under the terms of the 2010 Inducement Plan, the maximum number of shares that may be issued shall not exceed the total of 975,000. In June 2014, in connection with the Company’s adoption of the 2014 Plan described below, no further awards may be granted under the 2010 Inducement Plan. Although the 2010 Inducement Plan has terminated, all outstanding options under the 2010 Inducement Plan will continue to be governed by their existing terms. 2014 Equity Incentive Plan The terms of the 2014 Plan provide for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, other stock awards and performance awards that may be settled in cash, stock or other property, that may be granted by the board of directors or the independent compensation committee of the board of directors. Options granted may be either incentive stock options or non-statutory stock options. Incentive stock options may be granted to employees with exercise prices of no less than the fair value, and non-statutory options may be granted to employees, directors or consultants at exercise prices of no less than fair value, of the common stock on the grant date. Options vest as determined by the board of directors or the compensation committee of the board of directors, generally at the rate of 25% at the end of the first year, with the remaining balance vesting ratably over the next three years and ratably over four years for subsequent grants. Options granted under the 2014 Plan expire no more than ten years after the date of grant. The terms of the 2014 Plan also provides for the grant of restricted awards, which have no exercise price, are valued using the closing market price on the date of grant and vest as determined by the board of directors or the compensation committee of the board of directors, typically in annual tranches over a four-year period at the rate of 25% at the end of each year. The 2014 Plan also provides for the grant of performance stock or cash awards that may vest or become payable upon the attainment of pre-determined performance goals during a performance period. In January 2015, the Company granted stock options subject to market conditions to its executive officers under the 2014 Plan. Each market condition stock option is subject to two, equally weighted, market conditions. One market condition vests if the Company’s common stock is greater or equal to $11.00 per share for 30 consecutive trading days ending on or prior to December 31, 2016. The other market condition vests if the Company’s common stock is greater or equal to $13.00 per share for 30 consecutive trading days ending on or prior to December 31, 2018. The Company estimated the fair value of these market condition stock options using a Monte Carlo simulation model, which involves a series of random scenarios that may take different future price paths over the award’s contractual life. The grant date fair value is determined by taking the average of the grant date fair values under each of many Monte Carlo simulations. The determination of the fair value is affected by the Company’s stock price, as well as assumptions regarding a number of complex and subjective variables including its expected stock price volatility over the expected term of the awards, risk-free interest rates, and estimated forfeitures. The target amount of shares of common stock that are subject to issuance under these market condition stock options was 225,000 shares, and the grant date fair value using the Monte Carlo simulation model was $1,216,000. During the year ended December 31, 2015, the Company recognized $1,156,000 in expense associated with these market condition stock options. Under the terms of the 2014 Plan, any individual who first becomes a non-employee director automatically receives an option to purchase 30,000 shares subject to vesting in 24 successive equal monthly installments. Non-employee directors serving on the date of each annual meeting of stockholders receives an option to purchase 15,000 shares subject to vesting in 12 successive equal monthly installments measured from the grant date. Stock options are granted at exercise prices no less than the fair value on the grant date and expire no more than ten years after the date of grant. In addition, any individual who serves as a non-employee director on the date of each annual meeting receives a restricted stock unit award of 5,000 shares. These restricted stock unit awards vest in full on the earlier of: (1) the one-year anniversary of the grant date or (2) the date of the next annual meeting following the grant date. The total number of shares of the Company’s common stock available for issuance under the 2014 Plan is initially 4,471,059 shares plus up to an additional 7,847,852 Returning Shares (as defined below) as such shares become available from time to time. “Returning Shares” means the shares subject to outstanding awards granted under the Prior Plans and the 1999 Stock Plan that, from and after the effective date of the 2014 Plan: (a) expire or terminate for any reason prior to exercise or settlement; (b) are forfeited, cancelled or otherwise returned to the Company because of the failure to meet a contingency or condition required for the vesting of such shares; or (c) other than with respect to outstanding stock options and stock appreciation rights granted under the Prior Plans or the 1999 Stock Plan with an exercise or strike price of at least 100% of the fair market value of the underlying Company common stock on the date of grant, are reacquired or withheld (or not issued) by the Company to satisfy a tax withholding obligation in connection with a stock award. Eligible participants under the 2014 Plan include the Company’s employees and directors, including the Company’s executive officers and consultants. At December 31, 2015, there were 2,900,588 shares remaining and available for future grant under the 2014 Plan. A summary of option activity as of and for the year ended December 31, 2015 is presented below: Shares Weighted- Average Weighted- Average Aggregrate Intrinsic Value (In Thousands) Outstanding at January 1, 2014 6,628,612 $ 14.49 Options granted 2,367,410 8.64 Options cancelled (1,346,627 ) 11.77 Options exercised (368,236 ) 5.24 Outstanding at December 31, 2015 7,281,159 13.55 5.91 $ 452 Exercisable at December 31, 2015 4,812,353 $ 16.52 4.42 $ 354 A summary of restricted stock unit activity for the year ended December 31, 2015 is presented below: Shares Weighted- Average Outstanding at January 1, 2015 1,021,344 $ 6.70 Awards granted 857,012 5.43 Awards cancelled (226,340 ) 7.62 Awards vested (458,102 ) 6.25 Outstanding at December 31, 2015 1,193,914 $ 5.79 The weighted-average grant date fair values of options granted in the years ended December 31, 2015, 2014 and 2013 were $5.48, $4.05 and $5.22 per share, respectively. The weighted-average grant date fair values of restricted stock units granted in the years ended December 31, 2015, 2014 and 2013 were $5.44, $6.07 and $8.13 per share, respectively. The aggregate intrinsic value of all options outstanding and exercisable at December 31, 2015 was based on a closing stock price of $5.49. The total intrinsic value of options exercised in the years ended December 31, 2015, 2014 and 2013 was $683,000, $758,000 and $304,000, respectively. The total fair value of options that vested in the years ended December 31, 2015, 2014 and 2013 was $6,904,000, $4,572,000 and $4,786,000, respectively. The total fair value of restricted stock units that vested in the years ended December 31, 2015, 2014 and 2013 was $2,864,000, $4,656,700 and $6,202,000, respectively. As of December 31, 2015, the total compensation cost related to 2,468,806 unvested options and unvested awards covering 1,193,914 shares not yet recognized was $15,375,000. This amount will be recognized over an estimated weighted-average amortization period of 2.68 years. Employee Stock Purchase Plan In January 2005, the Company adopted the 2005 Employee Stock Purchase Plan, or 2005 ESPP, which became effective in June 2005 in connection with its initial public offering. The 2005 ESPP allowed for qualified employees to purchase shares of its common stock at a price equal to the lower of 85% of the closing price of the Company’s common stock at the beginning of the offering period or 85% of the closing price of the Company’s common stock on the date of purchase. A total of 250,000 shares of the Company’s common stock were initially authorized for issuance under the 2005 ESPP. The Company’s board of directors could increase the share reserve of the ESPP as of each January 1, from January 1, 2006 through January 1, 2015, by an amount determined by its board; provided, however that the increase for any year could not exceed the lesser of (1) 1% of the total number of shares of the Company’s common stock outstanding on the December 31st of the preceding calendar year or (2) 250,000 shares. During the years ended December 31, 2015, 2014 and 2013, 236,657 shares, 227,720 shares and 142,455 shares, respectively, were purchased under the 2005 ESPP. In May 2015, in connection with the adoption of the 2015 Employee Stock Purchase Plan, described below, no further shares may be granted under the 2005 ESPP. On May 19, 2015, the Company’s stockholders approved the XenoPort, Inc. 2015 Employee Stock Purchase Plan, or the 2015 ESPP, which became effective on May 19, 2015. The Company’s prior plan, the 2005 ESPP, was terminated as a result of this approval. The 2015 ESPP was implemented by offerings of rights to purchase the Company’s common stock to all eligible employees. The plan administrator will determine the duration of each offering period, provided that in no event may an offering period exceed 27 months. Each offering period will have one or more purchase dates, as determined by the plan administrator prior to the commencement of the offering period. The purchase price per share at which shares of the Company’s common stock are purchased on each purchase date during an offering period will not be less than the lower of (i) 85% of the fair market value of a share of the Company’s common stock on the first day of the offering period or (ii) 85% of the fair market value of a share of the Company’s common stock on the purchase date. The maximum number of shares of the Company’s common stock that may be issued under the 2015 ESPP is 4,000,000 shares, subject to adjustment for certain changes in the Company’s capitalization. During the year ended December 31, 2015, 89,254 shares were purchased under the 2015 ESPP. At December 31, 2015, there were 3,910,746 shares available for future grant under the 2015 ESPP.

Preferred Stock

Preferred Stock	12 Months Ended
	Dec. 31, 2015
Preferred Stock	10. Preferred Stock At December 31, 2015 and 2014, the Company was authorized to issue 5,000,000 shares of preferred stock, of which 1,000,000 shares were authorized for issuance as Series A junior participating preferred stock.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Taxes	11. Income Taxes Deferred income taxes reflect the net tax effects of net operating loss, or NOL, and tax credit carryovers and temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s net deferred tax assets were as follows (in thousands): December 31, 2015 2014 Net operating loss carryforwards $ 209,834 $ 182,791 Research credit carryforwards 32,104 31,249 Capitalized research and development 1,188 3,760 Deferred revenue 4,139 4,824 Stock awards 16,371 16,901 Other 2,334 3,043 Total net deferred tax assets 265,970 242,568 Valuation allowance $ (265,970 ) $ (242,568 ) Net deferred tax assets $ — $ — Realization of net deferred tax assets is dependent upon the Company generating future taxable income, the timing and amount of which are uncertain. Accordingly, the net deferred tax assets have been fully offset by a valuation allowance. The valuation allowance increased by $23,402,000, $24,238,000 and $27,210,000 during 2015, 2014 and 2013, respectively. As of December 31, 2015, the Company had NOL carryforwards for federal income tax purposes of $549,241,000, which expire in the years 2022 through 2035, and federal research and development tax credits of $24,713,000, which expire in the years 2021 through 2035. As of December 31, 2015, the Company had NOL carryforwards for state income tax purposes of $351,563,000, which expire in the years 2016 through 2035, and state research and development tax credits of $12,790,000, which do not expire. Approximately $529,000 of the valuation allowance for net deferred tax assets relates to benefits of stock option deductions that, when recognized, will be allocated directly to additional paid-in capital. The Company files income tax returns in the U.S. federal jurisdiction and various state jurisdictions. To date, the Company has not been audited by the Internal Revenue Service or any state income tax jurisdiction. Tax years 2000 to 2015 remain subject to examination by the U.S. federal jurisdiction and various state jurisdictions. NOL carryforwards created by excess tax benefits from stock awards are not recorded as deferred tax assets. To the extent such NOL carryforwards are utilized, the benefits realized will increase stockholders’ equity. The Company had $2,077,000 of excess tax benefits at December 31, 2015. Future utilization of the Company’s NOL and research credit carryforwards to offset its future taxable income may be subject to substantial annual limitation due to the ownership change limitations provided by the Internal Revenue Code Section 382. Such annual limitation could result in the expiration of the NOL and research credit carryforwards before utilization. The Company completed an updated Section 382 analysis regarding the limitation of the NOL and tax credit carryforwards as of December 31, 2015. Based upon the analysis, the Company has not had an ownership change as of December 31, 2015 that would limit the use of its NOL and tax credit carryforwards. On December 31, 2015, the California Supreme Court overturned the California Appellate court decision on The Gillette Company et al. v. California Franchise Tax Board. The court held that the taxpayers couldn’t elect an evenly weighted, three-factor apportionment formula pursuant to the Multistate Tax Compact, or MTC. The Company had elected the three-factor apportionment formula pursuant to the MTC for 2013 and 2014. As a result of the California Supreme Court decision, the Company is reducing its deferred tax assets and offsetting valuation allowance related to the California NOL calculated in 2013 and 2014 pursuant to the MTC election. The Company’s unrecognized tax benefits relate to state research and development tax credits claimed on the Company’s state tax returns. The state research and development tax credits have not been utilized, are fully offset by a valuation allowance and currently have no tax impact. A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is as follows (in thousands): January 1, 2013 $ — Increases related to prior year tax positions 1,340 December 31, 2013 1,340 Increases related to prior year tax positions 39 December 31, 2014 1,379 Increases related to current year tax positions 40 December 31, 2015 $ 1,419

Quarterly Financial Data (Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data (Unaudited)	12. Quarterly Financial Data (Unaudited) The following table summarizes the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share data): Quarter Ended Dec. 31, Sept. 30, June 30, March 31, Dec. 31, Sept. 30, June 30, March 31, Selected Quarterly Data: Total revenues $ 14,079 $ 11,393 $ 8,621 $ 7,067 $ 7,091 $ 31,068 $ 5,334 $ 3,375 Gross profit(2) $ 12,898 $ 10,302 $ 7,708 $ 6,185 $ 6,143 $ 5,088 $ 4,321 $ 2,527 Net income (loss) $ (13,359 ) $ (24,064 ) $ (24,481 ) $ (20,409 ) $ (17,657 ) $ 8,259 $ (19,387 ) $ (20,548 ) Basic and diluted net income (loss) per share $ (0.21 ) $ (0.38 ) $ (0.39 ) $ (0.33 ) $ (0.28 ) $ 0.13 $ (0.31 ) $ (0.36 ) (1) Total revenues and net income was primarily from the recognition of $25,000,000 in collaboration revenue resulting from the Indivior licensing agreement (see Note 2 for more information). (2) Gross profit relates solely to HORIZANT drug product sales.

Organization and Summary of S19

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Basis of Preparation	Basis of Preparation The Company’s financial statements are prepared in accordance with the Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or the Codification, which is the single source of authoritative U.S. generally accepted accounting principles, or GAAP.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from these estimates.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of certain of the Company’s financial instruments, including cash and cash equivalents and short-term investments, restricted investments, accounts receivables and accounts payables, approximate fair value due to their short-term maturities. The Company accounts for the fair value of its financial instruments in accordance with the provisions of the Fair Value Measurement Fair value is the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the measurement date. The Company applies the market approach valuation technique for fair value measurements on a recurring basis and attempts to maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value into three broad levels. All of the Company’s cash equivalents and short-term investments are measured using inputs classified at Level 1 or Level 2 within the fair value hierarchy. Level 1 inputs are quoted prices in active markets for identical assets. Level 2 inputs are based upon quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Level 3 inputs are unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Where applicable, these models project future cash flows and discount the future amounts to a present value using market-based observable inputs obtained from various third-party data providers, including but not limited to, benchmark yields, interest rate curves, reported trades, broker/dealer quotes and market reference data.
Cash Equivalents and Short-Term Investments	Cash Equivalents and Short-Term Investments The Company considers all highly liquid investments with original maturities of 90 days or less at the time of purchase to be cash equivalents, which primarily consist of money market funds, U.S. government-sponsored agencies and corporate debt securities. Management determines the appropriate classification of securities at the time of purchase. All investments have been designated as available-for-sale. The Company views its available-for-sale portfolio as available for use in current operations. Accordingly, the Company has classified all investments as short-term, even though the stated maturity may be one year or more beyond the current balance sheet date. Available-for-sale securities are carried at estimated fair value with unrealized gains and losses reported as a component of other comprehensive loss in the statements of comprehensive loss. The cost of securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary on available-for-sale securities, if any, are recorded in interest income and expense. The cost of securities sold is based on the specific-identification method. Interest and dividends are included in interest income.
Restricted Investments	Restricted Investments Under a facilities operating lease agreement, the Company is required to secure a letter of credit with cash or securities. At December 31, 2015 and 2014, the Company recorded $1,500,000 of restricted investments related to the letter of credit (see Note 8 for more information). The $1,500,000 was classified as “Prepaids and other current assets” as of December 31, 2015 and “Restricted investments and other assets” as of December 31, 2014. In connection with the Company’s license to use radioactive materials in its research facilities, it must maintain a $225,000 letter of credit with the Radiological Health Branch of the State of California. This requirement has been fulfilled through certificates of deposit with a financial institution. The fair value of the $225,000 secured amount was classified as “Prepaids and other current assets” as of December 31, 2015 and “Restricted investments and other assets” as of December 31, 2014.
Segment Information	Segment Information The Company operates in one operating segment, which is the development and commercialization of product candidates for the treatment of neurological and other disorders, and has operations solely in the United States. To date, all of the Company’s revenues from product sales are related to sales of HORIZANT in the United States. The Company also has recognized upfront and milestone payments and royalty revenue from its partnership with Astellas Pharma Inc. and recognized upfront and additional payments from its partnership with Indivior (see Note 2 for more information on these arrangements).
Concentrations of Risk	Concentrations of Risk The Company invests cash that is not being used for operational purposes. This exposes the Company to credit risk in the event of default by the institutions holding the cash and cash equivalents and available-for-sale securities to the extent of the amounts on its balance sheets. The credit risk is mitigated by the Company’s investment policy, which allows for the purchase of low risk debt securities issued by the U.S. government, U.S. government-sponsored agencies and highly rated banks and corporations, subject to certain concentration limits. The maturities of these securities are maintained at no longer than 16 months. The Company believes its established guidelines for investment of its excess cash enhances safety and liquidity through its policies on diversification and investment maturity. Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash and cash equivalents and available-for-sale investment securities in high-credit quality debt securities issued by the U.S. government, U.S. government-sponsored enterprises and highly rated banks and corporations. The carrying amounts of cash equivalents and available-for-sale investment securities are stated at fair value. The Company is subject to credit risk from its accounts receivable related to product sales. The Company’s trade accounts receivable arises from product sales in the United States. Three wholesale distributors represented 41%, 28% and 25%, respectively, of product sales for the year ended December 31, 2015. These three customers individually comprised 38%, 31% and 22%, respectively, of accounts receivable as of December 31, 2015. Three wholesale distributors represented 41%, 28% and 26%, respectively, of product sales for the year ended December 31, 2014. These three customers individually comprised 48%, 26% and 22%, respectively, of accounts receivable as of December 31, 2014. To date, the Company has not experienced any losses with respect to the collection of its accounts receivable and believes that its accounts receivable are collectible. The Company relies on a single third-party contract manufacturer organization to manufacture HORIZANT.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation and amortization. Depreciation and amortization is computed using the straight-line method over the estimated useful lives of the respective assets, which is generally five to ten years for the Company’s laboratory equipment, furniture and fixtures and manufacturing property and equipment and generally three years for the Company’s computer equipment and software. Leasehold improvements are amortized over their estimated useful lives or the remaining lease term, whichever is shorter.
Revenue Recognition	Revenue Recognition Product Sales The Company began selling HORIZANT to wholesalers in May 2013 following the acquisition of the HORIZANT business from GSK. The Company recognizes revenue from HORIZANT drug product sales when there is persuasive evidence that an arrangement exists, delivery to the customer has occurred, the price is fixed or determinable and collectability is reasonably assured. Revenue from product sales is recorded net of estimated allowances for customer incentives such as cash discounts for prompt payment, distributor fees, expected returns, as appropriate (which are based on an analysis of historical return rates and deductions of HORIZANT, since its commercial launch by GSK in the second quarter of 2011), government rebates such as Medicaid reimbursements and patient assistance programs. Calculating certain of these items involves estimates and judgments based on contractual terms, historical utilization rates data for HORIZANT and new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future utilization rates for these programs and channel inventory data. If future actual results vary from the Company’s estimates, the Company may need to adjust these estimates, which could have an effect on net product sales and earnings in the period of adjustment. Items Deducted from Gross Product Sales Prompt Pay Discount The Company offers cash discounts to its customers, generally 2% of the sales price, as an incentive for prompt payment. Based on the Company’s commercialization experience, the Company expects customers to continue to comply with the prompt payment terms to earn the cash discount as the Company is selling HORIZANT to the same customers under similar prompt payment terms and conditions. The Company estimates cash discounts for prompt payment based on contractual terms and the Company’s historical customer utilization rates. The Company accounts for cash discounts by reducing accounts receivable by the full amount and recognizing the discount as a reduction of revenue in the same period the related revenue is recognized. Distributor Fees Under the Company’s inventory management agreements with significant wholesalers, the Company pays the wholesalers a fee primarily for distribution services as well as the maintenance of inventory levels. These distributor fees are based on a contractually determined fixed percentage of sales. The Company accrues the contractual amount and recognizes the discount as a reduction of revenue in the same period the related revenue is recognized. Product Returns The Company does not provide its customers with a general right of product return, but permits returns if the product is damaged or defective when received by the customer, or if the product has or is nearly expired. HORIZANT tablets currently have a shelf-life of 36 months from the date of manufacture. The Company will accept returns for products that will expire within six months or that have expired up to one year after their expiration dates. The Company obtained actual return history classified by the reasons for returns from GSK since GSK’s product launch in 2011, which provides a basis to reasonably estimate the Company’s future product returns. The Company estimates returns taking into consideration Company-specific adjustments to GSK’s returns history, the Company’s returns history, the shelf life of product, shipment and prescription trends and estimated distribution channel inventory levels. Government Rebates and Chargebacks The Company participates in a number of government rebate programs, such as the Medicaid Drug Rebate Program that provides assistance to eligible low-income patients based on each individual state’s guidelines regarding eligibility and services, Public Health Services or 340b programs, and the Medicare Part D Coverage Gap Discount Program, which provides rebates on prescriptions that fall within the “donut hole” coverage gap; and the Department of Veterans Affairs that offers discounts to authorized users of HORIZANT. HORIZANT is also listed on the Federal Supply Schedule, or FSS, of the General Services Administration which provides a discount to the Department of Defense, Department of Veterans Affairs, and TriCare. The Company estimates reductions to the Company’s revenues for government rebate programs based on product pricing, current rebates, GSK’s historical utilization rates, the Company’s actual utilization rates, new information regarding changes in these programs’ regulations and guidelines that would impact the amount of the actual rebates, the Company’s expectations regarding future rebates for these programs and estimated levels of inventory in the distribution channel. Patient Assistance The Company offers a co-pay card program to assist commercially insured patients with the cost of their HORIZANT related co-payments. Participating retail pharmacies get reimbursed by the Company for the amount of the co-pay assistance provided to eligible patients. The Company estimates and accrues the cost of the co-pay program based on historical and current redemption activity for this program. The Company reimburses the participating pharmacies approximately one month after the prescriptions subject to co-pay assistance are filled. Multiple-Element Arrangements Revenue arrangements are accounted for in accordance with the provisions of the Revenue Recognition-Multiple-Element Arrangements In evaluating arrangements with multiple elements, the Company considers whether components of the arrangement represent separate units of accounting based upon whether certain criteria are met, including whether the delivered element has stand-alone value to the customer and whether there is objective and reliable evidence of the fair value of the undelivered items. This evaluation requires subjective determinations and requires management to make judgments about the fair value of individual elements and whether such elements are separable from other aspects of the contractual relationship. The consideration received in such arrangements is allocated among the separate units of accounting based on the relative selling price method under which the selling price for each deliverable is determined using vendor-specific objective evidence of selling price, if it exists; otherwise, third-party evidence of selling price. If vendor-specific objective evidence and third-party evidence of selling price are not available for a deliverable, the Company will use its best estimate of the selling price for that deliverable when applying the relative selling price method. The applicable revenue recognition criteria are applied to each of the separate units. Revenues from multiple deliverables combined as a single unit of accounting are deferred and recognized over the period during which the Company remains obligated to perform services. The specific methodology for the recognition of the revenue (e.g., straight-line or according to specific performance criteria) is determined on a case-by-case basis according to the facts and circumstances applicable to a given agreement. Payments received in excess of revenues recognized are recorded as deferred revenue until such time as the revenue recognition criteria have been met. Collaboration revenue consisted of the recognition of revenues from upfront and milestone payments from the Company’s partnership with Astellas Pharma Inc. and from upfront and additional payments from its license agreement with Indivior. The Company accounts for the revenue-related activities of these collaboration agreements as follows: • Up-front, licensing-type payments. • Milestones. The Company will assess the nature of contingent payments, and appropriate accounting for, these payments on a case-by-case basis in accordance with the provisions of the Revenue Recognition • Product royalties.
Cost of Product Sales	Cost of Product Sales Cost of product sales includes direct and indirect costs to manufacture product sold, including tableting, packaging, storage, shipping and handling costs and inventory write-downs, if any, related to product sales of HORIZANT.
Accounts Receivable	Accounts Receivable Trade accounts receivable are recorded net of allowances for cash discounts for prompt payment, wholesaler discounts and chargebacks. The need for bad debt allowance is evaluated each reporting period based on the Company’s assessment of the credit worthiness of its customers.
Inventories	Inventories Inventories are stated at the lower of cost or market. Cost is determined on a first-in, first-out, or FIFO, basis. Inventories include active pharmaceutical ingredient, or API, contract manufacturing costs and overhead allocations. The Company regularly evaluates the Company’s inventories for excess quantities and obsolescence (expiration), taking into account such factors as historical and anticipated future sales compared to quantities on hand and the remaining shelf life of HORIZANT. Write-downs of inventories are considered to be permanent reductions in the cost basis of inventories. Inventories that are not expected to be consumed within 12 months following the balance sheet date are classified as long-term inventories. Inventories as of December 31, 2015 and 2014 are summarized as follows (in thousands): Year Ended 2015 2014 Raw materials $ 7,396 $ 9,273 Work in progress 134 517 Finished goods 2,119 766 Total inventory 9,649 10,556 Less: Long-term inventories 7,581 9,098 Total inventory classified as current $ 2,068 $ 1,458 Long-term inventories primarily consist of gabapentin enacarbil API used for production of HORIZANT. The Company evaluates demand for HORIZANT and expected consumption of the API based on projected sales of HORIZANT.
Research and Development	Research and Development All research and development costs, including those funded by third parties, are expensed as incurred. Research and development expenses consist of costs associated with conducting preclinical studies and clinical trials, manufacturing development efforts for clinical trials and activities related to development-related regulatory filings.
Clinical Trials	Clinical Trials The Company accrues and expenses the costs for clinical trial activities performed by third parties based upon estimates of the percentage of work completed over the life of the individual study in accordance with agreements established with contract research organizations and clinical trial sites. The Company determines the estimates through discussions with internal clinical personnel and external service providers as to progress or stage of completion of trials or services and the agreed upon fee to be paid for such services. Costs of setting up clinical trial sites for participation in the trials are expensed immediately as research and development expenses. Clinical trial site costs related to patient visits are accrued as patients’ progress through the trial and are reduced by any payments made to the clinical trial site. Non-refundable advance payments for research and development goods or services are recognized as expense as the related goods are delivered or the related services are provided in accordance with the provisions of the Research and Development Arrangements
Stock-Based Compensation	Stock-Based Compensation The Compensation — Stock Compensation The Company accounts for stock compensation arrangements to non-employees in accordance with the Equity-Based Payments to Non-Employees The effect of recording stock-based compensation under the Compensation — Stock Compensation Year Ended December 31, 2015 2014 2013 (In thousands, except per share amounts) Stock-based compensation by type of award: Stock options and awards $ 9,410 $ 8,531 $ 10,083 ESPP 768 510 461 Total stock-based compensation $ 10,178 $ 9,041 $ 10,544 Effect on basic and diluted net loss per share $ (0.16 ) $ (0.15 ) $ (0.22 ) The Company’s employee non-cash stock-based compensation was reported as follows: Year Ended December 31, 2015 2014 2013 (In thousands) Research and development $ 1,637 $ 2,062 $ 3,059 Selling, general and administrative 8,541 6,979 7,485 $ 10,178 $ 9,041 $ 10,544 Valuation Assumptions The Company estimates the fair value of its stock options without market conditions and stock purchase rights on the date of grant using a Black-Scholes valuation model that requires the input of highly subjective assumptions, including the option’s expected life and the price volatility of the underlying stock. The Company derived the expected life assumptions using data obtained from similar entities, taking into consideration factors such as industry, stage of life cycle, size and financial leverage. The Company has determined that its historical volatility can be used to derive the expected stock price volatility assumption. The Company expenses the resulting charge using the straight-line attribution method over the vesting period. Restricted stock units, or RSUs, without market conditions are measured at the fair value of the Company’s common stock on the date of grant and expensed over the period of vesting using the straight-line attribution approach. The calculation of the Black-Scholes valuations used the following weighted-average assumptions: Year Ended December 31, 2015 2014 2013 Dividend yield 0 % 0 % 0 % Volatility for options 0.76 0.81 0.82 Volatility for ESPP 0.50 0.55 0.59 Weighted-average expected life of options (years) 5.39 5.25 5.25 Weighted-average expected life of ESPP rights (years) 0.75 0.75 0.75 Risk-free interest rate for options 1.35-1.68 % 1.52-1.77 % 0.70-1.60 % Risk-free interest rate for ESPP rights 0.05-0.27 % 0.05-0.17 % 0.07-0.17 % The Company estimates the fair value of stock options and RSUs subject to market conditions using a Monte Carlo simulation model, which involves a series of random scenarios that may take different future price paths over the award’s contractual life. The grant date fair value is determined by taking the average of the grant date fair values under each of many Monte Carlo simulations. The determination of the fair value is affected by the Company’s stock price, as well as assumptions regarding a number of complex and subjective variables including its expected stock price volatility over the expected term of the awards, risk-free interest rates, and estimated forfeitures.
Income Taxes	Income Taxes Income taxes are accounted for in accordance with the Income Taxes The recognition, derecognition and measurement of a tax position is based on management’s best judgment given the facts, circumstances and information available at the reporting date. As of December 31, 2015, the Company had unrecognized tax benefits and expects no significant changes in unrecognized tax benefits in the next 12 months (see Note 11 for more information). The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense. To date, there have been no interest or penalties charged to the Company in relation to the underpayment of income taxes.
Comprehensive Loss	Comprehensive Loss The Company presents all non-owner changes in stockholders’ equity in a single continuous statement of comprehensive loss and shows: (i) each component of net loss along with total net loss; (ii) each component of other comprehensive loss along with a total for other comprehensive loss; and (iii) a total amount for comprehensive loss. The Company’s other comprehensive loss is comprised of unrealized gains (losses) on available-for-sale securities.
Advertising Costs	Advertising Costs Advertising costs, included in selling, general and administrative expenses, are charged to expense as incurred. Advertising expenses for the year ended December 31, 2015, 2014 and 2013, was $7,619,000, $9,568,000 and $8,244,000, respectively.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period without consideration for potential common shares. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares outstanding for the period plus any dilutive potential common shares for the period determined using the treasury-stock method for restricted stock units and options to purchase stock and using the if-converted method for the convertible senior notes. For purposes of this calculation, restricted stock units, options to purchase stock and convertible senior notes are considered to be potential common shares and are only included in the calculation of diluted net loss per share when their effect is dilutive. Year Ended December 31, 2015 2014 2013 (In thousands, except per share amounts) Numerator: Net loss $ (82,313 ) $ (49,333 ) $ (85,883 ) Denominator: Weighted-average common shares outstanding 63,193 60,856 47,545 Basic and diluted net loss per share $ (1.30 ) $ (0.81 ) $ (1.81 ) Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect: Restricted stock units and options to purchase common stock 8,475 7,650 6,824 Warrants outstanding — — 283 Convertible senior notes 10,729 — — 19,204 7,650 7,107 On January 29, 2014, the Company completed an underwritten public offering of 12,000,000 shares of its common stock at a price to the public of $6.00 per share. On February 21, 2014, the underwriters exercised in full their option to purchase 1,800,000 additional shares. On February 3, 2015, the Company completed a private placement of $115,000,000 aggregate principal amount of 2.50% Convertible Senior Notes due 2022, or the 2022 Notes. The 2022 Notes are convertible at an initial conversion rate of 93.2945 shares of the Company’s common stock per $1,000 principal amount of the 2022 Notes, which is equal to an initial conversion price of approximately $10.72 per share of common stock. As of December 31, 2015, 10,728,867 shares of the Company’s common stock were issuable upon conversion of the 2022 Notes (see Note 7 for more information).
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-09, Revenue from Contracts with Customers: Topic 606 Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements — Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In April 2015, the FASB issued ASU No. 2015-03, Interest — Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory In November 2015, the FASB issued ASU No. 2015-17, Income Taxes (Topic 740): Balance Sheet Classification of Deferred Taxes In January 2016, the FASB issued ASU 2016-01, Financial Instruments — Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities

Organization and Summary of S20

Organization and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Inventory	Inventories as of December 31, 2015 and 2014 are summarized as follows (in thousands): Year Ended 2015 2014 Raw materials $ 7,396 $ 9,273 Work in progress 134 517 Finished goods 2,119 766 Total inventory 9,649 10,556 Less: Long-term inventories 7,581 9,098 Total inventory classified as current $ 2,068 $ 1,458
Stock-Based Compensation by Type of Award	The effect of recording stock-based compensation under the Compensation — Stock Compensation Year Ended December 31, 2015 2014 2013 (In thousands, except per share amounts) Stock-based compensation by type of award: Stock options and awards $ 9,410 $ 8,531 $ 10,083 ESPP 768 510 461 Total stock-based compensation $ 10,178 $ 9,041 $ 10,544 Effect on basic and diluted net loss per share $ (0.16 ) $ (0.15 ) $ (0.22 )
Employee Non-Cash Stock-Based Compensation Excluding Non-Cash Stock-Based Compensation Resulting from Twenty Ten Restructuring Plan	The Company’s employee non-cash stock-based compensation was reported as follows: Year Ended December 31, 2015 2014 2013 (In thousands) Research and development $ 1,637 $ 2,062 $ 3,059 Selling, general and administrative 8,541 6,979 7,485 $ 10,178 $ 9,041 $ 10,544
Black-Scholes Valuation Assumptions to Estimates Fair Value of Stock Options and Stock Purchase Rights	The calculation of the Black-Scholes valuations used the following weighted-average assumptions: Year Ended December 31, 2015 2014 2013 Dividend yield 0 % 0 % 0 % Volatility for options 0.76 0.81 0.82 Volatility for ESPP 0.50 0.55 0.59 Weighted-average expected life of options (years) 5.39 5.25 5.25 Weighted-average expected life of ESPP rights (years) 0.75 0.75 0.75 Risk-free interest rate for options 1.35-1.68 % 1.52-1.77 % 0.70-1.60 % Risk-free interest rate for ESPP rights 0.05-0.27 % 0.05-0.17 % 0.07-0.17 %
Net Loss Per Share	Year Ended December 31, 2015 2014 2013 (In thousands, except per share amounts) Numerator: Net loss $ (82,313 ) $ (49,333 ) $ (85,883 ) Denominator: Weighted-average common shares outstanding 63,193 60,856 47,545 Basic and diluted net loss per share $ (1.30 ) $ (0.81 ) $ (1.81 ) Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect: Restricted stock units and options to purchase common stock 8,475 7,650 6,824 Warrants outstanding — — 283 Convertible senior notes 10,729 — — 19,204 7,650 7,107

License and Collaboration Agr21

License and Collaboration Agreements (Tables)	12 Months Ended
	Dec. 31, 2015
Revenue from License Agreement	The following table presents the Company’s total revenues that have been recognized during the year indicated pursuant to its current license agreements with Astellas and Indivior (in thousands): Year Ended December 31, 2015 2014 2013 Astellas $ 1,701 $ 1,695 $ 1,537 Indivior — 25,000 — $ 1,701 $ 26,695 $ 1,537

Cash and Cash Equivalents, Sh22

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments (Tables)	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents, Short-Term Investments and Restricted Investments	The following are summaries of cash and cash equivalents, short-term investments and restricted investments (in thousands): Cost Gross Gross Estimated As of December 31, 2015: Cash $ 5,311 $ — $ — $ 5,311 Money market funds 17,261 — — 17,261 U.S. government-sponsored agencies 12,249 1 — 12,250 Corporate debt securities 104,618 63 (17 ) 104,664 Certificates of deposit 1,725 — — 1,725 $ 141,164 $ 64 $ (17 ) $ 141,211 Reported as: Cash and cash equivalents $ 61,317 Short-term investments 78,169 Restricted investments(1) 1,725 $ 141,211 Cost Gross Gross Estimated As of December 31, 2014: Cash $ 3,383 $ — $ — $ 3,383 Money market funds 8,576 — — 8,576 U.S. government-sponsored agencies 2,000 — (2 ) 1,998 Corporate debt securities 88,127 12 (40 ) 88,099 Certificates of deposit 1,725 — — 1,725 $ 103,811 $ 12 $ (42 ) $ 103,781 Reported as: Cash and cash equivalents $ 11,958 Short-term investments 90,098 Restricted investments(1) 1,725 $ 103,781 (1) Included in “Prepaids and other current assets” as of December 31, 2015 and “Restricted investments and other assets” as of December 31, 2014.
Available-For-Sale Investments Measured at Fair Value	Fair Value Measurements at Reporting Date Using Description Total As of 2015 Quoted Prices in Active Markets for Identical (Level 1) Significant Other (Level 2) Significant (Level 3) Money market funds $ 17,261 $ 17,261 $ — $ — U.S. government-sponsored agencies 12,250 — 12,250 — Corporate debt securities 104,664 — 104,664 — Certificates of deposit 1,725 — 1,725 — Total $ 135,900 $ 17,261 $ 118,639 $ — Fair Value Measurements at Reporting Date Using Description Total As of Quoted Prices in Active Markets for Identical (Level 1) Significant (Level 2) Significant (Level 3) Money market funds $ 8,576 $ 8,576 $ — $ — U.S. government-sponsored agencies 1,998 — 1,998 — Corporate debt securities 88,099 — 88,099 — Certificates of deposit 1,725 — 1,725 — Total $ 100,398 $ 8,576 $ 91,822 $ —

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2015
Property and Equipment	Property and equipment at December 31, 2015 and 2014 consisted of the following (in thousands): December 31, 2015 2014 Laboratory equipment $ 9,878 $ 10,561 Manufacturing property and equipment 1,980 1,975 Furniture and fixtures 1,076 1,076 Computer equipment and software 5,482 5,656 Leasehold improvements 3,405 3,405 21,821 22,673 Less: Accumulated depreciation and amortization (20,029 ) (20,251 ) Property and equipment, net $ 1,792 $ 2,422

Other Accrued Liabilities (Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Other Accrued Liabilities	Other accrued liabilities at December 31, 2015 and 2014 were as follows (in thousands): December 31, 2015 2014 Accrued product costs $ 446 $ 2,009 Accrued selling and marketing expenses 1,931 1,210 Accrued general and administrative expenses 643 466 Accrued rebates, allowances and returns 1,878 986 Interest payable — convertible senior notes 1,182 — GSK liability — current portion 923 — Other liabilities 607 446 Total other accrued liabilities $ 7,610 $ 5,117

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Non-cancelable Facility Operating Lease
Future Minimum Payments under Operating Lease	At December 31, 2015, future minimum payments under the Company’s non-cancelable facility operating lease were as follows (in thousands): Year ended December 31: 2016 $ 789 Total minimum lease payments $ 789
Non-cancelable Fleet Operating Lease
Future Minimum Payments under Operating Lease	At December 31, 2015, future minimum payments under the Company’s non-cancelable fleet operating lease were as follows (in thousands): Year ended December 31: 2016 $ 489 2017 39 Total minimum lease payments $ 528

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Option Activity	A summary of option activity as of and for the year ended December 31, 2015 is presented below: Shares Weighted- Average Weighted- Average Aggregrate Intrinsic Value (In Thousands) Outstanding at January 1, 2014 6,628,612 $ 14.49 Options granted 2,367,410 8.64 Options cancelled (1,346,627 ) 11.77 Options exercised (368,236 ) 5.24 Outstanding at December 31, 2015 7,281,159 13.55 5.91 $ 452 Exercisable at December 31, 2015 4,812,353 $ 16.52 4.42 $ 354
Restricted Stock Unit Activity	A summary of restricted stock unit activity for the year ended December 31, 2015 is presented below: Shares Weighted- Average Outstanding at January 1, 2015 1,021,344 $ 6.70 Awards granted 857,012 5.43 Awards cancelled (226,340 ) 7.62 Awards vested (458,102 ) 6.25 Outstanding at December 31, 2015 1,193,914 $ 5.79

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Significant Components of Net Deferred Tax Assets	Significant components of the Company’s net deferred tax assets were as follows (in thousands): December 31, 2015 2014 Net operating loss carryforwards $ 209,834 $ 182,791 Research credit carryforwards 32,104 31,249 Capitalized research and development 1,188 3,760 Deferred revenue 4,139 4,824 Stock awards 16,371 16,901 Other 2,334 3,043 Total net deferred tax assets 265,970 242,568 Valuation allowance $ (265,970 ) $ (242,568 ) Net deferred tax assets $ — $ —
Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits	A reconciliation of the Company’s beginning and ending amount of unrecognized tax benefits is as follows (in thousands): January 1, 2013 $ — Increases related to prior year tax positions 1,340 December 31, 2013 1,340 Increases related to prior year tax positions 39 December 31, 2014 1,379 Increases related to current year tax positions 40 December 31, 2015 $ 1,419

Quarterly Financial Data (Una28

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Data	The following table summarizes the unaudited quarterly financial data for the last two fiscal years (in thousands, except per share data): Quarter Ended Dec. 31, Sept. 30, June 30, March 31, Dec. 31, Sept. 30, June 30, March 31, Selected Quarterly Data: Total revenues $ 14,079 $ 11,393 $ 8,621 $ 7,067 $ 7,091 $ 31,068 $ 5,334 $ 3,375 Gross profit(2) $ 12,898 $ 10,302 $ 7,708 $ 6,185 $ 6,143 $ 5,088 $ 4,321 $ 2,527 Net income (loss) $ (13,359 ) $ (24,064 ) $ (24,481 ) $ (20,409 ) $ (17,657 ) $ 8,259 $ (19,387 ) $ (20,548 ) Basic and diluted net income (loss) per share $ (0.21 ) $ (0.38 ) $ (0.39 ) $ (0.33 ) $ (0.28 ) $ 0.13 $ (0.31 ) $ (0.36 ) (1) Total revenues and net income was primarily from the recognition of $25,000,000 in collaboration revenue resulting from the Indivior licensing agreement (see Note 2 for more information). (2) Gross profit relates solely to HORIZANT drug product sales.

Organization and Summary of S29

Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	Feb. 03, 2015USD ($)$ / shares	Jan. 29, 2014$ / sharesshares	Mar. 31, 2015USD ($)	Dec. 31, 2015USD ($)CustomerDistributorSegmentshares	Dec. 31, 2014USD ($)CustomerDistributor	Dec. 31, 2013USD ($)	Feb. 21, 2014shares	Dec. 31, 2006USD ($)
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Payment for inventory of gabapentin enacarbil in GSK's possession, Year 1				$ 1,000,000
Payment for inventory of gabapentin enacarbil in GSK's possession, Year 2				1,000,000
Payment for inventory of gabapentin enacarbil in GSK's possession, Year 3				1,000,000
Payment for inventory of gabapentin enacarbil in GSK's possession, Year 4				1,000,000
Payment for inventory of gabapentin enacarbil in GSK's possession, Year 5				1,000,000
Payment for inventory of gabapentin enacarbil in GSK's possession, after year 5				$ 1,000,000
Long term commitment period				6 years
Long term commitment effective period				2,016
Letter of credit pledged				$ 225,000				$ 1,500,000
Number of operating segment | Segment				1
Low risk debt securities, maturity period				16 months
Cash discount offers to customers				2.00%
Advertising expenses				$ 7,619,000	$ 9,568,000	$ 8,244,000
Underwriters exercised the full option to purchase additional shares | shares							1,800,000
Glaxo Group Limited | Other Accrued Liabilities
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
GSK liability, current portion				923,000
Glaxo Group Limited | Other Noncurrent Liabilities
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
GSK liability, noncurrent portion				$ 2,918,000	$ 3,269,000
Computer Equipment and Software
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Property and equipment estimated useful lives				3 years
Sales Revenue, Net
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Number of wholesale distributors | Distributor				3	3
Sales Revenue, Net | Customer Concentration Risk | Wholesale Distributor One
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Concentration risk, percentage				41.00%	41.00%
Sales Revenue, Net | Customer Concentration Risk | Wholesale Distributor Two
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Concentration risk, percentage				28.00%	28.00%
Sales Revenue, Net | Customer Concentration Risk | Wholesale Distributor Three
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Concentration risk, percentage				25.00%	26.00%
Accounts Receivable
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Number of customers | Customer				3	3
Accounts Receivable | Customer Concentration Risk | Wholesale Distributor One
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Concentration risk, percentage				38.00%	48.00%
Accounts Receivable | Customer Concentration Risk | Wholesale Distributor Two
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Concentration risk, percentage				31.00%	26.00%
Accounts Receivable | Customer Concentration Risk | Wholesale Distributor Three
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Concentration risk, percentage				22.00%	22.00%
Certificates of deposit
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Restricted investments				$ 225,000	$ 225,000
Deposits on Leased Facilities
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Restricted investments				$ 1,500,000	$ 1,500,000
Maximum
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Maturity period of highly liquid investments classified as cash equivalents				90 days
Maximum | Furniture, Fixtures and Equipment
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Property and equipment estimated useful lives				10 years
Minimum | Furniture, Fixtures and Equipment
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Property and equipment estimated useful lives				5 years
Convertible Senior Notes Due 2022
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Convertible senior notes, principal offer amount	$ 115,000,000			$ 115,000,000
Convertible senior notes, stated interest rate	2.50%
Convertible senior notes, due date	2,022
Convertible senior notes, conversion share per 1000 principal amount	93.2945
Convertible senior notes, initial conversion price | $ / shares	$ 10.72
Common stock issuable upon conversion of convertible senior notes | shares				10,728,867
Debt issuance cost			$ 568,000	$ 568,000
Underwritten Public Offering
Organization and Summary of Significant Accounting Policies Disclosure [Line Items]
Common stock issued in underwritten public offering | shares		12,000,000
Common stock price | $ / shares		$ 6

Inventory (Detail)

Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Inventory Disclosure [Abstract]
Raw materials	$ 7,396	$ 9,273
Work in progress	134	517
Finished goods	2,119	766
Total inventory	9,649	10,556
Less: Long-term inventories	7,581	9,098
Total inventory classified as current	$ 2,068	$ 1,458

Stock-Based Compensation by Typ

Stock-Based Compensation by Type of Award (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 10,178	$ 9,041	$ 10,544
Effect on basic and diluted net loss per share	$ (0.16)	$ (0.15)	$ (0.22)
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 9,410	$ 8,531	$ 10,083
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 768	$ 510	$ 461

Employee Non-Cash Stock-Based C

Employee Non-Cash Stock-Based Compensation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Non-cash stock-based compensation	$ 10,178	$ 9,041	$ 10,544
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Non-cash stock-based compensation	1,637	2,062	3,059
Selling, general and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Non-cash stock-based compensation	$ 8,541	$ 6,979	$ 7,485

Black-Scholes Valuation Assumpt

Black-Scholes Valuation Assumptions to Estimates Fair Value of Stock Options and Stock Purchase Rights (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility rate	0.76%	0.81%	0.82%
Weighted-average expected life	5 years 4 months 21 days	5 years 3 months	5 years 3 months
Risk-free interest rate, minimum	1.35%	1.52%	0.70%
Risk-free interest rate, maximum	1.68%	1.77%	1.60%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility rate	0.50%	0.55%	0.59%
Weighted-average expected life	9 months	9 months	9 months
Risk-free interest rate, minimum	0.05%	0.05%	0.07%
Risk-free interest rate, maximum	0.27%	0.17%	0.17%

Net Loss Per Share (Detail)

Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	[1]	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net loss	$ (13,359)	$ (24,064)	$ (24,481)	$ (20,409)	$ (17,657)	$ 8,259		$ (19,387)	$ (20,548)	$ (82,313)	$ (49,333)	$ (85,883)
Denominator:
Weighted-average common shares outstanding										63,193	60,856	47,545
Basic and diluted net loss per share	$ (0.21)	$ (0.38)	$ (0.39)	$ (0.33)	$ (0.28)	$ 0.13		$ (0.31)	$ (0.36)	$ (1.30)	$ (0.81)	$ (1.81)
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Outstanding securities not included in the computation of diluted net loss per share										19,204	7,650	7,107
Restricted stock units and options to purchase common stock
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Outstanding securities not included in the computation of diluted net loss per share										8,475	7,650	6,824
Warrants outstanding
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Outstanding securities not included in the computation of diluted net loss per share												283
Convertible Senior Notes
Outstanding securities at period end not included in the computation of diluted net loss per share as they had an anti-dilutive effect:
Outstanding securities not included in the computation of diluted net loss per share										10,729
[1]	Total revenues and net income was primarily from the recognition of $25,000,000 in collaboration revenue resulting from the Indivior licensing agreement (see Note 2 for more information).

License and Collaboration Arran

License and Collaboration Arrangements - Additional Information (Detail) - USD ($)	1 Months Ended		3 Months Ended									12 Months Ended
	Jul. 31, 2014	Jun. 30, 2014	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014		Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May. 31, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue												$ 1,134,000	$ 26,134,000	$ 1,137,000
Revenue recognized			$ 14,079,000	$ 11,393,000	$ 8,621,000	$ 7,067,000	$ 7,091,000	$ 31,068,000	[1]	$ 5,334,000	$ 3,375,000	41,160,000	46,868,000	7,951,000
Royalty revenue												567,000	561,000	400,000
Deferred revenue, current			1,134,000				1,134,000					1,134,000	1,134,000
Deferred revenue, non-current			9,730,000				$ 10,864,000					9,730,000	10,864,000
Licensing Agreements | Indivior UK Ltd | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate cash payments receivable upon achievement of certain predefined milestones																$ 120,000,000
Licensing Agreements | Indivior UK Ltd | Upfront, non-refundable cash payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, initial up-front license payment and payment for specified materials received		$ 20,000,000
Collaboration revenue								20,000,000
Licensing Agreements | Indivior UK Ltd | Additional payment for specified materials
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue, initial up-front license payment and payment for specified materials received	$ 5,000,000
Collaboration revenue								$ 5,000,000
Licensing Agreements | Indivior UK Ltd | Regulatory and development-based milestones | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate cash payments receivable upon achievement of certain predefined milestones																70,000,000
Licensing Agreements | Indivior UK Ltd | Commercialization-based milestones | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate cash payments receivable upon achievement of certain predefined milestones																$ 50,000,000
Licensing Agreements | Astellas Pharma Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized												55,774,000			$ 10,000,000
Royalty revenue												567,000	561,000	400,000
Deferred revenue			10,864,000									10,864,000
Deferred revenue, current			1,134,000									1,134,000
Deferred revenue, non-current			$ 9,730,000									9,730,000
Licensing Agreements | Astellas Pharma Inc. | Upfront, non-refundable cash payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue												$ 1,134,000	$ 1,134,000	$ 1,137,000
[1]	Total revenues and net income was primarily from the recognition of $25,000,000 in collaboration revenue resulting from the Indivior licensing agreement (see Note 2 for more information).

Total Revenues Recognized Pursu

Total Revenues Recognized Pursuant to Current License Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	[1]	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue										$ 1,134	$ 26,134	$ 1,137
Total revenues	$ 14,079	$ 11,393	$ 8,621	$ 7,067	$ 7,091	$ 31,068		$ 5,334	$ 3,375	41,160	46,868	7,951
Collaborative Arrangement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenues										1,701	26,695	1,537
Astellas Pharma Inc.
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration and royalty revenue										$ 1,701	1,695	$ 1,537
Indivior PLC
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration revenue											$ 25,000
[1]	Total revenues and net income was primarily from the recognition of $25,000,000 in collaboration revenue resulting from the Indivior licensing agreement (see Note 2 for more information).

Cash and Cash Equivalents, Sh37

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Cost		$ 141,164	$ 103,811
Gross Unrealized Gains		64	12
Gross Unrealized Losses		(17)	(42)
Estimated Fair Value		141,211	103,781
Cash
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Available for Sale Securities Cost		5,311	3,383
Available-for-sale investments		5,311	3,383
Money market funds
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Available for Sale Securities Cost		17,261	8,576
Available-for-sale investments		17,261	8,576
Corporate debt securities
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Available for Sale Securities Cost		104,618	88,127
Gross Unrealized Gains		63	12
Gross Unrealized Losses		(17)	(40)
Available-for-sale investments		104,664	88,099
Certificates of deposit
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Restricted Cost		1,725	1,725
Restricted Fair Value		1,725	1,725
Cash and cash equivalents
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Available-for-sale investments		61,317	11,958
Short-term investments
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Available-for-sale investments		78,169	90,098
Restricted Investments
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Restricted Fair Value	[1]	1,725	1,725
U.S. government-sponsored agencies
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Available for Sale Securities Cost		12,249	2,000
Gross Unrealized Gains		1
Gross Unrealized Losses			(2)
Available-for-sale investments		$ 12,250	$ 1,998
[1]	Included in "Prepaids and other current assets" as of December 31, 2015 and "Restricted investments and other assets" as of December 31, 2014.

Cash and Cash Equivalents, Sh38

Cash and Cash Equivalents, Short-Term Investments and Restricted Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Gross realized gains or losses recognized	$ 0	$ 0	$ 0
Amounts reclassified out of accumulated other comprehensive loss to earnings	$ 0	$ 0	$ 0
Maximum
Cash Cash Equivalents Short Term Investments and Restricted Investments [Line Items]
Contractual maturities of investments held	12 months	16 months

Available-For-Sale Investments

Available-For-Sale Investments Measured at Fair Value (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	$ 141,211	$ 103,781
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	17,261	8,576
U.S. government-sponsored agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	12,250	1,998
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	104,664	88,099
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Fair Value	1,725	1,725
Fair Value Measurements, Recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	135,900	100,398
Fair Value Measurements, Recurring basis | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	17,261	8,576
Fair Value Measurements, Recurring basis | U.S. government-sponsored agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	12,250	1,998
Fair Value Measurements, Recurring basis | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	104,664	88,099
Fair Value Measurements, Recurring basis | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Fair Value	1,725	1,725
Fair Value Measurements, Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	17,261	8,576
Fair Value Measurements, Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	17,261	8,576
Fair Value Measurements, Recurring basis | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	118,639	91,822
Fair Value Measurements, Recurring basis | Significant Other Observable Inputs (Level 2) | U.S. government-sponsored agencies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	12,250	1,998
Fair Value Measurements, Recurring basis | Significant Other Observable Inputs (Level 2) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale investments	104,664	88,099
Fair Value Measurements, Recurring basis | Significant Other Observable Inputs (Level 2) | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Restricted Fair Value	$ 1,725	$ 1,725

Property and Equipment (Detail)

Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Laboratory equipment	$ 9,878	$ 10,561
Manufacturing property and equipment	1,980	1,975
Furniture and fixtures	1,076	1,076
Computer equipment and software	5,482	5,656
Leasehold improvements	3,405	3,405
Property, Plant and Equipment, Gross, Total	21,821	22,673
Less: Accumulated depreciation and amortization	(20,029)	(20,251)
Property and equipment, net	$ 1,792	$ 2,422

Other Accrued Liabilities (Deta

Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accrued product costs	$ 446	$ 2,009
Accrued selling and marketing expenses	1,931	1,210
Accrued general and administrative expenses	643	466
Accrued rebates, allowances and returns	1,878	986
Interest payable - convertible senior notes	1,182
Other liabilities	607	446
Total other accrued liabilities	7,610	$ 5,117
Glaxo Group Limited | Other Accrued Liabilities
Payables And Accruals [Abstract]
GSK liability - current portion	$ 923

Restructuring and Severance - A

Restructuring and Severance - Additional Information (Detail)	Sep. 29, 2015Employee	Dec. 31, 2015USD ($)	Dec. 31, 2013USD ($)
Restructuring Cost and Reserve [Line Items]
Number of impacted employees due to Reduction in Workforce | Employee	25
Restructuring charges		$ 1,671,000
Expected severance payment date		Mar. 31, 2016
Restructuring charges paid or settled		$ 767,000
Accrued Compensation
Restructuring Cost and Reserve [Line Items]
Restructuring reserve		$ 904,000
Nonretirement Postemployment Benefits
Restructuring Cost and Reserve [Line Items]
Severance expense			$ 703,000
Former Chief Executive Officer
Restructuring Cost and Reserve [Line Items]
Expected severance payment date		Mar. 31, 2017
Restructuring charges paid or settled		$ 147,000
Former Chief Executive Officer | Accrued Compensation
Restructuring Cost and Reserve [Line Items]
Restructuring reserve		1,078,000
Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring charges		685,000
Selling, general and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring charges		986,000
Selling, general and administrative | Former Chief Executive Officer
Restructuring Cost and Reserve [Line Items]
Severance expense		$ 1,225,000

Convertible Senior Notes - Addi

Convertible Senior Notes - Additional Information (Detail) - USD ($)	Feb. 03, 2015	Mar. 31, 2015	Dec. 31, 2015
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes, net of discount and debt issuance costs			$ 111,327,000
Carrying value of convertible senior notes			111,761,000
Convertible Senior Notes Due 2022
Debt Instrument [Line Items]
Convertible senior notes, principal offer amount	$ 115,000,000		115,000,000
Convertible senior notes, due date	2,022
Proceeds from issuance of convertible senior notes, net of discount and debt issuance costs			$ 111,327,000
Convertible senior notes, repayment terms	Beginning on August 1, 2015, interest on the 2022 Notes is payable semi-annually in cash in arrears on February 1 and August 1 of each year, at a rate of 2.50% per year.
Convertible senior notes, interest payment commencement date	Aug. 1, 2015
Convertible senior notes, maturity date	Feb. 1, 2022
Convertible senior notes, stated interest rate	2.50%
Convertible senior notes, conversion share per 1000 principal amount	93.2945
Convertible senior notes, initial conversion price	$ 10.72
Repurchase price of principal amount	100.00%
Common stock issuable upon conversion of notes			10,728,867
Debt issuance cost		$ 568,000	$ 568,000
Carrying value of convertible senior notes			111,800,000
Convertible Senior Notes Due 2022 | Significant Other Observable Inputs (Level 2)
Debt Instrument [Line Items]
Fair value of convertible senior			$ 93,900,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2006
Commitments and Contingencies Disclosure [Line Items]
Lease commencement date	2001-12
Letter of credit pledged	$ 225,000			$ 1,500,000
Rent expense	2,495,000	$ 2,615,000	$ 2,626,000
Net deferred rent asset	53,000	180,000
Deferred rent asset, current	53,000	127,000
Deferred rent asset, noncurrent		53,000
Non-cancelable Fleet Operating Lease
Commitments and Contingencies Disclosure [Line Items]
Rent expense	$ 649,000
Operating lease term	1 year
Prepaids And Other Current Assets
Commitments and Contingencies Disclosure [Line Items]
Certificate of Deposit	$ 1,500,000	1,500,000
Restricted Investments And Other Assets
Commitments and Contingencies Disclosure [Line Items]
Certificate of Deposit	$ 1,500,000	$ 1,500,000
Third Amendment
Commitments and Contingencies Disclosure [Line Items]
Lease expiration date	May 31, 2016

Future Minimum Payments under C

Future Minimum Payments under Company's Non-Cancelable Facility Operating Lease (Detail) - Non-cancelable Facility Operating Lease $ in Thousands	Dec. 31, 2015USD ($)
Schedule of Operating Leases [Line Items]
2,016	$ 789
Total minimum lease payments	$ 789

Future Minimum Payments under46

Future Minimum Payments under Company's Non-Cancelable Fleet Operating Lease (Detail) - Non-cancelable Fleet Operating Lease $ in Thousands	Dec. 31, 2015USD ($)
Schedule of Operating Leases [Line Items]
2,016	$ 489
2,017	39
Total minimum lease payments	$ 528

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) - USD ($)

Jan. 29, 2015

Jun. 11, 2014

Feb. 21, 2014

Jan. 29, 2014

Dec. 16, 2005

Jan. 31, 2015

Feb. 28, 2014

May. 31, 2010

Jan. 31, 2007

Jan. 31, 2005

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2011

Dec. 31, 2010

Jun. 10, 2014

May. 19, 2015

May. 18, 2015

Jun. 30, 2014

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock, shares authorized

200,000,000

100,000,000

200,000,000

100,000,000

Stockholders' rights plan, expiration date

Jan. 13, 2016

Equity Incentive Plans, weighted average exercise price

$ 8.64

Stock-based compensation expense

$ 10,178,000

$ 9,041,000

$ 10,544,000

Equity Incentive Plans, granted

2,367,410

Equity Incentive Plans, weighted-average grant date fair values of options granted

$ 5.48

$ 4.05

$ 5.22

Closing stock price

$ 5.49

Equity Incentive Plans, total intrinsic value of options exercised

$ 683,000

$ 758,000

$ 304,000

Total fair value of options vested

$ 6,904,000

4,572,000

4,786,000

Equity Incentive Plans, unvested options

2,468,806

Equity Incentive Plans, unvested awards

1,193,914

Equity Incentive Plans, total compensation cost not yet recognized

$ 15,375,000

Equity Incentive Plans, estimated weighted-average amortization period

2 years 8 months 5 days

Underwritten Public Offering

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock issued in underwritten public offering

12,000,000

Common stock price

$ 6

Net cash proceeds from shares offering

$ 67,300,000

Underwriters Over Allotment Option Exercised In Full

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock issued in underwritten public offering

1,800,000

Net cash proceeds from shares offering

$ 10,100,000

Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based compensation expense

$ 9,410,000

8,531,000

10,083,000

Restricted Stock Units (RSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, granted

857,012

Equity Incentive Plans, cancelled

226,340

Equity Incentive Plans, weighted-average grant date fair values

$ 5.43

Equity Incentive Plans, total fair value of restricted stock units vested

$ 2,864,000

$ 4,656,700

$ 6,202,000

Equity Incentive Plans, unvested awards

1,193,914

1,021,344

Employee Stock Purchase Plan 2005

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, granted

236,657

227,720

142,455

Employee Stock Purchase Plan 2015

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, shares available for future grant

3,910,746

Equity Incentive Plans, granted

89,254

Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Acquisition percentage of common stock to triggers exercise of preferred stock rights

15.00%

Tender offer percentage of common stock to trigger exercise of preferred stock right

15.00%

Percentage of common stock shares from convertible debt

14.99%

Maximum | Employee Stock Purchase Plan 2005

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, annual increase in shares issuable as a percentage of common shares outstanding

1.00%

Equity Incentive Plans, annual increase in number of shares issuable

250,000

Equity Incentive Plans, exercise prices as a percentage of fair value of common stock

85.00%

Maximum | Employee Stock Purchase Plan 2015

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, shares authorized for issuance

4,000,000

Equity Incentive Plans, exercise prices as a percentage of fair value of common stock

85.00%

Equity Incentive Plans, exercise prices as a percentage of fair value of common stock on purchase date

85.00%

Stockholder Rights Plan | Series A Junior Participating Preferred Stock

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, weighted average exercise price

$ 140

2005 Stock Incentive Plan | Vested Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

25.00%

2005 Stock Incentive Plan | Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, remaining vesting period

36 months

Equity Incentive Plans, vesting period

48 months

2005 Stock Incentive Plan | Restricted Stock Units (RSUs) | Vesting Scenario One

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

25.00%

Equity Incentive Plans, vesting period

4 years

2005 Stock Incentive Plan | Restricted Stock Units (RSUs) | Vesting Scenario Two

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

3 years

Equity Incentive Plans, vesting percentage in year one

25.00%

Equity Incentive Plans, annual vesting percentage in year two

25.00%

Equity Incentive Plans, annual vesting percentage in year three

50.00%

2005 Stock Incentive Plan | Restricted Stock Units (RSUs) | Vesting Scenario Three

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

3 years

Equity Incentive Plans, annual vesting percentage in year two

50.00%

Equity Incentive Plans, annual vesting percentage in year three

50.00%

2005 Stock Incentive Plan | Performance Stock Units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

3 years

Equity Incentive Plans, granted

140,000

Equity Incentive Plans, granted date fair value

$ 2,675,000

Equity Incentive Plans, cancelled

97,300

40,000

Equity Incentive Plans, outstanding

0

0

Stock-based compensation expense

$ 0

$ 0

$ 232,000

2005 Stock Incentive Plan | Stock purchase rights, stock bonus rights, stock appreciation rights

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, shares authorized for issuance

2,000,000

Equity Incentive Plans, shares available for future grant

0

2005 Stock Incentive Plan | Performance Stock Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, granted

316,000

Equity Incentive Plans, granted date fair value

$ 1,334,000

Stock-based compensation expense

$ 445,000

$ 547,000

Equity Incentive Plans, conditions achieved due to vesting percentage

50.00%

2005 Stock Incentive Plan | Performance Stock Options | Vested Options | Vest up on One-Year Anniversary Date of Initial Vest Date

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

50.00%

2005 Stock Incentive Plan | Performance Stock Options | Vested Options | Upon Achievement of Performance Condition

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

50.00%

2005 Stock Incentive Plan | Minimum | Performance Stock Units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, common stock subject to issuance

0.00%

2005 Stock Incentive Plan | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, option expiration period

10 years

2005 Stock Incentive Plan | Maximum | Performance Stock Units

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, common stock subject to issuance

200.00%

2005 Stock Incentive Plan | Maximum | Stock purchase rights, stock bonus rights, stock appreciation rights

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, annual increase in shares issuable as a percentage of common shares outstanding

2.50%

Equity Incentive Plans, annual increase in number of shares issuable

2,000,000

2005 Non-Employee Directors Stock Option Plan | Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, shares available for future grant

0

2005 Non-Employee Directors Stock Option Plan | Employee Stock Option | Initial Grant

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

4 years

24 months

Equity Incentive Plans, granted

25,000

30,000

2005 Non-Employee Directors Stock Option Plan | Employee Stock Option | On Date Of Annual Meeting Of Shareholders

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

12 months

12 months

Equity Incentive Plans, granted

10,000

15,000

2005 Non-Employee Directors Stock Option Plan | Restricted Stock Units (RSUs) | On Date Of Annual Meeting Of Shareholders

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

1 year

Equity Incentive Plans, granted

5,000

2005 Non-Employee Directors Stock Option Plan | Maximum | Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, option expiration period

10 years

Equity Incentive Plans, shares authorized for issuance

150,000

2010 Inducement Plan | Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, remaining vesting period

36 months

Equity Incentive Plans, shares authorized for issuance

350,000

Equity Incentive Plans, shares available for future grant

0

Equity Incentive Plans, additional shares authorized for issuance

625,000

2010 Inducement Plan | Employee Stock Option | Vested Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

25.00%

2010 Inducement Plan | Restricted Stock Units (RSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

4 years

2010 Inducement Plan | Restricted Stock Units (RSUs) | Vested Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

25.00%

2010 Inducement Plan | Maximum | Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, option expiration period

10 years

Equity Incentive Plans, shares authorized for issuance

975,000

2014 Equity Incentive Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, shares available for future grant

4,471,059

2,900,588

2014 Equity Incentive Plan | Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, remaining vesting period

36 months

Equity Incentive Plans, vesting period

48 months

Equity Incentive Plans, option expiration period

10 years

Equity Incentive Plans, granted

225,000

Equity Incentive Plans, granted date fair value

$ 1,216,000

Stock-based compensation expense

$ 1,156,000,000

2014 Equity Incentive Plan | Employee Stock Option | Initial Grant

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

24 months

Equity Incentive Plans, granted

30,000

2014 Equity Incentive Plan | Employee Stock Option | On Date Of Annual Meeting Of Shareholders

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

12 months

Equity Incentive Plans, granted

15,000

2014 Equity Incentive Plan | Employee Stock Option | Vested Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

25.00%

2014 Equity Incentive Plan | Employee Stock Option | Share-based Compensation Award, Tranche One

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock target price per share

$ 11

Number of consecutive trading days to determine number of shares begin vesting under condition One

30 days

2014 Equity Incentive Plan | Employee Stock Option | Vesting Option Two

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Common stock target price per share

$ 13

Number of consecutive trading days to determine number of shares begin vesting under condition two

30 days

2014 Equity Incentive Plan | Restricted Stock

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

4 years

2014 Equity Incentive Plan | Restricted Stock | On Date Of Annual Meeting Of Shareholders

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting period

1 year

Equity Incentive Plans, granted

5,000

2014 Equity Incentive Plan | Restricted Stock | Vested Options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, vesting percentage

25.00%

2014 Equity Incentive Plan | Maximum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, additional shares authorized for issuance

7,847,852

2014 Equity Incentive Plan | Maximum | Employee Stock Option

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, option expiration period

10 years

Stock Incentive Plan 1999 | Minimum

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, exercise prices as a percentage of fair value of common stock

100.00%

Equity Incentive Plan | Restricted Stock Units (RSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity Incentive Plans, weighted-average grant date fair values

$ 5.44

$ 6.07

$ 8.13

Option Activity (Detail)

Option Activity (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)$ / sharesshares
Shares
Outstanding at January 1, 2014 | shares	6,628,612
Options granted | shares	2,367,410
Options cancelled | shares	(1,346,627)
Options exercised | shares	(368,236)
Outstanding at December 31, 2015 | shares	7,281,159
Exercisable at December 31, 2015 | shares	4,812,353
Weighted-Average Exercise Price
Outstanding at January 1, 2014 | $ / shares	$ 14.49
Options granted | $ / shares	8.64
Options cancelled | $ / shares	11.77
Options exercised | $ / shares	5.24
Outstanding at December 31, 2015 | $ / shares	13.55
Exercisable at December 31, 2015 | $ / shares	$ 16.52
Weighted-Average Remaining Contractual Term
Outstanding at December 31, 2015	5 years 10 months 28 days
Exercisable at December 31, 2015	4 years 5 months 1 day
Aggregate Intrinsic Value
Outstanding at December 31, 2015 | $	$ 452
Exercisable at December 31, 2015 | $	$ 354

Restricted Stock Unit Activity

Restricted Stock Unit Activity (Detail)	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Shares
Outstanding at December 31, 2015	1,193,914
Restricted Stock Units (RSUs)
Shares
Outstanding at January 1, 2015	1,021,344
Awards granted	857,012
Awards cancelled	(226,340)
Awards vested	(458,102)
Outstanding at December 31, 2015	1,193,914
Weighted-Average Grant Date Fair Value
Outstanding at January 1, 2015 | $ / shares	$ 6.70
Awards granted | $ / shares	5.43
Awards cancelled | $ / shares	7.62
Awards vested | $ / shares	6.25
Outstanding at December 31, 2015 | $ / shares	$ 5.79

Preferred Stock - Additional In

Preferred Stock - Additional Information (Detail) - shares	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Preferred stock, shares authorized	5,000,000	5,000,000
Series A Junior Participating Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized	1,000,000	1,000,000

Significant Components of Net D

Significant Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Deferred Tax Assets and Liabilities [Line Items]
Net operating loss carryforwards	$ 209,834	$ 182,791
Research credit carryforwards	32,104	31,249
Capitalized research and development	1,188	3,760
Deferred revenue	4,139	4,824
Stock awards	16,371	16,901
Other	2,334	3,043
Total net deferred tax assets	265,970	242,568
Valuation allowance	(265,970)	(242,568)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Line Items]
Increase in valuation allowance	$ 23,402,000	$ 24,238,000	$ 27,210,000
Valuation allowance	265,970,000	$ 242,568,000
Excess tax benefit from share-based compensation	2,077,000
Valuation allowance related to stock option
Income Tax Disclosure [Line Items]
Valuation allowance	529,000
Federal
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	549,241,000
Research and development tax credit	$ 24,713,000
Federal | Expiration Beginning Year
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2,022
Research and development tax credit, expiration year	2,021
Federal | Expiration Ending Year
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2,035
Research and development tax credit, expiration year	2,035
State
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 351,563,000
Research and development tax credit	$ 12,790,000
State | Expiration Beginning Year
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2,016
State | Expiration Ending Year
Income Tax Disclosure [Line Items]
Net operating loss carryforwards, expiration year	2,035

Reconciliation of Beginning and

Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Beginning balance	$ 1,379	$ 1,340
Increases related to current year tax positions	40
Increases related to prior year tax positions		39	$ 1,340
Ending balance	$ 1,419	$ 1,379	$ 1,340

Quarterly Financial Data (Detai

Quarterly Financial Data (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended									12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	[1]	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information [Line Items]
Total revenues		$ 14,079	$ 11,393	$ 8,621	$ 7,067	$ 7,091	$ 31,068		$ 5,334	$ 3,375	$ 41,160	$ 46,868	$ 7,951
Gross profit	[2]	12,898	10,302	7,708	6,185	6,143	5,088		4,321	2,527
Net income (loss)		$ (13,359)	$ (24,064)	$ (24,481)	$ (20,409)	$ (17,657)	$ 8,259		$ (19,387)	$ (20,548)	$ (82,313)	$ (49,333)	$ (85,883)
Basic and diluted net income (loss) per share		$ (0.21)	$ (0.38)	$ (0.39)	$ (0.33)	$ (0.28)	$ 0.13		$ (0.31)	$ (0.36)	$ (1.30)	$ (0.81)	$ (1.81)
[1]	Total revenues and net income was primarily from the recognition of $25,000,000 in collaboration revenue resulting from the Indivior licensing agreement (see Note 2 for more information).
[2]	Gross profit relates solely to HORIZANT drug product sales.

Quarterly Financial Data (Paren

Quarterly Financial Data (Parenthetical) (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information [Line Items]
Collaboration revenue		$ 1,134,000	$ 26,134,000	$ 1,137,000
Indivior PLC
Quarterly Financial Information [Line Items]
Collaboration revenue			$ 25,000,000
Licensing Agreements | Indivior PLC
Quarterly Financial Information [Line Items]
Collaboration revenue	$ 25,000,000