Arena Pharmaceuticals (ARNA) 10-Q 9 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Nov. 04, 2015
Document And Entity Information [Abstract]
Entity Registrant Name	ARENA PHARMACEUTICALS INC
Trading Symbol	ARNA
Entity Central Index Key	1,080,709
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		242,549,640

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	[1]
Current assets:
Cash and cash equivalents	$ 181,280	$ 163,209
Accounts receivable	3,514	3,712
Inventory	10,243	10,831
Prepaid expenses and other current assets	5,179	4,144
Total current assets	200,216	181,896
Land, property and equipment, net	74,752	82,919
Intangibles, net	8,121	8,482
Other non-current assets	3,038	3,088
Total assets	286,127	276,385
Current liabilities:
Accounts payable and other accrued liabilities	7,318	10,209
Accrued clinical and preclinical study fees	3,627	7,027
Payable to Eisai	10,566	23,705
Current portion of deferred revenues	23,215	15,238
Current portion of lease financing obligations	2,852	2,492
Payable to Siegfried for acquisition of land and building	0	8,217
Derivative liabilities	0	474
Total current liabilities	47,578	67,362
Deferred rent	447	369
Deferred revenues, less current portion	89,845	93,064
Lease financing obligations, less current portion	$ 66,056	$ 68,245
Commitments and contingencies
Stockholders’ equity:
Common stock	$ 24	$ 22
Additional paid-in capital	1,427,529	1,312,656
Accumulated other comprehensive income	409	2,908
Accumulated deficit	(1,345,761)	(1,268,241)
Total stockholders’ equity	82,201	47,345
Total liabilities and stockholders’ equity	$ 286,127	$ 276,385
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues:
Net product sales	$ 4,884	$ 5,726	$ 15,787	$ 12,137
Toll manufacturing	1,463	158	3,199	1,184
Total revenues	9,138	8,164	30,575	27,779
Operating Costs and Expenses:
Cost of product sales	1,635	1,755	6,129	4,049
Cost of toll manufacturing	1,584	81	3,798	1,124
Research and development	22,072	24,508	68,241	72,521
General and administrative	9,028	8,029	26,311	25,198
Total operating costs and expenses	34,319	34,373	104,479	102,892
Loss from operations	(25,181)	(26,209)	(73,904)	(75,113)
Interest and Other Income (Expense):
Interest income	37	16	105	69
Interest expense	(1,683)	(1,723)	(5,133)	(5,205)
Gain from valuation of derivative liabilities	852	2,593	474	3,489
Gain on sale of available-for-sale securities	0	16,276	0	49,553
Other	(443)	(1,625)	938	(1,240)
Total interest and other income (expense), net	(1,237)	15,537	(3,616)	46,666
Net loss	$ (26,418)	$ (10,672)	$ (77,520)	$ (28,447)
Net loss per share:
Basic, in dollars per share	$ (0.11)	$ (0.05)	$ (0.32)	$ (0.13)
Diluted, in dollars per share	$ (0.11)	$ (0.05)	$ (0.32)	$ (0.13)
Shares used in calculating net loss per share:
Basic, in shares	242,257	219,866	240,033	219,592
Diluted, in shares	242,257	219,866	240,033	219,592
Comprehensive Loss:
Net loss	$ (26,418)	$ (10,672)	$ (77,520)	$ (28,447)
Foreign currency translation loss	(2,881)	(1,626)	(2,499)	(2,019)
Reclassification adjustment for realized gain on sale of available-for-sale securities	0	(16,276)	0	(49,553)
Unrealized holding gain (loss) on available-for-sale securities	0	(2,037)	0	49,553
Comprehensive loss	(29,299)	(30,611)	(80,019)	(30,466)
Eisai
Revenues:
Net product sales	3,274	5,726	11,603	12,137
Other collaborative revenue	2,065	2,133	7,414	14,034
Total revenues	5,339	7,859	19,017	26,171
Other
Revenues:
Other collaborative revenue	$ 726	$ 147	$ 4,175	$ 424

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015		Sep. 30, 2014
Operating Activities
Net loss	$ (77,520)		$ (28,447)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,401		6,434
Amortization of intangibles	147		394
Share-based compensation	11,795		9,941
Gain from valuation of derivative liabilities	(474)		(3,489)
Gain on sale of available-for-sale securities	0		(49,553)
Amortization of prepaid financing costs	102		102
Loss on sale of property and equipment	1,007		172
Changes in assets and liabilities:
Accounts receivable	116		7,279
Inventory	1,240		211
Prepaid expenses and other assets	(366)		(2,551)
Payables and accrued liabilities	(21,271)		3,420
Deferred revenues	4,506		(22,998)
Deferred rent	78		93
Net cash used in operating activities	(73,239)		(78,992)
Investing Activities
Proceeds from sale of available-for-sale securities	0		49,553
Purchases of property and equipment	(10,800)		(6,444)
Proceeds from sale of property and equipment	2,232		47
Other non-current assets	(55)		209
Net cash provided by (used in) investing activities	(8,623)		43,365
Financing Activities
Principal payments on lease financing obligations	(1,829)		(1,507)
Proceeds from issuance of common stock	102,934		4,892
Net cash provided by financing activities	101,105		3,385
Effect of exchange rate changes on cash	(1,172)		(1,308)
Net increase (decrease) in cash and cash equivalents	18,071		(33,550)
Cash and cash equivalents at beginning of period	163,209	[1]	221,878
Cash and cash equivalents at end of period	$ 181,280		$ 188,328
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of Arena Pharmaceuticals, Inc., which include our wholly owned subsidiaries, should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014, as filed with the Securities and Exchange Commission, or SEC, from which we derived our balance sheet as of December 31, 2014. The accompanying financial statements have been prepared in accordance with US generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, since they are interim statements, the accompanying financial statements do not include all of the information and notes required by GAAP for complete financial statements. The accompanying financial statements reflect all adjustments, consisting of normal recurring adjustments, that are, in the opinion of our management, necessary to a fair statement of the results for the interim periods presented. Interim results are not necessarily indicative of results for a full year. In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2014-09, “Revenue from Contracts with Customers.” ASU No. 2014-09 outlines a comprehensive revenue recognition model which will supersede most current revenue recognition guidance. ASU No. 2014-09 is effective for annual reporting periods, and interim periods within those periods, beginning after December 15, 2017. ASU No. 2014-09 allows for two methods of adoption: (a) “full retrospective” adoption, meaning the standard is applied to all periods presented, or (b) “modified retrospective” adoption, meaning the cumulative effect of applying ASU No. 2014-09 is recognized as an adjustment to the opening retained earnings balance for the year of implementation. We have not yet selected an adoption method as we are currently evaluating the impact of ASU No. 2014-09 on our consolidated financial statements. In August 2014, the FASB issued ASU No. 2014-15, “Presentation of Financial Statements – Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern.” Under GAAP, continuation of a reporting entity as a going concern is presumed as the basis for preparing financial statements unless and until the entity’s liquidation becomes imminent. Preparation of financial statements under this presumption is commonly referred to as the going concern basis of accounting. If and when an entity’s liquidation becomes imminent, financial statements should be prepared under the liquidation basis of accounting. Even when an entity’s liquidation is not imminent, there may be conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern. In those situations, financial statements should continue to be prepared under the going concern basis of accounting, but ASU No. 2014-15 should be followed to determine whether to disclose information about any relevant conditions and events. ASU No. 2014-15 is effective for the annual reporting period ending after December 15, 2016, and for annual and interim periods thereafter. We do not expect the adoption of ASU No. 2014-15 to have a material impact on our consolidated financial statements. The preparation of financial statements in accordance with GAAP requires our management to make estimates and assumptions that affect the reported amounts (including assets, liabilities, revenues and expenses) and related disclosures. The amounts reported could differ under different estimates and assumptions.

Fair Value Disclosures

Fair Value Disclosures	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Disclosures We measure our financial assets and liabilities at fair value, which is defined as the exit price, or the amount that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. We use the following three-level valuation hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs to value our financial assets and liabilities: Level 1 - Observable inputs such as unadjusted quoted prices in active markets for identical instruments. Level 2 - Quoted prices for similar instruments in active markets or inputs that are observable for the asset or liability, either directly or indirectly. Level 3 - Significant unobservable inputs based on our assumptions. The following tables present our valuation hierarchy for our financial assets and liabilities that are measured at fair value on a recurring basis, in thousands: Fair Value Measurements at September 30, 2015 Balance Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds 1 $ 133,026 $ 133,026 $ 0 $ 0 Fair Value Measurements at December 31, 2014 Balance Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds 1 $ 143,913 $ 143,913 $ 0 $ 0 Liabilities: Warrant derivative liabilities $ 474 $ 0 $ 474 $ 0 ______________________ (1) Included in cash and cash equivalents on our condensed consolidated balance sheets. On August 14, 2015, the warrant expired pursuant to its terms. (See Note 6.)

Inventory

Inventory	9 Months Ended
	Sep. 30, 2015
Inventory Disclosure [Abstract]
Inventory	Inventory Inventory consisted of the following, in thousands: September 30, 2015 December 31, 2014 Raw materials $ 2,412 $ 1,167 Work in process 3,043 3,520 Finished goods at Arena GmbH 828 3,681 Finished goods at Eisai 2,922 2,463 Finished goods at Ildong 1,038 0 Total inventory $ 10,243 $ 10,831

Land, Property and Equipment

Land, Property and Equipment	9 Months Ended
	Sep. 30, 2015
Property, Plant and Equipment [Abstract]
Land, Property and Equipment	Land, Property and Equipment Land, property and equipment consisted of the following, in thousands: September 30, 2015 December 31, 2014 Cost $ 173,820 $ 174,938 Less accumulated depreciation and amortization (99,068 ) (92,019 ) Land, property and equipment, net $ 74,752 $ 82,919

Accounts Payable and Other Accr

Accounts Payable and Other Accrued Liabilities	9 Months Ended
	Sep. 30, 2015
Payables and Accruals [Abstract]
Accounts Payable and Other Accrued Liabilities	Accounts Payable and Other Accrued Liabilities Accounts payable and other accrued liabilities consisted of the following, in thousands: September 30, 2015 December 31, 2014 Accounts payable $ 1,556 $ 2,844 Accrued compensation 4,222 4,792 Other accrued liabilities 1,540 2,573 Total accounts payable and other accrued liabilities $ 7,318 $ 10,209

Derivative Liabilities

Derivative Liabilities	9 Months Ended
	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Liabilities	Derivative Liabilities In August 2008, we issued a warrant to purchase 1,106,344 shares of our common stock at an exercise price of $7.71 per share that expired on August 14, 2015. As a result of the warrant’s anti-dilution provision and certain of our subsequent equity issuances, the number of shares issuable upon exercise of the warrant increased and the exercise price decreased. The warrant, which was valued at $0.5 million at December 31, 2014, was recorded as a current derivative liability on our condensed consolidated balance sheets. On August 14, 2015, the warrant expired pursuant to its terms, and, thus, we recorded a gain in our condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2015 . The warrant was revalued on each balance sheet date, with changes in the fair value between reporting periods recorded in the interest and other income (expense) section of our condensed consolidated statements of operations and comprehensive loss.

Marketing and Supply Agreement

Marketing and Supply Agreement with Eisai	9 Months Ended
	Sep. 30, 2015
Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Marketing and Supply Agreement with Eisai/Ildong	Marketing and Supply Agreement with Eisai In November 2013, our wholly owned subsidiary, Arena Pharmaceuticals GmbH, or Arena GmbH, and Eisai Inc. and Eisai Co., Ltd. (collectively with Eisai Inc., Eisai) entered into the Second Amended and Restated Marketing and Supply Agreement, or Eisai Agreement. The Eisai Agreement expanded Eisai’s exclusive commercialization rights for lorcaserin to all of the countries in the world, except for South Korea, Taiwan, Australia, New Zealand and Israel. Lorcaserin is approved in the United States for chronic weight management in adults who are overweight with a comorbidity or obese, and was made available to patients by prescription in the United States by Eisai in June 2013. In addition to providing commercialization rights, which are subject to applicable regulatory approval, we manufacture and sell lorcaserin to Eisai and provide Eisai with services related to development and regulatory activities. Under the Eisai Agreement, we have received an upfront payment and payments from sales of lorcaserin, and are entitled to receive payments from future sales of lorcaserin, milestone payments based on the achievement of regulatory filings and approvals, one-time purchase price adjustment payments and other payments. Prior to entering into the Eisai Agreement, Arena GmbH and Eisai Inc. entered into the original marketing and supply agreement in July 2010, under which we granted Eisai Inc. exclusive commercialization rights for lorcaserin solely in the United States and its territories and possessions. In May 2012, Arena GmbH and Eisai Inc. amended and restated such agreement by entering into the first amended agreement, which expanded Eisai Inc.’s exclusive commercialization rights to include most of North and South America. The following table summarizes the revenues we recognized under our collaboration with Eisai for the periods presented, in thousands: Three months ended Nine months ended 2015 2014 2015 2014 Net product sales $ 3,274 $ 5,726 $ 11,603 $ 12,137 Amortization of upfront payments 1,886 1,885 5,656 5,745 Reimbursement of development expenses 107 143 1,454 7,456 Milestone payment 0 0 0 500 Reimbursement of patent and trademark expenses 72 105 304 333 Subtotal other Eisai collaborative revenue 2,065 2,133 7,414 14,034 Total $ 5,339 $ 7,859 $ 19,017 $ 26,171 The following table summarizes the deferred revenues under our collaboration with Eisai, in thousands: September 30, 2015 December 31, 2014 Upfront payments $ 88,818 $ 94,474 Net product sales 12,520 7,081 Total deferred revenues attributable to Eisai 101,338 101,555 Less current portion (20,061 ) (14,622 ) Deferred revenues attributable to Eisai, less current portion $ 81,277 $ 86,933 Upfront and Milestone Payments. In connection with entering into the Eisai Agreement, we received from Eisai an upfront payment of $60.0 million . This payment is in addition to the $50.0 million and $5.0 million in upfront payments we received from Eisai in connection with entering into the original agreement and the first amended agreement, respectively. Revenues from these upfront payments were deferred, as we determined that the exclusive rights did not have standalone value without our ongoing development and regulatory activities. Accordingly, these payments are recognized ratably as revenue over the periods in which we expect the services to be rendered, which are approximately 15 years for the Eisai Agreement and first amended agreement and 16 years for the original agreement. In addition to the upfront payments, we have received from Eisai a total of $86.5 million in milestones payments, and we are eligible to receive up to an aggregate of $176.0 million in additional regulatory and development milestone payments. Product Purchase Price and Purchase Price Adjustment Payments. We manufacture lorcaserin at our facility in Switzerland, and sell lorcaserin to Eisai for Eisai’s commercialization in the United States and, subject to applicable regulatory approval, in the other territories under the Eisai Agreement (other than Europe, China and Japan) for a purchase price starting at 31.5% and 30.75% , respectively (and starting at 27.5% in Europe, China and Japan), of Eisai’s aggregate annual net product sales (which are the gross invoiced sales less certain deductions described in the Eisai Agreement), or the Eisai Product Purchase Price, in the respective territory. The Eisai Product Purchase Price will increase on a tiered basis in the United States and the other territories (other than Europe, China and Japan) to as high as 36.5% and 35.75% , respectively, on the portion of Eisai’s annual aggregate net product sales exceeding $750.0 million in all territories other than Europe, China and Japan. The Eisai Product Purchase Price will increase to 35% in Europe, China and Japan on the portion of Eisai’s annual aggregate net product sales exceeding $500.0 million in such territories. The Eisai Product Purchase Price is subject to reduction (for sales in a particular country), including in the event of generic competition in the applicable country. The revenue we recognize for BELVIQ product revenue related to the use of vouchers and product samples is based on our cost of goods sold. In addition to payments for purchases of lorcaserin, we are eligible to receive up to an aggregate of $1.56 billion in one-time purchase price adjustment payments and other payments. These payments include up to an aggregate of $1.19 billion that are based on Eisai’s annual net product sales of lorcaserin in all of the territories under the Eisai Agreement on an aggregate basis, with the first and last amounts payable with annual net product sales of $250.0 million and $2.5 billion , respectively. Of these payments, Eisai will pay us a total of $330.0 million for annual net product sales of up to $1.0 billion . The $1.56 billion also includes $370.0 million in one-time purchase price adjustment payments we are eligible to receive based on annual net product sales in the non-US territories, comprised of $185.0 million based on Eisai’s annual net product sales in the non-US territories in North and South America and $185.0 million based on Eisai’s annual net product sales in the territories outside of North and South America. The first and last amounts are payable upon first achievement of annual net product sales of $100.0 million and $1.0 billion , respectively, with respect to each of the following areas: (i) the non-US territories in North and South America and (ii) the territories outside of North and South America. In addition, we are also eligible to receive certain payments by Eisai if certain annual minimum sales requirements in Mexico, Canada and Brazil are not met during the first ten years after initial commercial sale in such territories. The amount that Eisai pays us for lorcaserin product supply is based on Eisai’s estimated price at the time the order is shipped, which is Eisai’s estimate of the Eisai Product Purchase Price, and is subject to change on April 1 and October 1 of each year. At the end of Eisai’s fiscal year (March 31), the estimated price paid to us for product that Eisai sold to their distributors is compared to the Eisai Product Purchase Price of such product, and the difference is either refunded back to Eisai (for overpayments) or paid to us (for underpayments). On a monthly basis, Eisai provides us the total amount of net product sales for the month, details of the total deductions from gross to net product sales and the sales in units. We recognize our revenues monthly based on our percentage of Eisai’s monthly net product sales figures. When the revenues we recognize differ from the estimated price that Eisai paid us for such product, the difference is reclassified from deferred revenues to a receivable or payable account, as appropriate. We also adjust the deferred revenues balance for the product supply held at Eisai based on the most current net product sales figures provided to us, with the difference reclassified from deferred revenues to a receivable or payable account. The Eisai Product Purchase Price for the product Eisai has sold to date has been lower than the initial estimated price that Eisai has paid us for such product, primarily due to an increase in deductions from savings cards and returns, partially offset by a decrease in vouchers. In January 2015, Eisai announced the launch of a new savings card which enables eligible patients without commercial coverage for BELVIQ to pay no more than $75 for each monthly prescription while those patients with commercial coverage for BELVIQ are able to use the card to obtain additional savings if their copay is greater than $50 per monthly prescription. Subsequent to the end of Eisai’s fiscal year, we refund the portion of these excess payments, which total the $10.6 million classified as Payable to Eisai on our condensed consolidated balance sheet at September 30, 2015 , related to product sold by Eisai to their distributors through March 31. Development Payments. In connection with the US approval of BELVIQ, the US Food and Drug Administration, or FDA, is requiring (i) an evaluation as part of the cardiovascular outcomes trial, or CVOT, of the effect of long-term treatment with BELVIQ on the incidence of major adverse cardiovascular events, or MACE, in overweight and obese patients with cardiovascular disease or multiple cardiovascular risk factors and (ii) the conduct of postmarketing studies to assess the safety and efficacy of BELVIQ for weight management in obese pediatric and adolescent patients. In addition to the FDA-required studies, we and Eisai have prioritized the development and approval of a once-daily formulation of lorcaserin, as well as potentially exploring, including as part of the CVOT, BELVIQ’s effect on conversion to type 2 diabetes and improvements in cardiovascular outcomes. The chart below summarizes the general agreement regarding cost sharing between Eisai and us for significant development activities under the Eisai Agreement. In addition, Eisai or we may from time to time conduct approved development of lorcaserin at such party’s own expense. Eisai Second Amended and Restated Marketing and Supply Agreement: Cost Sharing for Development United States Rest of North and South America Remaining Territories BELVIQ - Pre-approval* Not Applicable General Eisai: 90%; Arena: 10% Certain stability work Eisai: 50%; Arena: 50% Up to a total of $100.0 million - Eisai: 50%; Arena: 50% Thereafter, Eisai: 100% BELVIQ - Post-approval* General Eisai: 90%; Arena 10% Non-FDA required portion of CVOT Up to $80.0 million - Eisai: 50%; Arena: 50% Thereafter, Eisai: 100% Certain pediatric studies Eisai: 50%; Arena: 50% General Eisai: 90%; Arena: 10% Certain stability work Eisai: 50%; Arena: 50% Up to a total of $50.0 million - Eisai: 50%; Arena: 50% Thereafter, Eisai: 90%; Arena: 10% Lorcaserin products other than BELVIQ - Pre-approval Up to a total of $250.0 million (as reduced by up to $80.0 million for non-FDA required portion of CVOT) -Eisai: 50%; Arena: 50% Lorcaserin products other than BELVIQ - Post-approval Up to a total of $100.0 million in the aggregate across all additional products - Eisai: 50%; Arena: 50% Thereafter, Eisai: 90%; Arena: 10% ______________________ * Development required by a regulatory authority, with the exception of the non-FDA required portions of the CVOT. Certain Other Terms. Please refer to our Annual Report on Form 10-K for the year ended December 31, 2014 , for additional information regarding termination, indemnification, product liability, certain limitations and other provisions included in the Eisai Agreement.

Marketing and Supply Agreemen12

Marketing and Supply Agreement with Ildong	9 Months Ended
	Sep. 30, 2015
Ildong
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Marketing and Supply Agreement with Eisai/Ildong	Marketing and Supply Agreement with Ildong In November 2012, Arena GmbH and Ildong Pharmaceutical Co., Ltd., or Ildong, entered into the Marketing and Supply Agreement, or Ildong Agreement. Under this agreement, we granted Ildong exclusive rights to commercialize BELVIQ in South Korea for weight loss or weight management in obese and overweight patients. We also provide certain services and will manufacture and sell BELVIQ to Ildong. Ildong has agreed not to conduct activities outside of our agreement related to the approval or commercialization of any other pharmaceutical product for weight loss, weight management or obesity in South Korea, with the exception of phentermine. In connection with entering into the Ildong Agreement, we received from Ildong an upfront payment of $5.0 million , less withholding taxes. Revenues from this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoing development and regulatory activities. Accordingly, this payment is recognized ratably as revenue over the period in which we expect the services to be rendered, which is approximately 14 years. In addition to the upfront payment, we received a milestone payment of $3.0 million , less withholding taxes, in March 2015, which we earned upon the February 2015 approval of BELVIQ for marketing in South Korea for weight management. We manufacture BELVIQ at our facility in Switzerland, and sell BELVIQ to Ildong for a purchase price starting at the higher of the defined minimum amount or 35% of Ildong’s annual net product sales (which are the gross invoiced sales less certain deductions described in the Ildong Agreement), or the Ildong Product Purchase Price. The Ildong Product Purchase Price will increase on a tiered basis up to the higher of the defined minimum amount or 45% on the portion of annual net product sales exceeding $15.0 million . However, in no event will the Ildong Product Purchase Price be less than a defined minimum amount adjusted annually based on a consumer price index. For the three and nine months ended September 30, 2015 , the Ildong Product Purchase Price equaled the defined minimum amount (which exceeded the amounts calculated using the applicable percentages for the applicable tiers of Ildong’s annual net product sales for these periods). If certain annual net product sales amounts are not met, we can convert Ildong’s right to commercialize BELVIQ in South Korea to be non-exclusive. We recognized revenues from our portion of Ildong net product sales of BELVIQ of $1.6 million and $4.2 million for the three and nine months ended September 30, 2015 , respectively.

Share-based Activity

Share-based Activity	9 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Activity	Share-based Activity Share-based Compensation . We recognized share-based compensation expense as follows, in thousands: Three months ended Nine months ended 2015 2014 2015 2014 Research and development $ 2,097 $ 1,753 $ 6,338 $ 5,276 General and administrative 1,751 1,645 5,457 4,665 Total share-based compensation expense $ 3,848 $ 3,398 $ 11,795 $ 9,941 Total share-based compensation expense capitalized into inventory $ 41 $ 22 $ 146 $ 61 Share-based Award Activity. The following table summarizes our stock option activity during the nine months ended September 30, 2015 , in thousands (except per share data): Options Weighted- Average Exercise Price Outstanding at January 1, 2015 15,831 $ 5.25 Granted 3,072 4.46 Exercised (801 ) 2.05 Forfeited/cancelled/expired (750 ) 6.40 Outstanding at September 30, 2015 17,352 $ 5.20 The following table summarizes activity with respect to our time-based restricted stock unit awards, or RSUs, during the nine months ended September 30, 2015 , in thousands (except per share data): RSUs Weighted- Average Grant-Date Fair Value Unvested at January 1, 2015 456 $ 5.72 Granted 281 4.11 Vested (159 ) 5.44 Forfeited/cancelled 0 Unvested at September 30, 2015 578 $ 5.02 In March 2015, March 2014 and March 2013, we granted our executive officers Total Stockholder Return, or TSR, performance restricted stock unit, or PRSU, awards. The PRSUs may be earned and converted into outstanding shares of our common stock based on the TSR of our common stock relative to the TSR over a three-year performance period beginning March 1 of the year granted of the NASDAQ Biotechnology Index. In the aggregate, the target number of shares of common stock that could be be earned under the PRSUs granted in March 2015, March 2014 and March 2013 were originally 745,000 , 695,000 and 780,000 , respectively; however, the actual number of shares that may be earned ranges from 0% to 200% of such amount. In addition, there is a cap on the number of shares that can be earned under the PRSUs equal to six times the grant-date fair value of each award, and funding is capped at 100% if the absolute 3 -year TSR is negative even if performance is above the median. As these awards contain a market condition, we used a Monte Carlo simulation model to estimate the grant-date fair value, which totaled $3.4 million , $5.0 million and $5.9 million for the March 2015, March 2014 and March 2013 grants, respectively, and which is being recognized ratably as services are provided by the executive officers over the performance period. The following table sets forth the assumptions used to value the PRSUs granted in March 2015 and their estimated grant-date fair value: Risk-free interest rate 1.1 % Dividend yield 0 % Expected volatility 75 % Remaining performance period (years) 2.97 Estimated fair value per share of PRSUs granted $ 4.50 Of the target number of shares of 745,000 for the March 2015 grants, 695,000 for the March 2014 grants and 780,000 for the March 2013 grants, 276,389 , 169,445 and 113,334 , respectively, will not be eligible to vest at the end of the performance period due to our former Chief Executive Officer’s retirement on October 5, 2015, and our former Chief Financial Officer’s resignation on July 10, 2015. (See Note 15.) All of the PRSUs granted to date were outstanding and unvested at September 30, 2015 .

Concentrations of Credit Risk a

Concentrations of Credit Risk and Major Customers	9 Months Ended
	Sep. 30, 2015
Risks and Uncertainties [Abstract]
Concentrations of Credit Risk and Major Customers	Concentrations of Credit Risk and Major Customers Financial instruments, which potentially subject us to concentrations of credit risk, consist primarily of cash and cash equivalents. We limit our exposure to credit loss by holding our cash primarily in US dollars or, from time to time, placing our cash and investments in US government, agency and government-sponsored enterprise obligations and in corporate debt instruments that are rated investment grade, in accordance with an investment policy approved by our Board of Directors. Eisai and Ildong are the exclusive distributors of BELVIQ in the United States and South Korea, respectively, which are the only jurisdictions for which BELVIQ has received regulatory approval for marketing. We also produce drug products for Siegfried AG, or Siegfried, under a toll manufacturing agreement, and most of our toll manufacturing revenues are attributable to Siegfried. Percentages of our total revenues are as follows: Three months ended Nine months ended 2015 2014 2015 2014 Eisai Agreement 58.4 % 96.3 % 62.2 % 94.2 % Ildong Agreement 18.6 % 1.1 % 24.4 % 1.0 % Toll manufacturing agreements 16.0 % 1.9 % 10.5 % 4.3 % Other collaborative agreements 7.0 % 0.7 % 2.9 % 0.5 % Total percentage of revenues 100.0 % 100.0 % 100.0 % 100.0 %

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share We calculate basic and diluted net loss per share using the weighted-average number of shares of common stock outstanding during the period. Since we are in a net loss position, in addition to excluding potentially dilutive out-of-the money securities, we exclude from our calculation of diluted net loss per share all potentially dilutive in-the-money (i) stock options, (ii) RSUs, (iii) PRSUs, (iv) unvested restricted stock in our deferred compensation plan and (v) our previously outstanding warrant, and our diluted net loss per share is the same as our basic net loss per share. The following table presents the weighted-average number of potentially dilutive securities that were excluded from our calculation of diluted net loss per share for the periods presented, in thousands: Three months ended Nine months ended 2015 2014 2015 2014 Stock options 17,462 15,729 17,033 15,541 Warrant 0 55 26 490 RSUs, PRSUs and unvested restricted stock 690 537 576 467 Total 18,152 16,321 17,635 16,498 Because the market condition for 745,000 PRSUs issued in March 2015, 695,000 PRSUs issued in March 2014, and 780,000 PRSUs issued in March 2013, was not satisfied at September 30, 2015 , such securities are excluded from the table above for the three and nine months ended September 30, 2015 . Because the market condition for 695,000 PRSUs issued in March 2014, and 780,000 PRSUs issued in March 2013, was not satisfied at September 30, 2014 , such securities are excluded from the table above for the three and nine months ended September 30, 2014 .

Legal Proceedings

Legal Proceedings	9 Months Ended
	Sep. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Legal Proceedings	Legal Proceedings Beginning on September 20, 2010, a number of complaints were filed in the US District Court for the Southern District of California against us and certain of our current and former employees and directors on behalf of certain purchasers of our common stock. The complaints were brought as purported stockholder class actions, and, in general, include allegations that we and certain of our current and former employees and directors violated federal securities laws by making materially false and misleading statements regarding our BELVIQ program, thereby artificially inflating the price of our common stock. The plaintiffs sought unspecified monetary damages and other relief. On August 8, 2011, the Court consolidated the actions and appointed a lead plaintiff and lead counsel. On November 1, 2011, the lead plaintiff filed a consolidated amended complaint. On March 28, 2013, the Court dismissed the consolidated amended complaint without prejudice. On May 13, 2013, the lead plaintiff filed a second consolidated amended complaint. On November 5, 2013, the Court dismissed the second consolidated amended complaint without prejudice as to all parties except for Robert E. Hoffman, who was dismissed from the action with prejudice. On November 27, 2013, the lead plaintiff filed a motion for leave to amend the second consolidated amended complaint. On March 20, 2014, the Court denied plaintiff’s motion and dismissed the second consolidated amended complaint with prejudice. On April 18, 2014, the lead plaintiff filed a notice of appeal, and on August 27, 2014, the lead plaintiff filed his appellate brief in the US Court of Appeals for the Ninth Circuit. On October 24, 2014, we filed our answering brief in response to the lead plaintiff’s appeal. On December 5, 2014, the lead plaintiff filed his reply brief. Due to the stage of these proceedings, we are not able to predict or reasonably estimate the ultimate outcome or possible losses relating to these claims.

Issuance of Common Stock

Issuance of Common Stock	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Issuance of Common Stock	Issuance of Common Stock In January 2015, we sold 21,000,000 shares of our common stock, par value $0.0001 per share, at a price of $4.8139 per share to the underwriters. We received approximately $100.7 million in net proceeds from this offering after deducting offering expenses.

Development, Marketing and Supp

Development, Marketing and Supply Agreement with Riovant	9 Months Ended
	Sep. 30, 2015
Roivant
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development, Marketing and Supply Agreement with Riovant	Development, Marketing and Supply Agreement with Roivant In May 2015, Arena GmbH and Roivant Sciences Ltd., or Roivant, entered into a Development, Marketing and Supply Agreement for nelotanserin, our internally discovered inverse agonist of the serotonin 2A receptor that we previously studied for insomnia before discontinuing development for such indication. Under this agreement, we granted Roivant exclusive worldwide rights to develop and commercialize nelotanserin, subject to regulatory approval. In connection with entering into the agreement, we received an upfront payment of $4.0 million from Roivant in May 2015. Revenues from this upfront payment were deferred, as we determined that the exclusive rights did not have standalone value without our ongoing development and regulatory activities. Accordingly, this payment is recognized ratably as revenue over the period in which we expect the services to be rendered, which is approximately five years . We are also eligible to receive up to $41.5 million in development and regulatory milestone payments and are eligible to receive payments from sales of nelotanserin and purchase price adjustment payments based on the annual net product sales of nelotanserin. In October 2015, Roivant assigned the exclusive rights to develop and commercialize nelotanserin to its subsidiary, Axovant Sciences Ltd.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Retirement of Former President and Chief Executive Officer. On October 5, 2015, at the request of our Board of Directors, Jack Lief, our former President, Chief Executive Officer and principal financial officer, retired from the company, including from our Board of Directors. In connection with his retirement, we entered into a separation agreement with Mr. Lief, which provides that he will be entitled to receive the following severance compensation and other benefits (which amounts are consistent with our Amended and Restated Severance Benefit Plan, dated effective December 30, 2008, as amended): (1) a cash severance payment of approximately $1.8 million (subject to applicable withholdings); (2) continuation of health insurance coverage for a period of 18 months ; (3) acceleration of the stock options and restricted stock units (other than performance-based restricted stock units, or PRSUs) held by Mr. Lief that would otherwise have vested through the 18-month period following the date of his resignation; and (4) continued stock option exercisability until the later of (i) the original post-termination exercise period provided in the applicable stock option agreement or (ii) 18 months (but not beyond the original contractual life of the option). In addition, with respect to outstanding PRSUs, when the Compensation Committee of our Board of Directors determines our relative performance for an applicable performance period, a pro-rata portion of the relevant PRSUs held by Mr. Lief is eligible to vest (based on the percentage of the performance period that Mr. Lief provided service prior to his retirement). The pro-rata vesting may be accelerated if we undergo a change in control before the scheduled end of the performance period. We expect to record a charge of $2.9 million , which includes a non-cash, share-based compensation charge of $1.1 million , related to these benefits in the fourth quarter of 2015. Appointment of Interim Chief Executive Officer. On October 5, 2015, our Board of Directors appointed Harry F. Hixson, Jr., Ph.D., one of our directors, as our interim Chief Executive Officer and interim principal financial officer. Workforce Reduction. On October 27, 2015, as part of a restructuring plan, we committed to a reduction in our US workforce of approximately 35% , or a total of approximately 80 employees, which we plan to substantially complete by December 31, 2015. As a result of this workforce reduction, we expect to incur restructuring charges, primarily in the fourth quarter of 2015, of approximately $3.3 million (substantially all of which is cash expenditures) in connection with one-time employee termination costs, including severance and other benefits.

Basis of Presentation (Policies

Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements of Arena Pharmaceuticals, Inc., which include our wholly owned subsidiaries, should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2014, as filed with the Securities and Exchange Commission, or SEC, from which we derived our balance sheet as of December 31, 2014. The accompanying financial statements have been prepared in accordance with US generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, since they are interim statements, the accompanying financial statements do not include all of the information and notes required by GAAP for complete financial statements. The accompanying financial statements reflect all adjustments, consisting of normal recurring adjustments, that are, in the opinion of our management, necessary to a fair statement of the results for the interim periods presented. Interim results are not necessarily indicative of results for a full year.
New Accounting Guidance	In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2014-09, “Revenue from Contracts with Customers.” ASU No. 2014-09 outlines a comprehensive revenue recognition model which will supersede most current revenue recognition guidance. ASU No. 2014-09 is effective for annual reporting periods, and interim periods within those periods, beginning after December 15, 2017. ASU No. 2014-09 allows for two methods of adoption: (a) “full retrospective” adoption, meaning the standard is applied to all periods presented, or (b) “modified retrospective” adoption, meaning the cumulative effect of applying ASU No. 2014-09 is recognized as an adjustment to the opening retained earnings balance for the year of implementation. We have not yet selected an adoption method as we are currently evaluating the impact of ASU No. 2014-09 on our consolidated financial statements. In August 2014, the FASB issued ASU No. 2014-15, “Presentation of Financial Statements – Going Concern: Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern.” Under GAAP, continuation of a reporting entity as a going concern is presumed as the basis for preparing financial statements unless and until the entity’s liquidation becomes imminent. Preparation of financial statements under this presumption is commonly referred to as the going concern basis of accounting. If and when an entity’s liquidation becomes imminent, financial statements should be prepared under the liquidation basis of accounting. Even when an entity’s liquidation is not imminent, there may be conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern. In those situations, financial statements should continue to be prepared under the going concern basis of accounting, but ASU No. 2014-15 should be followed to determine whether to disclose information about any relevant conditions and events. ASU No. 2014-15 is effective for the annual reporting period ending after December 15, 2016, and for annual and interim periods thereafter. We do not expect the adoption of ASU No. 2014-15 to have a material impact on our consolidated financial statements.
Use of Estimates	The preparation of financial statements in accordance with GAAP requires our management to make estimates and assumptions that affect the reported amounts (including assets, liabilities, revenues and expenses) and related disclosures. The amounts reported could differ under different estimates and assumptions.
Fair Value Measurements	We measure our financial assets and liabilities at fair value, which is defined as the exit price, or the amount that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. We use the following three-level valuation hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs to value our financial assets and liabilities: Level 1 - Observable inputs such as unadjusted quoted prices in active markets for identical instruments. Level 2 - Quoted prices for similar instruments in active markets or inputs that are observable for the asset or liability, either directly or indirectly. Level 3 - Significant unobservable inputs based on our assumptions.
Derivative Liabilities	The warrant was revalued on each balance sheet date, with changes in the fair value between reporting periods recorded in the interest and other income (expense) section of our condensed consolidated statements of operations and comprehensive loss.
Concentration of Credit Risk and Major Customers	Financial instruments, which potentially subject us to concentrations of credit risk, consist primarily of cash and cash equivalents. We limit our exposure to credit loss by holding our cash primarily in US dollars or, from time to time, placing our cash and investments in US government, agency and government-sponsored enterprise obligations and in corporate debt instruments that are rated investment grade, in accordance with an investment policy approved by our Board of Directors. Eisai and Ildong are the exclusive distributors of BELVIQ in the United States and South Korea, respectively, which are the only jurisdictions for which BELVIQ has received regulatory approval for marketing. We also produce drug products for Siegfried AG, or Siegfried, under a toll manufacturing agreement, and most of our toll manufacturing revenues are attributable to Siegfried.
Net Loss Per Share	We calculate basic and diluted net loss per share using the weighted-average number of shares of common stock outstanding during the period. Since we are in a net loss position, in addition to excluding potentially dilutive out-of-the money securities, we exclude from our calculation of diluted net loss per share all potentially dilutive in-the-money (i) stock options, (ii) RSUs, (iii) PRSUs, (iv) unvested restricted stock in our deferred compensation plan and (v) our previously outstanding warrant, and our diluted net loss per share is the same as our basic net loss per share.

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables present our valuation hierarchy for our financial assets and liabilities that are measured at fair value on a recurring basis, in thousands: Fair Value Measurements at September 30, 2015 Balance Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds 1 $ 133,026 $ 133,026 $ 0 $ 0 Fair Value Measurements at December 31, 2014 Balance Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Money market funds 1 $ 143,913 $ 143,913 $ 0 $ 0 Liabilities: Warrant derivative liabilities $ 474 $ 0 $ 474 $ 0 ______________________ (1) Included in cash and cash equivalents on our condensed consolidated balance sheets.

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2015
Inventory Disclosure [Abstract]
Components of Inventory	Inventory consisted of the following, in thousands: September 30, 2015 December 31, 2014 Raw materials $ 2,412 $ 1,167 Work in process 3,043 3,520 Finished goods at Arena GmbH 828 3,681 Finished goods at Eisai 2,922 2,463 Finished goods at Ildong 1,038 0 Total inventory $ 10,243 $ 10,831

Land, Property and Equipment (T

Land, Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2015
Property, Plant and Equipment [Abstract]
Land, Property and Equipment	Land, property and equipment consisted of the following, in thousands: September 30, 2015 December 31, 2014 Cost $ 173,820 $ 174,938 Less accumulated depreciation and amortization (99,068 ) (92,019 ) Land, property and equipment, net $ 74,752 $ 82,919

Accounts Payable and Other Ac24

Accounts Payable and Other Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2015
Payables and Accruals [Abstract]
Accounts Payable and Other Accrued Liabilities	Accounts payable and other accrued liabilities consisted of the following, in thousands: September 30, 2015 December 31, 2014 Accounts payable $ 1,556 $ 2,844 Accrued compensation 4,222 4,792 Other accrued liabilities 1,540 2,573 Total accounts payable and other accrued liabilities $ 7,318 $ 10,209

Marketing and Supply Agreemen25

Marketing and Supply Agreement with Eisai (Tables)	9 Months Ended
	Sep. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenues Recognized under Eisai Agreement	The following table summarizes the revenues we recognized under our collaboration with Eisai for the periods presented, in thousands: Three months ended Nine months ended 2015 2014 2015 2014 Net product sales $ 3,274 $ 5,726 $ 11,603 $ 12,137 Amortization of upfront payments 1,886 1,885 5,656 5,745 Reimbursement of development expenses 107 143 1,454 7,456 Milestone payment 0 0 0 500 Reimbursement of patent and trademark expenses 72 105 304 333 Subtotal other Eisai collaborative revenue 2,065 2,133 7,414 14,034 Total $ 5,339 $ 7,859 $ 19,017 $ 26,171
Deferred Revenues Attributable to Eisa	The following table summarizes the deferred revenues under our collaboration with Eisai, in thousands: September 30, 2015 December 31, 2014 Upfront payments $ 88,818 $ 94,474 Net product sales 12,520 7,081 Total deferred revenues attributable to Eisai 101,338 101,555 Less current portion (20,061 ) (14,622 ) Deferred revenues attributable to Eisai, less current portion $ 81,277 $ 86,933
Summary of Cost Sharing Allocation	The chart below summarizes the general agreement regarding cost sharing between Eisai and us for significant development activities under the Eisai Agreement. In addition, Eisai or we may from time to time conduct approved development of lorcaserin at such party’s own expense. Eisai Second Amended and Restated Marketing and Supply Agreement: Cost Sharing for Development United States Rest of North and South America Remaining Territories BELVIQ - Pre-approval* Not Applicable General Eisai: 90%; Arena: 10% Certain stability work Eisai: 50%; Arena: 50% Up to a total of $100.0 million - Eisai: 50%; Arena: 50% Thereafter, Eisai: 100% BELVIQ - Post-approval* General Eisai: 90%; Arena 10% Non-FDA required portion of CVOT Up to $80.0 million - Eisai: 50%; Arena: 50% Thereafter, Eisai: 100% Certain pediatric studies Eisai: 50%; Arena: 50% General Eisai: 90%; Arena: 10% Certain stability work Eisai: 50%; Arena: 50% Up to a total of $50.0 million - Eisai: 50%; Arena: 50% Thereafter, Eisai: 90%; Arena: 10% Lorcaserin products other than BELVIQ - Pre-approval Up to a total of $250.0 million (as reduced by up to $80.0 million for non-FDA required portion of CVOT) -Eisai: 50%; Arena: 50% Lorcaserin products other than BELVIQ - Post-approval Up to a total of $100.0 million in the aggregate across all additional products - Eisai: 50%; Arena: 50% Thereafter, Eisai: 90%; Arena: 10% ______________________ * Development required by a regulatory authority, with the exception of the non-FDA required portions of the CVOT.

Share-based Activity (Tables)

Share-based Activity (Tables)	9 Months Ended
	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Based Compensation Expense	We recognized share-based compensation expense as follows, in thousands: Three months ended Nine months ended 2015 2014 2015 2014 Research and development $ 2,097 $ 1,753 $ 6,338 $ 5,276 General and administrative 1,751 1,645 5,457 4,665 Total share-based compensation expense $ 3,848 $ 3,398 $ 11,795 $ 9,941 Total share-based compensation expense capitalized into inventory $ 41 $ 22 $ 146 $ 61
Summary of Stock Option Activity	The following table summarizes our stock option activity during the nine months ended September 30, 2015 , in thousands (except per share data): Options Weighted- Average Exercise Price Outstanding at January 1, 2015 15,831 $ 5.25 Granted 3,072 4.46 Exercised (801 ) 2.05 Forfeited/cancelled/expired (750 ) 6.40 Outstanding at September 30, 2015 17,352 $ 5.20
Summary of Restricted Stock Unit Awards Activity	The following table summarizes activity with respect to our time-based restricted stock unit awards, or RSUs, during the nine months ended September 30, 2015 , in thousands (except per share data): RSUs Weighted- Average Grant-Date Fair Value Unvested at January 1, 2015 456 $ 5.72 Granted 281 4.11 Vested (159 ) 5.44 Forfeited/cancelled 0 Unvested at September 30, 2015 578 $ 5.02
Assumptions used to Value Performance Restricted Stock Unit Awards Granted and Estimated Grant Date Fair Value	The following table sets forth the assumptions used to value the PRSUs granted in March 2015 and their estimated grant-date fair value: Risk-free interest rate 1.1 % Dividend yield 0 % Expected volatility 75 % Remaining performance period (years) 2.97 Estimated fair value per share of PRSUs granted $ 4.50

Concentrations of Credit Risk27

Concentrations of Credit Risk and Major Customers (Tables)	9 Months Ended
	Sep. 30, 2015
Risks and Uncertainties [Abstract]
Percentages of Total Revenues	Percentages of our total revenues are as follows: Three months ended Nine months ended 2015 2014 2015 2014 Eisai Agreement 58.4 % 96.3 % 62.2 % 94.2 % Ildong Agreement 18.6 % 1.1 % 24.4 % 1.0 % Toll manufacturing agreements 16.0 % 1.9 % 10.5 % 4.3 % Other collaborative agreements 7.0 % 0.7 % 2.9 % 0.5 % Total percentage of revenues 100.0 % 100.0 % 100.0 % 100.0 %

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2015
Earnings Per Share [Abstract]
Potentially Dilutive Securities Excluded from Calculation of Diluted Net Income Loss Per Share	The following table presents the weighted-average number of potentially dilutive securities that were excluded from our calculation of diluted net loss per share for the periods presented, in thousands: Three months ended Nine months ended 2015 2014 2015 2014 Stock options 17,462 15,729 17,033 15,541 Warrant 0 55 26 490 RSUs, PRSUs and unvested restricted stock 690 537 576 467 Total 18,152 16,321 17,635 16,498

Fair Value Disclosures - Financ

Fair Value Disclosures - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Money market funds	$ 133,026	$ 143,913
Liabilities:
Warrant derivative liabilities		474
Quoted Prices in Active Markets (Level 1)
Assets:
Money market funds	133,026	143,913
Liabilities:
Warrant derivative liabilities		0
Significant Other Observable Inputs (Level 2)
Assets:
Money market funds	0	0
Liabilities:
Warrant derivative liabilities		474
Significant Unobservable Inputs (Level 3)
Assets:
Money market funds	$ 0	0
Liabilities:
Warrant derivative liabilities		$ 0

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Inventory [Line Items]
Raw materials	$ 2,412	$ 1,167
Work in process	3,043	3,520
Inventory	10,243	10,831	[1]
Arena GmbH
Inventory [Line Items]
Finished goods	828	3,681
Eisai
Inventory [Line Items]
Finished goods	2,922	2,463
Ildong
Inventory [Line Items]
Finished goods	$ 1,038	$ 0
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Land, Property and Equipment (D

Land, Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Cost	$ 173,820	$ 174,938
Less accumulated depreciation and amortization	(99,068)	(92,019)
Land, property and equipment, net	$ 74,752	$ 82,919	[1]
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Accounts Payable and Other Ac32

Accounts Payable and Other Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Accounts payable	$ 1,556	$ 2,844
Accrued compensation	4,222	4,792
Other accrued liabilities	1,540	2,573
Total accounts payable and other accrued liabilities	$ 7,318	$ 10,209	[1]
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Derivative Liabilities - Additi

Derivative Liabilities - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	[1]	Aug. 31, 2008
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Issuance of warrant to purchase stock, number of shares				1,106,344
Original exercise price of warrant ($ per warrant)				$ 7.71
Derivative liabilities, current	$ 0	$ 474
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Marketing and Supply Agreemen34

Marketing and Supply Agreement with Eisai - Additional Information (Detail)	1 Months Ended				3 Months Ended		9 Months Ended		60 Months Ended
	Jan. 31, 2015$ / prescription	Nov. 30, 2013USD ($)	May. 31, 2012USD ($)	Jul. 31, 2010USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)	Jun. 30, 2015USD ($)	Dec. 31, 2014USD ($)	[1]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Payable to Eisai					$ 10,566,000		$ 10,566,000			$ 23,705,000
Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Recognized milestone revenue					0	$ 0	0	$ 500,000
Payable to Eisai					10,600,000		10,600,000
Maximum | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Prescription cost for patients without commercial coverage | $ / prescription	75
Minimum | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Copay threshold for patients with commercial coverage | $ / prescription	50
UNITED STATES | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase price range minimum		31.50%
Purchase price range maximum		36.50%
Annual net product sales threshold for maximum purchase price		$ 750,000,000
Non US Territories Other Than Europe, China and Japan | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase price range minimum		30.75%
Purchase price range maximum		35.75%
Annual net product sales threshold for maximum purchase price		$ 750,000,000
Europe, China and Japan | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Purchase price range minimum		27.50%
Purchase price range maximum		35.00%
Annual net product sales threshold for maximum purchase price		$ 500,000,000
Original Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative agreement initiation date				2010-07
Collaborative agreement upfront payments				$ 50,000,000
Collaborative agreement, revenue recognition period				16 years
Eisai First Amended Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative agreement initiation date			2012-05
Collaborative agreement upfront payments			$ 5,000,000
Collaborative agreement, revenue recognition period			15 years
Eisai Second Amended Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative agreement initiation date		2013-11
Collaborative agreement upfront payments		$ 60,000,000
Collaborative agreement, revenue recognition period		15 years
Recognized milestone revenue									$ 86,500,000
Additional milestone payments on achievement					176,000,000		176,000,000
Aggregate one-time purchase price adjustments					1,560,000,000		1,560,000,000
Eisai Second Amended Agreement | All Territories
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate one-time purchase price adjustments					1,190,000,000		1,190,000,000
First annual net sales threshold to earn purchase price adjustments in all territories		$ 250,000,000
Last annual net sales threshold to earn purchase price adjustments in all territories		2,500,000,000
Portion of purchase price adjustment payments		330,000,000
Annual net sales threshold to earn portion of purchase price adjustments in all territories		1,000,000,000
Eisai Second Amended Agreement | All Non-US territories
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional one-time purchase price adjustment payments					370,000,000		370,000,000
Eisai Second Amended Agreement | Non-US Territories in North and South America
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional one-time purchase price adjustment payments					185,000,000		185,000,000
First annual net sales threshold to earn purchase price adjustments outside of the US		100,000,000
Last annual net sales threshold to earn additional purchase price adjustments outside of the US		1,000,000,000
Eisai Second Amended Agreement | Territories Outside of North and South America
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional one-time purchase price adjustment payments					$ 185,000,000		$ 185,000,000
First annual net sales threshold to earn purchase price adjustments outside of the US		100,000,000
Last annual net sales threshold to earn additional purchase price adjustments outside of the US		$ 1,000,000,000
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Marketing and Supply Agreemen35

Marketing and Supply Agreement with Eisai - Revenues Recognized under Collaboration with Eisai (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net product sales	$ 4,884	$ 5,726	$ 15,787	$ 12,137
Total revenues	9,138	8,164	30,575	27,779
Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net product sales	3,274	5,726	11,603	12,137
Amortization of upfront payments	1,886	1,885	5,656	5,745
Milestone payment	0	0	0	500
Subtotal other Eisai collaborative revenue	2,065	2,133	7,414	14,034
Total revenues	5,339	7,859	19,017	26,171
Eisai | Research and development
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses	107	143	1,454	7,456
Eisai | Patent and trademark expenses
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of expenses	$ 72	$ 105	$ 304	$ 333

Marketing and Supply Agreemen36

Marketing and Supply Agreement with Eisai - Deferred Revenues under Collaboration with Eisai (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Deferred Revenue Arrangement [Line Items]
Less current portion	$ (23,215)	$ (15,238)	[1]
Deferred revenues, less current portion	89,845	93,064	[1]
Eisai
Deferred Revenue Arrangement [Line Items]
Total deferred revenues	101,338	101,555
Less current portion	(20,061)	(14,622)
Deferred revenues, less current portion	81,277	86,933
Eisai | Upfront payments
Deferred Revenue Arrangement [Line Items]
Total deferred revenues	88,818	94,474
Eisai | Net product sales
Deferred Revenue Arrangement [Line Items]
Total deferred revenues	$ 12,520	$ 7,081
[1]	The balance sheet data at December 31, 2014, has been derived from audited financial statements at that date. It does not include, however, all of the information and notes required by US generally accepted accounting principles for complete financial statements.

Marketing and Supply Agreemen37

Marketing and Supply Agreement with Eisai - Summary of Cost Sharing Allocation (Detail)	9 Months Ended
	Sep. 30, 2015USD ($)
Belviq Product Pre Approval Up To One Hundred Million Dollars | Territories Outside of North and South America | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate expense cap on equal split of development expenses	$ 100,000,000
Portion of expenses	50.00%
Belviq Product Pre Approval Up To One Hundred Million Dollars | Territories Outside of North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Pre Approval More Than One Hundred Million Dollars | Territories Outside of North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	100.00%
Belviq Product Post Approval Up To Fifty Million Dollars | Territories Outside of North and South America | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate expense cap on equal split of development expenses	$ 50,000,000
Portion of expenses	50.00%
Belviq Product Post Approval Up To Fifty Million Dollars | Territories Outside of North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Post Approval More Than Fifty Million Dollars | Territories Outside of North and South America | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	10.00%
Belviq Product Post Approval More Than Fifty Million Dollars | Territories Outside of North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	90.00%
Belviq Product Pre Approval | Non-US Territories in North and South America | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	10.00%
Belviq Product Pre Approval | Non-US Territories in North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	90.00%
Belviq Product Pre Approval Certain Stability Work | Non-US Territories in North and South America | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Pre Approval Certain Stability Work | Non-US Territories in North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Post Approval | Non-US Territories in North and South America | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	10.00%
Belviq Product Post Approval | Non-US Territories in North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	90.00%
Belviq Product Post Approval | UNITED STATES | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	10.00%
Belviq Product Post Approval | UNITED STATES | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	90.00%
Belviq Product Post Approval Certain Stability Work | Non-US Territories in North and South America | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Post Approval Certain Stability Work | Non-US Territories in North and South America | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Post Approval Certain Pediatric Studies | UNITED STATES | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Post Approval Certain Pediatric Studies | UNITED STATES | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Post Approval Non Fda Required Portion Of Cardiovascular Outcomes Trial Up To Eighty Million Dollars | UNITED STATES | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate expense cap on equal split of development expenses	$ 80,000,000
Portion of expenses	50.00%
Belviq Product Post Approval Non Fda Required Portion Of Cardiovascular Outcomes Trial Up To Eighty Million Dollars | UNITED STATES | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Belviq Product Post Approval Non Fda Required Portion Of Cardiovascular Outcomes Trial More Than Eighty Million Dollars | UNITED STATES | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	100.00%
Lorcaserin Product Other Than Belviq Pre Approval | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Lorcaserin Product Other Than Belviq Pre Approval | Arena GmbH | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate expense cap on equal split of development expenses	$ 250,000,000
Lorcaserin Product Other Than Belviq Pre Approval | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Lorcaserin Product Other Than Belviq Post Approval Up To One Hundred Million Dollars | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate expense cap on equal split of development expenses	$ 100,000,000
Portion of expenses	50.00%
Lorcaserin Product Other Than Belviq Post Approval Up To One Hundred Million Dollars | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	50.00%
Lorcaserin Product Other Than Belviq Post Approval More Than One Hundred Million Dollars | Arena GmbH
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	10.00%
Lorcaserin Product Other Than Belviq Post Approval More Than One Hundred Million Dollars | Eisai
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Portion of expenses	90.00%

Marketing and Supply Agreemen38

Marketing and Supply Agreement with Ildong (Detail) - USD ($)	1 Months Ended			3 Months Ended		9 Months Ended
	May. 31, 2015	Mar. 31, 2015	Nov. 30, 2012	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Net product sales				$ 4,884,000	$ 5,726,000	$ 15,787,000	$ 12,137,000
Ildong
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative agreement upfront payments			$ 5,000,000
Collaborative agreement, revenue recognition period	5 years		14 years
Milestone payment		$ 3,000,000
Purchase price range minimum			35.00%
Purchase price range maximum			45.00%
Annual net product sales threshold for maximum purchase price			$ 15,000,000
Net product sales				$ 1,600,000		$ 4,200,000

Share-based Activity - Share Ba

Share-based Activity - Share Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 3,848	$ 3,398	$ 11,795	$ 9,941
Total share-based compensation expense capitalized into inventory	41	22	146	61
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	2,097	1,753	6,338	5,276
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 1,751	$ 1,645	$ 5,457	$ 4,665

Share-based Activity - Summary

Share-based Activity - Summary of Stock Option Activity (Detail) - Stock options shares in Thousands	9 Months Ended
	Sep. 30, 2015$ / sharesshares
Number of stock options
Outstanding at January 1, 2015	15,831
Granted	3,072
Exercised	(801)
Forfeited/cancelled/expired	(750)
Outstanding at September 30, 2015	17,352
Weighted- Average Exercise Price
Outstanding at January 1, 2015 | $ / shares	$ 5.25
Granted | $ / shares	4.46
Exercised | $ / shares	2.05
Forfeited/cancelled/expired | $ / shares	6.40
Outstanding at September 30, 2015 | $ / shares	$ 5.20

Share-based Activity - Summar41

Share-based Activity - Summary of Restricted Stock Unit Awards Activity (Detail) - Restricted Stock Units (RSU) shares in Thousands	9 Months Ended
	Sep. 30, 2015$ / sharesshares
Number of Restricted Stock Units
Unvested at January 1, 2015	456
Granted	281
Vested	(159)
Forfeited/cancelled	0
Unvested at September 30, 2015	578
Weighted- Average Grant-Date Fair Value
Unvested at January 1, 2015 | $ / shares	$ 5.72
Granted | $ / shares	4.11
Vested | $ / shares	5.44
Unvested at September 30, 2015 | $ / shares	$ 5.02

Share-based Activity - Addition

Share-based Activity - Additional Information (Detail) $ in Millions	1 Months Ended
	Mar. 31, 2015USD ($)shares	Mar. 31, 2014USD ($)shares	Mar. 31, 2013USD ($)shares
Stockholders Equity [Line Items]
Multiplier of grant-date fair value for cap on number of PRSUs that may be granted	6
Performance restricted stock units
Stockholders Equity [Line Items]
Units granted (shares)	745,000	695,000	780,000
Cap on percentage of funding if the absolute 3-year TSR is negative	100.00%
Vesting period	3 years
PRSU grant-date fair value | $	$ 3.4	$ 5	$ 5.9
Performance restricted stock units | Share Based Compensation
Stockholders Equity [Line Items]
Units granted (shares)	745,000	695,000	780,000
Performance restricted stock units | Minimum
Stockholders Equity [Line Items]
Number of shares to be awarded as a percentage of target amounts	0.00%
Performance restricted stock units | Maximum
Stockholders Equity [Line Items]
Number of shares to be awarded as a percentage of target amounts	200.00%
Awards to former Chief Executive Officer no longer eligible to vest | Performance restricted stock units | Share Based Compensation
Stockholders Equity [Line Items]
Units granted (shares)	276,389	169,445	113,334

Share-based Activity - Assumpti

Share-based Activity - Assumptions and Estimated Fair Value of Performance Restricted Stock Unit Awards (Detail) - Performance restricted stock units	9 Months Ended
	Sep. 30, 2015$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.10%
Dividend yield	0.00%
Expected volatility	75.00%
Remaining performance period (years)	2 years 11 months 19 days
Estimated fair value per share of PRSUs granted	$ 4.50

Concentrations of Credit Risk44

Concentrations of Credit Risk and Major Customers - Percentages of Total Revenues (Detail) - Sales Revenue, Net	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Concentration Risk [Line Items]
Percentage of revenues	100.00%	100.00%	100.00%	100.00%
Eisai Agreement
Concentration Risk [Line Items]
Percentage of revenues	58.40%	96.30%	62.20%	94.20%
Ildong Agreement
Concentration Risk [Line Items]
Percentage of revenues	18.60%	1.10%	24.40%	1.00%
Toll manufacturing agreements
Concentration Risk [Line Items]
Percentage of revenues	16.00%	1.90%	10.50%	4.30%
Other collaborative agreements
Concentration Risk [Line Items]
Percentage of revenues	7.00%	0.70%	2.90%	0.50%

Net Loss Per Share - Potentiall

Net Loss Per Share - Potentially Dilutive Securities Excluded From Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from calculation of diluted net loss per share (shares)	18,152	16,321	17,635	16,498
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from calculation of diluted net loss per share (shares)	17,462	15,729	17,033	15,541
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from calculation of diluted net loss per share (shares)	0	55	26	490
RSUs, PRSUs and unvested restricted stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total antidilutive securities excluded from calculation of diluted net loss per share (shares)	690	537	576	467

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail) - shares	1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Performance restricted stock units
Earnings Per Share [Line Items]
Units granted (shares)	745,000	695,000	780,000

Issuance of Common Stock - Addi

Issuance of Common Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	9 Months Ended
	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014
Equity [Abstract]
Issuance of common stock	21,000,000
Common stock, par value ($ per share)	$ 0.0001
Sale of stock, price per share ($ per share)	$ 4.8139
Net proceeds from sale of common stock	$ 100,700	$ 102,934	$ 4,892

Development, Marketing and Su48

Development, Marketing and Supply Agreement with Riovant - Additional Information (Detail) - USD ($)	1 Months Ended
	May. 31, 2015	Nov. 30, 2012	Sep. 30, 2015
Roivant
Subsequent Event [Line Items]
Expected collaborative agreement upfront payment	$ 4,000,000
Additional milestone payments on achievement			$ 41,500,000
Ildong
Subsequent Event [Line Items]
Expected collaborative agreement upfront payment		$ 5,000,000
Collaborative agreement, revenue recognition period	5 years	14 years

Subsequent Events (Details)

Subsequent Events (Details) $ in Thousands	Oct. 05, 2015USD ($)	Dec. 31, 2015USD ($)employee	Sep. 30, 2015USD ($)	Sep. 30, 2014USD ($)
Subsequent Event [Line Items]
Share-based compensation			$ 11,795	$ 9,941
Subsequent Event | Scenario, Forecast
Subsequent Event [Line Items]
Positions to be eliminated		35.00%
Positions to be eliminated | employee		80
Restructuring charges		$ 3,300
President | Subsequent Event
Subsequent Event [Line Items]
Severance costs	$ 1,800
Health coverage	18 months
President | Subsequent Event | Scenario, Forecast
Subsequent Event [Line Items]
Total charge		2,900
Share-based compensation		$ 1,100