FibroGen (FGEN) 10-Q 9 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2016	Apr. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Trading Symbol	FGEN
Entity Registrant Name	FIBROGEN INC
Entity Central Index Key	921,299
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		62,450,875

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 140,959	$ 153,324
Short-term investments	32,454	27,847
Accounts receivable ($3,662 and $4,455 from a related party)	5,937	15,405
Prepaid expenses and other current assets	4,651	3,988
Total current assets	184,001	200,564
Restricted cash	7,254	7,254
Long-term investments	122,009	131,720
Property and equipment, net	127,613	129,020
Other assets	1,658	2,016
Total assets	442,535	470,574
Current liabilities:
Accounts payable	1,543	6,521
Accrued liabilities ($1,639 and $2,045 to related parties)	44,038	47,932
Deferred revenue	12,722	12,728
Total current liabilities	58,303	67,181
Long-term portion of lease financing obligations	97,077	97,042
Product development obligations	15,786	15,085
Deferred rent	4,581	4,702
Deferred revenue, net of current	85,328	85,132
Other long-term liabilities	5,237	4,607
Total liabilities	266,312	273,749
Commitments and Contingencies	0	0
Stockholders’ equity:
Preferred stock, $0.01 par value; 125,000 shares authorized at March 31, 2016 and December 31, 2015; no shares issued and outstanding at March 31, 2016 and December 31, 2015	0	0
Common stock, $0.01 par value; 225,000 shares authorized at March 31, 2016 and December 31, 2015; 62,425 and 61,985 shares issued and outstanding at March 31, 2016 and December 31, 2015	624	620
Additional paid-in capital	593,935	586,647
Accumulated other comprehensive loss	(1,704)	(1,651)
Accumulated deficit	(435,903)	(408,062)
Total stockholders’ equity	156,952	177,554
Non-controlling interests	19,271	19,271
Total equity	176,223	196,825
Total liabilities, stockholders’ equity and non-controlling interests	$ 442,535	$ 470,574

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Accounts receivable from related party	$ 3,662	$ 4,455
Accrued liabilities to related parties	$ 1,639	$ 2,045
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	125,000,000	125,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	225,000,000	225,000,000
Common stock, shares issued	62,425,000	61,985,000
Common stock, shares outstanding	62,425,000	61,985,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenue:
License and milestone revenue (includes $3,231 and $4,692 from a related party)	$ 19,738	$ 11,506
Collaboration services and other revenue (includes $344 and $634 from a related party)	8,544	4,792
Total revenue	28,282	16,298
Operating expenses:
Research and development	43,650	50,539
General and administrative	11,417	10,482
Total operating expenses	55,067	61,021
Loss from operations	(26,785)	(44,723)
Interest and other, net
Interest expense	(2,777)	(2,758)
Interest income and other, net	1,416	843
Total interest and other, net	(1,361)	(1,915)
Loss before income taxes	(28,146)	(46,638)
Benefit from income taxes	(305)	(271)
Net loss	$ (27,841)	$ (46,367)
Net loss per share - basic and diluted	$ (0.45)	$ (0.78)
Weighted average number of common shares used to calculate net loss per share - basic and diluted	62,184	59,197

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Operations (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
License and milestone revenue from a related party	$ 19,738	$ 11,506
Collaboration services and other revenue from a related party	8,544	4,792
Astellas Agreement [Member]
License and milestone revenue from a related party	3,313	4,692
Collaboration services and other revenue from a related party	$ 352	$ 634

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (27,841)	$ (46,367)
Other comprehensive income (loss):
Foreign currency translation adjustments	(642)	1,705
Available-for-sale investments:
Unrealized gain on investments, net of tax effect	589	711
Reclassification from accumulated other comprehensive loss	0	(5)
Net change in unrealized loss on available-for-sale investments	589	706
Other comprehensive income, net of taxes	(53)	2,411
Comprehensive loss	$ (27,894)	$ (43,956)

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities
Net loss	$ (27,841)	$ (46,367)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,502	1,388
Amortization of premium on investments	695	768
Unrealized foreign exchange gain on short-term investments	(620)	0
Stock-based compensation	7,340	6,446
Tax benefit on unrealized gain on available-for-sale securities	(339)	(271)
Changes in operating assets and liabilities:
Accounts receivable	9,468	6,490
Prepaid expenses and other current assets	(663)	(780)
Other assets	358	(112)
Accounts payable	(4,978)	(2,118)
Accrued liabilities	(3,214)	(7,048)
Deferred revenue	190	(822)
Lease financing liability	136	156
Other long-term liabilities	708	80
Net cash used in operating activities	(17,258)	(42,190)
Investing activities
Purchases of property and equipment	(898)	(448)
Purchases of available-for-sale securities	(19)	0
Proceeds from maturities of available-for-sale securities	5,976	5,000
Net cash provided by investing activities	5,059	4,552
Financing activities
Repayments of lease liability	(101)	(101)
Cash paid for payroll taxes on restricted stock unit releases	(1,261)	0
Proceeds from issuance of common stock	1,213	721
Net cash provided by (used in) financing activities	(149)	620
Effect of exchange rate change on cash and cash equivalents	(17)	(68)
Net decrease in cash and cash equivalents	(12,365)	(37,086)
Cash and cash equivalents at beginning of period	153,324	165,455
Cash and cash equivalents at end of period	$ 140,959	$ 128,369

Description of Operations and S

Description of Operations and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Significant Accounting Policies	1. Significant Accounting Policies Description of Operations FibroGen, Inc. (“FibroGen” or the “Company”) was incorporated in 1993 in Delaware and is a research-based biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutics agents to treat serious unmet medical needs. The Company’s focus in the areas of fibrosis and hypoxia-inducible factor (“HIF”) biology has generated multiple programs targeting various therapeutic areas. The Company’s most advanced product candidate, roxadustat, or FG-4592, is an oral small molecule inhibitor of HIF prolyl hydroxylases in Phase 3 clinical development for the treatment of anemia in chronic kidney disease. FG-3019 is the Company’s monoclonal antibody in Phase 2 clinical development for the treatment of idiopathic pulmonary fibrosis, pancreatic cancer, Duchenne muscular dystrophy and liver fibrosis. We have taken a global approach with respect to the development and future commercialization of our product candidates, and this includes development and commercialization in the People’s Republic of China (“China”). Basis of Presentation and Principles of Consolidation The condensed consolidated financial statements include the accounts of FibroGen, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe Oy and FibroGen China Anemia Holdings, Ltd. (“FibroGen China”). All inter-company transactions and balances have been eliminated in consolidation. The Company operates in one segment — the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs. The unaudited condensed consolidated financial statements and related disclosures have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) applicable to interim financial reporting and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X The financial information included herein should be read in conjunction with the consolidated financial statements and related notes in the 2015 Form 10-K. The accounting policies used by the Company in its presentation of interim financial results are consistent with those presented in Note 2 to the consolidated financial statements included in the 2015 Form 10-K. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. In our opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair presentation of our financial position, results of operations and cash flows for the interim periods presented. Recently Issued Accounting Guidance Not Yet Adopted In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718) In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10) In August 2014, the FASB issued ASU 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 May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606)

Collaboration Agreements

Collaboration Agreements	3 Months Ended
	Mar. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration Agreements	2. Collaboration Agreements Astellas Agreements Japan Agreement In June 2005, the Company entered into a collaboration agreement with Astellas Pharma Inc. (“Astellas”) for the development and commercialization (but not manufacture) of roxadustat for the treatment of anemia in Japan (“Japan Agreement”). Under this agreement, Astellas paid license fees and other consideration totaling $40.1 million (such amounts were fully received as of February 2009). The Japan Agreement also provides for additional development and regulatory approval milestone payments up to $117.5 million, a commercial sales related milestone of $15.0 million and additional consideration based on net sales (as defined) in the low 20% range after commercial launch. A clinical milestone payment of $12.5 million was received in 2013. The Company evaluated the criteria under ASC 605-28 and concluded that the aforementioned milestone was substantive. Europe Agreement In April 2006, the Company entered into a separate collaboration agreement with Astellas for the development and commercialization of roxadustat for the treatment of anemia in Europe, the Middle East, the Commonwealth of Independent States and South Africa (“Europe Agreement”). Under the terms of the Europe Agreement, Astellas paid license fees and other upfront consideration totaling $320.0 million (such amounts were fully received as of February 2009). The Europe Agreement also provides for additional development and regulatory approval milestone payments up to $425.0 million. Clinical milestone payments of $40.0 million and $50.0 million were received in 2010 and 2012, respectively. The Company evaluated the criteria under ASC 605-28 and concluded that each of those milestones was substantive. Under the Europe Agreement, Astellas committed to fund 50% of joint development costs for Europe and North America, and all territory-specific costs. The Europe Agreement also provides for tiered payments based on net sales of product (as defined) in the low 20% range. AstraZeneca Agreements U.S./Rest of World Agreement Effective July 30, 2013, the Company entered into a collaboration agreement with AstraZeneca AB (“AstraZeneca”) for the development and commercialization of roxadustat for the treatment of anemia in the U.S. and all other countries in the world, other than China, not previously licensed under the Astellas Europe and Astellas Japan Agreements (“U.S./RoW Agreement”). It also excludes China, which is covered by a separate agreement with AstraZeneca described below. Under the terms of the U.S./RoW Agreement, AstraZeneca has agreed to pay upfront, non-contingent and time-based payments totaling $374.0 million, which the Company expects to receive in various amounts through June 2016, of which $312.0 million was received as of March 31, 2016. The remaining payment of $62.0 million is contingent upon the occurrence of a specified event and accordingly is also not considered fixed or determinable. In addition, the U.S./RoW Agreement also provides for development and regulatory approval based milestone payments of up to $550.0 million, which include potential future indications which the companies choose to pursue, and commercial related milestone payments of up to $325.0 million. During the second quarter of 2015, the Company received a $15.0 million development milestone payment as a result of the finalization of its two audited pre-clinical carcinogenicity study reports. The Company evaluated the criteria under ASC 605-28 and concluded that the aforementioned milestone was substantive. Under the U.S./RoW Agreement, the Company and AstraZeneca will share equally in the development costs of roxadustat not already paid for by Astellas, up to a total of $233.0 million (i.e. the Company’s share of development costs is $116.5 million). Any additional development costs incurred by FibroGen during the development period in excess of the $233.0 million (aggregated spend) will be fully reimbursed by AstraZeneca. AstraZeneca will pay the Company tiered royalty payments on AstraZeneca’s future net sales (as defined in the agreement) of roxadustat in the low 20% range. In addition, the Company will receive a transfer price for delivery of commercial product based on a percentage of AstraZeneca’s net sales (as defined in the agreement) in the low- to mid-single digit range. China Agreement Effective July 30, 2013, the Company (through its subsidiaries affiliated with China) entered into a collaboration agreement with AstraZeneca for the development and commercialization (but not manufacture) of roxadustat for the treatment of anemia in China (“China Agreement”). Under the terms of the China Agreement, AstraZeneca agreed to pay upfront consideration totaling $28.2 million (such amounts were fully received as of March 31, 2014). In addition, the China Agreement provides for AstraZeneca to pay regulatory approval and other approval related milestones of up to $161.0 million. The China Agreement also provides for sales related milestone payments of up to $167.5 million and contingent payments of $20.0 million related to possible future compounds. The China Agreement is structured as a 50/50 profit or loss share (as defined) and provides for joint development costs (including capital and equipment costs for construction of the manufacturing plant in China), to be shared equally during the development. Summary of Revenue Recognized Under the Collaboration Agreements The table below summarizes the accounting treatment for the various deliverables pursuant to each of the Astellas and AstraZeneca agreements. License amounts identified below are included in the “License and milestone revenue” line item in the condensed consolidated statements of operations. All other elements identified below are included in the “Collaboration services and other revenue” line item in the condensed consolidated statements of operations. Amounts recognized as revenue under the Japan Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2016 2015 Japan License $ 75 $ 437 Milestones — — Total license and milestone revenue $ 75 $ 437 Collaboration services revenue* $ 4 $ 58 * When and if available compounds, manufacturing — clinical supplies and committee services have each been identified as separate units of accounting with standalone value and amounts allocable to these elements have been recognized and classified within the Collaboration services revenue line item within the condensed consolidated statements of operations. The total arrangement consideration has been allocated to each of the following deliverables under the Japan Agreement, along with any associated deferred revenue as follows (in thousands): Cumulative Revenue Through March 31, 2016 Deferred Revenue at March 31, 2016 Total Consideration Through March 31, 2016 License $ 42,320 $ — $ 42,320 When and if available compounds 15 27 42 Manufacturing--clinical supplies 1,969 — 1,969 Committee services 17 — 17 Total license and collaboration services revenue $ 44,321 $ 27 $ 44,348 Amounts recognized as revenue under the Europe Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2016 2015 Europe License $ 3,238 $ 4,255 Milestones — — Total license and milestone revenue 3,238 4,255 Collaboration services revenue* $ 348 $ 576 * When and if available compounds, manufacturing — clinical supplies, development services — in progress at the time of signing of the agreement, and committee services have each been identified as a separate unit of accounting with standalone value and amounts allocable to these units have been recognized in revenue as services are performed and classified within the Collaboration services revenue line item within the condensed consolidated statements of operations. The total arrangement consideration has been allocated to each of the following deliverables under the Europe Agreement, along with any associated deferred revenue as follows (in thousands): Cumulative Revenue Through March 31, 2016 Deferred Revenue at March 31, 2016 Total Consideration Through March 31, 2016 License $ 404,554 $ — $ 404,554 When and if available compounds 343 427 770 Manufacturing--clinical supplies 9,690 — 9,690 Development services--in progress 32,413 — 32,413 Committee services 278 2 280 Total license and collaboration services revenue $ 447,278 $ 429 $ 447,707 Amounts recognized as revenue under the U.S./RoW Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2016 2015 U.S. / RoW and China License $ 16,425 $ 6,814 Milestones — — Total license and milestone revenue 16,425 6,814 Collaboration services revenue* 8,184 4,138 China single unit of accounting** $ — $ — * Co-development, information sharing, and committee services have been combined into a single unit of accounting because the requirements to share information and serve on committees are useful only in combination with the development services, and because all three items are delivered over the same period while manufacturing — clinical supplies has been identified as a separate unit of accounting with standalone value and amounts allocable to this unit of accounting have been recognized and classified within the Collaboration services revenue line item within the condensed consolidated statements of operations. ** All revenues attributable to the China unit of accounting are deferred until all deliverables are met. The China license and collaboration services elements have been combined into a single unit of accounting and consideration allocable to this unit is being deferred due to FibroGen’s retention of manufacturing rights and lack of standalone value. The total arrangement consideration has been allocated to each of the following deliverables under the U.S./RoW Agreement, along with any associated deferred revenue as follows (in thousands): Cumulative Revenue Through March 31, 2016 Deferred Revenue at March 31, 2016 Total Consideration Through March 31, 2016 License $ 306,191 $ — $ 306,191 Co-development, information sharing & committee services 58,317 34,775 93,092 Manufacturing--clinical supplies 261 57 318 China-single unit of accounting — 62,761 62,761 Total license and collaboration services revenue $ 364,769 $ 97,593 $ 462,362 Other Revenues Other revenues consist of royalty payments received, which are recorded on a monthly basis as they are reported to the Company, and collagen feasibility sales. Other revenues were immaterial for all periods presented. Deferred Revenue Deferred revenue represents amounts billed to the Company’s collaboration partners for which the related revenues have not been recognized because one or more of the revenue recognition criteria have not been met. The current portion of deferred revenue represents the amount to be recognized within one year from the balance sheet date based on the estimated performance period of the underlying deliverables. The long term portion of deferred revenue represents amounts to be recognized after one year through the end of the non-contingent performance period of the underlying deliverables. The long term portion of deferred revenue also includes amounts allocated to the China unit of accounting under the AstraZeneca arrangement as revenue recognition associated with this unit of accounting is tied to the commercial launch of the products within China, which is not expected to occur within the next year.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The fair values of our financial assets that are measured on a recurring basis are as follows (in thousands): March 31, 2016 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 126,279 $ — $ 126,279 Bond and mutual funds 25,712 — — 25,712 Equity investments 231 — — 231 Money market funds 44,761 — — 44,761 Certificate of deposits — 2,241 — 2,241 Total $ 70,704 $ 128,520 $ — $ 199,224 December 31, 2015 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 126,103 $ — $ 126,103 Bond and mutual funds 25,052 — — 25,052 Equity investments 197 — — 197 Money market funds 77,639 — — 77,639 Certificate of deposits — 8,215 — 8,215 Total $ 102,888 $ 134,318 $ — $ 237,206 Our Level 2 investments are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar investments, issuer credit spreads, benchmark investments, prepayment/default projections based on historical data and other observable inputs. The fair values of our financial liabilities that are carried at historical cost are as follows (in thousands): March 31, 2016 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,480 $ 97,480 December 31, 2015 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,445 $ 97,445 The fair values of our financial liabilities were derived by using an income approach, which required Level 3 inputs such as discounted estimated future cash flows. There were no transfers of assets or liabilities between levels for any of the periods presented.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	4. Balance Sheet Components Cash and Cash Equivalents Cash and cash equivalents consisted of the following (in thousands): March 31, 2016 December 31, 2015 Cash $ 96,198 $ 75,685 Money market funds 44,761 77,639 Total cash and cash equivalents $ 140,959 $ 153,324 At March 31, 2016, a total of $26.0 million of our cash and cash equivalents were held outside of the U.S. in our foreign subsidiaries to be used primarily for our China operations. Investments All investments are classified as available-for-sale. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale investments by major investments type are summarized in the tables below (in thousands): March 31, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 125,825 $ 529 $ (75 ) $ 126,279 Certificate of deposits 2,241 — — 2,241 Bond and mutual funds 25,712 — — 25,712 Equity investments 126 105 — 231 Total investments $ 153,904 $ 634 $ (75 ) $ 154,463 December 31, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 126,522 $ 54 $ (473 ) $ 126,103 Certificate of deposits 8,217 — (2 ) 8,215 Bond and mutual funds 25,052 — — 25,052 Equity investments 126 71 — 197 Total investments $ 159,917 $ 125 $ (475 ) $ 159,567 At March 31, 2016, all of the available-for-sale investments had contractual maturities within three years. The Company periodically reviews its available-for-sale investments for other-than-temporary impairment. The Company considers factors such as the duration, severity and the reason for the decline in value, the potential recovery period and our intent to sell. For debt securities, the Company also considers whether (i) it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. During the three months ended March 31, 2016 and 2015, the Company did not recognize any other-than-temporary impairment loss. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): March 31, 2016 December 31, 2015 Preclinical and clinical trial accruals $ 29,023 $ 27,973 Payroll and related accruals 9,511 13,535 Professional services 1,338 1,662 Other 4,166 4,762 Total accrued liabilities $ 44,038 $ 47,932

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	5. Stock-Based Compensation Stock-based compensation expense was allocated to research and development and general and administrative expense as follows (in thousands): Three Months Ended March 31, 2016 2015 Research and development $ 4,496 $ 4,222 General and administrative 2,844 2,224 Total stock-based compensation expense $ 7,340 $ 6,446 The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows: Three Months Ended March 31, 2016 2015 Stock Options Expected term (in years) 5.3 5.2 Expected volatility 69 % 70 % Risk-free interest rate 1.4 1.4 Expected dividend yield — — Weighted average estimated fair value $ 11.46 $ 17.49 ESPPs Expected term (in years) 0.4 - 2.0 0.4 - 2.0 Expected volatility 58.5 - 70.3% 58.5 - 68.3% Risk-free interest rate 0.1 - 0.9% 0.1 - 0.4% Expected dividend yield — — Weighted average estimated fair value $ 12.80 $ 13.27

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes The benefit from income taxes for the three months ended March 31, 2016 was primarily due to the discrete tax effect arising from other comprehensive income related to available-for-sale securitie s Based upon the weight of available evidence, which includes our historical operating performance, reported cumulative net losses since inception and expected continuing net loss, we have established and continue to maintain a full valuation allowance against our deferred tax assets as we do not currently believe that realization of those assets is more likely than not.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	7. Related Party Transactions Astellas is an equity investor in the Company and considered a related party. During the quarter ended March 31, 2016 and 2015, the Company recorded revenue related to collaboration agreements with Astellas of $3.7 million and $5.3 million, respectively. During the quarter ended March 31, 2016 and 2015, the Company recorded expense related to collaboration agreements with Astellas of $1.6 million and $3.0 million, respectively. As of March 31, 2016 and December 31, 2015, accounts receivable from Astellas were $3.7 million and $4.5 million, respectively, and amounts due to Astellas were $1.6 million and $2.0 million, respectively. Julian N. Stern, a director of the Company since November 1996, is of counsel to the law firm of Goodwin Procter LLP, which he joined in 2008. He has received, and continues to receive, no compensation from Goodwin Procter LLP since joining it as of counsel. The Company retains Goodwin Procter LLP as legal counsel for various matters, primarily consisting of intellectual property matters. During the three months ended March 31, 2016 and 2015, the Company made payments to Goodwin Procter LLP of less than $0.1 million, respectively. As of March 31, 2016 and December 31, 2015, the balance of accrued liability for Goodwin Proctor LLP was immaterial.

Description of Operations and15

Description of Operations and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2016
Accounting Policies [Abstract]
Description of Operations	Description of Operations FibroGen, Inc. (“FibroGen” or the “Company”) was incorporated in 1993 in Delaware and is a research-based biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutics agents to treat serious unmet medical needs. The Company’s focus in the areas of fibrosis and hypoxia-inducible factor (“HIF”) biology has generated multiple programs targeting various therapeutic areas. The Company’s most advanced product candidate, roxadustat, or FG-4592, is an oral small molecule inhibitor of HIF prolyl hydroxylases in Phase 3 clinical development for the treatment of anemia in chronic kidney disease. FG-3019 is the Company’s monoclonal antibody in Phase 2 clinical development for the treatment of idiopathic pulmonary fibrosis, pancreatic cancer, Duchenne muscular dystrophy and liver fibrosis. We have taken a global approach with respect to the development and future commercialization of our product candidates, and this includes development and commercialization in the People’s Republic of China (“China”).
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The condensed consolidated financial statements include the accounts of FibroGen, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe Oy and FibroGen China Anemia Holdings, Ltd. (“FibroGen China”). All inter-company transactions and balances have been eliminated in consolidation. The Company operates in one segment — the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs. The unaudited condensed consolidated financial statements and related disclosures have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) applicable to interim financial reporting and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X The financial information included herein should be read in conjunction with the consolidated financial statements and related notes in the 2015 Form 10-K. The accounting policies used by the Company in its presentation of interim financial results are consistent with those presented in Note 2 to the consolidated financial statements included in the 2015 Form 10-K.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. In our opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair presentation of our financial position, results of operations and cash flows for the interim periods presented.
Recently Issued Accounting Guidance Not Yet Adopted	Recently Issued Accounting Guidance Not Yet Adopted In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-09, Compensation - Stock Compensation (Topic 718) In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10) In August 2014, the FASB issued ASU 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 May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606)

Collaboration Agreements (Table

Collaboration Agreements (Tables)	3 Months Ended
	Mar. 31, 2016
Japan [Member]
Summary of Revenue Recognized under Agreement	Three Months Ended March 31, Agreement Deliverable 2016 2015 Japan License $ 75 $ 437 Milestones — — Total license and milestone revenue $ 75 $ 437 Collaboration services revenue* $ 4 $ 58 * When and if available compounds, manufacturing — clinical supplies and committee services have each been identified as separate units of accounting with standalone value and amounts allocable to these elements have been recognized and classified within the Collaboration services revenue line item within the condensed consolidated statements of operations.
Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue	The total arrangement consideration has been allocated to each of the following deliverables under the Japan Agreement, along with any associated deferred revenue as follows (in thousands): Cumulative Revenue Through March 31, 2016 Deferred Revenue at March 31, 2016 Total Consideration Through March 31, 2016 License $ 42,320 $ — $ 42,320 When and if available compounds 15 27 42 Manufacturing--clinical supplies 1,969 — 1,969 Committee services 17 — 17 Total license and collaboration services revenue $ 44,321 $ 27 $ 44,348
Europe [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the Europe Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2016 2015 Europe License $ 3,238 $ 4,255 Milestones — — Total license and milestone revenue 3,238 4,255 Collaboration services revenue* $ 348 $ 576 * When and if available compounds, manufacturing — clinical supplies, development services — in progress at the time of signing of the agreement, and committee services have each been identified as a separate unit of accounting with standalone value and amounts allocable to these units have been recognized in revenue as services are performed and classified within the Collaboration services revenue line item within the condensed consolidated statements of operations.
Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue	The total arrangement consideration has been allocated to each of the following deliverables under the Europe Agreement, along with any associated deferred revenue as follows (in thousands): Cumulative Revenue Through March 31, 2016 Deferred Revenue at March 31, 2016 Total Consideration Through March 31, 2016 License $ 404,554 $ — $ 404,554 When and if available compounds 343 427 770 Manufacturing--clinical supplies 9,690 — 9,690 Development services--in progress 32,413 — 32,413 Committee services 278 2 280 Total license and collaboration services revenue $ 447,278 $ 429 $ 447,707
U.S./RoW [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the U.S./RoW Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2016 2015 U.S. / RoW and China License $ 16,425 $ 6,814 Milestones — — Total license and milestone revenue 16,425 6,814 Collaboration services revenue* 8,184 4,138 China single unit of accounting** $ — $ — * Co-development, information sharing, and committee services have been combined into a single unit of accounting because the requirements to share information and serve on committees are useful only in combination with the development services, and because all three items are delivered over the same period while manufacturing — clinical supplies has been identified as a separate unit of accounting with standalone value and amounts allocable to this unit of accounting have been recognized and classified within the Collaboration services revenue line item within the condensed consolidated statements of operations. ** All revenues attributable to the China unit of accounting are deferred until all deliverables are met. The China license and collaboration services elements have been combined into a single unit of accounting and consideration allocable to this unit is being deferred due to FibroGen’s retention of manufacturing rights and lack of standalone value.
Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue	The total arrangement consideration has been allocated to each of the following deliverables under the U.S./RoW Agreement, along with any associated deferred revenue as follows (in thousands): Cumulative Revenue Through March 31, 2016 Deferred Revenue at March 31, 2016 Total Consideration Through March 31, 2016 License $ 306,191 $ — $ 306,191 Co-development, information sharing & committee services 58,317 34,775 93,092 Manufacturing--clinical supplies 261 57 318 China-single unit of accounting — 62,761 62,761 Total license and collaboration services revenue $ 364,769 $ 97,593 $ 462,362

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2016
Fair Value Disclosures [Abstract]
Fair Values of Financial Assets Measured on Recurring Basis	The fair values of our financial assets that are measured on a recurring basis are as follows (in thousands): March 31, 2016 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 126,279 $ — $ 126,279 Bond and mutual funds 25,712 — — 25,712 Equity investments 231 — — 231 Money market funds 44,761 — — 44,761 Certificate of deposits — 2,241 — 2,241 Total $ 70,704 $ 128,520 $ — $ 199,224 December 31, 2015 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 126,103 $ — $ 126,103 Bond and mutual funds 25,052 — — 25,052 Equity investments 197 — — 197 Money market funds 77,639 — — 77,639 Certificate of deposits — 8,215 — 8,215 Total $ 102,888 $ 134,318 $ — $ 237,206
Fair Values of Financial Liabilities Carried at Historical Cost	The fair values of our financial liabilities that are carried at historical cost are as follows (in thousands): March 31, 2016 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,480 $ 97,480 December 31, 2015 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,445 $ 97,445

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Cash and Cash Equivalents	Cash and cash equivalents consisted of the following (in thousands): March 31, 2016 December 31, 2015 Cash $ 96,198 $ 75,685 Money market funds 44,761 77,639 Total cash and cash equivalents $ 140,959 $ 153,324
Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments	All investments are classified as available-for-sale. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale investments by major investments type are summarized in the tables below (in thousands): March 31, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 125,825 $ 529 $ (75 ) $ 126,279 Certificate of deposits 2,241 — — 2,241 Bond and mutual funds 25,712 — — 25,712 Equity investments 126 105 — 231 Total investments $ 153,904 $ 634 $ (75 ) $ 154,463 December 31, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 126,522 $ 54 $ (473 ) $ 126,103 Certificate of deposits 8,217 — (2 ) 8,215 Bond and mutual funds 25,052 — — 25,052 Equity investments 126 71 — 197 Total investments $ 159,917 $ 125 $ (475 ) $ 159,567
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): March 31, 2016 December 31, 2015 Preclinical and clinical trial accruals $ 29,023 $ 27,973 Payroll and related accruals 9,511 13,535 Professional services 1,338 1,662 Other 4,166 4,762 Total accrued liabilities $ 44,038 $ 47,932

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Allocated Stock-Based Compensation Expense	Stock-based compensation expense was allocated to research and development and general and administrative expense as follows (in thousands): Three Months Ended March 31, 2016 2015 Research and development $ 4,496 $ 4,222 General and administrative 2,844 2,224 Total stock-based compensation expense $ 7,340 $ 6,446
Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans	The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows: Three Months Ended March 31, 2016 2015 Stock Options Expected term (in years) 5.3 5.2 Expected volatility 69 % 70 % Risk-free interest rate 1.4 1.4 Expected dividend yield — — Weighted average estimated fair value $ 11.46 $ 17.49 ESPPs Expected term (in years) 0.4 - 2.0 0.4 - 2.0 Expected volatility 58.5 - 70.3% 58.5 - 68.3% Risk-free interest rate 0.1 - 0.9% 0.1 - 0.4% Expected dividend yield — — Weighted average estimated fair value $ 12.80 $ 13.27

Description of Operations and20

Description of Operations and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2016Segment
Accounting Policies [Abstract]
Number of operating segment	1

Collaboration Agreements - Aste

Collaboration Agreements - Astellas Agreements - Additional Information (Detail) - Astellas Agreement [Member] - USD ($) $ in Millions	1 Months Ended		3 Months Ended	12 Months Ended			35 Months Ended	45 Months Ended
	Apr. 30, 2006	Jun. 30, 2005	Mar. 31, 2016	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010	Feb. 28, 2009	Feb. 28, 2009
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received								$ 40.1
Development and regulatory approval milestones		$ 117.5
Commercial sales milestone		$ 15
Additional consideration based on net sales description			Low 20% range
Clinical development milestones				$ 12.5
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received							$ 320
Development and regulatory approval milestones	$ 425
Additional consideration based on net sales description			Low 20% range
Clinical development milestones					$ 50	$ 40
Percentage of joint development costs committed to fund	50.00%

Collaboration Agreements - Astr

Collaboration Agreements - AstraZeneca Agreements - Additional Information 1 (Detail) - AstraZeneca Agreements [Member] - USD ($) $ in Millions	Jul. 30, 2013	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2016
U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected upfront, non-contingent and time-based payments	$ 374
Upfront, non-contingent and time-based payments received				$ 312
Contingent payment	62
Development and regulatory approval milestones	550
Commercial sales milestone	325
Shared development costs	233
Additional consideration based on net sales description		Low 20% range
U.S./RoW [Member] | FibroGen, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shared development costs	116.5
U.S./RoW [Member] | Development Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receipt of development milestone payment			$ 15
China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contingent payment	20
Development and regulatory approval milestones	161
Commercial sales milestone	167.5
Proceeds from upfront payments	$ 28.2

Collaboration Agreements - Summ

Collaboration Agreements - Summary of Revenue Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	$ 19,738	$ 11,506
Collaboration services and other revenue from a related party	8,544	4,792
Revenue recognized	28,282	16,298
Astellas Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	3,313	4,692
Collaboration services and other revenue from a related party	352	634
Astellas Agreement [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	75	437
Milestones revenue	0	0
Total license and milestone revenue	75	437
Collaboration services and other revenue from a related party	4	58
Astellas Agreement [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	3,238	4,255
Milestones revenue	0	0
Total license and milestone revenue	3,238	4,255
Collaboration services and other revenue from a related party	348	576
AstraZeneca Agreements [Member] | China-single unit of accounting [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue recognized	0	0
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	16,425	6,814
Milestones revenue	0	0
Total license and milestone revenue	16,425	6,814
Collaboration services and other revenue from a related party	$ 8,184	$ 4,138

Collaboration Agreements - Tota

Collaboration Agreements - Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue (Detail) $ in Thousands	Mar. 31, 2016USD ($)
Astellas Agreement [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	$ 44,321
Deferred Revenue	27
Total Consideration	44,348
Astellas Agreement [Member] | Japan [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	42,320
Deferred Revenue	0
Total Consideration	42,320
Astellas Agreement [Member] | Japan [Member] | When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	15
Deferred Revenue	27
Total Consideration	42
Astellas Agreement [Member] | Japan [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	1,969
Deferred Revenue	0
Total Consideration	1,969
Astellas Agreement [Member] | Japan [Member] | Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	17
Deferred Revenue	0
Total Consideration	17
Astellas Agreement [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	447,278
Deferred Revenue	429
Total Consideration	447,707
Astellas Agreement [Member] | Europe [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	404,554
Deferred Revenue	0
Total Consideration	404,554
Astellas Agreement [Member] | Europe [Member] | When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	343
Deferred Revenue	427
Total Consideration	770
Astellas Agreement [Member] | Europe [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	9,690
Deferred Revenue	0
Total Consideration	9,690
Astellas Agreement [Member] | Europe [Member] | Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	278
Deferred Revenue	2
Total Consideration	280
Astellas Agreement [Member] | Europe [Member] | Development services-in progress [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	32,413
Deferred Revenue	0
Total Consideration	32,413
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	364,769
Deferred Revenue	97,593
Total Consideration	462,362
AstraZeneca Agreements [Member] | U.S./RoW [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	306,191
Deferred Revenue	0
Total Consideration	306,191
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	261
Deferred Revenue	57
Total Consideration	318
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Co-development, information sharing & committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	58,317
Deferred Revenue	34,775
Total Consideration	93,092
AstraZeneca Agreements [Member] | U.S./RoW [Member] | China-single unit of accounting [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	0
Deferred Revenue	62,761
Total Consideration	$ 62,761

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 154,463	$ 159,567
Total fair value of financial assets	199,224	237,206
Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	126,279	126,103
Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	25,712	25,052
Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	231	197
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	44,761	77,639
Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	2,241	8,215
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	70,704	102,888
Level 1 [Member] | Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 1 [Member] | Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	25,712	25,052
Level 1 [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	231	197
Level 1 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	44,761	77,639
Level 1 [Member] | Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	128,520	134,318
Level 2 [Member] | Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	126,279	126,103
Level 2 [Member] | Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 2 [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 2 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	0
Level 2 [Member] | Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	2,241	8,215
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Level 3 [Member] | Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 3 [Member] | Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 3 [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Level 3 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	0
Level 3 [Member] | Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 0	$ 0

Fair Value Measurements - Fai26

Fair Value Measurements - Fair Values of Financial Liabilities Carried at Historical Cost (Detail) - Lease financing obligations [Member] - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 97,480	$ 97,445
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	0	0
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	0	0
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 97,480	$ 97,445

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Transfers of assets from level 1 to 2	$ 0	$ 0
Transfers of assets from level 2 to 1	0	0
Transfers of liabilities from level 1 to 2	0	0
Transfers of liabilities from level 2 to 1	0	0
Transfers of assets into level 3	0	0
Transfers of assets out of level 3	0	0
Transfers of liabilities into level 3	0	0
Transfers of liabilities out of level 3	$ 0	$ 0

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Cash And Cash Equivalents [Abstract]
Cash	$ 96,198	$ 75,685
Money market funds	44,761	77,639
Total cash and cash equivalents	$ 140,959	$ 153,324	$ 128,369	$ 165,455

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 140,959,000	$ 140,959,000	$ 128,369,000	$ 153,324,000	$ 165,455,000
Contractual maturities of available-for-sale investments	3 years
Other-than-temporary impairment loss		0	$ 0
Foreign subsidiaries [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 26,000,000	$ 26,000,000

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 153,904	$ 159,917
Gross Unrealized Holding Gains	634	125
Gross Unrealized Holding Losses	(75)	(475)
Estimated Fair Value	154,463	159,567
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	125,825	126,522
Gross Unrealized Holding Gains	529	54
Gross Unrealized Holding Losses	(75)	(473)
Estimated Fair Value	126,279	126,103
Certificate of deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,241	8,217
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	(2)
Estimated Fair Value	2,241	8,215
Bond and mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	25,712	25,052
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	25,712	25,052
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126	126
Gross Unrealized Holding Gains	105	71
Gross Unrealized Holding Losses	0	0
Estimated Fair Value	$ 231	$ 197

Balance Sheet Components - Sc31

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Accrued Liabilities Current [Abstract]
Preclinical and clinical trial accruals	$ 29,023	$ 27,973
Payroll and related accruals	9,511	13,535
Professional services	1,338	1,662
Other	4,166	4,762
Total accrued liabilities	$ 44,038	$ 47,932

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Allocated Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 7,340	$ 6,446
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	4,496	4,222
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,844	$ 2,224

Stock-Based Compensation - Sc33

Stock-Based Compensation - Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Employee stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 18 days	5 years 2 months 12 days
Expected volatility	69.00%	70.00%
Risk-free interest rate	1.40%	1.40%
Expected dividend yield	0.00%	0.00%
Weighted average estimated fair value	$ 11.46	$ 17.49
Employee stock purchase plans [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%
Weighted average estimated fair value	$ 12.80	$ 13.27
Expected volatility, minimum	58.50%	58.50%
Expected volatility, maximum	70.30%	68.30%
Risk-free interest rate, minimum	0.10%	0.10%
Risk-free interest rate, maximum	0.90%	0.40%
Employee stock purchase plans [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	4 months 24 days	4 months 24 days
Employee stock purchase plans [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	2 years	2 years

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Accounts receivable from related party	$ 3,662,000		$ 4,455,000
Accrued liabilities to related parties	1,639,000		2,045,000
Goodwin Procter LLP [Member] | Intellectual Property [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Payments for legal matters	100,000	$ 100,000
Astellas [Member] | Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	3,700,000	5,300,000
Expense related to collaboration agreements	1,600,000	$ 3,000,000
Accounts receivable from related party	3,700,000		4,500,000
Accrued liabilities to related parties	$ 1,600,000		$ 2,000,000