FibroGen (FGEN) 10-Q 9 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	Apr. 28, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
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		69,944,209

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 170,598	$ 173,782
Short-term investments	72,824	79,397
Accounts receivable ($3,604 and $4,102 from a related party)	7,248	10,448
Prepaid expenses and other current assets	5,911	2,889
Total current assets	256,581	266,516
Restricted time deposits	6,217	6,217
Long-term investments	53,155	71,010
Property and equipment, net	122,818	123,657
Other assets	2,985	2,152
Total assets	441,756	469,552
Current liabilities:
Accounts payable	2,950	6,223
Accrued liabilities ($289 and $1,615 to related parties)	49,179	50,914
Deferred revenue	7,984	7,988
Total current liabilities	60,113	65,125
Long-term portion of lease financing obligations	97,536	97,352
Product development obligations	15,152	14,854
Deferred rent	4,075	4,212
Deferred revenue, net of current	108,068	106,709
Other long-term liabilities	5,840	6,191
Total liabilities	290,784	294,443
Commitments and Contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value; 125,000 shares authorized at March 31, 2017 and December 31, 2016; no shares issued and outstanding at March 31, 2017 and December 31, 2016	0	0
Common stock, $0.01 par value; 225,000 shares authorized at March 31, 2017 and December 31, 2016; 64,422 and 63,665 shares issued and outstanding at March 31, 2017 and December 31, 2016	644	637
Additional paid-in capital	634,980	625,903
Accumulated other comprehensive loss	(1,020)	(960)
Accumulated deficit	(502,903)	(469,742)
Total stockholders’ equity	131,701	155,838
Non-controlling interests	19,271	19,271
Total equity	150,972	175,109
Total liabilities, stockholders’ equity and non-controlling interests	$ 441,756	$ 469,552

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Accounts receivable from related party	$ 3,604	$ 4,102
Accrued liabilities to related parties	$ 289	$ 1,615
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	64,422,000	63,665,000
Common stock, shares outstanding	64,422,000	63,665,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenue:
License and milestone revenue (includes $3,249 and $3,313 from a related party)	$ 19,581	$ 19,738
Collaboration services and other revenue (includes $340 and $352 from a related party)	7,310	8,544
Total revenue	26,891	28,282
Operating expenses:
Research and development	46,732	43,650
General and administrative	11,530	11,417
Total operating expenses	58,262	55,067
Loss from operations	(31,371)	(26,785)
Interest and other, net
Interest expense	(2,375)	(2,777)
Interest income and other, net	645	1,416
Total interest and other, net	(1,730)	(1,361)
Loss before income taxes	(33,101)	(28,146)
Provision for (benefit from) income taxes	60	(305)
Net loss	$ (33,161)	$ (27,841)
Net loss per share - basic and diluted	$ (0.52)	$ (0.45)
Weighted average number of common shares used to calculate net loss per share - basic and diluted	64,037	62,184

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Operations (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
License and milestone revenue from a related party	$ 19,581	$ 19,738
Collaboration services and other revenue from a related party	7,310	8,544
Astellas Agreement [Member]
License and milestone revenue from a related party	3,249	3,313
Collaboration services and other revenue from a related party	$ 340	$ 352

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (33,161)	$ (27,841)
Other comprehensive income (loss):
Foreign currency translation adjustments	(255)	(642)
Available-for-sale investments:
Unrealized gain on investments, net of tax effect	179	589
Reclassification from accumulated other comprehensive loss	16	0
Net change in unrealized gain on available-for-sale investments	195	589
Other comprehensive loss, net of taxes	(60)	(53)
Comprehensive loss	$ (33,221)	$ (27,894)

Condensed Consolidated Stateme7

Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities
Net loss	$ (33,161)	$ (27,841)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	1,525	1,502
Amortization of premium on investments	613	695
Unrealized loss (gain) on short-term investments	1	(620)
Loss on disposal of property and equipment	(4)	0
Stock-based compensation	8,409	7,340
Tax benefit on unrealized gain on available-for-sale securities	0	(339)
Realized gain on sales of available-for-sale securities	(30)	0
Changes in operating assets and liabilities:
Accounts receivable	3,200	9,468
Prepaid expenses and other current assets	(2,943)	(663)
Other assets	(833)	358
Accounts payable	(3,273)	(4,978)
Accrued liabilities	(1,916)	(3,214)
Deferred revenue	1,355	190
Lease financing liability	335	136
Other long-term liabilities	(413)	708
Net cash used in operating activities	(27,135)	(17,258)
Investing activities
Purchases of property and equipment	(636)	(898)
Proceeds from sale of property and equipment	5	0
Purchases of available-for-sale securities	(30)	(19)
Proceeds from sales of available-for-sale securities	10,205	0
Proceeds from maturities of available-for-sale securities	13,864	5,976
Net cash provided by investing activities	23,408	5,059
Financing activities
Repayments of lease liability	(101)	(101)
Cash paid for payroll taxes on restricted stock unit releases	(2,424)	(1,261)
Proceeds from issuance of common stock	3,099	1,213
Net cash provided by (used in) financing activities	574	(149)
Effect of exchange rate change on cash and cash equivalents	(31)	(17)
Net decrease in cash and cash equivalents	(3,184)	(12,365)
Total cash and cash equivalents at beginning of period	173,782	153,324
Total cash and cash equivalents at end of period	$ 170,598	$ 140,959

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2017
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 (“HIF-PHs”) in Phase 3 clinical development for the treatment of anemia in chronic kidney disease (“CKD”). Pamrevlumab, or FG-3019, is the Company’s monoclonal antibody in Phase 2 clinical development for the treatment of idiopathic pulmonary fibrosis (“IPF”), pancreatic cancer, Duchenne muscular dystrophy (“DMD”) and liver fibrosis. The Company has taken a global approach with respect to the development and future commercialization of its product candidates, and this includes development and commercialization in the People’s Republic of China (“China”). The Company is capitalizing on its extensive experience in fibrosis and hypoxia inducible factor (“HIF”) biology and clinical development to advance a pipeline of innovative medicines for the treatment of anemia, fibrotic disease cancer, corneal blindness and other serious unmet medical needs. 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 of the United States (“U.S.”) Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and footnote disclosures normally included in the annual consolidated financial statements. The December 31, 2016 condensed consolidated balance sheet data contained within this Form 10-Q was derived from audited consolidated financial statements included in the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2016 (“2016 Form 10-K”), but does not include all disclosures required by U.S. GAAP. The financial information included herein should be read in conjunction with the consolidated financial statements and related notes in the 2016 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 2016 Form 10-K. Use of Estimates The preparation of the 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. The more significant areas requiring the use of management estimates and assumptions include valuation and recognition of revenue, estimates of accruals related to clinical trial costs, valuation allowances for deferred tax assets, and valuation and recognition of stock-based compensation. On an ongoing basis, management reviews these estimates and assumptions. Changes in facts and circumstances may alter such estimates and 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 statement of our financial position, results of operations and cash flows for the interim periods presented. Recently Issued and Adopted Accounting Guidance In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) Compensation - Stock Compensation (Topic 718) . Recently Issued Accounting Guidance Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments 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 May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers

Collaboration Agreements

Collaboration Agreements	3 Months Ended
	Mar. 31, 2017
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. During the second quarter of 2016, the Company recognized $10.0 million of revenue as a result of the initiation by Astellas of the first Phase 3 clinical study in Japan of roxadustat for treatment of anemia associated with chronic kidney disease in patients on dialysis. The amount was received in early July 2016. 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 (“RoW”) 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 were fully received in various amounts through June 2016. 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 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, which was reached during the fourth quarter of 2015). 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, which were fully received in 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. In September 2016, AstraZeneca approved the protocol related to the development of roxadustat for the treatment of anemia in patients with myelodysplastic syndromes (“MDS”), for which the Company has received approval from the China Food and Drug Administration for its clinical trial application for a Phase 2/3 trial and acceptance of its investigational new drug application from the U.S. Food and Drug Administration for a Phase 3 trial. As a result, for revenue recognition purposes, during the third quarter of 2016, the Company extended the estimated joint development service period for the AstraZeneca agreements from the end of 2018 to the end of 2020, to allow for development of MDS. 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 2017 2016 Japan License $ 212 $ 75 Milestones — — Total license and milestone revenue 212 $ 75 Collaboration services revenue* 11 $ 4 * 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, 2017 Deferred Revenue at March 31, 2017 Total Consideration Through March 31, 2017 License $ 45,922 $ — $ 45,922 When and if available compounds 22 25 47 Manufacturing--clinical supplies 2,131 — 2,131 Committee services 20 — 20 Total license and collaboration services revenue $ 48,095 $ 25 $ 48,120 Amounts recognized as revenue under the Europe Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2017 2016 Europe License $ 3,037 $ 3,238 Milestones — — Total license and milestone revenue 3,037 3,238 Collaboration services revenue* $ 329 $ 348 * 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, 2017 Deferred Revenue at March 31, 2017 Total Consideration Through March 31, 2017 License $ 415,309 $ — $ 415,309 When and if available compounds 387 404 791 Manufacturing--clinical supplies 9,948 — 9,948 Development services--in progress 33,275 — 33,275 Committee services 287 — 287 Total license and collaboration services revenue $ 459,206 $ 404 $ 459,610 Amounts recognized as revenue under the U.S./RoW Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2017 2016 U.S. / RoW and China License $ 16,332 $ 16,425 Milestones — — Total license and milestone revenue 16,332 16,425 Collaboration services revenue* 6,970 8,184 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, 2017 Deferred Revenue at March 31, 2017 Total Consideration Through March 31, 2017 License $ 419,029 $ — $ 419,029 Co-development, information sharing & committee services 97,719 29,680 127,399 Manufacturing--clinical supplies 383 53 436 China-single unit of accounting — 85,890 85,890 Total license and collaboration services revenue $ 517,131 $ 115,623 $ 632,754 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, 2017
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, 2017 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 102,004 $ — $ 102,004 Bond and mutual funds 22,734 — — 22,734 Equity investments 205 — — 205 Money market funds 83,919 — — 83,919 Certificate of deposits — 1,036 — 1,036 Total $ 106,858 $ 103,040 $ — $ 209,898 December 31, 2016 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 126,683 $ — $ 126,683 Bond and mutual funds 22,462 — — 22,462 Equity investments 225 — — 225 Money market funds 94,543 — — 94,543 Certificate of deposits — 1,037 — 1,037 Total $ 117,230 $ 127,720 $ — $ 244,950 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, 2017 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 98,090 $ 98,090 December 31, 2016 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,856 $ 97,856 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, 2017
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, 2017 December 31, 2016 Cash $ 86,679 $ 79,239 Money market funds 83,919 94,543 Total cash and cash equivalents $ 170,598 $ 173,782 At March 31, 2017 and December 31, 2016, a total of $24.4 million and $24.3 million, respectively, 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, 2017 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 101,898 $ 147 $ (41 ) $ 102,004 Certificate of deposits 1,036 — — 1,036 Bond and mutual funds 22,704 205 (175 ) 22,734 Equity investments 126 79 — 205 Total investments $ 125,764 $ 431 $ (216 ) $ 125,979 December 31, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 126,550 $ 182 $ (49 ) $ 126,683 Certificate of deposits 1,037 — — 1,037 Bond and mutual funds 22,305 157 — 22,462 Equity investments 125 100 — 225 Total investments $ 150,017 $ 439 $ (49 ) $ 150,407 At March 31, 2017, all of the available-for-sale investments had contractual maturities within two 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, 2017, the Company did not recognize any other-than-temporary impairment loss. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): March 31, 2017 December 31, 2016 Preclinical and clinical trial accruals $ 31,052 $ 29,550 Payroll and related accruals 9,050 14,232 Professional services 1,434 1,252 Other 7,643 5,880 Total accrued liabilities $ 49,179 $ 50,914

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2017
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, 2017 2016 Research and development $ 4,901 $ 4,496 General and administrative 3,508 2,844 Total stock-based compensation expense $ 8,409 $ 7,340 The assumptions used to estimate the fair value of stock options granted and purchases under the Company’s 2014 Employee Share Purchase Plan (“ESPP”) using the Black-Scholes option valuation model were as follows: Three Months Ended March 31, 2017 2016 Stock Options Expected term (in years) 5.8 5.3 Expected volatility 71.7 % 69.5 % Risk-free interest rate 2.3 1.4 Expected dividend yield — — Weighted average estimated fair value $ 16.16 $ 11.46 ESPPs Expected term (in years) 0.5 - 2.0 0.5 - 2.0 Expected volatility 63.7 - 77.2 % 69.1 - 70.3 % Risk-free interest rate 0.5 - 1.0 % 0.2 - 0.9 % Expected dividend yield — — Weighted average estimated fair value $ 8.86 $ 13.70

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes The provision for income taxes for the three months ended March 31, 2017 was due to foreign 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 securities. Based upon the weight of available evidence, which includes its historical operating performance, reported cumulative net losses since inception and expected continuing net loss, the Company has established and continue to maintain a full valuation allowance against its deferred tax assets as it does not currently believe that realization of those assets is more likely than not.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	7. Related Party Transactions Astellas is an equity investor in the Company and considered a related party. The Company recorded revenue related to collaboration agreements with Astellas of $3.6 million and $3.7 million during the three months ended March 31, 2017 and 2016, respectively. The Company recorded expense related to collaboration agreements with Astellas of $0.3 million and $1.6 million during the three months ended March 31, 2017 and 2016, respectively. As of March 31, 2017 and December 31, 2016, accounts receivable from Astellas were $3.6 million and $4.1 million, respectively, and amounts due to Astellas were $0.3 million and $1.6 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, 2017 and 2016, the Company’s payments to Goodwin Procter LLP were immaterial. As of March 31, 2017 and December 31, 2016, the balance of the accrued liability for Goodwin Proctor LLP was immaterial.

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2017
Subsequent Events [Abstract]
Subsequent Event	8. Subsequent Event On April 11, 2017, the Company closed the follow-on offering of its common stock. In this offering, the Company sold 5,228,750 shares of its common stock at a public offering price of $22.95 per share. Net proceeds from this offering were $115.1 million, after deducting underwriting discounts and commissions of $4.9 million. In addition, the offering expenses were approximately $0.4 million.

Significant Accounting Polici16

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
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 (“HIF-PHs”) in Phase 3 clinical development for the treatment of anemia in chronic kidney disease (“CKD”). Pamrevlumab, or FG-3019, is the Company’s monoclonal antibody in Phase 2 clinical development for the treatment of idiopathic pulmonary fibrosis (“IPF”), pancreatic cancer, Duchenne muscular dystrophy (“DMD”) and liver fibrosis. The Company has taken a global approach with respect to the development and future commercialization of its product candidates, and this includes development and commercialization in the People’s Republic of China (“China”). The Company is capitalizing on its extensive experience in fibrosis and hypoxia inducible factor (“HIF”) biology and clinical development to advance a pipeline of innovative medicines for the treatment of anemia, fibrotic disease cancer, corneal blindness and other serious unmet medical needs.
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 of the United States (“U.S.”) Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and footnote disclosures normally included in the annual consolidated financial statements. The December 31, 2016 condensed consolidated balance sheet data contained within this Form 10-Q was derived from audited consolidated financial statements included in the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2016 (“2016 Form 10-K”), but does not include all disclosures required by U.S. GAAP. The financial information included herein should be read in conjunction with the consolidated financial statements and related notes in the 2016 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 2016 Form 10-K.
Use of Estimates	Use of Estimates The preparation of the 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. The more significant areas requiring the use of management estimates and assumptions include valuation and recognition of revenue, estimates of accruals related to clinical trial costs, valuation allowances for deferred tax assets, and valuation and recognition of stock-based compensation. On an ongoing basis, management reviews these estimates and assumptions. Changes in facts and circumstances may alter such estimates and 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 statement of our financial position, results of operations and cash flows for the interim periods presented.
Recently Issued and Adopted Accounting Guidance	Recently Issued and Adopted Accounting Guidance In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) Compensation - Stock Compensation (Topic 718) .
Recently Issued Accounting Guidance Not Yet Adopted	Recently Issued Accounting Guidance Not Yet Adopted In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments 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 May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606) Revenue Recognition Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers

Collaboration Agreements (Table

Collaboration Agreements (Tables)	3 Months Ended
	Mar. 31, 2017
Japan [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the Japan Agreement were as follows (in thousands): Three Months Ended March 31, Agreement Deliverable 2017 2016 Japan License $ 212 $ 75 Milestones — — Total license and milestone revenue 212 $ 75 Collaboration services revenue* 11 $ 4 * 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, 2017 Deferred Revenue at March 31, 2017 Total Consideration Through March 31, 2017 License $ 45,922 $ — $ 45,922 When and if available compounds 22 25 47 Manufacturing--clinical supplies 2,131 — 2,131 Committee services 20 — 20 Total license and collaboration services revenue $ 48,095 $ 25 $ 48,120
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 2017 2016 Europe License $ 3,037 $ 3,238 Milestones — — Total license and milestone revenue 3,037 3,238 Collaboration services revenue* $ 329 $ 348 * 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, 2017 Deferred Revenue at March 31, 2017 Total Consideration Through March 31, 2017 License $ 415,309 $ — $ 415,309 When and if available compounds 387 404 791 Manufacturing--clinical supplies 9,948 — 9,948 Development services--in progress 33,275 — 33,275 Committee services 287 — 287 Total license and collaboration services revenue $ 459,206 $ 404 $ 459,610
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 2017 2016 U.S. / RoW and China License $ 16,332 $ 16,425 Milestones — — Total license and milestone revenue 16,332 16,425 Collaboration services revenue* 6,970 8,184 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, 2017 Deferred Revenue at March 31, 2017 Total Consideration Through March 31, 2017 License $ 419,029 $ — $ 419,029 Co-development, information sharing & committee services 97,719 29,680 127,399 Manufacturing--clinical supplies 383 53 436 China-single unit of accounting — 85,890 85,890 Total license and collaboration services revenue $ 517,131 $ 115,623 $ 632,754

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 102,004 $ — $ 102,004 Bond and mutual funds 22,734 — — 22,734 Equity investments 205 — — 205 Money market funds 83,919 — — 83,919 Certificate of deposits — 1,036 — 1,036 Total $ 106,858 $ 103,040 $ — $ 209,898 December 31, 2016 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 126,683 $ — $ 126,683 Bond and mutual funds 22,462 — — 22,462 Equity investments 225 — — 225 Money market funds 94,543 — — 94,543 Certificate of deposits — 1,037 — 1,037 Total $ 117,230 $ 127,720 $ — $ 244,950
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, 2017 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 98,090 $ 98,090 December 31, 2016 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,856 $ 97,856

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 December 31, 2016 Cash $ 86,679 $ 79,239 Money market funds 83,919 94,543 Total cash and cash equivalents $ 170,598 $ 173,782
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, 2017 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 101,898 $ 147 $ (41 ) $ 102,004 Certificate of deposits 1,036 — — 1,036 Bond and mutual funds 22,704 205 (175 ) 22,734 Equity investments 126 79 — 205 Total investments $ 125,764 $ 431 $ (216 ) $ 125,979 December 31, 2016 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value Corporate bonds $ 126,550 $ 182 $ (49 ) $ 126,683 Certificate of deposits 1,037 — — 1,037 Bond and mutual funds 22,305 157 — 22,462 Equity investments 125 100 — 225 Total investments $ 150,017 $ 439 $ (49 ) $ 150,407
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): March 31, 2017 December 31, 2016 Preclinical and clinical trial accruals $ 31,052 $ 29,550 Payroll and related accruals 9,050 14,232 Professional services 1,434 1,252 Other 7,643 5,880 Total accrued liabilities $ 49,179 $ 50,914

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2017
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, 2017 2016 Research and development $ 4,901 $ 4,496 General and administrative 3,508 2,844 Total stock-based compensation expense $ 8,409 $ 7,340
Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Purchases under 2014 Employee Share Purchase Plan	The assumptions used to estimate the fair value of stock options granted and purchases under the Company’s 2014 Employee Share Purchase Plan (“ESPP”) using the Black-Scholes option valuation model were as follows: Three Months Ended March 31, 2017 2016 Stock Options Expected term (in years) 5.8 5.3 Expected volatility 71.7 % 69.5 % Risk-free interest rate 2.3 1.4 Expected dividend yield — — Weighted average estimated fair value $ 16.16 $ 11.46 ESPPs Expected term (in years) 0.5 - 2.0 0.5 - 2.0 Expected volatility 63.7 - 77.2 % 69.1 - 70.3 % Risk-free interest rate 0.5 - 1.0 % 0.2 - 0.9 % Expected dividend yield — — Weighted average estimated fair value $ 8.86 $ 13.70

Significant Accounting Polici21

Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2017USD ($)Segment
Accounting Policy [Line Items]
Number of operating segment | Segment	1
ASU 2016-09 [Member]
Accounting Policy [Line Items]
Retrospective increase in deferred tax assets for previously unrecognized excess tax benefits	$ 19,500,000
Increase in valuation allowance	19,500,000
Net impact to accumulated deficit	$ 0

Collaboration Agreements - Aste

Collaboration Agreements - Astellas Agreements - Additional Information (Detail) - Astellas Agreement [Member] - USD ($) $ in Thousands	1 Months Ended		3 Months Ended			12 Months Ended			35 Months Ended	45 Months Ended
	Apr. 30, 2006	Jun. 30, 2005	Mar. 31, 2017	Jun. 30, 2016	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										$ 40,100
Development and regulatory approval milestones		$ 117,500
Commercial sales milestone		$ 15,000
Additional consideration based on net sales description			Low 20% range
Clinical development milestones						$ 12,500
Milestones revenue			$ 0	$ 10,000	$ 0
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received									$ 320,000
Development and regulatory approval milestones	$ 425,000
Additional consideration based on net sales description			Low 20% range
Clinical development milestones							$ 50,000	$ 40,000
Milestones revenue			$ 0		$ 0
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, 2017	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2015
U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected upfront, non-contingent and time-based payments	$ 374
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]
Development and regulatory approval milestones	161
Commercial sales milestone	167.5
Proceeds from upfront payments	28.2
Contingent payment	$ 20
Estimated joint development service period			2,018
Estimated joint development extended service period			2,020

Collaboration Agreements - Summ

Collaboration Agreements - Summary of Revenue Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Jun. 30, 2016	Mar. 31, 2016
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	$ 19,581		$ 19,738
Collaboration services and other revenue from a related party	7,310		8,544
Revenue recognized	26,891		28,282
Astellas Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	3,249		3,313
Collaboration services and other revenue from a related party	340		352
Astellas Agreement [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	212		75
Milestones revenue	0	$ 10,000	0
Total license and milestone revenue	212		75
Collaboration services and other revenue from a related party	11		4
Astellas Agreement [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	3,037		3,238
Milestones revenue	0		0
Total license and milestone revenue	3,037		3,238
Collaboration services and other revenue from a related party	329		348
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	16,332		16,425
Milestones revenue	0		0
Total license and milestone revenue	16,332		16,425
Collaboration services and other revenue from a related party	$ 6,970		$ 8,184

Collaboration Agreements - Tota

Collaboration Agreements - Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue (Detail) $ in Thousands	Mar. 31, 2017USD ($)
Astellas Agreement [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	$ 48,095
Deferred Revenue	25
Total Consideration	48,120
Astellas Agreement [Member] | Japan [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	45,922
Deferred Revenue	0
Total Consideration	45,922
Astellas Agreement [Member] | Japan [Member] | When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	22
Deferred Revenue	25
Total Consideration	47
Astellas Agreement [Member] | Japan [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	2,131
Deferred Revenue	0
Total Consideration	2,131
Astellas Agreement [Member] | Japan [Member] | Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	20
Deferred Revenue	0
Total Consideration	20
Astellas Agreement [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	459,206
Deferred Revenue	404
Total Consideration	459,610
Astellas Agreement [Member] | Europe [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	415,309
Deferred Revenue	0
Total Consideration	415,309
Astellas Agreement [Member] | Europe [Member] | When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	387
Deferred Revenue	404
Total Consideration	791
Astellas Agreement [Member] | Europe [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	9,948
Deferred Revenue	0
Total Consideration	9,948
Astellas Agreement [Member] | Europe [Member] | Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	287
Deferred Revenue	0
Total Consideration	287
Astellas Agreement [Member] | Europe [Member] | Development services-in progress [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	33,275
Deferred Revenue	0
Total Consideration	33,275
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	517,131
Deferred Revenue	115,623
Total Consideration	632,754
AstraZeneca Agreements [Member] | U.S./RoW [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	419,029
Deferred Revenue	0
Total Consideration	419,029
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	383
Deferred Revenue	53
Total Consideration	436
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Co-development, information sharing & committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	97,719
Deferred Revenue	29,680
Total Consideration	127,399
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	85,890
Total Consideration	$ 85,890

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 125,979	$ 150,407
Total fair value of financial assets	209,898	244,950
Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	102,004	126,683
Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	22,734	22,462
Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	205	225
Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	83,919	94,543
Certificate of deposits [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	1,036	1,037
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	106,858	117,230
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	22,734	22,462
Level 1 [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	205	225
Level 1 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	83,919	94,543
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	103,040	127,720
Level 2 [Member] | Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	102,004	126,683
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	1,036	1,037
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 - Fai27

Fair Value Measurements - Fair Values of Financial Liabilities Carried at Historical Cost (Detail) - Lease financing obligations [Member] - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 98,090	$ 97,856
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	$ 98,090	$ 97,856

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
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, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Cash And Cash Equivalents [Abstract]
Cash	$ 86,679	$ 79,239
Money market funds	83,919	94,543
Total cash and cash equivalents	$ 170,598	$ 173,782	$ 140,959	$ 153,324

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($)	Mar. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 170,598,000	$ 170,598,000	$ 173,782,000	$ 140,959,000	$ 153,324,000
Contractual maturities of available-for-sale investments	2 years
Other-than-temporary impairment loss		0
Foreign subsidiaries [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 24,400,000	$ 24,400,000	$ 24,300,000

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, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 125,764	$ 150,017
Gross Unrealized Holding Gains	431	439
Gross Unrealized Holding Losses	(216)	(49)
Fair Value	125,979	150,407
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	101,898	126,550
Gross Unrealized Holding Gains	147	182
Gross Unrealized Holding Losses	(41)	(49)
Fair Value	102,004	126,683
Certificate of deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,036	1,037
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	1,036	1,037
Bond and mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	22,704	22,305
Gross Unrealized Holding Gains	205	157
Gross Unrealized Holding Losses	(175)	0
Fair Value	22,734	22,462
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126	125
Gross Unrealized Holding Gains	79	100
Gross Unrealized Holding Losses	0	0
Fair Value	$ 205	$ 225

Balance Sheet Components - Sc32

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accrued Liabilities Current [Abstract]
Preclinical and clinical trial accruals	$ 31,052	$ 29,550
Payroll and related accruals	9,050	14,232
Professional services	1,434	1,252
Other	7,643	5,880
Total accrued liabilities	$ 49,179	$ 50,914

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Allocated Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 8,409	$ 7,340
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	4,901	4,496
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 3,508	$ 2,844

Stock-Based Compensation - Sc34

Stock-Based Compensation - Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Purchases under 2014 Employee Share Purchase Plan (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Employee stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 9 months 18 days	5 years 3 months 18 days
Expected volatility	71.70%	69.50%
Risk-free interest rate	2.30%	1.40%
Expected dividend yield	0.00%	0.00%
Weighted average estimated fair value	$ 16.16	$ 11.46
2014 Employee Share Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	63.70%	69.10%
Expected volatility, maximum	77.20%	70.30%
Risk-free interest rate, minimum	0.50%	0.20%
Risk-free interest rate, maximum	1.00%	0.90%
Expected dividend yield	0.00%	0.00%
Weighted average estimated fair value	$ 8.86	$ 13.70
2014 Employee Share Purchase Plan [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months
2014 Employee Share Purchase Plan [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 ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Related Party Transaction [Line Items]
Accounts receivable from related party	$ 3,604		$ 4,102
Accrued liabilities to related parties	289		1,615
Astellas [Member] | Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	3,600	$ 3,700
Expense related to collaboration agreements	300	$ 1,600
Accounts receivable from related party	3,600		4,100
Accrued liabilities to related parties	$ 300		$ 1,600

Subsequent Event - Additional I

Subsequent Event - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 11, 2017	Mar. 31, 2017	Mar. 31, 2016
Subsequent Event [Line Items]
Net proceeds from offering		$ 3,099	$ 1,213
Subsequent Event [Member] | Follow-on Offering [Member]
Subsequent Event [Line Items]
Common stock shares sold	5,228,750
Public offering price	$ 22.95
Net proceeds from offering	$ 115,100
Underwriting discounts and commissions	4,900
Offering expenses	$ 400