FibroGen (FGEN) 10-Q 13 Aug 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Jul. 31, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Trading Symbol	FGEN
Entity Registrant Name	FIBROGEN INC
Entity Central Index Key	921,299
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		60,564,900

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 236,536	$ 165,455
Short-term investments	12,129	14,364
Accounts receivable ($10,331 and $5,033 from a related party)	12,183	13,453
Prepaid expenses and other current assets	2,731	4,966
Total current assets	263,579	198,238
Restricted cash	7,254	7,254
Long-term investments	138,310	144,269
Property and equipment, net	130,451	132,171
Other assets	1,801	1,596
Total assets	541,395	483,528
Current liabilities:
Accounts payable	3,915	4,551
Accrued liabilities ($5,817 and $4,594 to related parties)	46,240	48,985
Deferred revenue	13,347	9,218
Total current liabilities	63,502	62,754
Long-term portion of lease financing obligations	96,929	96,818
Product development obligations	15,186	16,465
Deferred rent	4,917	5,131
Deferred revenue, net of current	87,273	60,988
Other long-term liabilities	702	696
Total liabilities	$ 268,509	$ 242,852
Commitments and Contingencies
Stockholders' equity:
Preferred stock, $0.01 par value; 125,000 shares authorized at June 30, 2015 and December 31, 2014; no shares issued and outstanding at June 30, 2015 and December 31, 2014	$ 0	$ 0
Common stock, $0.01 par value; 225,000 shares authorized at June 30, 2015 and December 31, 2014; 60,370 and 59,046 shares issued and outstanding at June 30, 2015 and December 31, 2014	604	590
Additional paid-in capital	565,229	546,247
Accumulated other comprehensive loss	(623)	(3,149)
Accumulated deficit	(311,595)	(322,283)
Total stockholders' equity	253,615	221,405
Non-controlling interests	19,271	19,271
Total equity	272,886	240,676
Total liabilities and equity	$ 541,395	$ 483,528

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Accounts receivable from related party	$ 10,331	$ 5,033
Accrued liabilities to related parties	$ 5,817	$ 4,594
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	60,370,000	59,046,000
Common stock, shares outstanding	60,370,000	59,046,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue:
License and milestone revenue (includes $4,860, $3,718, $9,552 and $6,460 from a related party)	$ 106,879	$ 82,463	$ 118,385	$ 97,148
Collaboration services and other revenue (includes $719, $866, $1,353 and $1,617 from a related party)	13,671	7,495	18,463	10,686
Total revenue	120,550	89,958	136,848	107,834
Operating expenses:
Research and development	51,555	33,269	102,094	58,919
General and administrative	9,680	7,516	20,162	13,948
Total operating expenses	61,235	40,785	122,256	72,867
Income from operations	59,315	49,173	14,592	34,967
Interest expense	(2,762)	(2,725)	(5,520)	(5,451)
Interest and other income, net	707	383	1,550	1,075
Income before income taxes	57,260	46,831	10,622	30,591
Provision (benefit) from income taxes	205	0	(66)	0
Net income	$ 57,055	$ 46,831	$ 10,688	$ 30,591
Net income per share:
Basic	$ 0.95	$ 1.36	$ 0.18	$ 0.74
Diluted	$ 0.83	$ 0.58	$ 0.15	$ 0.46
Weighted average number of common shares used to calculate net income per share:
Basic	59,798	13,347	59,499	13,279
Diluted	68,752	37,106	69,354	21,639

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Operations (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
License and milestone revenue from a related party	$ 106,879	$ 82,463	$ 118,385	$ 97,148
Collaboration services and other revenue from a related party	13,671	7,495	18,463	10,686
Astellas Agreement [Member]
License and milestone revenue from a related party	4,860	3,718	9,552	6,460
Collaboration services and other revenue from a related party	$ 719	$ 866	$ 1,353	$ 1,617

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 57,055	$ 46,831	$ 10,688	$ 30,591
Other comprehensive income (loss):
Foreign currency translation adjustments	508	185	2,213	195
Available-for-sale investments:
Unrealized gain (loss) on investments, net of tax effect	(368)	(280)	343	(820)
Reclassification from accumulated other comprehensive loss	(25)	0	(30)	0
Net change in unrealized gain (loss) on available-for-sale investments	(393)	(280)	313	(820)
Other comprehensive income (loss), net of taxes	115	(95)	2,526	(625)
Comprehensive income	$ 57,170	$ 46,736	$ 13,214	$ 29,966

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating activities
Net income	$ 10,688	$ 30,591
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	2,796	1,843
Amortization of premium on investments	1,538	307
Loss on disposal of property and equipment	100	0
Stock-based compensation	13,388	1,465
Tax benefit on unrealized gain on available-for-sale securities	(66)	0
Changes in operating assets and liabilities:
Accounts receivable	1,270	1,329
Prepaid expenses and other current assets	2,235	964
Other assets	(205)	(694)
Accounts payable	(636)	190
Accrued liabilities	(3,140)	4,828
Deferred revenue	30,414	36,287
Lease financing liability	312	306
Other long-term liabilities	163	(178)
Net cash provided by operating activities	58,857	77,238
Investing activities
Purchases of property and equipment	(989)	(3,952)
Proceeds from maturities of available-for-sale securities	7,035	33,546
Net cash provided by investing activities	6,046	29,594
Financing activities
Repayments of lease liability	(201)	(201)
Proceeds from issuance of common stock, net	5,608	831
Payments of equity issuance costs	0	(1,167)
Net cash provided by (used in) financing activities	5,407	(537)
Effect of exchange rate change on cash and cash equivalents	771	35
Net increase in cash and cash equivalents	71,081	106,330
Cash and cash equivalents at beginning of period	165,455	76,332
Cash and cash equivalents at end of period	$ 236,536	$ 182,662

Description of Operations and S

Description of Operations and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Description of Operations and Summary of Significant Accounting Policies	1. Description of Operations and Summary of Significant Accounting Policies Description of Operations FibroGen, Inc. (“FibroGen,” the “Company,” or “we” and other similar pronouns) was incorporated in 1993 in Delaware and is a research-based biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs. Our focus in the areas of fibrosis and hypoxia-inducible factor (“HIF”) biology has generated multiple programs targeting various therapeutic areas. Our 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”). FG-3019 is our monoclonal antibody in Phase 2 clinical development for the treatment of idiopathic pulmonary fibrosis (“IPF”), pancreatic cancer 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”). On November 10, 2014, we effected a 1-for-2.5 reverse split of our common stock. Upon the effectiveness of the reverse stock split, (i) every 2.5 shares of outstanding common stock were combined into one share of common stock, (ii) the number of shares of common stock for which each outstanding option or warrant to purchase common stock is exercisable was proportionally decreased on a 1-for-2.5 basis, (iii) the exercise price of each outstanding option or warrant to purchase common stock was proportionately increased on a 1-for- 2.5 basis, (iv) the exchange ratio for each share of outstanding FibroGen Europe Oy (“FibroGen Europe”) share of stock which is exchangeable into our common stock was proportionately reduced on a 1-for-2.5 basis, and (v) the conversion ratio for each share of outstanding preferred stock which is convertible into our common stock was proportionately reduced on a 1-for-2.5 basis. All of the outstanding common stock share numbers (including shares of common stock which our outstanding preferred stock shares were convertible into), common stock warrants, share prices, exercise prices and per share amounts have been adjusted in these condensed consolidated financial statements, on a retroactive basis, to reflect this 1-for-2.5 reverse stock split for all periods presented. The par value per share and the authorized number of shares of common stock and preferred stock were not adjusted as a result of the reverse stock split. On November 19, 2014, we closed the initial public offering (“IPO”) of our common stock. In our IPO, we sold 9,315,000 shares of our common stock at a public offering price of $18.00 per share. Net proceeds from our IPO and concurrent private placement were $171.8 million, after deducting underwriting discounts and commissions of $11.7 million and offering expenses of $4.1 million. AstraZeneca AB (“AstraZeneca”), one of our collaboration partners, agreed to purchase from us concurrently with the closing of our IPO in a private placement shares of our common stock with an aggregate purchase price of $20.0 million at a price per share equal to the IPO price. Upon the closing of our IPO, all outstanding shares of our convertible preferred stock automatically converted into 33,919,954 shares of common stock and 958,996 shares of FibroGen Europe convertible preferred stock were converted into shares of our common stock. Our proceeds from the sale of the common stock sold in the concurrent private placement were $20.0 million. Basis of Presentation The condensed consolidated financial statements include the accounts of FibroGen, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe and FibroGen China Anemia Holdings, Ltd. All inter-company transactions and balances have been eliminated in consolidation. We operate in one segment—the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs. The condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and the rules and regulations of the 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, 2014 condensed consolidated balance sheet data contained within this Form 10-Q was derived from audited consolidated financial statements included in our Form 10-K for the year ended December 31, 2014, but does not include all disclosures required by accounting principles generally accepted in the United States. 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. Fair Value of Financial Instruments We define fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Our valuation techniques are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect our market assumptions. We classify these inputs into the following hierarchy: Level 1— Level 2 Level 3 The assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and considers factors specific to the asset or liability. In addition, the categories presented do not suggest how prices may be affected by the size of the purchases or sales, particularly with the largest highly liquid financial issuers who are in markets continuously with non-equity instruments, or how any such financial assets may be impacted by other factors such as U.S. government guarantees. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Carrying amounts of certain of our financial instruments including cash equivalents, investments, receivables, accounts payable and accrued liabilities approximate fair value due to their short maturities. Revenue Recognition Substantially all of our revenues to date have been generated from our collaboration agreements. Our collaboration agreements include multiple deliverables, and we, therefore, follow the guidance in Accounting Standards Codification (“ASC”) Topic 605-25, “Revenue Recognition–Multiple-Element Arrangements” (“ASC 605-25”). ASC 605-25: • provides guidance on how revenue arrangements with multiple deliverables should be separated and how the arrangement consideration should be allocated among the separate units of accounting; • requires an entity to determine the selling price of a separate deliverable using a hierarchy of (i) vendor-specific objective evidence (“VSOE”), (ii) third-party evidence (“TPE”), or (iii) best estimate of selling price (“BESP”); and • requires the allocation of the arrangement consideration, at the inception of the arrangement, to the separate units of accounting based on relative selling price. We evaluate all deliverables within an arrangement to determine whether or not they provide value on a stand-alone basis. Based on this evaluation, the deliverables are separated into units of accounting. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. Significant judgment may be required in determining whether a deliverable provides stand-alone value, determining the amount of arrangement consideration that is fixed or determinable, and estimating the stand-alone selling price of each unit of accounting. To date, we have determined that the selling price for the deliverables within our collaboration agreements should be determined using BESP, as neither VSOE nor TPE is available. The process for determining BESP involves significant judgment on our part and includes consideration of multiple factors, including assumptions related to the market opportunity and the time needed to commercialize a product candidate pursuant to the relevant license, estimated direct expenses and other costs, which include the rates normally charged by contract research and contract manufacturing organizations for development and manufacturing obligations, and rates that would be charged by qualified outsiders for committee services. For each unit of accounting identified within an arrangement, we determine the period over which the deliverables are provided and the performance obligation is satisfied. Service revenue is recognized using a proportional performance method. Direct labor hours or full time equivalents are typically used as the measurement of performance. Revenue may be recognized using a straight line method when performance is expected to occur roughly consistently over a period of time. Payments or reimbursements resulting from our research and development efforts for those arrangements where such efforts are considered as deliverables are recognized as the services are performed and are presented on a gross basis. To the extent payments are required to be made to the collaboration partners pursuant to research and development efforts, those costs are charged to research and development using the guidance pursuant to ASC Topic 605-250, “Customer Payments and Incentives”, which states that cash consideration given by a vendor to a customer is presumed to be a reduction of the selling prices unless the vendor receives an identifiable benefit in exchange for the consideration that is sufficiently separable from the recipient’s purchase of the vendor’s products, and the vendor can reasonably estimate the fair value of the benefit. Each of our collaboration agreements includes milestones for which we follow ASC Topic 605-28, “Revenue Recognition—Milestone Method” (“ASC 605-28”). ASC 605-28 establishes the milestone method as an acceptable method of revenue recognition for certain contingent event-based payments under research and development arrangements. Under the milestone method, a payment that is contingent upon the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved. A milestone is an event (i) that can only be achieved based in whole or in part on either our performance or on the occurrence of a specific outcome resulting from our performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event will be achieved and (iii) that would result in additional payments being due to us. Determining whether a milestone is substantive is a matter of judgment and that assessment must be made at the inception of the arrangement. Milestones are considered substantive when the consideration earned from the achievement of the milestone is (i) commensurate with either our performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from our performance to achieve the milestone, (ii) relates solely to past performance and (iii) is reasonable relative to all deliverables and payment terms in the arrangement. Payments for achieving milestones which are not considered substantive are treated as additional arrangement consideration and are allocated following the relative selling price method previously described. Net Income per Share Immediately prior to the IPO, the Company had authorized 125,000,000 shares of Preferred Stock with a par value of $0.01 per share. The Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock, Series D Preferred Stock, Royalty Acquisition Preferred Stock and Series G-1 Preferred Stock are collectively referred to as the “Junior Preferred Stock”. The Series E Redeemable Convertible Preferred Stock and Series F Redeemable Convertible Preferred Stock are collectively referred to as the “Senior Preferred Stock”. As of December 31, 2014, there was no outstanding convertible preferred stock as all issued and outstanding preferred stock were converted to common stock at the closing of the Company’s IPO in November 2014. Prior to the IPO, we applied the two-class method to calculate basic and diluted net income per share of common stock. The two-class method is an earnings allocation method under which earnings per share is calculated for common stock considering a participating security’s rights to undistributed earnings as if all such earnings had been distributed during the period. The Junior Preferred Stock were participating securities due to their dividend rights and the Senior Preferred Stock had stated dividend rates. During periods of net income, the calculation of basic net income per share was reclassified to exclude the income attributable to all participating securities from the numerator and exclude the dilutive impact of those shares from the denominator. During periods of net loss, all participating securities were not included in the calculation of net loss per share because the preferred stockholders had no contractual obligation to participate in losses. The following is a reconciliation of the basic and diluted net income per share calculation for the periods presented (in thousands, except per share data): Quarter Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net income $ 57,055 $ 46,831 $ 10,688 $ 30,591 Less: Undistributed earnings allocated to Junior Preferred stockholders — (25,234 ) — (13,790 ) Net income attributable to Senior Preferred and common stockholders $ 57,055 $ 21,597 $ 10,688 $ 16,801 Less: Undistributed earnings allocated to Senior Preferred stockholders $ — $ (3,474 ) $ — $ (6,948 ) Net income attributable to common stockholders $ 57,055 $ 18,123 $ 10,688 $ 9,853 Weighted average shares used to compute net income per share: Basic 59,798 13,347 59,499 13,279 Dilutive effect of Senior Preferred stock — 15,336 — — Dilutive effect of potential common shares 8,954 8,423 9,855 8,360 Diluted 68,752 37,106 69,354 21,639 Net income per share: Basic $ 0.95 $ 1.36 $ 0.18 $ 0.74 Diluted $ 0.83 $ 0.58 $ 0.15 $ 0.46 Diluted net income per share does not include the effect of 3.8 million and 18.6 million securities for the quarters ended June 30, 2015 and 2014 and 1.8 million and 33.9 million securities for the six months ended June 30, 2015 and 2014. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers Revenue Recognition

Collaboration Agreements

Collaboration Agreements	6 Months Ended
	Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration Agreements	2. Collaboration Agreements Astellas Agreements Japan Agreement In June 2005, we 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. We evaluated the criteria under ASC 605-28 (as disclosed in Note 1) and concluded that the aforementioned milestone was substantive. Europe Agreement In April 2006, we 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. We evaluated the criteria under ASC 605-28 (as disclosed in Note 1) 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, we entered into a collaboration agreement with AstraZeneca for the development and commercialization of roxadustat for the treatment of anemia in the United States 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 we expect to receive in various amounts through June 2016, of which $312.0 million was received as of June 30, 2015. 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, we received a $15.0 million development milestone payment as a result of the finalization of our two audited pre-clinical carcinogenicity study reports. We evaluated the criteria under ASC 605-28 (as disclosed in Note 1) and concluded that each of those milestones was substantive. Under the U.S./RoW Agreement, we 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. Any additional development costs incurred by us during the development period in excess of the $233.0 million (aggregated spend) will be fully reimbursed by AstraZeneca. AstraZeneca will pay us tiered royalty payments on AstraZeneca’s future net sales (as defined in the agreement) of roxadustat in the low 20% range. In addition we 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, we (through our 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. Accounting for the Astellas Agreements For each of the Astellas agreements, we evaluated the deliverables within the respective arrangements and separated them into various units of accounting. Deliverables that did not provide standalone value have been combined with other deliverables to form a unit of accounting that collectively has standalone value, with revenue being recognized on the combined unit of accounting, rather than the individual deliverables. There are no right-of-return provisions for the delivered items in the Astellas agreements. For the Astellas agreements, we allocated arrangement consideration to various units of accounting based on BESP of each deliverable within each unit of accounting using the relative selling price method as we did not have VSOE or TPE of selling price for such deliverables. Arrangement consideration includes non-contingent upfront payments of $360.1 million and cumulative co-development billings of $114.5 million (for the Europe Agreement) as of June 30, 2015. For the technology license under the Japan Agreement and Europe Agreement, BESP was determined primarily by using the discounted cash flow (“DCF”) method, which aggregates the present value of future cash flows to determine the valuation as of the effective date of each of the agreements. The DCF method involves the following key steps: 1) the determination of cash flow forecasts and 2) the selection of a range of comparative risk-adjusted discount rates to apply against the cash flow forecasts. The discount rates selected were based on expectations of the total rate of return, the rate at which capital would be attracted to the Company and the level of risk inherent within the Company. The discounts applied in the DCF analysis ranged from 17.5% to 20.0%. Our cash flow forecasts were derived from probability-adjusted revenue and expense projections by territory. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. BESP also considered certain future royalty payments associated with commercial performance of our compounds, transfer prices and expected gross margins. The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows: • License to our technology existing at the effective date of the agreements. • Manufacturing rights. • License to our technology developed during the term of the agreement and development (referred to as “when and if available”) and information sharing services • Co-development services (Europe Agreement). • Manufacturing of clinical supplies of products. • Manufacturing commercial supplies of products. • Committee service. Any consideration received for each Astellas agreement after the initial proceeds on the agreement signing date were also (and will be also) allocated to the various units of accounting above per agreement using the relative selling price method under ASC 605-25-30-2 and 30-5. Under the Japan Agreement, we are also eligible to receive from Astellas an aggregate of approximately $132.5 million in potential milestone payments, comprised of (i) up to $22.5 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $95.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $15.0 million in milestone payments upon the achievement of specified commercial sales milestone. Under the Europe Agreement, we are also eligible to receive from Astellas an aggregate of approximately $425.0 million in potential milestone payments, comprised of (i) up to $90.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $335.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, including up to $25.0 million in milestone payments in connection with receipt of marketing approval in Russia. Accounting for the AstraZeneca Agreements We evaluated whether or not the U.S./RoW and China Agreements should be accounted for as a single arrangement and concluded that the agreements should be accounted for as a single arrangement with the presumption that two or more agreements executed with a single customer at or around the same time are a single arrangement. Accordingly, upfront and other non-contingent arrangement consideration received and to be received has been and will be pooled together and allocated to each of the units of accounting in both the U.S./RoW and China Agreements based on their relative fair values. We evaluated the deliverables within the arrangement and separated them into various units of accounting. Deliverables that did not provide stand-alone value have been combined with other deliverables to form a unit of accounting that collectively has stand-alone value, with revenue being recognized on the combined unit of accounting, rather than the individual deliverables. There are no right-of-return provisions for the delivered items in the agreements. For the technology license under the AstraZeneca U.S./RoW Agreement, BESP was determined based on a two-step process. The first step involved determining an implied royalty rate that would result in the net present value of future cash flows to equal to zero (i.e. where the IRR on the transaction would equal the target return for the investment). This results in an upper bound estimation of the magnitude of royalties that a hypothetical acquirer would reasonably pay for the forecasted cash flow stream. Our cash flow forecasts were derived from probability-adjusted revenue and expense projections. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. The second step involved applying the implied royalty rate, which was determined to be 40%, against the probability-adjusted projected net revenues by territory and determining the value of the license as the net present value of future cash flows after adjusting for taxes. The discount rate utilized was 17.5%. U.S./RoW Agreement: The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows: • License to our technology existing at the effective date of the agreements. • Co-development services. • Manufacturing of clinical supplies of products. • Manufacturing commercial supplies of products. • Committee service. 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 we expect to receive in various amounts through June 2016, of which $82.0 million was received as of December 31, 2013 and was determined to be fixed and determinable upon the execution of the collaboration agreement. Out of the remaining payments of $292.0 million, which are contractually due, $230.0 million have extended payment terms and, accordingly, were not considered to be fixed or determinable upon the execution of the agreement. As such, for these remaining payments, the amount of revenue recognized is limited to the amount of cash consideration received; additionally, for each of the amounts received, the amount of revenue recognized is determined on the basis of applying the relative selling price method to each of the units of accounting underlying the agreement. Further, $62.0 million of the remaining payment is contingent upon the occurrence of a specified event and accordingly is also not considered fixed or determinable. Under the U.S./RoW Agreement, we are also eligible to receive from AstraZeneca an aggregate of approximately $875.0 million in potential milestone payments, comprised of (i) up to $65.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $325.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, (iii) up to $160.0 million in a non-substantive deferred approval milestone, which would be paid if certain competitors do not launch a HIF compound in the U.S. on or before January 1, 2023, and (iv) up to approximately $325.0 million in milestone payments upon the achievement of specified commercial sales events. China Agreement: The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows: • License to our technology existing at the effective date of the agreement. For the China Agreement, we retained manufacturing rights as an essential part of a strategy to pursue domestic regulatory pathway for product approval which requires the regulatory licensure of the manufacturing facility in order to commence commercial shipment. The prospects for the collaboration as a whole would have been substantially different had manufacturing rights been provided to AstraZeneca. Because the retention of manufacturing rights by us was a significant factor in the collaboration strategy, rather than simply a mechanism to properly compensate us, we concluded that the license and development services do not have stand-alone value apart from the manufacturing rights. Accordingly, all the deliverables identified, including co-development services, under the China Agreement have been treated as a single unit of account and all revenue allocable to this unit of account is deferred until delivery of commercial drug product has begun. Upon commencement of delivery of commercial drug product, revenue would be recognized in a pattern consistent with estimated deliveries of the commercial drug product. Under the terms of the China Agreement, AstraZeneca agreed to pay upfront consideration totaling $28.2 million, of which $16.2 million was received as of December 31, 2013 and was determined to be fixed and determinable upon the execution of the collaboration agreement. The remainder of the upfront payments of $12.0 million had extended payment terms and, accordingly, is not considered to be fixed or determinable upon the execution of the agreement. This payment of $12.0 million was received as of March 31, 2014. Under the China Agreement, we are also eligible to receive from AstraZeneca an aggregate of approximately $328.5 million in potential milestone payments, comprised of (i) up to $15.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $146.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $167.5 million in milestone payments upon the achievement of specified commercial sales events. As we are accounting for both the U.S./RoW and China Agreements as one arrangement, any consideration received after the initial proceeds on the agreement signing date were also (and will be also) allocated to the various units of accounting above using the relative selling price method under ASC 605-25-30-2 and 30-5. 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): Quarter Ended June 30, Six Months Ended June 30, Agreement Deliverable 2015 2014 2015 2014 Japan License $ 91 $ 155 $ 528 $ 230 Milestones — — — — Total license and milestone revenue 91 155 528 230 Collaboration services revenue* $ 42 $ 89 $ 100 $ 176 As of June 30, 2015, 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 June 30, 2015 Deferred Revenue at June 30, 2015 Total Consideration Through June 30, 2015 License $ 41,749 $ — $ 41,749 When and if available compounds 12 29 41 Manufacturing—clinical supplies 1,871 72 1,943 Committee services 15 2 17 Total license and collaboration services revenue $ 43,647 $ 103 $ 43,750 * 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. Amounts recognized as revenue under the Europe Agreement were as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, Agreement Deliverable 2015 2014 2015 2014 Europe License $ 4,769 $ 3,563 $ 9,024 $ 6,230 Milestones — — — — Total license and milestone revenue 4,769 3,563 9,024 6,230 Collaboration services revenue* $ 677 $ 777 $ 1,253 $ 1,441 As of June 30, 2015, 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 June 30, 2015 Deferred Revenue at June 30, 2015 Total Consideration Through June 30, 2015 License $ 392,663 $ — $ 392,663 When and if available compounds 305 442 747 Manufacturing—clinical supplies 8,911 494 9,405 Development services—in progress 31,460 — 31,460 Committee services 256 16 272 Total license and collaboration services revenue $ 433,595 $ 952 $ 434,547 * 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. Amounts recognized as revenue under the U.S./RoW Agreement were as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, Agreement Deliverable 2015 2014 2015 2014 U.S. / RoW License $ 87,019 $ 78,745 $ 93,833 $ 90,688 Milestones 15,000 — 15,000 — Total license and milestone revenue 102,019 78,745 108,833 90,688 Collaboration services revenue* 12,942 6,590 17,080 9,025 China single unit of accounting** $ — $ — $ — $ — As of June 30, 2015, 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 June 30, 2015 Deferred Revenue at June 30, 2015 Total Consideration Through June 30, 2015 License $ 269,207 $ — $ 269,207 Co-development, information sharing & committee services 37,589 44,259 81,848 Manufacturing—clinical supplies 154 126 280 China-single unit of accounting — 55,180 55,180 Total license and collaboration services revenue $ 306,950 $ 99,565 $ 406,515 * 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. Other Revenues Other revenues consist of royalty payments received, which are recorded on a monthly basis as they are reported to us, and collagen feasibility sales. Other revenues were immaterial for all periods presented. Deferred Revenue Deferred revenue represents amounts billed to our 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	6 Months Ended
	Jun. 30, 2015
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): June 30, 2015 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 150,240 $ — $ 150,240 Equity investments 199 — — 199 Sub-total 199 150,240 — 150,439 Money market funds 127,643 — — 127,643 Total $ 127,842 $ 150,240 $ — $ 278,082 December 31, 2014 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 158,432 $ — $ 158,432 Equity investments 201 — — 201 Sub-total 201 158,432 — 158,633 Money market funds 13,802 — — 13,802 Total $ 14,003 $ 158,432 $ — $ 172,435 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): June 30, 2015 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,332 $ 97,332 December 31, 2014 Level 1 Level 2 Level 3 Total Cease-use liability $ — $ — $ 184 $ 184 Lease financing obligations — — 97,221 97,221 Total $ — $ — $ 97,405 $ 97,405 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	6 Months Ended
	Jun. 30, 2015
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): June 30, 2015 December 31, 2014 Cash $ 108,893 $ 151,653 Money market funds 127,643 13,802 Total cash and cash equivalents $ 236,536 $ 165,455 Investments All investments are classified as available-for-sale. The amortized cost, gross unrealized holding gains or losses, and fair value of our available-for-sale investments by major investments type are summarized in the tables below (in thousands): June 30, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Corporate bonds $ 150,119 $ 287 $ (166 ) $ 150,240 Equity investments 124 75 — 199 Total investments $ 150,243 $ 362 $ (166 ) $ 150,439 December 31, 2014 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Corporate bonds $ 158,692 $ 254 $ (514 ) $ 158,432 Equity investments 124 77 — 201 Total investments $ 158,816 $ 331 $ (514 ) $ 158,633 At June 30, 2015 all of the available-for-sale investments had contractual maturities within four years. We periodically review our available-for-sale investments for other-than-temporary impairment. We consider 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, we also consider whether (i) it is more likely than not that we 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 quarters and six months ended June 30, 2015 and 2014, we did not recognize any other-than-temporary impairment loss. At June 30, 2015, a total of $30.9 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. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): June 30, 2015 December 31, 2014 Preclinical and clinical trial accruals $ 32,251 $ 25,418 Payroll and related accruals 9,625 15,608 Professional services 1,121 2,401 Other 3,243 5,558 Total accrued liabilities $ 46,240 $ 48,985

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	5. Stock-Based Compensation Stock-based compensation expense was allocated to research and development and general and administrative expense for the periods presented as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Research and development $ 4,434 $ 408 $ 8,656 $ 883 General and administrative 2,508 262 4,732 582 Total stock-based compensation expense $ 6,942 $ 670 $ 13,388 $ 1,465 The weighted-average assumptions used to estimate the fair value of stock options using the Black-Scholes option valuation model and the resulting weighted average fair value of stock options granted during the periods presented were as follows: Quarter Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Stock Options Expected term (in years) 5.2 — 5.2 — Expected volatility 70 % — % 70 % — % Risk-free interest rate 1.7 — 1.7 — Expected dividend yield — — — — Weighted average estimated fair value $ 12.27 $ — $ 16.68 $ — Employee Stock Purchase Plans Expected term (in years) 1.3 — 1.3 — Expected volatility 65 % — % 65 % — % Risk-free interest rate 0.3 — 0.3 — Expected dividend yield — — — — Weighted average estimated fair value $ 9.75 $ — $ 9.75 $ —

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2015
Income Tax Disclosure [Abstract]
Income Taxes	6. Income Taxes We recorded a provision for income taxes for the quarter ended June 30, 2015 due to the discrete tax effect arising from a change in the valuation of our available-for-sale securities portfolio. We recorded a benefit for income taxes for the six months ended June 30, 2015 due to the discrete tax effect arising from other comprehensive income related to available-for-sale securities. We did not record a provision for income taxes for the quarter and six months ended June 30, 2014 as we generated a net operating loss for the year ended December 31, 2014. 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	6 Months Ended
	Jun. 30, 2015
Related Party Transactions [Abstract]
Related Party Transactions	7. Related Party Transactions Astellas is an equity investor of ours and, therefore, considered a related party. We recorded revenue related to collaboration agreements with Astellas of $5.6 million and $4.6 million during the quarter ended June 30, 2015 and 2014 and $10.9 million and $8.1 million during the six months ended June 30, 2015 and 2014. We recorded expense related to collaboration agreements with Astellas of $1.3 million and $2.4 million during the quarter ended June 30, 2015 and 2014 and $4.4 million and $4.5 million during the six months ended June 30, 2015 and 2014. As of June 30, 2015 and December 31, 2014, accounts receivable from Astellas were $10.3 million and $5.0 million and amounts due to Astellas were $5.8 million and $4.3 million. Julian N. Stern, a director of ours 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. We retain Goodwin Procter LLP as legal counsel for various matters, primarily consisting of intellectual property. During the quarter and six months ended June 30, 2015 and 2014, the payments made by us to Goodwin Procter LLP were not material. As of June 30, 2015 and December 31, 2014, amounts due to Goodwin Proctor LLP were not material.

Description of Operations and15

Description of Operations and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The condensed consolidated financial statements include the accounts of FibroGen, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe and FibroGen China Anemia Holdings, Ltd. All inter-company transactions and balances have been eliminated in consolidation. We operate in one segment—the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs. The condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) for interim financial reporting and the rules and regulations of the 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, 2014 condensed consolidated balance sheet data contained within this Form 10-Q was derived from audited consolidated financial statements included in our Form 10-K for the year ended December 31, 2014, but does not include all disclosures required by accounting principles generally accepted in the United States. 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.
Fair Value of Financial Instruments	Fair Value of Financial Instruments We define fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Our valuation techniques are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect our market assumptions. We classify these inputs into the following hierarchy: Level 1— Level 2 Level 3 The assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and considers factors specific to the asset or liability. In addition, the categories presented do not suggest how prices may be affected by the size of the purchases or sales, particularly with the largest highly liquid financial issuers who are in markets continuously with non-equity instruments, or how any such financial assets may be impacted by other factors such as U.S. government guarantees. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. Carrying amounts of certain of our financial instruments including cash equivalents, investments, receivables, accounts payable and accrued liabilities approximate fair value due to their short maturities.
Revenue Recognition	Revenue Recognition Substantially all of our revenues to date have been generated from our collaboration agreements. Our collaboration agreements include multiple deliverables, and we, therefore, follow the guidance in Accounting Standards Codification (“ASC”) Topic 605-25, “Revenue Recognition–Multiple-Element Arrangements” (“ASC 605-25”). ASC 605-25: • provides guidance on how revenue arrangements with multiple deliverables should be separated and how the arrangement consideration should be allocated among the separate units of accounting; • requires an entity to determine the selling price of a separate deliverable using a hierarchy of (i) vendor-specific objective evidence (“VSOE”), (ii) third-party evidence (“TPE”), or (iii) best estimate of selling price (“BESP”); and • requires the allocation of the arrangement consideration, at the inception of the arrangement, to the separate units of accounting based on relative selling price. We evaluate all deliverables within an arrangement to determine whether or not they provide value on a stand-alone basis. Based on this evaluation, the deliverables are separated into units of accounting. The arrangement consideration that is fixed or determinable at the inception of the arrangement is allocated to the separate units of accounting based on their relative selling prices. Significant judgment may be required in determining whether a deliverable provides stand-alone value, determining the amount of arrangement consideration that is fixed or determinable, and estimating the stand-alone selling price of each unit of accounting. To date, we have determined that the selling price for the deliverables within our collaboration agreements should be determined using BESP, as neither VSOE nor TPE is available. The process for determining BESP involves significant judgment on our part and includes consideration of multiple factors, including assumptions related to the market opportunity and the time needed to commercialize a product candidate pursuant to the relevant license, estimated direct expenses and other costs, which include the rates normally charged by contract research and contract manufacturing organizations for development and manufacturing obligations, and rates that would be charged by qualified outsiders for committee services. For each unit of accounting identified within an arrangement, we determine the period over which the deliverables are provided and the performance obligation is satisfied. Service revenue is recognized using a proportional performance method. Direct labor hours or full time equivalents are typically used as the measurement of performance. Revenue may be recognized using a straight line method when performance is expected to occur roughly consistently over a period of time. Payments or reimbursements resulting from our research and development efforts for those arrangements where such efforts are considered as deliverables are recognized as the services are performed and are presented on a gross basis. To the extent payments are required to be made to the collaboration partners pursuant to research and development efforts, those costs are charged to research and development using the guidance pursuant to ASC Topic 605-250, “Customer Payments and Incentives”, which states that cash consideration given by a vendor to a customer is presumed to be a reduction of the selling prices unless the vendor receives an identifiable benefit in exchange for the consideration that is sufficiently separable from the recipient’s purchase of the vendor’s products, and the vendor can reasonably estimate the fair value of the benefit. Each of our collaboration agreements includes milestones for which we follow ASC Topic 605-28, “Revenue Recognition—Milestone Method” (“ASC 605-28”). ASC 605-28 establishes the milestone method as an acceptable method of revenue recognition for certain contingent event-based payments under research and development arrangements. Under the milestone method, a payment that is contingent upon the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved. A milestone is an event (i) that can only be achieved based in whole or in part on either our performance or on the occurrence of a specific outcome resulting from our performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event will be achieved and (iii) that would result in additional payments being due to us. Determining whether a milestone is substantive is a matter of judgment and that assessment must be made at the inception of the arrangement. Milestones are considered substantive when the consideration earned from the achievement of the milestone is (i) commensurate with either our performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from our performance to achieve the milestone, (ii) relates solely to past performance and (iii) is reasonable relative to all deliverables and payment terms in the arrangement. Payments for achieving milestones which are not considered substantive are treated as additional arrangement consideration and are allocated following the relative selling price method previously described.
Net Income per Share	Net Income per Share Immediately prior to the IPO, the Company had authorized 125,000,000 shares of Preferred Stock with a par value of $0.01 per share. The Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock, Series D Preferred Stock, Royalty Acquisition Preferred Stock and Series G-1 Preferred Stock are collectively referred to as the “Junior Preferred Stock”. The Series E Redeemable Convertible Preferred Stock and Series F Redeemable Convertible Preferred Stock are collectively referred to as the “Senior Preferred Stock”. As of December 31, 2014, there was no outstanding convertible preferred stock as all issued and outstanding preferred stock were converted to common stock at the closing of the Company’s IPO in November 2014. Prior to the IPO, we applied the two-class method to calculate basic and diluted net income per share of common stock. The two-class method is an earnings allocation method under which earnings per share is calculated for common stock considering a participating security’s rights to undistributed earnings as if all such earnings had been distributed during the period. The Junior Preferred Stock were participating securities due to their dividend rights and the Senior Preferred Stock had stated dividend rates. During periods of net income, the calculation of basic net income per share was reclassified to exclude the income attributable to all participating securities from the numerator and exclude the dilutive impact of those shares from the denominator. During periods of net loss, all participating securities were not included in the calculation of net loss per share because the preferred stockholders had no contractual obligation to participate in losses. The following is a reconciliation of the basic and diluted net income per share calculation for the periods presented (in thousands, except per share data): Quarter Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net income $ 57,055 $ 46,831 $ 10,688 $ 30,591 Less: Undistributed earnings allocated to Junior Preferred stockholders — (25,234 ) — (13,790 ) Net income attributable to Senior Preferred and common stockholders $ 57,055 $ 21,597 $ 10,688 $ 16,801 Less: Undistributed earnings allocated to Senior Preferred stockholders $ — $ (3,474 ) $ — $ (6,948 ) Net income attributable to common stockholders $ 57,055 $ 18,123 $ 10,688 $ 9,853 Weighted average shares used to compute net income per share: Basic 59,798 13,347 59,499 13,279 Dilutive effect of Senior Preferred stock — 15,336 — — Dilutive effect of potential common shares 8,954 8,423 9,855 8,360 Diluted 68,752 37,106 69,354 21,639 Net income per share: Basic $ 0.95 $ 1.36 $ 0.18 $ 0.74 Diluted $ 0.83 $ 0.58 $ 0.15 $ 0.46 Diluted net income per share does not include the effect of 3.8 million and 18.6 million securities for the quarters ended June 30, 2015 and 2014 and 1.8 million and 33.9 million securities for the six months ended June 30, 2015 and 2014.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers Revenue Recognition
Collaboration Agreements	Accounting for the Astellas Agreements For each of the Astellas agreements, we evaluated the deliverables within the respective arrangements and separated them into various units of accounting. Deliverables that did not provide standalone value have been combined with other deliverables to form a unit of accounting that collectively has standalone value, with revenue being recognized on the combined unit of accounting, rather than the individual deliverables. There are no right-of-return provisions for the delivered items in the Astellas agreements. For the Astellas agreements, we allocated arrangement consideration to various units of accounting based on BESP of each deliverable within each unit of accounting using the relative selling price method as we did not have VSOE or TPE of selling price for such deliverables. Arrangement consideration includes non-contingent upfront payments of $360.1 million and cumulative co-development billings of $114.5 million (for the Europe Agreement) as of June 30, 2015. For the technology license under the Japan Agreement and Europe Agreement, BESP was determined primarily by using the discounted cash flow (“DCF”) method, which aggregates the present value of future cash flows to determine the valuation as of the effective date of each of the agreements. The DCF method involves the following key steps: 1) the determination of cash flow forecasts and 2) the selection of a range of comparative risk-adjusted discount rates to apply against the cash flow forecasts. The discount rates selected were based on expectations of the total rate of return, the rate at which capital would be attracted to the Company and the level of risk inherent within the Company. The discounts applied in the DCF analysis ranged from 17.5% to 20.0%. Our cash flow forecasts were derived from probability-adjusted revenue and expense projections by territory. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. BESP also considered certain future royalty payments associated with commercial performance of our compounds, transfer prices and expected gross margins. The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows: • License to our technology existing at the effective date of the agreements. • Manufacturing rights. • License to our technology developed during the term of the agreement and development (referred to as “when and if available”) and information sharing services • Co-development services (Europe Agreement). • Manufacturing of clinical supplies of products. • Manufacturing commercial supplies of products. • Committee service. Any consideration received for each Astellas agreement after the initial proceeds on the agreement signing date were also (and will be also) allocated to the various units of accounting above per agreement using the relative selling price method under ASC 605-25-30-2 and 30-5. Under the Japan Agreement, we are also eligible to receive from Astellas an aggregate of approximately $132.5 million in potential milestone payments, comprised of (i) up to $22.5 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $95.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $15.0 million in milestone payments upon the achievement of specified commercial sales milestone. Under the Europe Agreement, we are also eligible to receive from Astellas an aggregate of approximately $425.0 million in potential milestone payments, comprised of (i) up to $90.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $335.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, including up to $25.0 million in milestone payments in connection with receipt of marketing approval in Russia. Accounting for the AstraZeneca Agreements We evaluated whether or not the U.S./RoW and China Agreements should be accounted for as a single arrangement and concluded that the agreements should be accounted for as a single arrangement with the presumption that two or more agreements executed with a single customer at or around the same time are a single arrangement. Accordingly, upfront and other non-contingent arrangement consideration received and to be received has been and will be pooled together and allocated to each of the units of accounting in both the U.S./RoW and China Agreements based on their relative fair values. We evaluated the deliverables within the arrangement and separated them into various units of accounting. Deliverables that did not provide stand-alone value have been combined with other deliverables to form a unit of accounting that collectively has stand-alone value, with revenue being recognized on the combined unit of accounting, rather than the individual deliverables. There are no right-of-return provisions for the delivered items in the agreements. For the technology license under the AstraZeneca U.S./RoW Agreement, BESP was determined based on a two-step process. The first step involved determining an implied royalty rate that would result in the net present value of future cash flows to equal to zero (i.e. where the IRR on the transaction would equal the target return for the investment). This results in an upper bound estimation of the magnitude of royalties that a hypothetical acquirer would reasonably pay for the forecasted cash flow stream. Our cash flow forecasts were derived from probability-adjusted revenue and expense projections. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. The second step involved applying the implied royalty rate, which was determined to be 40%, against the probability-adjusted projected net revenues by territory and determining the value of the license as the net present value of future cash flows after adjusting for taxes. The discount rate utilized was 17.5%. U.S./RoW Agreement: The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows: • License to our technology existing at the effective date of the agreements. • Co-development services. • Manufacturing of clinical supplies of products. • Manufacturing commercial supplies of products. • Committee service. 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 we expect to receive in various amounts through June 2016, of which $82.0 million was received as of December 31, 2013 and was determined to be fixed and determinable upon the execution of the collaboration agreement. Out of the remaining payments of $292.0 million, which are contractually due, $230.0 million have extended payment terms and, accordingly, were not considered to be fixed or determinable upon the execution of the agreement. As such, for these remaining payments, the amount of revenue recognized is limited to the amount of cash consideration received; additionally, for each of the amounts received, the amount of revenue recognized is determined on the basis of applying the relative selling price method to each of the units of accounting underlying the agreement. Further, $62.0 million of the remaining payment is contingent upon the occurrence of a specified event and accordingly is also not considered fixed or determinable. Under the U.S./RoW Agreement, we are also eligible to receive from AstraZeneca an aggregate of approximately $875.0 million in potential milestone payments, comprised of (i) up to $65.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $325.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, (iii) up to $160.0 million in a non-substantive deferred approval milestone, which would be paid if certain competitors do not launch a HIF compound in the U.S. on or before January 1, 2023, and (iv) up to approximately $325.0 million in milestone payments upon the achievement of specified commercial sales events. China Agreement: The units of accounting that were analyzed, along with their general timing of delivery or performance of service and general timing of revenue recognition, are as follows: • License to our technology existing at the effective date of the agreement. For the China Agreement, we retained manufacturing rights as an essential part of a strategy to pursue domestic regulatory pathway for product approval which requires the regulatory licensure of the manufacturing facility in order to commence commercial shipment. The prospects for the collaboration as a whole would have been substantially different had manufacturing rights been provided to AstraZeneca. Because the retention of manufacturing rights by us was a significant factor in the collaboration strategy, rather than simply a mechanism to properly compensate us, we concluded that the license and development services do not have stand-alone value apart from the manufacturing rights. Accordingly, all the deliverables identified, including co-development services, under the China Agreement have been treated as a single unit of account and all revenue allocable to this unit of account is deferred until delivery of commercial drug product has begun. Upon commencement of delivery of commercial drug product, revenue would be recognized in a pattern consistent with estimated deliveries of the commercial drug product. Under the terms of the China Agreement, AstraZeneca agreed to pay upfront consideration totaling $28.2 million, of which $16.2 million was received as of December 31, 2013 and was determined to be fixed and determinable upon the execution of the collaboration agreement. The remainder of the upfront payments of $12.0 million had extended payment terms and, accordingly, is not considered to be fixed or determinable upon the execution of the agreement. This payment of $12.0 million was received as of March 31, 2014. Under the China Agreement, we are also eligible to receive from AstraZeneca an aggregate of approximately $328.5 million in potential milestone payments, comprised of (i) up to $15.0 million in substantive milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $146.0 million in substantive milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $167.5 million in milestone payments upon the achievement of specified commercial sales events. As we are accounting for both the U.S./RoW and China Agreements as one arrangement, any consideration received after the initial proceeds on the agreement signing date were also (and will be also) allocated to the various units of accounting above using the relative selling price method under ASC 605-25-30-2 and 30-5.

Description of Operations and16

Description of Operations and Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Schedule of Reconciliation of Basic and Diluted Net Income per Share Calculation	The following is a reconciliation of the basic and diluted net income per share calculation for the periods presented (in thousands, except per share data): Quarter Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Net income $ 57,055 $ 46,831 $ 10,688 $ 30,591 Less: Undistributed earnings allocated to Junior Preferred stockholders — (25,234 ) — (13,790 ) Net income attributable to Senior Preferred and common stockholders $ 57,055 $ 21,597 $ 10,688 $ 16,801 Less: Undistributed earnings allocated to Senior Preferred stockholders $ — $ (3,474 ) $ — $ (6,948 ) Net income attributable to common stockholders $ 57,055 $ 18,123 $ 10,688 $ 9,853 Weighted average shares used to compute net income per share: Basic 59,798 13,347 59,499 13,279 Dilutive effect of Senior Preferred stock — 15,336 — — Dilutive effect of potential common shares 8,954 8,423 9,855 8,360 Diluted 68,752 37,106 69,354 21,639 Net income per share: Basic $ 0.95 $ 1.36 $ 0.18 $ 0.74 Diluted $ 0.83 $ 0.58 $ 0.15 $ 0.46

Collaboration Agreements (Table

Collaboration Agreements (Tables)	6 Months Ended
	Jun. 30, 2015
Japan [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the Japan Agreement were as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, Agreement Deliverable 2015 2014 2015 2014 Japan License $ 91 $ 155 $ 528 $ 230 Milestones — — — — Total license and milestone revenue 91 155 528 230 Collaboration services revenue* $ 42 $ 89 $ 100 $ 176
Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue	As of June 30, 2015, 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 June 30, 2015 Deferred Revenue at June 30, 2015 Total Consideration Through June 30, 2015 License $ 41,749 $ — $ 41,749 When and if available compounds 12 29 41 Manufacturing—clinical supplies 1,871 72 1,943 Committee services 15 2 17 Total license and collaboration services revenue $ 43,647 $ 103 $ 43,750 * 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.
Europe [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the Europe Agreement were as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, Agreement Deliverable 2015 2014 2015 2014 Europe License $ 4,769 $ 3,563 $ 9,024 $ 6,230 Milestones — — — — Total license and milestone revenue 4,769 3,563 9,024 6,230 Collaboration services revenue* $ 677 $ 777 $ 1,253 $ 1,441
Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue	As of June 30, 2015, 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 June 30, 2015 Deferred Revenue at June 30, 2015 Total Consideration Through June 30, 2015 License $ 392,663 $ — $ 392,663 When and if available compounds 305 442 747 Manufacturing—clinical supplies 8,911 494 9,405 Development services—in progress 31,460 — 31,460 Committee services 256 16 272 Total license and collaboration services revenue $ 433,595 $ 952 $ 434,547 * 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.
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): Quarter Ended June 30, Six Months Ended June 30, Agreement Deliverable 2015 2014 2015 2014 U.S. / RoW License $ 87,019 $ 78,745 $ 93,833 $ 90,688 Milestones 15,000 — 15,000 — Total license and milestone revenue 102,019 78,745 108,833 90,688 Collaboration services revenue* 12,942 6,590 17,080 9,025 China single unit of accounting** $ — $ — $ — $ —
Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue	As of June 30, 2015, 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 June 30, 2015 Deferred Revenue at June 30, 2015 Total Consideration Through June 30, 2015 License $ 269,207 $ — $ 269,207 Co-development, information sharing & committee services 37,589 44,259 81,848 Manufacturing—clinical supplies 154 126 280 China-single unit of accounting — 55,180 55,180 Total license and collaboration services revenue $ 306,950 $ 99,565 $ 406,515 * 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.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2015
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): June 30, 2015 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 150,240 $ — $ 150,240 Equity investments 199 — — 199 Sub-total 199 150,240 — 150,439 Money market funds 127,643 — — 127,643 Total $ 127,842 $ 150,240 $ — $ 278,082 December 31, 2014 Level 1 Level 2 Level 3 Total Corporate bonds $ — $ 158,432 $ — $ 158,432 Equity investments 201 — — 201 Sub-total 201 158,432 — 158,633 Money market funds 13,802 — — 13,802 Total $ 14,003 $ 158,432 $ — $ 172,435
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): June 30, 2015 Level 1 Level 2 Level 3 Total Lease financing obligations $ — $ — $ 97,332 $ 97,332 December 31, 2014 Level 1 Level 2 Level 3 Total Cease-use liability $ — $ — $ 184 $ 184 Lease financing obligations — — 97,221 97,221 Total $ — $ — $ 97,405 $ 97,405

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Cash and Cash Equivalents	Cash and cash equivalents consisted of the following (in thousands): June 30, 2015 December 31, 2014 Cash $ 108,893 $ 151,653 Money market funds 127,643 13,802 Total cash and cash equivalents $ 236,536 $ 165,455
Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments	The amortized cost, gross unrealized holding gains or losses, and fair value of our available-for-sale investments by major investments type are summarized in the tables below (in thousands): June 30, 2015 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Corporate bonds $ 150,119 $ 287 $ (166 ) $ 150,240 Equity investments 124 75 — 199 Total investments $ 150,243 $ 362 $ (166 ) $ 150,439 December 31, 2014 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Estimated Fair Value Corporate bonds $ 158,692 $ 254 $ (514 ) $ 158,432 Equity investments 124 77 — 201 Total investments $ 158,816 $ 331 $ (514 ) $ 158,633
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): June 30, 2015 December 31, 2014 Preclinical and clinical trial accruals $ 32,251 $ 25,418 Payroll and related accruals 9,625 15,608 Professional services 1,121 2,401 Other 3,243 5,558 Total accrued liabilities $ 46,240 $ 48,985

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Allocated Stock-Based Compensation Expense	Stock-based compensation expense was allocated to research and development and general and administrative expense for the periods presented as follows (in thousands): Quarter Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Research and development $ 4,434 $ 408 $ 8,656 $ 883 General and administrative 2,508 262 4,732 582 Total stock-based compensation expense $ 6,942 $ 670 $ 13,388 $ 1,465
Schedule of Weighted-average Assumptions used to Estimate Fair Value of Stock Awards	The weighted-average assumptions used to estimate the fair value of stock options using the Black-Scholes option valuation model and the resulting weighted average fair value of stock options granted during the periods presented were as follows: Quarter Ended June 30, Six Months Ended June 30, 2015 2014 2015 2014 Stock Options Expected term (in years) 5.2 — 5.2 — Expected volatility 70 % — % 70 % — % Risk-free interest rate 1.7 — 1.7 — Expected dividend yield — — — — Weighted average estimated fair value $ 12.27 $ — $ 16.68 $ — Employee Stock Purchase Plans Expected term (in years) 1.3 — 1.3 — Expected volatility 65 % — % 65 % — % Risk-free interest rate 0.3 — 0.3 — Expected dividend yield — — — — Weighted average estimated fair value $ 9.75 $ — $ 9.75 $ —

Description of Operations and21

Description of Operations and Summary of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Millions	Nov. 19, 2014USD ($)$ / sharesshares	Nov. 10, 2014	Jun. 30, 2015$ / sharesshares	Jun. 30, 2014shares	Jun. 30, 2015Segment$ / sharesshares	Jun. 30, 2014shares	Dec. 31, 2014$ / sharesshares
Accounting Policy [Line Items]
Common stock shares sold	9,315,000
Public offering price | $ / shares	$ 18
Net proceeds from initial public offering and concurrent private placement | $	$ 171.8
Underwriting discounts and commissions | $	11.7
Offering expenses | $	4.1
Common stock, aggregate purchase price | $	$ 20
Convertible preferred stock converted into shares of common stock	33,919,954
Number of operating segment | Segment					1
Preferred stock, authorized shares			125,000,000		125,000,000		125,000,000
Preferred stock, par value | $ / shares			$ 0.01		$ 0.01		$ 0.01
Convertible preferred stock outstanding			0		0		0
Anti-dilutive securities excluded from computation of diluted net income per share			3,800,000	18,600,000	1,800,000	33,900,000
FibroGen Europe [Member]
Accounting Policy [Line Items]
Convertible preferred stock converted into shares of common stock	958,996
Common stock [Member]
Accounting Policy [Line Items]
Description reverse stock split					On November 10, 2014, we effected a 1-for-2.5 reverse split of our common stock. Upon the effectiveness of the reverse stock split, (i) every 2.5 shares of outstanding common stock were combined into one share of common stock, (ii) the number of shares of common stock for which each outstanding option or warrant to purchase common stock is exercisable was proportionally decreased on a 1-for-2.5 basis, (iii) the exercise price of each outstanding option or warrant to purchase common stock was proportionately increased on a 1-for- 2.5 basis, (iv) the exchange ratio for each share of outstanding FibroGen Europe Oy (“FibroGen Europe”) share of stock which is exchangeable into our common stock was proportionately reduced on a 1-for-2.5 basis, and (v) the conversion ratio for each share of outstanding preferred stock which is convertible into our common stock was proportionately reduced on a 1-for-2.5 basis. All of the outstanding common stock share numbers (including shares of common stock which our outstanding preferred stock shares were convertible into), common stock warrants, share prices, exercise prices and per share amounts have been adjusted in these condensed consolidated financial statements, on a retroactive basis, to reflect this 1-for-2.5 reverse stock split for all periods presented. The par value per share and the authorized number of shares of common stock and preferred stock were not adjusted as a result of the reverse stock split.
Reverse stock split ratio		0.4

Description of Operations and22

Description of Operations and Summary of Significant Accounting Policies - Schedule of Reconciliation of Basic and Diluted Net Income per Share Calculation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net income	$ 57,055	$ 46,831	$ 10,688	$ 30,591
Net income attributable to Senior Preferred and common stockholders	57,055	21,597	10,688	16,801
Net income attributable to common stockholders	$ 57,055	$ 18,123	$ 10,688	$ 9,853
Weighted average shares used to compute net income per share:
Basic	59,798	13,347	59,499	13,279
Dilutive effect of Senior Preferred stock	0	15,336	0	0
Dilutive effect of potential common shares	8,954	8,423	9,855	8,360
Diluted	68,752	37,106	69,354	21,639
Net income per share:
Basic	$ 0.95	$ 1.36	$ 0.18	$ 0.74
Diluted	$ 0.83	$ 0.58	$ 0.15	$ 0.46
Junior Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Less: Undistributed earnings allocated to Preferred stockholders	$ 0	$ (25,234)	$ 0	$ (13,790)
Senior Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Less: Undistributed earnings allocated to Preferred stockholders	$ 0	$ (3,474)	$ 0	$ (6,948)

Collaboration Agreements - Aste

Collaboration Agreements - Astellas Agreements - Additional Information (Detail) - Astellas Agreement [Member] - USD ($) $ in Millions	1 Months Ended			6 Months Ended	12 Months Ended
	Feb. 28, 2009	Apr. 30, 2006	Jun. 30, 2005	Jun. 30, 2015	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments	$ 360.1
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments	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	$ 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	Mar. 31, 2014	Jul. 30, 2013	Jun. 30, 2015	Jun. 30, 2015
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				$ 312
Development and regulatory approval milestones		550
Commercial sales milestone		325
Shared development costs		233
Additional consideration based on net sales description				Low 20% range
Contingent payment		62
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]
Upfront, non-contingent and time-based payments	$ 12
Development and regulatory approval milestones		161
Commercial sales milestone		167.5
Proceeds from upfront payments		28.2
Contingent payment		$ 20

Collaboration Agreements - Acco

Collaboration Agreements - Accounting for the Astellas Agreements - Additional Information 2 (Detail) - Astellas Agreement [Member] - USD ($) $ in Millions	1 Months Ended			6 Months Ended	111 Months Ended
	Feb. 28, 2009	Apr. 30, 2006	Jun. 30, 2005	Jun. 30, 2015	Jun. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments	$ 360.1
Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied				17.50%
Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied				20.00%
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments	320
Development costs					$ 114.5
Non-contingent performance period		36 months
Total potential milestones		$ 425
Europe [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		90
Europe [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		335
Europe [Member] | Marketing approval milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones		$ 25
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments	$ 40.1
Total potential milestones			$ 132.5
Japan [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones			22.5
Japan [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones			$ 95

Collaboration Agreements - Ac26

Collaboration Agreements - Accounting for the AstraZeneca Agreements - Additional Information 3 (Detail) - AstraZeneca Agreements [Member] - USD ($) $ in Millions	Mar. 31, 2014	Dec. 31, 2013	Jul. 30, 2013	Jul. 30, 2013	Jun. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty rate against projected net revenues					40.00%
Discount rate applied					17.50%
China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments		$ 16.2
Upfront, non-contingent and time-based payments with extended payment terms			$ 12
Contingent payment			20
Total potential milestones			328.5
Commercial sales milestone			167.5
Proceeds from upfront payments			28.2
Upfront payments received	$ 12
China [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones			15
China [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones			146
U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-contingent performance period				65 months
Expected upfront, non-contingent and time-based payments			374
Upfront, non-contingent and time-based payments		$ 82
Remaining up-front, non-contingent and time-based payments			292	$ 292
Upfront, non-contingent and time-based payments with extended payment terms			230
Contingent payment			62
Total potential milestones			875
Commercial sales milestone			325
Non-substantive milestones			160
Upfront payments received					$ 312
U.S./RoW [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones			65
U.S./RoW [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Substantive milestones			$ 325

Collaboration Agreements - Summ

Collaboration Agreements - Summary of Revenue Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	$ 106,879	$ 82,463	$ 118,385	$ 97,148
Collaboration services revenue	13,671	7,495	18,463	10,686
Revenue recognized	120,550	89,958	136,848	107,834
Astellas Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total license and milestone revenue	4,860	3,718	9,552	6,460
Collaboration services revenue	719	866	1,353	1,617
Astellas Agreement [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	91	155	528	230
Milestones revenue	0	0	0	0
Total license and milestone revenue	91	155	528	230
Collaboration services revenue	42	89	100	176
Astellas Agreement [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	4,769	3,563	9,024	6,230
Milestones revenue	0	0	0	0
Total license and milestone revenue	4,769	3,563	9,024	6,230
Collaboration services revenue	677	777	1,253	1,441
AstraZeneca Agreements [Member] | China-single unit of accounting [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Revenue recognized	0	0	0	0
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
License revenue	87,019	78,745	93,833	90,688
Milestones revenue	15,000	0	15,000	0
Total license and milestone revenue	102,019	78,745	108,833	90,688
Collaboration services revenue	$ 12,942	$ 6,590	$ 17,080	$ 9,025

Collaboration Agreements - Tota

Collaboration Agreements - Total Arrangement Consideration Allocated to Deliverables along with Associated Deferred Revenue (Detail) $ in Thousands	Jun. 30, 2015USD ($)
Astellas Agreement [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	$ 43,647
Deferred Revenue	103
Total Consideration	43,750
Astellas Agreement [Member] | Japan [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	41,749
Deferred Revenue	0
Total Consideration	41,749
Astellas Agreement [Member] | Japan [Member] | When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	12
Deferred Revenue	29
Total Consideration	41
Astellas Agreement [Member] | Japan [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	1,871
Deferred Revenue	72
Total Consideration	1,943
Astellas Agreement [Member] | Japan [Member] | Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	15
Deferred Revenue	2
Total Consideration	17
Astellas Agreement [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	433,595
Deferred Revenue	952
Total Consideration	434,547
Astellas Agreement [Member] | Europe [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	392,663
Deferred Revenue	0
Total Consideration	392,663
Astellas Agreement [Member] | Europe [Member] | When and if available compounds [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	305
Deferred Revenue	442
Total Consideration	747
Astellas Agreement [Member] | Europe [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	8,911
Deferred Revenue	494
Total Consideration	9,405
Astellas Agreement [Member] | Europe [Member] | Committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	256
Deferred Revenue	16
Total Consideration	272
Astellas Agreement [Member] | Europe [Member] | Development services-in progress [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	31,460
Deferred Revenue	0
Total Consideration	31,460
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	306,950
Deferred Revenue	99,565
Total Consideration	406,515
AstraZeneca Agreements [Member] | U.S./RoW [Member] | License [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	269,207
Deferred Revenue	0
Total Consideration	269,207
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Manufacturing-clinical supplies [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	154
Deferred Revenue	126
Total Consideration	280
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Co-development, information sharing & committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	37,589
Deferred Revenue	44,259
Total Consideration	81,848
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	55,180
Total Consideration	$ 55,180

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	$ 150,439	$ 158,633
Total fair value of financial assets	278,082	172,435
Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	150,240	158,432
Equity investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	199	201
Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	127,643	13,802
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	199	201
Total fair value of financial assets	127,842	14,003
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] | Equity investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	199	201
Level 1 [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets fair value disclosure	127,643	13,802
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	150,240	158,432
Total fair value of financial assets	150,240	158,432
Level 2 [Member] | Corporate bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	150,240	158,432
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 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments	0	0
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] | 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

Fair Value Measurements - Fai30

Fair Value Measurements - Fair Values of Financial Liabilities Carried at Historical Cost (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		$ 97,405
Cease-use liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		184
Lease financing obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 97,332	97,221
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		97,405
Level 3 [Member] | Cease-use liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		184
Level 3 [Member] | Lease financing obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 97,332	$ 97,221

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2014
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	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Abstract]
Cash	$ 108,893	$ 151,653
Money market funds	127,643	13,802
Total cash and cash equivalents	$ 236,536	$ 165,455	$ 182,662	$ 76,332

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	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 150,243	$ 158,816
Gross Unrealized Holding Gains	362	331
Gross Unrealized Holding Losses	(166)	(514)
Estimated Fair Value	150,439	158,633
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	150,119	158,692
Gross Unrealized Holding Gains	287	254
Gross Unrealized Holding Losses	(166)	(514)
Estimated Fair Value	150,240	158,432
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	124	124
Gross Unrealized Holding Gains	75	77
Estimated Fair Value	$ 199	$ 201

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Contractual maturities of available-for-sale investments			4 years
Other-than-temporary impairment loss	$ 0	$ 0	$ 0	$ 0
Cash and cash equivalents	236,536,000	$ 182,662,000	236,536,000	$ 182,662,000	$ 165,455,000	$ 76,332,000
Foreign subsidiaries [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 30,900,000		$ 30,900,000

Balance Sheet Components - Sc35

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Payables and Accruals [Abstract]
Preclinical and clinical trial accruals	$ 32,251	$ 25,418
Payroll and related accruals	9,625	15,608
Professional services	1,121	2,401
Other	3,243	5,558
Total accrued liabilities	$ 46,240	$ 48,985

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Allocated Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 6,942	$ 670	$ 13,388	$ 1,465
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	4,434	408	8,656	883
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,508	$ 262	$ 4,732	$ 582

Stock-Based Compensation - Sc37

Stock-Based Compensation - Schedule of Weighted-average Assumptions used to Estimate Fair Value of Stock Awards (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Employee stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 2 months 12 days		5 years 2 months 12 days
Expected volatility	70.00%	0.00%	70.00%	0.00%
Risk-free interest rate	1.70%	0.00%	1.70%	0.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Weighted average estimated fair value	$ 12.27	$ 0	$ 16.68	$ 0
Employee stock purchase plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	1 year 3 months 18 days		1 year 3 months 18 days
Expected volatility	65.00%	0.00%	65.00%	0.00%
Risk-free interest rate	0.30%	0.00%	0.30%	0.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Weighted average estimated fair value	$ 9.75	$ 0	$ 9.75	$ 0

Income Taxes - Additional infor

Income Taxes - Additional information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Tax Disclosure [Abstract]
Provision (benefit) for income taxes	$ 205	$ 0	$ (66)	$ 0

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Related Party Transaction [Line Items]
Accounts receivable from related party	$ 10,331		$ 10,331		$ 5,033
Accrued liabilities to related parties	5,817		5,817		4,594
Astellas Agreement [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	5,600	$ 4,600	10,900	$ 8,100
Expense related to collaboration agreements	1,300	$ 2,400	4,400	$ 4,500
Accounts receivable from related party	10,300		10,300		5,000
Accrued liabilities to related parties	$ 5,800		$ 5,800		$ 4,300