Five Prime Therapeutics (FPRX) 10-Q 4 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 31, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Trading Symbol	FPRX
Entity Registrant Name	FIVE PRIME THERAPEUTICS INC
Entity Central Index Key	1,175,505
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		28,441,594

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 56,375	$ 149,971
Marketable securities	384,323	367,495
Receivables from collaborative partners	2,307	4,054
Income tax receivable	3,193
Prepaid and other current assets	7,769	6,761
Total current assets	453,967	528,281
Property and equipment, net	5,418	4,539
Deferred tax asset	5,327	15,071
Other long-term assets	414	394
Total assets	465,126	548,285
Current liabilities:
Accounts payable	528	1,894
Accrued personnel-related expenses	5,931	6,878
Other accrued liabilities	9,810	5,882
Deferred revenue, current portion	15,014	17,509
Deferred rent, current portion	841	768
Income tax payable, current portion	7,013	46,437
Total current liabilities	39,137	79,368
Deferred revenue, long-term portion	21,209	31,268
Deferred rent, long-term portion	216	865
Income tax payable, long-term portion	515	3,283
Other long-term liabilities	74	295
Commitments
Stockholders' equity:
Common stock	27	26
Additional paid-in capital	388,752	372,605
Accumulated other comprehensive income (loss)	138	(74)
Retained earnings	15,058	60,649
Total stockholders' equity	403,975	433,206
Total liabilities and stockholders' equity	$ 465,126	$ 548,285

Condensed Statements of Operati

Condensed Statements of Operations - USD ($) shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Statement [Abstract]
Collaboration revenue	$ 6,680,000	$ 5,858,000	$ 22,429,000	$ 16,460,000
Operating expenses:
Research and development	23,890,000	24,720,000	64,923,000	49,241,000
General and administrative	9,146,000	5,213,000	25,309,000	14,029,000
Total operating expenses	33,036,000	29,933,000	90,232,000	63,270,000
Loss from operations	(26,356,000)	(24,075,000)	(67,803,000)	(46,810,000)
Interest and other income, net	639,000	104,000	1,821,000	329,000
Loss before income tax	(25,717,000)	(23,971,000)	(65,982,000)	(46,481,000)
Income tax benefit	6,303,000	0	20,391,000	0
Net loss	$ (19,414,000)	$ (23,971,000)	$ (45,591,000)	$ (46,481,000)
Basic and diluted net loss per common share	$ (0.72)	$ (0.93)	$ (1.70)	$ (1.82)
Weighted-average shares used to compute basic and diluted net loss per common share	27,139	25,825	26,794	25,532

Condensed Statements of Compreh

Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (19,414)	$ (23,971)	$ (45,591)	$ (46,481)
Other comprehensive income (loss):
Net unrealized gain (loss) on marketable securities, net of tax	(81)	(35)	212	36
Comprehensive loss	$ (19,495)	$ (24,006)	$ (45,379)	$ (46,445)

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities
Net loss	$ (45,591)	$ (46,481)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,233	1,275
Stock-based compensation expense	22,838	5,056
Excess tax benefits from employee equity incentive plans	(662)
Deferred income taxes	9,744
Amortization of premium on marketable securities	3,339	1,491
Loss on disposal of property and equipment	9	3
Changes in operating assets and liabilities:
Receivables from collaborative partners	1,747	(1,256)
Income tax receivable	(3,193)
Prepaid, other current assets, and other long-term assets	(1,028)	(3,490)
Accounts payable	(1,366)	469
Accrued personnel-related expenses	(947)	(338)
Deferred revenue	(12,554)	(3,274)
Deferred rent	(576)	(346)
Income tax payable	(41,530)
Other accrued liabilities and other long-term liabilities	3,707	2,401
Net cash used in operating activities	(64,830)	(44,490)
Investing activities
Purchases of marketable securities	(410,955)	(135,376)
Maturities of marketable securities	391,000	121,250
Purchases of property and equipment	(2,121)	(1,514)
Net cash used in investing activities	(22,076)	(15,640)
Financing activities
Proceeds from public offering of common stock, net		78,693
Proceeds from issuance of common stock under equity incentive plans	6,702	3,126
Repurchase of shares to satisfy tax withholding	(14,054)
Excess tax benefits from employee equity incentive plans	662
Net cash (used in) provided by financing activities	(6,690)	81,819
Net (decrease) increase in cash and cash equivalents	(93,596)	21,689
Cash and cash equivalents at beginning of period	149,971	15,267
Cash and cash equivalents at end of period	56,375	$ 36,956
Supplemental cash flow information
Cash paid for income taxes	$ 14,701

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Description of Business	1. Description of Business Five Prime Therapeutics, Inc. (we, us, our or the Company) is a clinical-stage biotechnology company focused on discovering and developing innovative protein therapeutics to improve the lives of patients with serious diseases. Protein therapeutics are antibodies or drugs developed from extracellular proteins or protein fragments that block disease processes, including cancer and inflammatory diseases. We were incorporated in December 2001 in Delaware. Our operations are based in South San Francisco, California and we operate in one segment. Unaudited Interim Financial Information The accompanying financial information as of September 30, 2016 is unaudited. The Condensed Financial Statements included in this report reflect all adjustments (consisting only of normal recurring adjustments) that our management considers necessary for the fair statement of the results of operations for the interim periods covered and of the financial condition of the Company at the date of the interim balance sheet. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information. Accordingly, they do not include all of the information and notes required by GAAP for complete financial statements. The results for interim periods are not necessarily indicative of the results for the entire year or any other interim period. The accompanying Condensed Financial Statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2015 filed with the U.S. Securities and Exchange Commission.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions about future events that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements as well as reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates. Fair Value of Financial Instruments We determine the fair value of financial and nonfinancial assets and liabilities using the fair value hierarchy, which describes three levels of inputs that may be used to measure fair value, as follows: Level 1 —Quoted prices in active markets for identical assets or liabilities; Level 2 —Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. We determine the fair value of Level 1 assets using quoted prices in active markets for identical assets. We review trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data. In certain cases where there is limited activity or less transparency around inputs to valuation, we classify securities as Level 3 within the valuation hierarchy. We do not have any assets or liabilities measured using Level 3 inputs as of September 30, 2016. The following table summarizes, for assets recorded at fair value, the respective fair values and the classifications by level of input within the fair value hierarchy defined above (in thousands): September 30, 2016 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 54,324 $ 54,324 $ — $ — U.S. Treasury securities 384,323 384,323 — — Total cash equivalents and marketable securities $ 438,647 $ 438,647 $ — $ — December 31, 2015 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 34,821 $ 34,821 $ — $ — U.S. Treasury securities 477,125 477,125 — — Total cash equivalents and marketable securities $ 511,946 $ 511,946 $ — $ — Net Loss Per Share of Common Stock We compute basic net loss per common share by dividing net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. We excluded the following options to purchase shares of common stock and restricted stock awards, or RSAs, from the calculation of diluted net loss per share for all periods presented as the effect would have been antidilutive (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Options to purchase common stock 3,100 2,833 2,815 2,670 RSAs 1,250 666 1,358 256 4,350 3,499 4,173 2,926 Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers: Topic 606 In March, April, and May 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations , ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing , and ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients to provide supplemental adoption guidance and clarification to ASU 2014-09. The effective date for these new standards is the same as the effective date and transition requirements for ASU 2014-09. We expect to adopt ASU 2014-09 in the first quarter of fiscal 2018 using the modified retrospective method. We are in the process of analyzing each of our collaboration agreements to determine the impact that the standards will have on our financial position and results of operations and expect to complete our assessment by the end of the fourth quarter of 2017. In February 2016, FASB issued ASU 2016-02, Leases. all annual and interim reporting periods thereafter. E In March 2016, FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting This standard makes several modifications to Topic 718 related to the accounting for forfeitures, employer tax withholding on share-based compensation and the financial statement presentation of excess tax benefits or deficiencies. ASU 2016-09 also clarifies the statement of cash flows presentation for certain components of share-based awards. The We are evaluating the impact that the adoption of ASU 2016-09 will have on our consolidated financial statements and related disclosures.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	9 Months Ended
	Sep. 30, 2016
Cash And Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	3. Cash Equivalents and Marketable Securities The following is a summary of our cash equivalents and marketable securities (in thousands): September 30, 2016 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 54,324 $ — $ — $ 54,324 U.S. Treasury securities 384,111 227 (15 ) 384,323 438,435 227 (15 ) 438,647 Less: cash equivalents (54,324 ) — — (54,324 ) Total marketable securities $ 384,111 $ 227 $ (15 ) $ 384,323 December 31, 2015 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 34,821 $ — $ — $ 34,821 U.S. Treasury securities 477,239 13 (127 ) 477,125 512,060 13 (127 ) 511,946 Less: cash equivalents (144,470 ) — 19 (144,451 ) Total marketable securities $ 367,590 $ 13 $ (108 ) $ 367,495 As of September 30, 2016, the amortized cost and estimated fair value of our available-for-sale securities by contractual maturity are shown below (in thousands): Amortized Estimated Cost Fair Value Debt securities maturing: In one year or less $ 384,111 $ 384,323 Total marketable securities $ 384,111 $ 384,323 We determined that the gross unrealized losses on our marketable securities as of September 30, 2016 were temporary in nature. We currently do not intend to sell these securities prior to maturity and do not consider these investments to be other-than-temporarily impaired at September 30, 2016. There were no sales of available-for-sale securities in any of the periods presented.

Equity Incentive Plans

Equity Incentive Plans	9 Months Ended
	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plans	4. Equity Incentive Plans The following table summarizes option activity under our equity incentive plans and related information: Options Outstanding Weighted Weighted Average Average Number of Exercise Price Remaining Shares Per Share Term Balance at December 31, 2015 3,028,714 $ 12.62 Options granted 1,333,000 $ 43.58 Options exercised (769,984 ) $ 7.68 Options forfeited (116,045 ) $ 19.09 Options expired (127 ) $ 18.33 Balance at September 30, 2016 3,475,558 $ 25.37 Options exercisable 1,230,889 $ 11.16 6.30 We have granted RSAs to certain of our employees. RSAs are share awards that entitle the holder to receive freely tradable shares of our common stock upon vesting and are unforfeitable once fully vested. We based the fair value of RSAs on the closing sales price of our common stock on the grant date. The following table summarizes RSA activity under our 2013 Omnibus Incentive Plan and related information: RSAs Outstanding Weighted-Average Number Grant-Date of Shares Fair Value Unvested balance at December 31, 2015 1,574,870 $ 19.71 RSAs granted 381,730 $ 42.46 RSAs vested (800,554 ) $ 19.04 RSAs forfeited (114,021 ) $ 19.50 Unvested balance at September 30, 2016 1,042,025 $ 28.59 As of September 30, 2016, there were 1,432,505 shares of common stock available for future issuance under our 2013 Omnibus Incentive Plan. Stock-Based Compensation We calculate employee stock-based compensation expense based on awards ultimately expected to vest reduced by estimated forfeitures. We estimate forfeitures at the time of grant and revise forfeitures, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Total stock-based compensation expense recognized was as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Research and development $ 4,500 $ 1,537 $ 12,643 $ 2,642 General and administrative 3,811 1,316 10,195 2,414 Total $ 8,311 $ 2,853 $ 22,838 $ 5,056 We estimated the fair value of stock options using the Black-Scholes option-pricing model based on the date of grant of such stock option with the following assumptions: Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Expected term (years) 6.0-6.3 6.0-6.1 5.5-6.3 5.5-6.1 Expected volatility 70% 71% 70-74% 71-73% Risk-free interest rate 1.3% 1.5-1.9% 1.3-1.5% 1.4-1.9% Expected dividend yield 0% 0% 0% 0% As of September 30, 2016, we had $40.1 million of total unrecognized compensation expense related to nonvested employee and director stock options that we expect to recognize over a weighted-average period of 3.1 years. Additionally, we had $20.5 million of total unrecognized compensation expense related to employee and director RSAs that we expect to recognize over a weighted-average period of 1.4 years.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	5. Income Taxes We realized an income tax benefit of $6.3 million and $20.4 million, respectively, for the three and nine months ended September 30, 2016 as compared to no tax expense for the three and nine months ended September 30, 2015. The income tax benefit represents our ability to recover taxes accrued in 2015 based on existing tax law that allows us to carryback our 2016 or 2017 tax losses and/or credits to recover prior taxes. The income tax benefit is based on the annual effective tax rate method and considers our forecasted 2016 pre-tax losses reduced by non-deductible stock based compensation expenses and other immaterial non-deductible permanent items. In addition, as a result of the forecasted loss, the income tax benefit was decreased by a valuation allowance recorded against certain deferred tax assets due to the uncertainty surrounding the realization of such assets in the future. As of the year ended December 31, 2015, we recognized approximately $15.1 million of net deferred tax assets based on our review of the reversal pattern of these deferred tax assets that may result in future recovery of tax paid in 2015. Based on our forecasted loss for 2016, we assessed the recoverability of deferred tax assets based on their reversal patterns. We will periodically review our ability to realize our deferred tax assets and any adjustment to this recoverability will impact our annual effective tax rate.

Summary of Significant Accoun11

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions about future events that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements as well as reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates.
Fair Value of Financial Instruments	Fair Value of Financial Instruments We determine the fair value of financial and nonfinancial assets and liabilities using the fair value hierarchy, which describes three levels of inputs that may be used to measure fair value, as follows: Level 1 —Quoted prices in active markets for identical assets or liabilities; Level 2 —Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. We determine the fair value of Level 1 assets using quoted prices in active markets for identical assets. We review trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data. In certain cases where there is limited activity or less transparency around inputs to valuation, we classify securities as Level 3 within the valuation hierarchy. We do not have any assets or liabilities measured using Level 3 inputs as of September 30, 2016. The following table summarizes, for assets recorded at fair value, the respective fair values and the classifications by level of input within the fair value hierarchy defined above (in thousands): September 30, 2016 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 54,324 $ 54,324 $ — $ — U.S. Treasury securities 384,323 384,323 — — Total cash equivalents and marketable securities $ 438,647 $ 438,647 $ — $ — December 31, 2015 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 34,821 $ 34,821 $ — $ — U.S. Treasury securities 477,125 477,125 — — Total cash equivalents and marketable securities $ 511,946 $ 511,946 $ — $ —
Net Loss Per Share of Common Stock	Net Loss Per Share of Common Stock We compute basic net loss per common share by dividing net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. We excluded the following options to purchase shares of common stock and restricted stock awards, or RSAs, from the calculation of diluted net loss per share for all periods presented as the effect would have been antidilutive (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Options to purchase common stock 3,100 2,833 2,815 2,670 RSAs 1,250 666 1,358 256 4,350 3,499 4,173 2,926
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers: Topic 606 In March, April, and May 2016, the FASB issued ASU 2016-08, Revenue from Contracts with Customers: Principal versus Agent Considerations , ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing , and ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients to provide supplemental adoption guidance and clarification to ASU 2014-09. The effective date for these new standards is the same as the effective date and transition requirements for ASU 2014-09. We expect to adopt ASU 2014-09 in the first quarter of fiscal 2018 using the modified retrospective method. We are in the process of analyzing each of our collaboration agreements to determine the impact that the standards will have on our financial position and results of operations and expect to complete our assessment by the end of the fourth quarter of 2017. In February 2016, FASB issued ASU 2016-02, Leases. all annual and interim reporting periods thereafter. E In March 2016, FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting This standard makes several modifications to Topic 718 related to the accounting for forfeitures, employer tax withholding on share-based compensation and the financial statement presentation of excess tax benefits or deficiencies. ASU 2016-09 also clarifies the statement of cash flows presentation for certain components of share-based awards. The We are evaluating the impact that the adoption of ASU 2016-09 will have on our consolidated financial statements and related disclosures.

Summary of Significant Accoun12

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Summary of Assets Recorded at Fair Value	The following table summarizes, for assets recorded at fair value, the respective fair values and the classifications by level of input within the fair value hierarchy defined above (in thousands): September 30, 2016 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 54,324 $ 54,324 $ — $ — U.S. Treasury securities 384,323 384,323 — — Total cash equivalents and marketable securities $ 438,647 $ 438,647 $ — $ — December 31, 2015 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 34,821 $ 34,821 $ — $ — U.S. Treasury securities 477,125 477,125 — — Total cash equivalents and marketable securities $ 511,946 $ 511,946 $ — $ —
Options and Restricted Stock Awards Excluded from Calculation of Diluted Net Loss Per Share	We excluded the following options to purchase shares of common stock and restricted stock awards, or RSAs, from the calculation of diluted net loss per share for all periods presented as the effect would have been antidilutive (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Options to purchase common stock 3,100 2,833 2,815 2,670 RSAs 1,250 666 1,358 256 4,350 3,499 4,173 2,926

Cash Equivalents and Marketab13

Cash Equivalents and Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2016
Cash And Cash Equivalents [Abstract]
Summary of Cash Equivalents and Marketable Securities	The following is a summary of our cash equivalents and marketable securities (in thousands): September 30, 2016 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 54,324 $ — $ — $ 54,324 U.S. Treasury securities 384,111 227 (15 ) 384,323 438,435 227 (15 ) 438,647 Less: cash equivalents (54,324 ) — — (54,324 ) Total marketable securities $ 384,111 $ 227 $ (15 ) $ 384,323 December 31, 2015 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 34,821 $ — $ — $ 34,821 U.S. Treasury securities 477,239 13 (127 ) 477,125 512,060 13 (127 ) 511,946 Less: cash equivalents (144,470 ) — 19 (144,451 ) Total marketable securities $ 367,590 $ 13 $ (108 ) $ 367,495
Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale Securities by Contractual Maturity	As of September 30, 2016, the amortized cost and estimated fair value of our available-for-sale securities by contractual maturity are shown below (in thousands): Amortized Estimated Cost Fair Value Debt securities maturing: In one year or less $ 384,111 $ 384,323 Total marketable securities $ 384,111 $ 384,323

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	9 Months Ended
	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Option Activity under Equity Incentive Plans and Related Information	The following table summarizes option activity under our equity incentive plans and related information: Options Outstanding Weighted Weighted Average Average Number of Exercise Price Remaining Shares Per Share Term Balance at December 31, 2015 3,028,714 $ 12.62 Options granted 1,333,000 $ 43.58 Options exercised (769,984 ) $ 7.68 Options forfeited (116,045 ) $ 19.09 Options expired (127 ) $ 18.33 Balance at September 30, 2016 3,475,558 $ 25.37 Options exercisable 1,230,889 $ 11.16 6.30
Schedule of Restricted Stock Award Activity under 2013 Omnibus Incentive Plan and Related Information	The following table summarizes RSA activity under our 2013 Omnibus Incentive Plan and related information: RSAs Outstanding Weighted-Average Number Grant-Date of Shares Fair Value Unvested balance at December 31, 2015 1,574,870 $ 19.71 RSAs granted 381,730 $ 42.46 RSAs vested (800,554 ) $ 19.04 RSAs forfeited (114,021 ) $ 19.50 Unvested balance at September 30, 2016 1,042,025 $ 28.59
Schedule of Stock-Based Compensation Expenses Recognized	Total stock-based compensation expense recognized was as follows (in thousands) Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Research and development $ 4,500 $ 1,537 $ 12,643 $ 2,642 General and administrative 3,811 1,316 10,195 2,414 Total $ 8,311 $ 2,853 $ 22,838 $ 5,056
Schedule of Stock Options Weighted-Average Assumptions	We estimated the fair value of stock options using the Black-Scholes option-pricing model based on the date of grant of such stock option with the following assumptions: Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Expected term (years) 6.0-6.3 6.0-6.1 5.5-6.3 5.5-6.1 Expected volatility 70% 71% 70-74% 71-73% Risk-free interest rate 1.3% 1.5-1.9% 1.3-1.5% 1.4-1.9% Expected dividend yield 0% 0% 0% 0%

Description of Business - Addit

Description of Business - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2016Segment
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating segment	1

Summary of Significant Accoun16

Summary of Significant Accounting Policies - Summary of Assets Recorded at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets
U.S. Treasury securities	$ 384,323	$ 367,495
Total cash equivalents and marketable securities	438,647	511,946
Money market funds [Member]
Assets
Money market funds	54,324	34,821
U.S. Treasury securities	54,324	34,821
U.S. Treasury securities [Member]
Assets
U.S. Treasury securities	384,323	477,125
Level 1 [Member]
Assets
Total cash equivalents and marketable securities	438,647	511,946
Level 1 [Member] | Money market funds [Member]
Assets
Money market funds	54,324	34,821
Level 1 [Member] | U.S. Treasury securities [Member]
Assets
U.S. Treasury securities	$ 384,323	$ 477,125

Summary of Significant Accoun17

Summary of Significant Accounting Policies - Options and Restricted Stock Awards Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of diluted net (loss) income per share	4,350	3,499	4,173	2,926
Options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of diluted net (loss) income per share	3,100	2,833	2,815	2,670
RSAs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of diluted net (loss) income per share	1,250	666	1,358	256

Cash Equivalents and Marketab18

Cash Equivalents and Marketable Securities - Summary of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	$ 384,111	$ 367,590
Unrealized Gains	227	13
Unrealized Losses	(15)	(108)
Estimated Fair Value	384,323	367,495
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	54,324	34,821
Estimated Fair Value	54,324	34,821
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	384,111	477,239
Unrealized Gains	227	13
Unrealized Losses	(15)	(127)
Estimated Fair Value	384,323	477,125
Marketable securities including cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	438,435	512,060
Unrealized Gains	227	13
Unrealized Losses	(15)	(127)
Estimated Fair Value	438,647	511,946
Cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	(54,324)	(144,470)
Unrealized Losses		19
Estimated Fair Value	$ (54,324)	$ (144,451)

Cash Equivalents and Marketab19

Cash Equivalents and Marketable Securities - Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale Securities by Contractual Maturity (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	$ 384,111	$ 367,590
Total marketable securities, Estimated Fair Value	384,323	367,495
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, In one year or less	384,111
Amortized Cost Basis	384,111	477,239
Estimated Fair Value, In one year or less	384,323
Total marketable securities, Estimated Fair Value	$ 384,323	$ 477,125

Cash Equivalents and Marketab20

Cash Equivalents and Marketable Securities - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2016USD ($)
Investments Debt And Equity Securities [Abstract]
Sales of available-for-sale securities	$ 0

Equity Incentive Plans - Schedu

Equity Incentive Plans - Schedule of Option Activity under Equity Incentive Plans and Related Information (Detail)	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance | shares	3,028,714
Number of Shares, Options granted | shares	1,333,000
Number of Shares, Options exercised | shares	(769,984)
Number of Shares, Options forfeited | shares	(116,045)
Number of Shares, Options expired | shares	(127)
Number of Shares, Ending balance | shares	3,475,558
Number of Shares, Options exercisable | shares	1,230,889
Weighted-Average Exercise Price Per Share, Options beginning balance | $ / shares	$ 12.62
Weighted-Average Exercise Price Per Share, Options granted | $ / shares	43.58
Weighted-Average Exercise Price Per Share, Options exercised | $ / shares	7.68
Weighted-Average Exercise Price Per Share, Options forfeited | $ / shares	19.09
Weighted-Average Exercise Price Per Share, Options expired | $ / shares	18.33
Weighted-Average Exercise Price Per Share, Options ending balance | $ / shares	25.37
Weighted-Average Exercise Price Per Share, Options exercisable | $ / shares	$ 11.16
Weighted-Average Remaining Contractual Terms, Options exercisable	6 years 3 months 18 days

Equity Incentive Plans - Sche22

Equity Incentive Plans - Schedule of Restricted Stock Award Activity under 2013 Omnibus Incentive Plan and Related Information (Detail) - Restricted Stock Awards [Member]	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning balance | shares	1,574,870
Granted, Number of Shares | shares	381,730
Vested, Number of Shares | shares	(800,554)
Forfeited, Number of Shares | shares	(114,021)
Number of Shares, Unvested, Ending balance | shares	1,042,025
Shares, Weighted-Average Grant-Date Fair Value balance at December 31, 2015 | $ / shares	$ 19.71
Shares Granted, Weighted-Average Grant-Date Fair Value | $ / shares	42.46
Shares Vested, Weighted-Average Grant-Date Fair Value | $ / shares	19.04
Shares Forfeited, Weighted-Average Grant-Date Fair Value | $ / shares	19.50
Shares, Weighted-Average Grant-Date Fair Value balance at September 30, 2016 | $ / shares	$ 28.59

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2016USD ($)shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense related to nonvested employee and director stock options	$ 40.1
Unrecognized compensation expense expected to recognize, weighted-average period	3 years 1 month 6 days
Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense expected to recognize, weighted-average period	1 year 4 months 24 days
Total unrecognized compensation expense related to employee and director RSAs	$ 20.5
2013 Omnibus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock reserved for future issuance | shares	1,432,505

Equity Incentive Plans - Sche24

Equity Incentive Plans - Schedule of Stock-Based Compensation Expenses Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense recognized	$ 8,311	$ 2,853	$ 22,838	$ 5,056
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense recognized	4,500	1,537	12,643	2,642
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense recognized	$ 3,811	$ 1,316	$ 10,195	$ 2,414

Equity Incentive Plans - Sche25

Equity Incentive Plans - Schedule of Stock Options Assumptions (Detail) - Options [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.30%
Risk-free interest rate, minimum		1.50%	1.30%	1.40%
Risk-free interest rate, maximum		1.90%	1.50%	1.90%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected volatility	70.00%	71.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years	6 years	5 years 6 months	5 years 6 months
Expected volatility			70.00%	71.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years 3 months 18 days	6 years 1 month 6 days	6 years 3 months 18 days	6 years 1 month 6 days
Expected volatility			74.00%	73.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax (benefit) expense	$ (6,303,000)	$ 0	$ (20,391,000)	$ 0
Net deferred tax assets					$ 15,100,000