Global Blood Therapeutics (GBT) 10-Q 7 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	GBT
Entity Registrant Name	Global Blood Therapeutics, Inc.
Entity Central Index Key	1,629,137
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		51,825,849

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 455,637	$ 198,332
Short-term marketable securities	87,949	116,493
Prepaid expenses and other current assets	10,264	9,487
Total current assets	553,850	324,312
Property and equipment, net	17,414	16,571
Long-term marketable securities	992	14,607
Restricted cash	906	1,046
Other assets, noncurrent	214	184
Total assets	573,376	356,720
Current liabilities:
Accounts payable	7,360	7,177
Accrued liabilities	11,220	10,135
Accrued compensation	4,723	8,579
Other liabilities, current	657	373
Total current liabilities	23,960	26,264
Other liabilities, noncurrent	11,652	11,652
Total liabilities	35,612	37,916
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized as of March 31, 2018 and December 31, 2017; no shares issued and outstanding
Common stock, $0.001 par value, 150,000,000 shares authorized as of March 31, 2018 (unaudited) and December 31, 2017, respectively; 51,637,003 and 46,131,723 shares issued and outstanding as of March 31, 2018 (unaudited) and December 31, 2017, respectively	52	46
Additional paid-in capital	877,550	617,051
Accumulated other comprehensive loss	(325)	(336)
Accumulated deficit	(339,513)	(297,957)
Total stockholders' equity	537,764	318,804
Total liabilities and stockholders' equity	$ 573,376	$ 356,720

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	51,637,003	46,131,723
Common stock, shares outstanding	51,637,003	46,131,723

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating expenses:
Research and development	$ 29,944	$ 17,283
General and administrative	12,751	6,438
Total operating expenses	42,695	23,721
Loss from operations	(42,695)	(23,721)
Other income (expense):
Interest income, net	1,173	441
Other expenses, net	(34)	(52)
Total other income, net	1,139	389
Net loss	(41,556)	(23,332)
Other comprehensive income (loss):
Net unrealized gain (loss) on marketable securities, net of tax	11	(13)
Comprehensive loss	$ (41,545)	$ (23,345)
Basic and diluted net loss per common share	$ (0.87)	$ (0.60)
Weighted-average number of shares used in computing basic and diluted net loss per common share	47,770,023	39,125,848

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (41,556)	$ (23,332)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	670	333
Amortization of premium on marketable securities	93	184
Stock-based compensation	7,784	2,574
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(677)	(1,348)
Accounts payable	262	(1,263)
Accrued liabilities	125	2,482
Accrued compensation	(3,856)	(2,192)
Other liabilities	389	(13)
Net cash used in operating activities	(36,766)	(22,575)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(502)	(174)
Purchase of marketable securities		(78,741)
Maturities of marketable securities	42,076	9,287
Net cash provided by (used in) investing activities	41,574	(69,628)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock in public offering, net	254,940	135,705
Proceeds from issuance of common stock in settlement of employee stock purchase plan and exercise of stock options	2,821	1,076
Tax paid related to net shares settlement of equity awards	(5,404)
Net cash provided by financing activities	252,357	136,781
Net increase in cash, cash equivalents and restricted cash	257,165	44,578
Cash, cash equivalents and restricted cash at beginning of period	199,378	92,212
Cash, cash equivalents and restricted cash at end of period	456,543	136,790
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Accrued purchase of property and equipment	1,087	110
Accrued offering costs	$ 127	$ 88

Organization and Basis of Prese

Organization and Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation Global Blood Therapeutics, Inc. (the “Company”, “we”, “us”, and “our”) was incorporated in Delaware in February 2011 and commenced operations in May 2012. We are a clinical-stage biopharmaceutical company determined to discover, develop and deliver innovative treatments that provide hope to underserved patient communities. Our primary activities have been establishing our facilities, recruiting personnel, conducting development of our product candidates, including clinical trials, and raising capital. Our principal operations are based in South San Francisco, California, and we operate in one segment. Follow-on In December 2017, we completed a follow-on In March 2018, we completed a follow-on Need for Additional Capital In the course of our development activities, we have sustained operating losses and we expect such losses to continue over the next several years. Our ultimate success depends on the outcome of our research and development activities. Since inception through March 31, 2018, we have incurred cumulative net losses of $339.5 million. We expect to incur additional losses in the future to conduct product research and development and we recognize the need to raise additional capital to fully implement our business plan. We intend to raise such capital through the issuance of additional equity, and potentially through borrowings, and strategic alliances with partner companies. However, if such financing is not available at adequate levels, we will need to re-evaluate

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Preparation The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2017 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as our annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of our financial information. The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any other interim period or for any other future year. The accompanying unaudited interim condensed consolidated financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2017 included in our Annual Report on Form 10-K, Use of Estimates The preparation of the accompanying unaudited interim condensed consolidated financial statements in accordance with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of costs and expenses during the reporting period. We base our estimates and assumptions on historical experience when available and on various factors that we believe to be reasonable under the circumstances. We evaluate our estimates and assumptions on an ongoing basis. Our actual results could differ from these estimates under different assumptions or conditions. Principles of Consolidation The accompanying unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated upon consolidation. Significant Accounting Policies There have been no material revisions in our significant accounting policies described in Note 2 to the consolidated financial statements included in our Annual Report on Form 10-K Accounting Pronouncements Adopted In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments No. 2016-15 In November 2016, the FASB issued ASU No. 2016-18, Restricted Cash beginning-of-period end-of-period No. 2016-18 In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718) No. 2017-09 Recent Accounting Pronouncements In February 2018, the FASB issued ASU No. 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income No. 2018-02 In March 2018, the FASB issued ASU No. 2018-04, Investments – Debt Securities (Topic 320) and Regulated Operations (Topic 980): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 117 and SEC Release No. 33-9273. No. 2018-03 Investments-Debt Securities Regulated Operations In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 No. 2018-05 Income Taxes

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the consolidated financial statements on a recurring basis (at least annually). Our financial instruments consist of cash and cash equivalents, marketable securities, other receivable as included in prepaid expenses and other current assets, restricted cash, accounts payable and accrued liabilities. Cash and cash equivalents, marketable securities and restricted cash are reported at their respective fair values on our condensed consolidated balance sheets. The remaining financial instruments are reported on our condensed consolidated balance sheets at cost that approximate current fair values due to their relatively short maturities. Assets and liabilities recorded at fair value on a recurring basis in the condensed consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 Level 2 Level 3 The following table summarizes our financial assets measured at fair value on a recurring basis (in thousands): March 31, 2018 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 455,554 $ 455,554 $ — $ — Corporate debt securities 33,261 — 33,261 — U.S. government agency securities 44,197 — 44,197 — Certificates of deposits 6,479 — 6,479 — U.S. government securities 5,004 — 5,004 — Total financial assets $ 544,495 $ 455,554 $ 88,941 $ — December 31, 2017 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 134,744 $ 134,744 $ — $ — Corporate debt securities 46,977 — 46,977 — U.S. government agency securities 54,989 — 54,989 — Certificates of deposits 9,129 — 9,129 — U.S. government securities 20,007 — 20,007 — Total financial assets $ 265,846 $ 134,744 $ 131,102 $ — We estimate the fair values of our investments in corporate debt securities, government and government related securities and certificates of deposits by taking into consideration valuations obtained from third-party pricing services. The fair value of our marketable securities classified within Level 2 is based upon observable inputs that may include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided A-1/P-1/F1

Available-for-Sale Securities

Available-for-Sale Securities	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale Securities	4. Available-for-Sale Estimated fair values of available-for-sale available-for-sale March 31, 2018 December 31, 2017 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Financial Assets: Money market funds $ 455,554 $ — $ — $ 455,554 $ 134,744 $ — $ — $ 134,744 Corporate debt securities 33,411 — (150 ) 33,261 47,108 — (131 ) 46,977 U.S. government agency securities 44,360 — (163 ) 44,197 55,170 — (181 ) 54,989 Certificates of deposits 6,489 — (10 ) 6,479 9,142 — (13 ) 9,129 U.S. government securities 5,006 — (2 ) 5,004 20,018 — (11 ) 20,007 Total $ 544,820 $ — $ (325 ) $ 544,495 $ 266,182 $ — $ (336 ) $ 265,846 The following table summarizes the classification of the available-for-sale March 31, 2018 December 31, 2017 Cash and cash equivalents $ 455,554 $ 134,746 Short-term marketable securities 87,949 116,493 Long-term marketable securities 992 14,607 Total $ 544,495 $ 265,846 We do not intend to sell the investments that are in an unrealized loss position, and it is unlikely that we will be required to sell the investments before recovery of their amortized cost basis, which may be maturity. We have determined that the gross unrealized losses on our marketable securities were temporary in nature during the periods presented. Gross unrealized gains or losses from all marketable securities were not significant at either March 31, 2018 or December 31, 2017.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	5. Balance Sheet Components Property and Equipment Property and equipment consists of the following (in thousands): March 31, 2018 December 31, 2017 Laboratory equipment $ 6,118 $ 5,715 Computer equipment 1,599 1,594 Leasehold improvements 13,785 12,642 Construction-in-progress 381 419 Total property and equipment 21,883 20,370 Less: accumulated depreciation and amortization (4,469 ) (3,799 ) Property and equipment, net $ 17,414 $ 16,571 Accrued liabilities Accrued liabilities consist of the following (in thousands): March 31, 2018 December 31, 2017 Accrued clinical and manufacturing expenses $ 9,890 $ 8,035 Accrued professional and consulting services 1,047 1,007 Other 283 1,093 Total accrued liabilities $ 11,220 $ 10,135 Other liabilities, current and noncurrent Other liabilities consist of the following (in thousands): March 31, 2018 December 31, 2017 Restricted shares subject to repurchase, current $ 350 $ 373 Deferred rent, current 276 — Other payable 31 — Total other liabilities, current $ 657 $ 373 Restricted shares subject to repurchase, noncurrent $ 80 $ 161 Deferred rent, noncurrent 11,572 11,491 Total other liabilities, noncurrent $ 11,652 $ 11,652

Stock Based Compensation

Stock Based Compensation	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Based Compensation	6. Stock Based Compensation We have three stock-based compensation plans – the 2017 Inducement Equity Plan (the “2017 Inducement Plan”), the 2015 Stock Option and Incentive Plan (the “2015 Plan”) and the 2012 Stock Option and Grant Plan (the “2012 Plan”). As of March 31, 2018, there were 67,550 shares reserved under the 2017 Inducement Plan and 2,439,771 shares reserved under the 2015 Plan for the future issuance of equity awards. Upon adoption of the 2015 Plan in July 2015, no new awards or grants are permitted under the 2012 Plan. See Note 7 to the Consolidated Financial Statements included in our Annual Report on Form 10-K Stock Options The following summarizes option activity under the 2017 Inducement Plan, 2015 Plan and 2012 Plan: Number of Options Weighted- Average Exercise Price Outstanding — December 31, 2017 2,945,901 $ 17.50 Options granted 705,708 59.16 Options exercised (259,150 ) 8.37 Options canceled (12,909 ) 33.21 Outstanding — March 31, 2018 3,379,550 $ 26.84 The fair values of stock options granted to employees were calculated using the following assumptions: Three Months Ended March 31, 2018 2017 Expected term (in years) 6.1 6.1 Volatility 69.1%-69.3% 71.9%-73.3% Risk-free interest rate 2.6%-2.7% 2.0%-2.2% Dividend yield — — Restricted Stock Units The following table summarizes activity of RSUs granted to employees with service-based vesting under the 2017 Inducement Plan and 2015 Plan and related information (in thousands, except share, per share amounts and vesting period): Number of RSUs Weighted- Average Grant Date Fair Value Non-vested 467,463 $ 24.93 RSUs granted 460,535 59.17 RSUs vested (48,476 ) 21.82 RSUs forfeited (3,566 ) 52.18 Non-vested 875,956 $ 42.87 Market-Condition Awards Granted to Employees On August 11, 2017, our Board of Directors approved awards up to an aggregate of 365,250 RSUs to certain of our senior management team under the 2015 Plan, the vesting of which are contingent upon a combination of continued employment and achieving certain market capitalization milestones. The market-condition awards do not vest until the achievement of their respective market capitalization milestones, which must occur on or before December 31, 2019. The grant date fair value of these market-condition awards was estimated using a Monte Carlo simulation model. The derived service periods, which are the estimated periods of time that would be required to satisfy the market conditions, are also determined at the grant date. We record expense on a straight-line basis over the applicable derived service periods. During the quarter ended March 31, 2018, certain market capitalization milestones were achieved, resulting in vesting of related market-condition RSUs. For the quarter ended March 31, 2018, we recognized $2.2 million in stock-based compensation expense related to the market-condition awards (allocated as $0.2 million for research and development expense and $2.0 million for general and administrative expense). The following table summarizes activity of the market-condition awards under the 2015 Plan and related information (in thousands, except share, per share amounts and vesting period): Number of units Weighted- Average Grant Date Fair Value Non-vested market-condition awards — 353,250 $ 15.15 Granted — — Vested (188,400 ) 18.22 Forfeited — — Non-vested 164,850 $ 11.64 Employee Stock Purchase Plan In July 2015, we adopted the 2015 Employee Stock Purchase Plan (the “2015 ESPP”). Under the 2015 ESPP our employees may purchase common stock through payroll deductions at a price equal to 85% of the lower of the fair market value of the stock at the beginning of the offering period or at the end of each applicable purchase period. As approved by the Compensation Committee of the Board of Directors in December 2017, the 2015 ESPP provides for offering periods of two years in duration with purchase periods occurring every six months during an offering period. Contributions under the 2015 ESPP are limited to a maximum of 15% of an employee’s eligible compensation. ESPP purchases are settled with common stock from the ESPP’s previously authorized and available pool of shares. The fair values of the rights granted under the 2015 ESPP were calculated using the following assumptions: Three Months Ended March 31, 2018 2017 Expected term (in years) 0.5 - 2 0.5 Volatility 64.6%-66.8% 63.5% Risk-free interest rate 1.6%-2.2% 0.7% Dividend yield — — Stock-Based Compensation Expense Total stock-based compensation recognized by function was as follows (in thousands): Three Months Ended March 31, 2018 2017 Research and development $ 2,968 $ 1,073 General and administrative 4,816 1,501 Total stock-based compensation expense $ 7,784 $ 2,574

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Net Loss per Share	7. Net Loss per Share Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding for the period. Since we were in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. The following securities were not included in the diluted net loss per share calculations because their effect was anti-dilutive: Three Months Ended March 31, 2018 2017 Options to purchase common stock 3,379,550 3,005,956 Restricted stock units 1,040,806 368,130 Restricted stock awards subject to future vesting 170,371 593,791 Common stock potentially issuable for ESPP purchases — 18,669 Total 4,590,727 3,986,546

Summary of Significant Accoun13

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Preparation	Basis of Preparation The accompanying unaudited interim condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2017 has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as our annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair presentation of our financial information. The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the year ending December 31, 2018 or for any other interim period or for any other future year. The accompanying unaudited interim condensed consolidated financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2017 included in our Annual Report on Form 10-K,
Use of Estimates	Use of Estimates The preparation of the accompanying unaudited interim condensed consolidated financial statements in accordance with U.S. GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of costs and expenses during the reporting period. We base our estimates and assumptions on historical experience when available and on various factors that we believe to be reasonable under the circumstances. We evaluate our estimates and assumptions on an ongoing basis. Our actual results could differ from these estimates under different assumptions or conditions.
Principles of Consolidation	Principles of Consolidation The accompanying unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated upon consolidation.
Significant Accounting Policies	Significant Accounting Policies There have been no material revisions in our significant accounting policies described in Note 2 to the consolidated financial statements included in our Annual Report on Form 10-K
Accounting Pronouncements Adopted/Recent Accounting Pronouncements	Accounting Pronouncements Adopted In August 2016, the FASB issued ASU No. 2016-15, Classification of Certain Cash Receipts and Cash Payments No. 2016-15 In November 2016, the FASB issued ASU No. 2016-18, Restricted Cash beginning-of-period end-of-period No. 2016-18 In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718) No. 2017-09 Recent Accounting Pronouncements In February 2018, the FASB issued ASU No. 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income No. 2018-02 In March 2018, the FASB issued ASU No. 2018-04, Investments – Debt Securities (Topic 320) and Regulated Operations (Topic 980): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 117 and SEC Release No. 33-9273. No. 2018-03 Investments-Debt Securities Regulated Operations In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 No. 2018-05 Income Taxes

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following table summarizes our financial assets measured at fair value on a recurring basis (in thousands): March 31, 2018 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 455,554 $ 455,554 $ — $ — Corporate debt securities 33,261 — 33,261 — U.S. government agency securities 44,197 — 44,197 — Certificates of deposits 6,479 — 6,479 — U.S. government securities 5,004 — 5,004 — Total financial assets $ 544,495 $ 455,554 $ 88,941 $ — December 31, 2017 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 134,744 $ 134,744 $ — $ — Corporate debt securities 46,977 — 46,977 — U.S. government agency securities 54,989 — 54,989 — Certificates of deposits 9,129 — 9,129 — U.S. government securities 20,007 — 20,007 — Total financial assets $ 265,846 $ 134,744 $ 131,102 $ —

Available-for-Sale Securities (

Available-for-Sale Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Securities	The following table is a summary of available-for-sale March 31, 2018 December 31, 2017 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Financial Assets: Money market funds $ 455,554 $ — $ — $ 455,554 $ 134,744 $ — $ — $ 134,744 Corporate debt securities 33,411 — (150 ) 33,261 47,108 — (131 ) 46,977 U.S. government agency securities 44,360 — (163 ) 44,197 55,170 — (181 ) 54,989 Certificates of deposits 6,489 — (10 ) 6,479 9,142 — (13 ) 9,129 U.S. government securities 5,006 — (2 ) 5,004 20,018 — (11 ) 20,007 Total $ 544,820 $ — $ (325 ) $ 544,495 $ 266,182 $ — $ (336 ) $ 265,846
Summary of Classification of Available-for-Sale Securities on Consolidated Balance Sheets	The following table summarizes the classification of the available-for-sale March 31, 2018 December 31, 2017 Cash and cash equivalents $ 455,554 $ 134,746 Short-term marketable securities 87,949 116,493 Long-term marketable securities 992 14,607 Total $ 544,495 $ 265,846

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Property and Equipment	Property and equipment consists of the following (in thousands): March 31, 2018 December 31, 2017 Laboratory equipment $ 6,118 $ 5,715 Computer equipment 1,599 1,594 Leasehold improvements 13,785 12,642 Construction-in-progress 381 419 Total property and equipment 21,883 20,370 Less: accumulated depreciation and amortization (4,469 ) (3,799 ) Property and equipment, net $ 17,414 $ 16,571
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): March 31, 2018 December 31, 2017 Accrued clinical and manufacturing expenses $ 9,890 $ 8,035 Accrued professional and consulting services 1,047 1,007 Other 283 1,093 Total accrued liabilities $ 11,220 $ 10,135
Other Liabilities	Other liabilities consist of the following (in thousands): March 31, 2018 December 31, 2017 Restricted shares subject to repurchase, current $ 350 $ 373 Deferred rent, current 276 — Other payable 31 — Total other liabilities, current $ 657 $ 373 Restricted shares subject to repurchase, noncurrent $ 80 $ 161 Deferred rent, noncurrent 11,572 11,491 Total other liabilities, noncurrent $ 11,652 $ 11,652

Stock Based Compensation (Table

Stock Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Stock Option Activity	The following summarizes option activity under the 2017 Inducement Plan, 2015 Plan and 2012 Plan: Number of Options Weighted- Average Exercise Price Outstanding — December 31, 2017 2,945,901 $ 17.50 Options granted 705,708 59.16 Options exercised (259,150 ) 8.37 Options canceled (12,909 ) 33.21 Outstanding — March 31, 2018 3,379,550 $ 26.84
Valuation Assumptions for Stock Awards	The fair values of stock options granted to employees were calculated using the following assumptions: Three Months Ended March 31, 2018 2017 Expected term (in years) 6.1 6.1 Volatility 69.1%-69.3% 71.9%-73.3% Risk-free interest rate 2.6%-2.7% 2.0%-2.2% Dividend yield — —
Stock-based Compensation Expense Recognized	Total stock-based compensation recognized by function was as follows (in thousands): Three Months Ended March 31, 2018 2017 Research and development $ 2,968 $ 1,073 General and administrative 4,816 1,501 Total stock-based compensation expense $ 7,784 $ 2,574
Restricted Stock Units [Member]
Non-Vested Restricted Stock Activity	The following table summarizes activity of RSUs granted to employees with service-based vesting under the 2017 Inducement Plan and 2015 Plan and related information (in thousands, except share, per share amounts and vesting period): Number of RSUs Weighted- Average Grant Date Fair Value Non-vested 467,463 $ 24.93 RSUs granted 460,535 59.17 RSUs vested (48,476 ) 21.82 RSUs forfeited (3,566 ) 52.18 Non-vested 875,956 $ 42.87
Market Condition Awards Granted to Employees [Member]
Summary of Activity of Market-Condition Awards	The following table summarizes activity of the market-condition awards under the 2015 Plan and related information (in thousands, except share, per share amounts and vesting period): Number of units Weighted- Average Grant Date Fair Value Non-vested market-condition awards — 353,250 $ 15.15 Granted — — Vested (188,400 ) 18.22 Forfeited — — Non-vested 164,850 $ 11.64
ESPP [Member]
Fair Value Assumptions for Employee Stock Purchase Plan	The fair values of the rights granted under the 2015 ESPP were calculated using the following assumptions: Three Months Ended March 31, 2018 2017 Expected term (in years) 0.5 - 2 0.5 Volatility 64.6%-66.8% 63.5% Risk-free interest rate 1.6%-2.2% 0.7% Dividend yield — —

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Potentially Dilutive Securities that were Not Included in Diluted Net Loss per Share Calculations	The following securities were not included in the diluted net loss per share calculations because their effect was anti-dilutive: Three Months Ended March 31, 2018 2017 Options to purchase common stock 3,379,550 3,005,956 Restricted stock units 1,040,806 368,130 Restricted stock awards subject to future vesting 170,371 593,791 Common stock potentially issuable for ESPP purchases — 18,669 Total 4,590,727 3,986,546

Organization and Basis of Pre19

Organization and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended
	Mar. 31, 2018USD ($)$ / sharesshares	Jan. 31, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Mar. 31, 2018USD ($)Segment$ / shares	Mar. 31, 2017USD ($)
Class of Stock [Line Items]
Number of operating segments | Segment				1
Proceeds from issuance of common stock, net of issuance costs				$ 254,940	$ 135,705
Cumulative net losses	$ (339,513)		$ (297,957)	$ (339,513)
Common Stock [Member]
Class of Stock [Line Items]
Common stock shares sold | shares	4,600,000		2,631,579
Share price per share | $ / shares	$ 54		$ 38	$ 54
Proceeds from issuance of common stock, net of issuance costs			$ 96,400
Common Stock [Member] | Over-Allotment Option [Member]
Class of Stock [Line Items]
Common stock shares sold | shares	600,000	394,736
Share price per share | $ / shares	$ 54	$ 38		$ 54
Proceeds from issuance of common stock, net of issuance costs	$ 240,500	$ 14,500

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Assets Measured on Recurring Basis (Detail) - Fair Value Measurements, Recurring [Member] - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	$ 544,495	$ 265,846
U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	5,004	20,007
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	455,554	134,744
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	88,941	131,102
Level 2 [Member] | U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	5,004	20,007
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	455,554	134,744
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	455,554	134,744
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	33,261	46,977
Corporate Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	33,261	46,977
U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	44,197	54,989
U.S. Government Agency Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	44,197	54,989
Certificates of Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	6,479	9,129
Certificates of Deposits [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	$ 6,479	$ 9,129

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value assets amount transfer from level 1 to level 2	$ 0	$ 0
Fair value assets amount transfer from level 2 to level 1	$ 0	$ 0

Available-for-Sale Securities -

Available-for-Sale Securities - Summary of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	$ 544,820	$ 266,182
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized (Losses)	(325)	(336)
Available for sale securities, Estimated Fair Value	544,495	265,846
U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	5,006	20,018
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized (Losses)	(2)	(11)
Available for sale securities, Estimated Fair Value	5,004	20,007
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	455,554	134,744
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Estimated Fair Value	455,554	134,744
Certificates of Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	6,489	9,142
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized (Losses)	(10)	(13)
Available for sale securities, Estimated Fair Value	6,479	9,129
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	33,411	47,108
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized (Losses)	(150)	(131)
Available for sale securities, Estimated Fair Value	33,261	46,977
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	44,360	55,170
Available for sale securities, Unrealized Gains	0	0
Available for sale securities, Unrealized (Losses)	(163)	(181)
Available for sale securities, Estimated Fair Value	$ 44,197	$ 54,989

Available-for-Sale Securities23

Available-for-Sale Securities - Summary of Classification of Available-for-Sale Securities on Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 455,554	$ 134,746
Short-term marketable securities	87,949	116,493
Long-term marketable securities	992	14,607
Total	$ 544,495	$ 265,846

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 21,883	$ 20,370
Less: accumulated depreciation and amortization	(4,469)	(3,799)
Property and equipment, net	17,414	16,571
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	6,118	5,715
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	1,599	1,594
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	13,785	12,642
Construction-in-Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 381	$ 419

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Balance Sheet Components [Abstract]
Accrued clinical and manufacturing expenses	$ 9,890	$ 8,035
Accrued professional and consulting services	1,047	1,007
Other	283	1,093
Total accrued liabilities	$ 11,220	$ 10,135

Balance Sheet Components - Othe

Balance Sheet Components - Other Liabilities (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Balance Sheet Components [Abstract]
Restricted shares subject to repurchase, current	$ 350	$ 373
Deferred rent, current	276
Other payable	31
Total other liabilities, current	657	373
Restricted shares subject to repurchase, noncurrent	80	161
Deferred rent, noncurrent	11,572	11,491
Total other liabilities, noncurrent	$ 11,652	$ 11,652

Stock Based Compensation - Plan

Stock Based Compensation - Plan Summary - Additional Information (Detail) - USD ($) $ in Thousands	Aug. 11, 2017	Jul. 31, 2015	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation			$ 7,784	$ 2,574
Market Condition Awards Granted to Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation			2,200
Market Condition Awards Granted to Employees [Member] | Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation			200
Market Condition Awards Granted to Employees [Member] | General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation			$ 2,000
2017 Inducement Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance			67,550
2015 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance			2,439,771
2015 Plan [Member] | RSU [Member] | Senior Management [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted in period	365,250
2015 Plan [Member] | Market Condition Awards Granted to Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted shares granted in period			0
2015 ESPP [Member] | ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price as a percentage of the fair market value		85.00%
Offering period		2 years
Maximum contribution to plan as a percent of employee's eligible compensation		15.00%

Stock Based Compensation - Stoc

Stock Based Compensation - Stock Option Activity (Detail)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance, outstanding, Number of Options | shares	2,945,901
Options granted, Number of Options | shares	705,708
Options exercised, Number of Options | shares	(259,150)
Options canceled, Number of Options | shares	(12,909)
Ending balance, outstanding, Number of Options | shares	3,379,550
Weighted- Average Exercise Price
Beginning balance, Outstanding, Weighted-Average Exercise Price | $ / shares	$ 17.50
Options granted, Weighted-Average Exercise Price | $ / shares	59.16
Options exercised, Weighted-Average Exercise Price | $ / shares	8.37
Options canceled, Weighted-Average Exercise Price | $ / shares	33.21
Ending balance, Outstanding, Weighted-Average Exercise Price | $ / shares	$ 26.84

Stock Based Compensation - Valu

Stock Based Compensation - Valuation Assumptions for Stock Options Granted (Detail) - Stock Options [Member]	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Volatility, minimum	69.10%	71.90%
Volatility, maximum	69.30%	73.30%
Risk-free interest rate, minimum	2.60%	2.00%
Risk-free interest rate, maximum	2.70%	2.20%
Dividend yield	0.00%	0.00%

Stock Based Compensation - Summ

Stock Based Compensation - Summary of RSU Activity Granted to Employees with Service-Based Vesting (Detail) - 2017 Inducement Plan and 2015 Plan [Member] - RSU [Member]	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance - Non-vested market-condition awards | shares	467,463
RSUs granted, Number of RSUs | shares	460,535
RSUs vested, Number of RSUs | shares	(48,476)
RSUs forfeited, Number of RSUs | shares	(3,566)
Ending Balance - Non-vested market-condition awards | shares	875,956
Beginning Balance - Non-vested units, Weighted-Average Grant Date Fair Value | $ / shares	$ 24.93
RSUs granted, Weighted-Average Grant Date Fair Value | $ / shares	59.17
RSUs vested, Weighted-Average Grant Date Fair Value | $ / shares	21.82
RSUs forfeited, Weighted-Average Grant Date Fair Value | $ / shares	52.18
Ending Balance - Non-vested units, Weighted-Average Grant Date Fair Value | $ / shares	$ 42.87

Stock Based Compensation - Su31

Stock Based Compensation - Summary of Activity of Market-Condition Awards (Detail) - 2015 Plan [Member] - Market Condition Awards Granted to Employees [Member]	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance - Non-vested market-condition awards | shares	353,250
Number of units granted | shares	0
Number of units vested | shares	(188,400)
Number of units forfeited | shares	0
Ending Balance - Non-vested market-condition awards | shares	164,850
Beginning Balance - Non-vested units, Weighted-Average Grant Date Fair Value | $ / shares	$ 15.15
Weighted-Average Grant Date Fair Value granted | $ / shares	0
Weighted-Average Grant Date Fair Value vested | $ / shares	18.22
Weighted-Average Grant Date Fair Value forfeited | $ / shares	0
Ending Balance - Non-vested units, Weighted-Average Grant Date Fair Value | $ / shares	$ 11.64

Stock Based Compensation - Fair

Stock Based Compensation - Fair Value Assumptions for Employee Stock Purchase Plan (Detail) - ESPP [Member]	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)		6 months
Volatility		63.50%
Volatility, minimum	64.60%
Volatility, maximum	66.80%
Risk-free interest rate		0.70%
Risk-free interest rate, minimum	1.60%
Risk-free interest rate, maximum	2.20%
Dividend yield	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	2 years

Stock Based Compensation - St33

Stock Based Compensation - Stock-based Compensation Expense Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 7,784	$ 2,574
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	2,968	1,073
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 4,816	$ 1,501

Net Loss per Share - Potentiall

Net Loss per Share - Potentially Dilutive Securities that were Not Included in Diluted Net Loss per Share Calculations (Detail) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	4,590,727	3,986,546
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	3,379,550	3,005,956
RSU [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	1,040,806	368,130
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	170,371	593,791
ESPP [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share		18,669