Global Blood Therapeutics (GBT) 10-Q 7 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Jul. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
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	Accelerated Filer
Entity Common Stock, Shares Outstanding		43,676,804

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 93,741	$ 92,072
Short-term marketable securities	136,075	55,202
Prepaid expenses and other current assets	5,036	2,495
Total current assets	234,852	149,769
Property and equipment, net	5,200	2,420
Long-term marketable securities	60,779	50,058
Restricted cash	1,046	140
Total assets	301,877	202,387
Current liabilities:
Accounts payable	4,966	4,320
Accrued liabilities	6,586	5,319
Accrued compensation	4,492	4,967
Other liabilities, current	1,104	909
Total current liabilities	17,148	15,515
Other liabilities, noncurrent	3,019	563
Total liabilities	20,167	16,078
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock, $0.001 par value, 5,000,000 shares authorized as of June 30, 2017 and December 31, 2016
Common stock, $0.001 par value, 150,000,000 shares authorized as of June 30, 2017 (unaudited) and December 31, 2016, respectively; 43,115,738 and 36,638,156 shares issued and outstanding as of June 30, 2017 (unaudited) and December 31, 2016, respectively	43	37
Additional paid-in capital	510,083	367,371
Accumulated other comprehensive loss	(268)	(166)
Accumulated deficit	(228,148)	(180,933)
Total stockholders' equity	281,710	186,309
Total liabilities and stockholders' equity	$ 301,877	$ 202,387

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	43,115,738	36,638,156
Common stock, shares outstanding	43,115,738	36,638,156

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating expenses:
Research and development	$ 18,278	$ 13,427	$ 35,561	$ 25,842
General and administrative	6,152	4,379	12,590	8,681
Total operating expenses	24,430	17,806	48,151	34,523
Loss from operations	(24,430)	(17,806)	(48,151)	(34,523)
Other income (expense):
Interest income, net	689	131	1,130	248
Other expenses, net	(142)		(194)
Total other income, net	547	131	936	248
Net loss	(23,883)	(17,675)	(47,215)	(34,275)
Other comprehensive loss:
Net unrealized loss on marketable securities, net of tax	(89)		(102)
Comprehensive loss	$ (23,972)	$ (17,675)	$ (47,317)	$ (34,275)
Basic and diluted net loss per common share	$ (0.55)	$ (0.58)	$ (1.15)	$ (1.15)
Weighted-average number of shares used in computing basic and diluted net loss per common share	43,063,996	30,381,948	41,112,266	29,911,678

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (47,215)	$ (34,275)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	608	520
Amortization of premium on marketable securities	380
Stock-based compensation	5,234	2,732
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(2,550)	(427)
Accounts payable	623	1,189
Accrued liabilities	1,375	796
Accrued compensation	(475)	614
Other liabilities	(33)	(12)
Net cash used in operating activities	(42,053)	(28,863)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(575)	(955)
Purchase of marketable securities	(124,861)
Maturities of marketable securities	32,785
Increase in restricted cash	(906)
Net cash used in investing activities	(93,557)	(955)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock in public offering, net	135,625	112,728
Proceeds from issuance of common stock in settlement of employee stock purchase plan and exercise of stock options	1,654	498
Net cash provided by financing activities	137,279	113,226
Net increase in cash and cash equivalents	1,669	83,408
Cash and cash equivalents at beginning of period	92,072	148,502
Cash and cash equivalents at end of period	93,741	231,910
SUPPLEMENTAL DISCLOSURES OF NON-CASH INVESTING AND FINANCING INFORMATION:
Acquired property and equipment	2,897
Accrued purchase of property and equipment	$ 30	13
Accrued offering costs		$ 449

Organization and Basis of Prese

Organization and Basis of Presentation	6 Months Ended
	Jun. 30, 2017
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 dedicated to discovering, developing and commercializing novel therapeutics to treat grievous blood-based disorders with significant unmet needs. 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 Offering In February 2017, we completed a follow-on offering and issued an aggregate of 5,867,347 shares of our common stock at a price of $24.50 per share, including 765,306 shares of our common stock sold directly to the underwriters when they exercised their over-allotment option at the price of $24.50 per share. We received total proceeds of $135.6 million from the offering, net of underwriting discounts and commissions and offering expenses. 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 June 30, 2017, we have incurred cumulative net losses of $228.1 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 our operating plans. We believe that our existing cash and cash equivalents and marketable securities will be sufficient to fund our cash requirements for at least the next twelve months.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2017
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, 2016 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 and six months ended June 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017 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, 2016 included in our Annual Report on Form 10-K, filed with the SEC on March 13, 2017. Reclassification Certain prior year amounts in the condensed consolidated statements of operations and comprehensive loss have been reclassified to conform to the current year’s presentation. This reclassification did not have an impact on our results of operations or financial condition as of June 30, 2016. 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 Except as noted below, 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 for the year ended December 31, 2016. Stock-based Compensation We measure and recognize stock-based compensation expense, including employee and non-employee equity awards, based on fair value at the grant date. We use the Black-Scholes option-pricing model to calculate fair value. Stock-based compensation expense recognized in the condensed consolidated statements of operations is based on stock awards ultimately vested, taking into consideration actual forfeitures. For options granted to non-employees, we revalue the unearned portion of the stock-based compensation and the resulting change in fair value is recognized in the condensed consolidated statements of operations over the period the related services are rendered. Recent Accounting Pronouncements In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718) Accounting Pronouncements Adopted In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting The impact of adopting ASU 2016-09 resulted in the following: • Classification of excess income tax benefits from stock-based compensation arrangement as a discrete item within income tax expense, rather than recognizing such excess income tax benefits in additional paid-in capital. The adoption of this guidance resulted in an increase of approximately $1.1 million of net operating losses, which has an impact of $0.4 million on our deferred tax assets before our full valuation allowance established against the related deferred tax assets. • Recognition of forfeitures as they occur. The cumulative effect adjustment as a result of the adoption of ASU 2016-09 on a modified retrospective basis was insignificant. • A change in classification of cash flows resulting from excess tax benefits and cash paid by us when directly withholding shares for tax-withholding purposes on a retrospective basis. The adoption of these provisions did not result in changes in our condensed consolidated statements of cash flow. There were no other material impacts to our condensed consolidated financial statements as a result of adopting this updated standard.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2017
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, 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): June 30, 2017 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 88,659 $ 88,659 $ — $ — Corporate debt securities 60,631 — 60,631 — U.S. government agency securities 76,287 — 76,287 — Certificates of deposits 14,919 — 14,919 — U.S. government securities 50,015 — 50,015 — Total financial assets $ 290,511 $ 88,659 $ 201,852 $ — December 31, 2016 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 72,597 $ 72,597 $ — $ — Corporate debt securities 48,531 — 48,531 — U.S. government agency securities 39,712 — 39,712 — Certificates of deposits 19,117 — 19,117 — U.S. government securities 7,999 — 7,999 — Total financial assets $ 187,956 $ 72,597 $ 115,359 $ — 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 markets, benchmark securities, bids, offers and reference data including market research publications. At June 30, 2017 and December 31, 2016, the weighted average remaining contractual maturities of our Level 2 investments was less than one year and all of these investments are rated A-1/P-1/F1 or A/A2, or higher by Moody’s, S&P and Fitch. There were no transfers between Level 1 and Level 2 during the periods presented.

Available-for-Sale Securities

Available-for-Sale Securities	6 Months Ended
	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale Securities	4. Available-for-Sale Securities Estimated fair values of available-for-sale securities are generally based on prices obtained from commercial pricing services. The following table is a summary of available-for-sale securities recorded in cash and cash equivalents, restricted cash, or marketable securities in our condensed consolidated balance sheets (in thousands): June 30, 2017 December 31, 2016 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Financial Assets: Money market funds $ 88,659 $ — $ — $ 88,659 $ 72,597 $ — $ — $ 72,597 Corporate debt securities 60,730 — (99 ) 60,631 48,594 2 (65 ) 48,531 U.S. government agency securities 76,402 2 (117 ) 76,287 39,763 1 (52 ) 39,712 Certificates of deposits 14,942 2 (25 ) 14,919 19,169 — (52 ) 19,117 U.S. government securities 50,046 — (31 ) 50,015 7,999 — — 7,999 Total $ 290,779 $ 4 $ (272 ) $ 290,511 $ 188,122 $ 3 $ (169 ) $ 187,956 The following table summarizes the classification of the available-for-sale securities on our condensed consolidated balance sheets (in thousands): June 30, 2017 December 31, 2016 Cash and cash equivalents $ 93,657 $ 82,696 Short-term marketable securities 136,075 55,202 Long-term marketable securities 60,779 50,058 Total $ 290,511 $ 187,956 Gross unrealized gains or losses were not significant at either June 30, 2017 or December 31, 2016. 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. All marketable securities with unrealized losses have been in a loss position for less than twelve months and the loss is not material as of June 30, 2017 and December 31, 2016.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2017
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): June 30, 2017 December 31, 2016 Laboratory equipment $ 4,202 $ 3,895 Computer equipment 995 972 Leasehold improvements 685 678 Construction-in-progress 3,188 137 Total property and equipment 9,070 5,682 Less: accumulated depreciation and amortization (3,870 ) (3,262 ) Property and equipment, net $ 5,200 $ 2,420 Accrued liabilities Accrued liabilities consist of the following (in thousands): June 30, 2017 December 31, 2016 Accrued clinical and manufacturing expenses $ 5,856 $ 4,759 Accrued professional and consulting services 520 507 Other 210 53 Total accrued liabilities $ 6,586 $ 5,319 Other liabilities, current and noncurrent Other liabilities consist of the following (in thousands): June 30, 2017 December 31, 2016 Restricted shares subject to repurchase, current $ 841 $ 846 Deferred rent, current 263 61 Other taxes payable — 2 Total other liabilities, current $ 1,104 $ 909 Restricted shares subject to repurchase, noncurrent $ 326 $ 534 Deferred rent, noncurrent 2,693 29 Total other liabilities, noncurrent $ 3,019 $ 563

Stock Based Compensation

Stock Based Compensation	6 Months Ended
	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Based Compensation	6. Stock Based Compensation In January 2017, we adopted the 2017 Inducement Equity Plan (the “2017 Inducement Plan”). Under the 2017 Inducement Plan, 300,000 shares of our common stock were initially reserved for the issuance of non-qualified stock options and other equity-based awards to induce highly-qualified prospective officers and employees who are not currently employed by us or our subsidiaries to become employed with our company. The number of shares initially reserved for grant is subject to adjustment for reorganization, recapitalization, stock dividend, stock split, or similar changes in our capital stock. As of June 30, 2017, there were no stock awards granted under the 2017 Plan. We have two additional stock-based compensation plans – the 2015 Stock Option and Incentive Plan (the “2015 Plan”) and the 2012 Stock Option and Grant Plan (the “2012 Plan”). As of June 30, 2017, there were 1,766,036 shares reserved for the future issuance of equity awards under the 2015 Plan. 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 for the year ended December 31, 2016 for additional information related to these stock-based compensation plans. Stock Options The following summarizes option activity under the 2012 Plan and 2015 Plan: Number of Options Weighted-Average Exercise Price Outstanding — December 31, 2016 2,769,702 $ 11.99 Options granted 803,615 22.94 Options exercised (415,665 ) 2.71 Options canceled (79,273 ) 20.45 Outstanding — June 30, 2017 3,078,379 $ 15.89 The fair values of stock options granted to employees were calculated using the following assumptions: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Expected term (in years) 5.3-6.1 5.3-6.1 5.3-6.1 5.3-6.1 Volatility 70.9%-75.6% 80.5%-82.3% 70.9%-75.6% 79.4%-82.3% Risk-free interest rate 1.8%-2.3% 1.1%-1.5% 1.8%-2.3% 1.1%-1.9% Dividend yield — — — — Restricted Stock Units In January 2017, the Compensation Committee of our Board of Directors approved the commencement of granting restricted stock units (“RSUs”) to our employees. RSUs are share awards that entitle the holder to receive freely tradable shares of our common stock upon the completion of a specific period of continued service. RSUs are generally subject to forfeiture if employment terminates prior to the release of vesting restrictions. RSUs granted are valued at the market price of our common stock on the date of grant. We recognize noncash compensation expense for the fair value of RSUs on a straight-line basis over the requisite service period of these awards. The following summarizes RSU activity under the 2015 Plan and related information (in thousands, except share, per share amounts and vesting period): Number of RSUs Weighted- Average Grant Date Fair Value Weighted- Average Remaining Vesting Period (years) Aggregate Intrinsic Value Non-vested units — December 31, 2016 — $ — — RSUs granted 404,485 22.44 RSUs vested — — RSUs forfeited (1,710 ) 29.75 Non-vested units — June 30, 2017 402,775 $ 22.40 1.90 $ 11,016 Stock-Based Compensation Expense Total stock-based compensation recognized by function was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Research and development $ 1,440 $ 602 $ 2,513 $ 1,147 General and administrative 1,220 863 2,721 1,585 Total stock-based compensation expense $ 2,660 $ 1,465 $ 5,234 $ 2,732

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2017
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 June 30, Six Months Ended June 30, 2017 2016 2017 2016 Options to purchase common stock 3,078,379 2,662,841 3,078,379 2,662,841 Restricted stock subject to future vesting 515,469 881,617 515,469 881,617 Restricted stock units 402,775 — 402,775 — Employee stock purchase plan 21,020 44,890 21,020 44,890 Total 4,017,643 3,589,348 4,017,643 3,589,348

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Facilities In March 2017, we entered into a noncancelable operating lease (the “Lease”) for approximately 67,185 square feet of space in South San Francisco, California (the “New Facility”). The date on which we will become responsible for paying rent under the Lease (the “Rent Commencement Date”) will be the earlier of December 15, 2017 or the date the New Facility is ready for occupancy. The Lease expires 10 years after the Rent Commencement Date. The Lease grants us an option to extend the Lease for an additional 10-year period. Future minimum rental payments under the Lease during the 10-year term are $45.8 million in the aggregate. The Lease further provides that we are obligated to pay to the landlord certain costs, including taxes and operating expenses. As of June 30, 2017, the Lease term has not commenced as we did not have the right to use or control physical access to the New Facility. We have capitalized $2.9 million of costs in construction-in-progress within property and equipment, net for construction of leasehold improvement at the New Facility as of June 30, 2017 acquired with the tenant inducement provided under the Lease. We provided a standby letter of credit of $0.9 million as security for our obligations under the Lease which was issued in March 2017. This standby letter of credit is classified as restricted cash. We currently lease approximately 36,740 square feet of office and lab space located in South San Francisco, California (the “Existing Facility”). All of our lease agreements associated with the Existing Facility expire on or before April 2018. We do not plan to cancel the existing lease agreements for our Existing Facility prior to their respective expiration dates. Future annual minimum lease payments due under the new and existing operating leases at December 31 of each year are as follows (in thousands): Year ending December 31, Amount 1 2017 (six months) $ 860 2018 3,462 2019 4,134 2020 4,279 2021 4,428 Thereafter 29,787 Total $ 46,950 (1) The table above is prepared under the assumption that the Rent Commencement Date at the New Facility starts on December 15, 2017. Rent expense for the three months ended June 30, 2017 and 2016 was $0.4 million and $0.3 million, respectively, and for the six months ended June 30, 2017 and 2016 was $0.8 million and $0.6 million, respectively. The operating leases require us to share in prorated operating expenses and property taxes based upon actual amounts incurred; those amounts are not fixed for future periods and, therefore, are not included in the future commitments listed above.

Summary of Significant Accoun14

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2017
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, 2016 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 and six months ended June 30, 2017 are not necessarily indicative of the results to be expected for the year ending December 31, 2017 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, 2016 included in our Annual Report on Form 10-K, filed with the SEC on March 13, 2017.
Reclassification	Reclassification Certain prior year amounts in the condensed consolidated statements of operations and comprehensive loss have been reclassified to conform to the current year’s presentation. This reclassification did not have an impact on our results of operations or financial condition as of June 30, 2016.
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 Except as noted below, 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 for the year ended December 31, 2016.
Stock-based Compensation	Stock-based Compensation We measure and recognize stock-based compensation expense, including employee and non-employee equity awards, based on fair value at the grant date. We use the Black-Scholes option-pricing model to calculate fair value. Stock-based compensation expense recognized in the condensed consolidated statements of operations is based on stock awards ultimately vested, taking into consideration actual forfeitures. For options granted to non-employees, we revalue the unearned portion of the stock-based compensation and the resulting change in fair value is recognized in the condensed consolidated statements of operations over the period the related services are rendered.
Recent Accounting Pronouncements/Accounting Pronouncements Adopted	Recent Accounting Pronouncements In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718) Accounting Pronouncements Adopted In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting The impact of adopting ASU 2016-09 resulted in the following: • Classification of excess income tax benefits from stock-based compensation arrangement as a discrete item within income tax expense, rather than recognizing such excess income tax benefits in additional paid-in capital. The adoption of this guidance resulted in an increase of approximately $1.1 million of net operating losses, which has an impact of $0.4 million on our deferred tax assets before our full valuation allowance established against the related deferred tax assets. • Recognition of forfeitures as they occur. The cumulative effect adjustment as a result of the adoption of ASU 2016-09 on a modified retrospective basis was insignificant. • A change in classification of cash flows resulting from excess tax benefits and cash paid by us when directly withholding shares for tax-withholding purposes on a retrospective basis. The adoption of these provisions did not result in changes in our condensed consolidated statements of cash flow. There were no other material impacts to our condensed consolidated financial statements as a result of adopting this updated standard.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2017
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): June 30, 2017 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 88,659 $ 88,659 $ — $ — Corporate debt securities 60,631 — 60,631 — U.S. government agency securities 76,287 — 76,287 — Certificates of deposits 14,919 — 14,919 — U.S. government securities 50,015 — 50,015 — Total financial assets $ 290,511 $ 88,659 $ 201,852 $ — December 31, 2016 Total Level 1 Level 2 Level 3 Financial Assets: Money market funds $ 72,597 $ 72,597 $ — $ — Corporate debt securities 48,531 — 48,531 — U.S. government agency securities 39,712 — 39,712 — Certificates of deposits 19,117 — 19,117 — U.S. government securities 7,999 — 7,999 — Total financial assets $ 187,956 $ 72,597 $ 115,359 $ —

Available-for-Sale Securities (

Available-for-Sale Securities (Tables)	6 Months Ended
	Jun. 30, 2017
Investments, Debt and Equity Securities [Abstract]
Summary of Available-for-Sale Securities	The following table is a summary of available-for-sale securities recorded in cash and cash equivalents, restricted cash, or marketable securities in our condensed consolidated balance sheets (in thousands): June 30, 2017 December 31, 2016 Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Amortized Cost Unrealized Gains Unrealized Losses Estimated Fair Value Financial Assets: Money market funds $ 88,659 $ — $ — $ 88,659 $ 72,597 $ — $ — $ 72,597 Corporate debt securities 60,730 — (99 ) 60,631 48,594 2 (65 ) 48,531 U.S. government agency securities 76,402 2 (117 ) 76,287 39,763 1 (52 ) 39,712 Certificates of deposits 14,942 2 (25 ) 14,919 19,169 — (52 ) 19,117 U.S. government securities 50,046 — (31 ) 50,015 7,999 — — 7,999 Total $ 290,779 $ 4 $ (272 ) $ 290,511 $ 188,122 $ 3 $ (169 ) $ 187,956
Summary of Classification of Available-for-Sale Securities on Consolidated Balance Sheets	The following table summarizes the classification of the available-for-sale securities on our condensed consolidated balance sheets (in thousands): June 30, 2017 December 31, 2016 Cash and cash equivalents $ 93,657 $ 82,696 Short-term marketable securities 136,075 55,202 Long-term marketable securities 60,779 50,058 Total $ 290,511 $ 187,956

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Property and Equipment	Property and equipment consists of the following (in thousands): June 30, 2017 December 31, 2016 Laboratory equipment $ 4,202 $ 3,895 Computer equipment 995 972 Leasehold improvements 685 678 Construction-in-progress 3,188 137 Total property and equipment 9,070 5,682 Less: accumulated depreciation and amortization (3,870 ) (3,262 ) Property and equipment, net $ 5,200 $ 2,420
Accrued Liabilities	Accrued liabilities consist of the following (in thousands): June 30, 2017 December 31, 2016 Accrued clinical and manufacturing expenses $ 5,856 $ 4,759 Accrued professional and consulting services 520 507 Other 210 53 Total accrued liabilities $ 6,586 $ 5,319
Other Liabilities	Other liabilities consist of the following (in thousands): June 30, 2017 December 31, 2016 Restricted shares subject to repurchase, current $ 841 $ 846 Deferred rent, current 263 61 Other taxes payable — 2 Total other liabilities, current $ 1,104 $ 909 Restricted shares subject to repurchase, noncurrent $ 326 $ 534 Deferred rent, noncurrent 2,693 29 Total other liabilities, noncurrent $ 3,019 $ 563

Stock Based Compensation (Table

Stock Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Activity	The following summarizes option activity under the 2012 Plan and 2015 Plan: Number of Options Weighted-Average Exercise Price Outstanding — December 31, 2016 2,769,702 $ 11.99 Options granted 803,615 22.94 Options exercised (415,665 ) 2.71 Options canceled (79,273 ) 20.45 Outstanding — June 30, 2017 3,078,379 $ 15.89
Valuation Assumptions for Stock Awards	The fair values of stock options granted to employees were calculated using the following assumptions: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Expected term (in years) 5.3-6.1 5.3-6.1 5.3-6.1 5.3-6.1 Volatility 70.9%-75.6% 80.5%-82.3% 70.9%-75.6% 79.4%-82.3% Risk-free interest rate 1.8%-2.3% 1.1%-1.5% 1.8%-2.3% 1.1%-1.9% Dividend yield — — — —
Summary of RSU Activity	The following summarizes RSU activity under the 2015 Plan and related information (in thousands, except share, per share amounts and vesting period): Number of RSUs Weighted- Average Grant Date Fair Value Weighted- Average Remaining Vesting Period (years) Aggregate Intrinsic Value Non-vested units — December 31, 2016 — $ — — RSUs granted 404,485 22.44 RSUs vested — — RSUs forfeited (1,710 ) 29.75 Non-vested units — June 30, 2017 402,775 $ 22.40 1.90 $ 11,016
Stock-based Compensation Expense Recognized	Total stock-based compensation recognized by function was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Research and development $ 1,440 $ 602 $ 2,513 $ 1,147 General and administrative 1,220 863 2,721 1,585 Total stock-based compensation expense $ 2,660 $ 1,465 $ 5,234 $ 2,732

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2017
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 June 30, Six Months Ended June 30, 2017 2016 2017 2016 Options to purchase common stock 3,078,379 2,662,841 3,078,379 2,662,841 Restricted stock subject to future vesting 515,469 881,617 515,469 881,617 Restricted stock units 402,775 — 402,775 — Employee stock purchase plan 21,020 44,890 21,020 44,890 Total 4,017,643 3,589,348 4,017,643 3,589,348

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Future Aggregate Minimum Lease Payments	Future annual minimum lease payments due under the new and existing operating leases at December 31 of each year are as follows (in thousands): Year ending December 31, Amount 1 2017 (six months) $ 860 2018 3,462 2019 4,134 2020 4,279 2021 4,428 Thereafter 29,787 Total $ 46,950 (1) The table above is prepared under the assumption that the Rent Commencement Date at the New Facility starts on December 15, 2017.

Organization and Basis of Pre21

Organization and Basis of Presentation - Additional Information (Detail) $ / shares in Units, $ in Thousands	1 Months Ended	6 Months Ended		77 Months Ended
	Feb. 28, 2017USD ($)$ / sharesshares	Jun. 30, 2017USD ($)Segment	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)
Class of Stock [Line Items]
Number of operating segments | Segment		1
Proceeds from issuance of common stock, net of issuance costs		$ 135,625	$ 112,728
Cumulative net losses incurred				$ 228,100
Common Stock [Member]
Class of Stock [Line Items]
Shares issued (in shares) | shares	5,867,347
Share price per share | $ / shares	$ 24.50
Common Stock [Member] | Over-Allotment Option [Member]
Class of Stock [Line Items]
Shares issued (in shares) | shares	765,306
Share price per share | $ / shares	$ 24.50
Proceeds from issuance of common stock, net of issuance costs	$ 135,600

Summary of Significant Accoun22

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)
Accounting Policies [Abstract]
Increase in net operating loss carryforwards	$ 1.1
Deferred tax assets	$ 0.4

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Assets Measured on Recurring Basis (Detail) - Fair Value Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	$ 290,511	$ 187,956
U.S. Government Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	50,015	7,999
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	88,659	72,597
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	201,852	115,359
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	50,015	7,999
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	88,659	72,597
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	88,659	72,597
Corporate Debt Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	60,631	48,531
Corporate Debt Securities [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	60,631	48,531
U.S. Government Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	76,287	39,712
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	76,287	39,712
Certificates of Deposits [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	14,919	19,117
Certificates of Deposits [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets, fair value	$ 14,919	$ 19,117

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
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	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	$ 290,779	$ 188,122
Available for sale securities, Unrealized Gains	4	3
Available for sale securities, Unrealized Losses	(272)	(169)
Available for sale securities, Estimated Fair Value	290,511	187,956
U.S. Government Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	50,046	7,999
Available for sale securities, Unrealized Losses	(31)
Available for sale securities, Estimated Fair Value	50,015	7,999
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	88,659	72,597
Available for sale securities, Estimated Fair Value	88,659	72,597
Certificates of Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	14,942	19,169
Available for sale securities, Unrealized Gains	2
Available for sale securities, Unrealized Losses	(25)	(52)
Available for sale securities, Estimated Fair Value	14,919	19,117
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	60,730	48,594
Available for sale securities, Unrealized Gains		2
Available for sale securities, Unrealized Losses	(99)	(65)
Available for sale securities, Estimated Fair Value	60,631	48,531
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, Amortized Cost	76,402	39,763
Available for sale securities, Unrealized Gains	2	1
Available for sale securities, Unrealized Losses	(117)	(52)
Available for sale securities, Estimated Fair Value	$ 76,287	$ 39,712

Available-for-Sale Securities26

Available-for-Sale Securities - Summary of Classification of Available-for-Sale Securities on Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Cash and cash equivalents	$ 93,657	$ 82,696
Short-term marketable securities	136,075	55,202
Long-term marketable securities	60,779	50,058
Total	$ 290,511	$ 187,956

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 9,070	$ 5,682
Less: accumulated depreciation and amortization	(3,870)	(3,262)
Property and equipment, net	5,200	2,420
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	4,202	3,895
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	995	972
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	685	678
Construction-in-Progress [Member]
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 3,188	$ 137

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Balance Sheet Components [Abstract]
Accrued clinical and manufacturing expenses	$ 5,856	$ 4,759
Accrued professional and consulting services	520	507
Other	210	53
Total accrued liabilities	$ 6,586	$ 5,319

Balance Sheet Components - Othe

Balance Sheet Components - Other Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Balance Sheet Components [Abstract]
Restricted shares subject to repurchase, current	$ 841	$ 846
Deferred rent, current	263	61
Other taxes payable		2
Total other liabilities, current	1,104	909
Restricted shares subject to repurchase, noncurrent	326	534
Deferred rent, noncurrent	2,693	29
Total other liabilities, noncurrent	$ 3,019	$ 563

Stock Based Compensation - Plan

Stock Based Compensation - Plan Summary - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2017shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock awards granted	803,615
2015 Plan [Member] | Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance	1,766,036
2017 Inducement Equity Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for issuance	300,000
Stock awards granted	0

Stock Based Compensation - Stoc

Stock Based Compensation - Stock Option Activity (Detail)	6 Months Ended
	Jun. 30, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance, outstanding, Number of Options | shares	2,769,702
Options granted, Number of Options | shares	803,615
Options exercised, Number of Options | shares	(415,665)
Options canceled, Number of Options | shares	(79,273)
Ending balance, outstanding, Number of Options | shares	3,078,379
Weighted- Average Exercise Price
Beginning balance, Outstanding, Weighted-Average Exercise Price | $ / shares	$ 11.99
Options granted, Weighted-Average Exercise Price | $ / shares	22.94
Options exercised, Weighted-Average Exercise Price | $ / shares	2.71
Options canceled, Weighted-Average Exercise Price | $ / shares	20.45
Ending balance, Outstanding, Weighted-Average Exercise Price | $ / shares	$ 15.89

Stock Based Compensation - Valu

Stock Based Compensation - Valuation Assumptions for Share-based Compensation (Detail) - Stock Options [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility, minimum	70.90%	80.50%	70.90%	79.40%
Volatility, maximum	75.60%	82.30%	75.60%	82.30%
Risk-free interest rate, minimum	1.80%	1.10%	1.80%	1.10%
Risk-free interest rate, maximum	2.30%	1.50%	2.30%	1.90%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 19 days	5 years 3 months 19 days	5 years 3 months 19 days	5 years 3 months 19 days
Maximum [Member]
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	6 years 1 month 6 days	6 years 1 month 6 days

Stock Based Compensation - Summ

Stock Based Compensation - Summary of RSU Activity (Detail) - RSU [Member] - 2015 Plan [Member]	6 Months Ended
	Jun. 30, 2017USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs granted, Number of RSUs | shares	404,485
RSUs vested, Number of RSUs | shares	0
RSUs forfeited, Number of RSUs | shares	(1,710)
Ending Balance - Non-vested units, Number of RSUs | shares	402,775
RSUs granted, Weighted-Average Grant Date Fair Value | $ / shares	$ 22.44
RSUs vested, Weighted-Average Grant Date Fair Value | $ / shares	0
RSUs forfeited, Weighted-Average Grant Date Fair Value | $ / shares	29.75
Ending Balance - Non-vested units, Weighted-Average Grant Date Fair Value | $ / shares	$ 22.40
Non-vested units, Weighted-Average remaining vesting period(years)	1 year 10 months 25 days
Non-vested units, Aggregate Intrinsic Value | $	$ 11,016

Stock Based Compensation - St34

Stock Based Compensation - Stock-based Compensation Expense Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,660	$ 1,465	$ 5,234	$ 2,732
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,440	602	2,513	1,147
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,220	$ 863	$ 2,721	$ 1,585

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		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	4,017,643	3,589,348	4,017,643	3,589,348
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	3,078,379	2,662,841	3,078,379	2,662,841
Restricted Stock Subject to Future Vesting [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	515,469	881,617	515,469	881,617
RSU [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	402,775		402,775
Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from earnings per share	21,020	44,890	21,020	44,890

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2017USD ($)ft²	Jun. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Jun. 30, 2017USD ($)ft²	Jun. 30, 2016USD ($)
Commitment And Contingencies [Line Items]
Facility size | ft²	67,185			36,740
Initial term	10 years
Future minimum rental payments under the Lease term	$ 45.8
Lease commencement date	Dec. 15, 2017
Operating lease term	10 years
Operating lease term, optional extension	10 years
Construction-in-progress	$ 2.9
Operating leases latest expiration date				2018-04
Rent expense		$ 0.4	$ 0.3	$ 0.8	$ 0.6
Standby Letters of Credit [Member]
Commitment And Contingencies [Line Items]
Restricted cash	$ 0.9

Commitments and Contingencies37

Commitments and Contingencies - Future Aggregate Minimum Lease Payments (Detail) $ in Thousands	Jun. 30, 2017USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017 (six months)	$ 860
2,018	3,462
2,019	4,134
2,020	4,279
2,021	4,428
Thereafter	29,787
Total	$ 46,950