Kineta (KANT) 10-Q 6 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 03, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Trading Symbol	PTI
Entity Registrant Name	PROTEOSTASIS THERAPEUTICS, INC.
Entity Central Index Key	0001445283
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		52,175,861
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Address, State or Province	MA
Entity File Number	001-37695
Entity Tax Identification Number	20-8436652
Entity Address, Address Line One	80 Guest Street
Entity Address, Address Line Two	Suite 500
Entity Address, City or Town	Boston
Entity Address, Postal Zip Code	02135
City Area Code	617
Local Phone Number	225-0096
Title of 12(b) Security	Common stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 42,868	$ 25,008
Short-term investments	5,998	44,459
Prepaids and other current assets	1,964	1,404
Total current assets	50,830	70,871
Operating lease, right-of-use asset	12,002	12,631
Property and equipment, net	308	394
Restricted cash	828	828
Total assets	63,968	84,724
Current liabilities:
Accounts payable	1,504	2,283
Accrued expenses	4,157	6,864
Operating lease liabilities	1,204	1,153
Short-term borrowings	735
Total current liabilities	7,600	10,300
Derivative liability	3	3
Operating lease liabilities, net of current portion	11,429	12,043
Total liabilities	19,032	22,346
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding as of June 30, 2020 and December 31, 2019
Common stock, $0.001 par value; 125,000,000 shares authorized; 52,147,656 and 52,116,629 shares issued and outstanding as of June 30, 2020 and December 31, 2019, respectively	52	52
Additional paid-in capital	400,315	398,979
Accumulated other comprehensive income		7
Accumulated deficit	(355,431)	(336,660)
Total stockholders’ equity	44,936	62,378
Total liabilities and stockholders’ equity	$ 63,968	$ 84,724

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
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	125,000,000	125,000,000
Common stock, shares issued	52,147,656	52,116,629
Common stock, shares outstanding	52,147,656	52,116,629

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Revenue				$ 5,000
Operating expenses:
Research and development	$ 4,584	$ 16,925	$ 11,102	33,072
General and administrative	4,366	3,682	7,953	7,626
Total operating expenses	8,950	20,607	19,055	40,698
Loss from operations	(8,950)	(20,607)	(19,055)	(35,698)
Interest income	54	297	261	654
Interest expense	(6)		(9)
Other income, net	9	292	32	608
Net loss	$ (8,893)	$ (20,018)	$ (18,771)	$ (34,436)
Net loss per share—basic and diluted	$ (0.17)	$ (0.39)	$ (0.36)	$ (0.67)
Weighted average common shares outstanding—basic and diluted	52,147,656	51,097,456	52,147,145	51,037,514
Other comprehensive income:
Unrealized gain (loss) on investments	$ (43)	$ 15	$ (7)	$ 32
Comprehensive loss	$ (8,936)	$ (20,003)	$ (18,778)	$ (34,404)

Condensed Statements of Stockho

Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2018	$ 114,342	$ 51	$ 391,825	$ 1	$ (277,535)
Beginning balance, shares at Dec. 31, 2018		50,808,422
Exercise of stock options	3		3
Exercise of stock options, shares		2,543
Stock-based compensation expense	1,749		1,749
Issuance of common stock for payment of consulting services	242		242
Issuance of common stock for payment of consulting services, shares		102,302
Issuance of common stock pursuant to employee stock purchase plan	53		53
Issuance of common stock pursuant to employee stock purchase plan, shares		22,615
Vesting of restricted stock units, shares		163,425
Other comprehensive income (loss)	32			32
Net loss	(34,436)				(34,436)
Ending balance at Jun. 30, 2019	81,985	$ 51	393,872	33	(311,971)
Ending balance, shares at Jun. 30, 2019		51,099,307
Beginning balance at Mar. 31, 2019	100,967	$ 51	392,851	18	(291,953)
Beginning balance, shares at Mar. 31, 2019		51,043,158
Stock-based compensation expense	949		949
Issuance of common stock for payment of consulting services	72		72
Issuance of common stock for payment of consulting services, shares		56,149
Other comprehensive income (loss)	15			15
Net loss	(20,018)				(20,018)
Ending balance at Jun. 30, 2019	81,985	$ 51	393,872	33	(311,971)
Ending balance, shares at Jun. 30, 2019		51,099,307
Beginning balance at Dec. 31, 2019	$ 62,378	$ 52	398,979	7	(336,660)
Beginning balance, shares at Dec. 31, 2019	52,116,629	52,116,629
Stock-based compensation expense	$ 1,310		1,310
Issuance of common stock for payment of consulting services	26		26
Issuance of common stock pursuant to employee stock purchase plan, shares		31,027
Other comprehensive income (loss)	(7)			(7)
Net loss	(18,771)				(18,771)
Ending balance at Jun. 30, 2020	$ 44,936	$ 52	400,315		(355,431)
Ending balance, shares at Jun. 30, 2020	52,147,656	52,147,656
Beginning balance at Mar. 31, 2020	$ 53,140	$ 52	399,583	43	(346,538)
Beginning balance, shares at Mar. 31, 2020		52,147,656
Stock-based compensation expense	732		732
Other comprehensive income (loss)	(43)			$ (43)
Net loss	(8,893)				(8,893)
Ending balance at Jun. 30, 2020	$ 44,936	$ 52	$ 400,315		$ (355,431)
Ending balance, shares at Jun. 30, 2020	52,147,656	52,147,656

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net loss	$ (18,771)	$ (34,436)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	86	101
Non-cash lease expense	629	603
Accretion of short-term investments	(34)	(614)
Stock-based compensation expense	1,310	1,749
Stock issued for consulting services		242
Changes in operating assets and liabilities:
Prepaids and other current assets	(560)	(585)
Other assets		(75)
Accounts payable	(779)	1,276
Accrued expenses	(2,707)	1,202
Operating lease liabilities	(563)	(514)
Net cash used in operating activities	(21,389)	(31,051)
Cash flows from investing activities:
Purchases of short-term investments	(11,229)	(43,170)
Proceeds received from maturities of short-term investments	49,717	74,000
Purchases of property and equipment		(9)
Net cash provided by investing activities	38,488	30,821
Cash flows from financing activities:
Proceeds from exercise of stock options		3
Proceeds from issuance of common stock pursuant to employee stock purchase plan	26	53
Proceeds from issuance of short-term borrowings	1,220
Repayment of short-term borrowings	(485)
Net cash provided by financing activities	761	56
Net increase in cash, cash equivalents and restricted cash	17,860	(174)
Cash, cash equivalents and restricted cash at beginning of period	25,836	29,638
Cash, cash equivalents and restricted cash at end of period	$ 43,696	$ 29,464

Nature of the Business

Nature of the Business	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of the Business	1. Nature of the Business Proteostasis Therapeutics, Inc. (the “Company”) was incorporated in Delaware on December 13, 2006. The Company is a clinical stage biopharmaceutical company committed to the discovery and development of novel therapeutics to treat cystic fibrosis (“CF”) through theratyping, or the process of matching modulators to individual response to treatment regardless of cystic fibrosis transmembrane conductance regulator (“CFTR”) mutations. CF is a disease caused by defects in the function or abundance of CFTR protein. Although, CF is defined as a monogenic recessive genetic disorder caused by mutations in the CFTR gene, there is a broad range of disease activity for different organ systems in CF, including lung disease, meconium ileus, diabetes, and liver disease, even for CF patients who are homozygous for the most common mutation, F508del mutation. In summary, CF genotype does not always match CF phenotype. Since its inception, the Company has devoted substantially all of its efforts to organizing and staffing the Company, business planning, raising capital, acquiring and developing product and technology rights, and conducting research and development activities. It has funded its operations to date with proceeds from the sale of preferred stock, the issuance of convertible promissory notes, proceeds from its initial public offering in February 2016, proceeds from its follow-on public offerings, and payments received in connection with collaboration agreements and a research grant, as well as funds from the sale of stock under the at-the-market offering program described below. The Company does not have any products approved for sale and has not generated any revenue from product sales. The Company has not generated any commercial revenue since inception. As a result, the Company has incurred recurring losses and requires significant cash resources to execute its business plans. In accordance with ASC 205-40, Going Concern . As of June 30, 2020, the Company had an accumulated deficit of $355.4 million. The Company has incurred losses and negative cash flows from operations since its inception. During the six months ended June 30, 2020, the Company incurred losses of $18.8 million and used $21.4 million of cash in operations. $48.9 million will be sufficient to fund its operating expenses and capital requirements, based upon its current operating plan, for at least 12 months from the date that these financial statements are issued. The novel coronavirus (“COVID-19”)

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Unaudited Interim Financial Information The condensed balance sheet as of December 31, 2019 was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed financial statements, as of June 30, 2020 and for the three and six months ended June 30, 2020, are unaudited and have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on March 10, 2020. In the opinion of management, all adjustments, consisting only of normal recurring adjustments, as necessary for the fair statement of the Company’s financial position as of June 30, 2020, results of its operations for the three and six months ended June 30, 2020, stockholders’ equity for the three and six months ended June 30, 2020, and cash flows for the six months ended June 30, 2020, have been made. The results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results of operations to be expected for the year ending December 31, 2020. Summary of Significant Accounting Policies The Company’s significant accounting policies, which are disclosed in the audited financial statements for the year ended December 31, 2019 and the notes thereto, are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 10, 2020. There were no changes to significant accounting policies during the three and six months ended June 30, 2020. Risks and Uncertainties The Company is monitoring the potential impact of COVID-19, if any, on the carrying value of certain assets. To date, the Company has not experienced material business disruption, nor has it incurred impairment of any assets as a result of COVID-19. The extent to which these events may impact the Company’s business, clinical development and regulatory efforts, and the value of its common stock, will depend on future developments, which are highly uncertain and cannot be predicted at this time. The duration and intensity of these impacts and resulting disruption to the Company’s operations is uncertain and the Company will continue to assess the financial impact. In addition, the Company is subject to other challenges and risks specific to its business and its ability to execute on its business plan and strategy, as well as risks and uncertainties common to companies in the biopharmaceutical industry with development and commercial operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of its late-stage product candidates; delays or problems in obtaining clinical supply, loss of single source suppliers or failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional products or product candidates; biopharmaceutical product development and the inherent uncertainty of clinical success; and the challenges of complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects our business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above. Use of Estimates The preparation of financial statements in conformity with GAAP requires management 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 financial statements, and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed financial statements include, but are not limited to, revenue recognition, the accrual for research and development expenses, and the valuation the derivative liability. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates. Reclassifications Certain prior year amounts have been reclassified for consistency with the current year presentation. An adjustment has also been made to the condensed statement of cash flows for the period ended June 30, 2019, to reclassify non-cash lease expense out of depreciation and amortization. Recently Issued and Adopted Accounting Pronouncements ASU No. 2018-13, Fair Value Measurement (Topic 820): Changes to the Disclosure Requirements for Fair Value Measurement In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement Recently Issued Accounting Pronouncements ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Short-Term Investments

Short-Term Investments	6 Months Ended
	Jun. 30, 2020
Cash Cash Equivalents And Short Term Investments [Abstract]
Short-Term Investments	3. Short-Term Investments The following table summarizes the Company’s short-term investments as of June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 5,998 $ — $ — $ 5,998 $ 5,998 $ — $ — $ 5,998 December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S government-sponsored enterprise securities $ 20,456 $ 2 $ (1 ) $ 20,457 U.S. treasury securities 23,996 7 (1 ) 24,002 $ 44,452 $ 9 $ (2 ) $ 44,459 Short-term investments represent holdings of available-for-sale debt securities and are reported at fair value with unrealized gains and losses reported net of taxes, if material, in other comprehensive income. The Company did not have any realized gains or losses on its short-term investments for the three and six months ended June 30, 2020 and 2019 2019

Fair Value of Financial Assets

Fair Value of Financial Assets and Liabilities	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value of Financial Assets and Liabilities	4. Fair Value of Financial Assets and Liabilities The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): Fair Value Measurements as of June 30, 2020 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 27,873 $ — $ — $ 27,873 U.S. treasury securities — 13,998 — 13,998 Short-term investments: U.S. treasury securities — 5,998 — 5,998 $ 27,873 $ 19,996 $ — $ 47,869 Liabilities: Derivative liability $ — $ — $ 3 $ 3 Fair Value Measurements as of December 31, 2019 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 23,906 $ — $ — $ 23,906 Short-term investments: U.S. government-sponsored enterprise securities — 20,457 — 20,457 U.S. treasury securities — 24,002 — 24,002 $ 23,906 $ 44,459 $ — $ 68,365 Liabilities: Derivative liability $ — $ — $ 3 $ 3 During the periods ended June 30, 2020 and December 31, 2019, there were no transfers between Level 1, Level 2 and Level 3. The derivative liability relates to a cash settlement option associated with the change of control provision in the Company’s Cystic Fibrosis Foundation, Inc. (“CFF”) agreement, which meets the definition of a derivative. The fair value of the derivative liability is based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of the derivative instrument was originally determined using the Monte-Carlo simulation analysis. In determining the fair value of the derivative liability, the inputs impacting fair value include the fair value of the Company’s common stock, expected term of the derivative instrument, expected volatility of the common stock price, risk-free interest rate, expected sales-based milestone payments, discount rate, probability of a change of control event, and the probability that the counterparty would elect to accept the alternative cash payment in lieu of its right to the future sales-based milestone payments. The fair value of the derivative liability was not material at June 30, 2020 and December 31, 2019.

Prepaids and Other Current Asse

Prepaids and Other Current Assets	6 Months Ended
	Jun. 30, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaids and Other Current Assets	5. Prepaids and Other Current Assets Prepaids and other current assets consisted of the following (in thousands): June 30, December 31, 2020 2019 Prepaid clinical, manufacturing and scientific expenses $ 398 $ 767 Prepaid insurance expenses 1,174 125 Other prepaid expenses and other current assets 392 512 $ 1,964 $ 1,404

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Accrued Expenses	6. Accrued Expenses Accrued expenses consisted of the following (in thousands): June 30, December 31, 2020 2019 Accrued payroll and related expenses 2,095 3,203 Accrued research and development expenses $ 1,075 $ 3,186 Accrued professional fees 964 397 Accrued other 23 78 $ 4,157 $ 6,864

Short-Term Borrowings

Short-Term Borrowings	6 Months Ended
	Jun. 30, 2020
Short Term Borrowings [Abstract]
Short-Term Borrowings	7. Short-Term Borrowings As of June 30, 2020, the Company had short-term borrowings of $0.7 million consisting of a Commercial Insurance Premium Finance and Security Agreement (the “Finance and Security Agreement”) entered into on February 27, 2020. The Finance and Security Agreement has a ten-month repayment period with an annual interest rate of 2.59% and a maturity of December 11, 2020. Collateral under the Finance and Security Agreement includes the right, title, and interest in the underlying business insurance policies. As of June 30, 2020, the Company has paid less than $0.1 million in interest on short-term borrowings.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	8 . Stock-Based Compensation 2016 Stock Option and Incentive Plan On February 3, 2016, the Company’s stockholders approved the 2016 Stock Option and Incentive Plan (the “2016 Plan”), which became effective on February 9, 2016. The 2016 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock units, restricted stock awards and other stock-based awards. The number of shares initially reserved for issuance under the 2016 Plan was 1,581,839 shares. The number of shares of common stock that may be issued under the 2016 Plan will automatically increase each January 1, beginning January 1, 2017, by the lesser of 3% of the shares of the Company’s common stock outstanding on the immediately preceding December 31, or an amount determined by the Company’s board of directors or the compensation committee of the board of directors. The shares of common stock underlying any awards that are forfeited, canceled, repurchased, or are otherwise terminated by the Company under the 2016 Plan and the 2008 Equity Incentive Plan, as amended (the “2008 Plan”) will be added back to the shares of common stock available for issuance under the 2016 Plan. On January 1, 2020, an additional 1,563,498 shares were reserved for issuance under the 2016 Plan. As of June 30, 2020, the total number of shares of the Company’s common stock reserved for issuance under the 2016 Plan was 6,914,838, of which 1,275,795 shares are available for future issuance under the 2016 Plan. 2016 Employee Stock Purchase Plan On February 3, 2016, the Company’s stockholders approved the 2016 Employee Stock Purchase Plan (the “2016 ESPP”), which became effective in connection with the completion of the Company’s initial public offering. A total of 138,757 shares of common stock were initially reserved for issuance under the 2016 ESPP. In addition, the number of shares of common stock that may be issued under the 2016 ESPP will automatically increase each January 1, beginning January 1, 2017, by the lesser of (i) 138,757 shares of common stock, (ii) 1% of the Company’s shares of common stock outstanding on the immediately preceding December 31, or (iii) an amount determined by the Company’s board of directors or the compensation committee of the board of directors. During the six months ended June 30, 2020, 31,027 shares of common stock were issued pursuant to the 2016 ESPP. As of June 30, 2020, the total number of shares reserved under the 2016 ESPP was 580,742 shares. The Company recognized less than $0.1 million of stock-based compensation during the three and six months ended June 30, 2020 related to the 2016 ESPP. Restricted Stock Units (RSUs) On February 4, 2020, the Company’s board approved payment to be made to a nonemployee through a grant of RSUs based on the February 4, 2020 closing share price of the Company’s common stock. The requisite service period for the awards is from February 4, 2020 to August 4, 2020 (the vesting period). The Company recognized employee stock-based compensation expense for the RSU grant on a straight-line basis over the vesting period of the awards. As of June 30, 2020, 4,519 RSUs were granted and the Company recognized less than $0.1 million of stock-based compensation expense during the three and six months ended June 30, 2020. On June 29, 2020, the Company’s board approved the grant of RSU awards with an aggregate fair market value equal to the RSU value of $1.2 million (each an “Award”) to two consultants (each, a “Grantee”) in consideration for services. Each Award shall vest in full immediately prior to, but subject to the occurrence of, a specific strategic event (the “Vesting Date”), so long as the respective Grantee remains in service to the Company through the Vesting Date. If the Awards vest as provided for above, the Company shall issue a number of shares of stock equal to the RSU value, divided by the volume-weighted average price per share of the Company’s stock for the 10-day period ending on the Vesting Date. The Company also has the option to issue each Grantee the respective cash equivalent of the Award in part or in full satisfaction of the delivery of the stock in connection with the vesting of each Award. As of June 30, 2020, the Company recognized no compensation costs associated with the Awards as the performance condition of the completion of certain strategic events is not considered probable. The following table summarizes the Company’s RSU activity for the six months ended June 30, 2020: Number of Shares Weighted Average Grant Date Fair Value Unvested balance at December 31, 2019 — $ — Granted 4,519 1.77 Vested — — Forfeited — — Unvested balance at June 30, 2020 4,519 $ — Stock-Based Compensation Stock-based compensation expense, including shares issued to consultants for services, was classified in the statements of operations as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Research and development $ 266 $ 399 $ 496 $ 769 General and administrative 465 622 814 1,222 $ 731 $ 1,021 $ 1,310 $ 1,991 The following table summarizes the Company’s stock option activity for the six months ended June 30, 2020 (in thousands except share and per share amounts): Number of Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (Years) Outstanding at December 31, 2019 4,364,839 $ 5.30 7.32 $ 132 Granted 1,663,000 1.56 Forfeited (388,796 ) 6.11 Outstanding at June 30, 2020 5,639,043 $ 4.14 7.65 $ 33 Exercisable at June 30, 2020 2,675,930 $ 5.72 6.34 $ 16 Vested and expected to vest at June 30, 2020 5,555,793 $ 4.17 7.76 $ 33 The grant date fair value of options granted during the period was $1.8 million, or $1.09 per share on a weighted-average basis, and will be recognized as compensation expense over the requisite service period of four years. As of June 30, 2020, there was $4.9 million of unrecognized compensation cost related to employee and nonemployee unvested stock options granted under the 2016 Plan, which is expected to be recognized over a weighted-average remaining service period of 2.4 years. Stock compensation costs have not been capitalized by the Company. Prior to 2013, the Company issued options to purchase 203,964 shares of common stock to nonemployees, primarily members of the Company’s scientific advisory board, that vest upon the achievement of specified development and clinical milestones. As of June 30, 2020, options for the purchase of 83,250 shares held by nonemployees remained unvested, pending achievement of the specified milestones.

Significant Agreements

Significant Agreements	6 Months Ended
	Jun. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant Agreements	9 . Significant Agreements Genentech In December 2018, the Company entered into a Technology Transfer and License Agreement (the “Genentech Agreement”) with Genentech, Inc. (“Genentech”) under which the Company granted Genentech an exclusive worldwide license for technology and materials relating to potential therapeutic small molecule modulators of an undisclosed target within the proteostasis network. The rights do not include CFTR modulators and are unrelated to the Company’s investigational medicines or other ongoing research programs in cystic fibrosis. In connection with the terms of the Genentech Agreement, the Company was entitled to a nonrefundable cash payment of $5.0 million following the successful completion of the technology and materials transfer to Genentech and future milestone payments in the aggregate of approximately $96.0 million upon the achievement of specified development, regulatory, and commercial milestones. In addition, Genentech is obligated to pay the Company tiered royalties in the low single-digits based on net sales of products covered by the licenses granted under the Genentech Agreement. There are no cancellation, termination, or refund provisions in the Genentech Agreement that contain material financial consequences to the Company. Unless earlier terminated, the Genentech Agreement continues in full force and effect until the passing or expiration of all royalty payment obligations. Reciprocal termination rights under the agreement include termination for breach and termination for bankruptcy. Genentech may terminate the Genentech Agreement in its entirety, for convenience, upon thirty days’ notice to the Company. The Company evaluated the Genentech Agreement in accordance with the provisions of Accounting Standards Codification Topic 606, Revenue from Contracts with Customers The Company measured the transaction price solely in reference to the $5.0 million payment due upon receipt of notice from Genentech regarding the satisfactory completion of the technology and materials transfer. None of the variable consideration payable under the arrangement has been included in the transaction price. As of June 30, 2020, the Company has not achieved any research, development, regulatory, or commercial milestones, or earned any royalties under the Genentech Agreement. The Company utilizes “the most likely” amount method to estimate the amount of research, development, and regulatory milestone payments to be received. As part of the evaluation for the research and development milestone payments, the Company considers several factors including the stage of research and development of the compounds included in the arrangement, the risk associated with the remaining research and development work required to achieve the milestone, and the Company’s level of involvement in the research and development activities. Regulatory milestone payments are triggered upon the first commercial sale following receipt of regulatory approval from the FDA or other global regulatory authorities; therefore, such amounts will be excluded from the transaction price until the associated regulatory approval is received. The commercial milestone payments and royalties are subject to the royalty recognition constraint whereby such amounts will be recognized as revenue upon the later of: (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the payment has been allocated has been satisfied, or partially satisfied, because the exclusive license is deemed to be the sole or predominant item to which the payments relate. As all performance obligations are satisfied, the Company will recognize royalty revenue at the date the sales occur. The Company did not adjust the promised amount of consideration for the effects of a significant financing component because the Company expects that the period between when the promised goods and services are transferred and when the customer pays for those goods and services will be one year or less. There were no changes in the transaction price for the six months ended June 30, 2020. The transaction price of $5.0 million allocated to the combined performance obligation was recognized as revenue in February 2019 at the point in time that Genentech provided notice regarding the satisfactory completion of the technology and materials transfer. Upon that successful execution of the technology and materials transfer, control was deemed to be transferred for both the exclusive license and the technology and materials transfer promises, therefore the risks and rewards of ownership had been conveyed. As of June 30, 2020, the Company did not have any receivables or deferred revenue related to the Genentech Agreement because no payments under the arrangement became due, nor had the underlying performance obligation been satisfied.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	10 . Income Taxes The Company did not record a federal or state income tax benefit for its losses for the three and six months ended June 30, 2020 and 2019, respectively, due to the conclusion that a full valuation allowance is required against the Company’s deferred tax assets. All the Company’s losses before income taxes were generated in the United States.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Net Loss per Share	1 1 . Net Loss per Share Basic and diluted net loss per share was calculated as follows (in thousands, except share and per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Numerator: Net loss $ (8,893 ) $ (20,018 ) $ (18,771 ) $ (34,436 ) Denominator: Weighted average number of common shares outstanding—basic and diluted 52,147,656 51,097,456 52,147,145 51,037,514 Net loss per share—basic and diluted $ (0.17 ) $ (0.39 ) $ (0.36 ) $ (0.67 ) The following common stock equivalents have been excluded from the computation of diluted weighted-average shares outstanding, because such securities had an antidilutive impact : June 30, 2020 2019 Options to purchase common stock 5,639,043 4,598,850 Restricted stock units 4,519 — 5,643,562 4,598,850

Leases

Leases	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Leases	12. Leases The Company has an operating lease for office and laboratory space for its corporate headquarters in Boston, Massachusetts. The lease commenced in January 2018 and rent payments began in April 2018. This lease has a ten-year initial term with an option to extend for seven additional years. The Company has the right to terminate the lease in the event of the inability to use the space due to substantial damage while the lessor has the right to terminate the lease if the Company defaults on the lease financial obligations. Per the terms of the lease agreement, the Company does not have any residual value guarantees. In calculating the present value of the lease payments, the Company utilized its incremental borrowing rate, which is based on rates that would be incurred to borrow on a collateralized basis over a term equal to the lease payments in a similar economic environment. The Company has allocated all the contract considerations to the one lease component. This may result in the initial and subsequent measurement of the balances of the right-of-use asset and lease liability for leases being greater than if the policy election was not applied. The Company’s real estate lease in Boston is considered a net lease, as the non-lease components (i.e., common area maintenance) are paid separately from rent, based on actual costs incurred. Therefore, the variable non-lease components were not included in the right-of-use asset and liability and are reflected as an expense in the period incurred. As of June 30, 2020, and December 31, 2019, assets under operating lease were $12.0 million and $12.6 million, respectively. The elements of lease expense were as follows (in thousands): For the Three Months Ended June 30, 2020 2019 Lease cost Operating lease cost $ 462 $ 459 Variable lease cost (1) 158 179 Total lease cost $ 620 $ 638 For the Six Months Ended June 30, 2020 2019 Lease cost Operating lease cost $ 925 $ 921 Variable lease cost (1) 261 316 Total lease cost $ 1,186 $ 1,237 Other information Operating cash flows used for operating leases $ 859 $ 836 Weighted-average remaining lease term 7.84 years 8.84 years Weighted-average discount rate 4.50 % 4.50 % (1) The variable lease costs for the three and six months ended June 30, 2020 and 2019 Future lease payments under no ncancelable leases as of June 30, 2020 (in thousands): Future Operating Lease Payments 2020 $ 874 2021 1,780 2022 1,829 2023 1,880 2024 1,931 Thereafter 6,825 Total lease payments 15,119 Less: imputed interest (2,486 ) Total operating lease liabilities $ 12,633

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Unaudited Interim Financial Information	Unaudited Interim Financial Information The condensed balance sheet as of December 31, 2019 was derived from audited financial statements but does not include all disclosures required by accounting principles generally accepted in the United States of America (“GAAP”). The accompanying condensed financial statements, as of June 30, 2020 and for the three and six months ended June 30, 2020, are unaudited and have been prepared by the Company pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial statements. Certain information and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. The Company believes that the disclosures are adequate to make the information presented not misleading. These unaudited condensed financial statements should be read in conjunction with the Company’s audited financial statements and the notes thereto for the year ended December 31, 2019 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on March 10, 2020. In the opinion of management, all adjustments, consisting only of normal recurring adjustments, as necessary for the fair statement of the Company’s financial position as of June 30, 2020, results of its operations for the three and six months ended June 30, 2020, stockholders’ equity for the three and six months ended June 30, 2020, and cash flows for the six months ended June 30, 2020, have been made. The results of operations for the three and six months ended June 30, 2020 are not necessarily indicative of the results of operations to be expected for the year ending December 31, 2020.
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The Company’s significant accounting policies, which are disclosed in the audited financial statements for the year ended December 31, 2019 and the notes thereto, are included in the Company’s Annual Report on Form 10-K that was filed with the SEC on March 10, 2020. There were no changes to significant accounting policies during the three and six months ended June 30, 2020.
Risks and Uncertainties	Risks and Uncertainties The Company is monitoring the potential impact of COVID-19, if any, on the carrying value of certain assets. To date, the Company has not experienced material business disruption, nor has it incurred impairment of any assets as a result of COVID-19. The extent to which these events may impact the Company’s business, clinical development and regulatory efforts, and the value of its common stock, will depend on future developments, which are highly uncertain and cannot be predicted at this time. The duration and intensity of these impacts and resulting disruption to the Company’s operations is uncertain and the Company will continue to assess the financial impact. In addition, the Company is subject to other challenges and risks specific to its business and its ability to execute on its business plan and strategy, as well as risks and uncertainties common to companies in the biopharmaceutical industry with development and commercial operations, including, without limitation, risks and uncertainties associated with: obtaining regulatory approval of its late-stage product candidates; delays or problems in obtaining clinical supply, loss of single source suppliers or failure to comply with manufacturing regulations; identifying, acquiring or in-licensing additional products or product candidates; biopharmaceutical product development and the inherent uncertainty of clinical success; and the challenges of complying with applicable regulatory requirements. In addition, to the extent the ongoing COVID-19 pandemic adversely affects our business and results of operations, it may also have the effect of heightening many of the other risks and uncertainties discussed above.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management 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 financial statements, and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed financial statements include, but are not limited to, revenue recognition, the accrual for research and development expenses, and the valuation the derivative liability. Estimates are periodically reviewed in light of changes in circumstances, facts, and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Reclassification	Reclassifications Certain prior year amounts have been reclassified for consistency with the current year presentation. An adjustment has also been made to the condensed statement of cash flows for the period ended June 30, 2019, to reclassify non-cash lease expense out of depreciation and amortization.
Recently Issued and Adopted Accounting Pronouncements	Recently Issued and Adopted Accounting Pronouncements ASU No. 2018-13, Fair Value Measurement (Topic 820): Changes to the Disclosure Requirements for Fair Value Measurement In August 2018, the FASB issued ASU No. 2018-13, Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement Recently Issued Accounting Pronouncements ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments

Short-Term Investments (Tables)

Short-Term Investments (Tables)	6 Months Ended
	Jun. 30, 2020
Cash Cash Equivalents And Short Term Investments [Abstract]
Summary of Short-Term Investments	The following table summarizes the Company’s short-term investments as of June 30, 2020 and December 31, 2019 (in thousands): June 30, 2020 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S. treasury securities $ 5,998 $ — $ — $ 5,998 $ 5,998 $ — $ — $ 5,998 December 31, 2019 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value U.S government-sponsored enterprise securities $ 20,456 $ 2 $ (1 ) $ 20,457 U.S. treasury securities 23,996 7 (1 ) 24,002 $ 44,452 $ 9 $ (2 ) $ 44,459

Fair Value of Financial Asset_2

Fair Value of Financial Assets and Liabilities (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following tables present information about the Company’s financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): Fair Value Measurements as of June 30, 2020 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 27,873 $ — $ — $ 27,873 U.S. treasury securities — 13,998 — 13,998 Short-term investments: U.S. treasury securities — 5,998 — 5,998 $ 27,873 $ 19,996 $ — $ 47,869 Liabilities: Derivative liability $ — $ — $ 3 $ 3 Fair Value Measurements as of December 31, 2019 using: Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 23,906 $ — $ — $ 23,906 Short-term investments: U.S. government-sponsored enterprise securities — 20,457 — 20,457 U.S. treasury securities — 24,002 — 24,002 $ 23,906 $ 44,459 $ — $ 68,365 Liabilities: Derivative liability $ — $ — $ 3 $ 3

Prepaids and Other Current As_2

Prepaids and Other Current Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Prepaid Expense And Other Assets Current [Abstract]
Schedule of Prepaids and Other Current Assets	Prepaids and other current assets consisted of the following (in thousands): June 30, December 31, 2020 2019 Prepaid clinical, manufacturing and scientific expenses $ 398 $ 767 Prepaid insurance expenses 1,174 125 Other prepaid expenses and other current assets 392 512 $ 1,964 $ 1,404

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2020
Payables And Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of the following (in thousands): June 30, December 31, 2020 2019 Accrued payroll and related expenses 2,095 3,203 Accrued research and development expenses $ 1,075 $ 3,186 Accrued professional fees 964 397 Accrued other 23 78 $ 4,157 $ 6,864

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Restricted Stock Unit Activity	The following table summarizes the Company’s RSU activity for the six months ended June 30, 2020: Number of Shares Weighted Average Grant Date Fair Value Unvested balance at December 31, 2019 — $ — Granted 4,519 1.77 Vested — — Forfeited — — Unvested balance at June 30, 2020 4,519 $ —
Summary of Stock-based Compensation Expense, Including Shares Issued to Consultants for Services	Stock-based compensation expense, including shares issued to consultants for services, was classified in the statements of operations as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Research and development $ 266 $ 399 $ 496 $ 769 General and administrative 465 622 814 1,222 $ 731 $ 1,021 $ 1,310 $ 1,991
Summary of Stock Option Activity	The following table summarizes the Company’s stock option activity for the six months ended June 30, 2020 (in thousands except share and per share amounts): Number of Shares Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (Years) Outstanding at December 31, 2019 4,364,839 $ 5.30 7.32 $ 132 Granted 1,663,000 1.56 Forfeited (388,796 ) 6.11 Outstanding at June 30, 2020 5,639,043 $ 4.14 7.65 $ 33 Exercisable at June 30, 2020 2,675,930 $ 5.72 6.34 $ 16 Vested and expected to vest at June 30, 2020 5,555,793 $ 4.17 7.76 $ 33

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss per Share	Basic and diluted net loss per share was calculated as follows (in thousands, except share and per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Numerator: Net loss $ (8,893 ) $ (20,018 ) $ (18,771 ) $ (34,436 ) Denominator: Weighted average number of common shares outstanding—basic and diluted 52,147,656 51,097,456 52,147,145 51,037,514 Net loss per share—basic and diluted $ (0.17 ) $ (0.39 ) $ (0.36 ) $ (0.67 )
Schedule of Antidilutive Securities Excluded from Computation of Diluted Weighted-average Shares Outstanding	The following common stock equivalents have been excluded from the computation of diluted weighted-average shares outstanding, because such securities had an antidilutive impact : June 30, 2020 2019 Options to purchase common stock 5,639,043 4,598,850 Restricted stock units 4,519 — 5,643,562 4,598,850

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2020
Lessee Disclosure [Abstract]
Elements of Lease Expense	The elements of lease expense were as follows (in thousands): For the Three Months Ended June 30, 2020 2019 Lease cost Operating lease cost $ 462 $ 459 Variable lease cost (1) 158 179 Total lease cost $ 620 $ 638 For the Six Months Ended June 30, 2020 2019 Lease cost Operating lease cost $ 925 $ 921 Variable lease cost (1) 261 316 Total lease cost $ 1,186 $ 1,237 Other information Operating cash flows used for operating leases $ 859 $ 836 Weighted-average remaining lease term 7.84 years 8.84 years Weighted-average discount rate 4.50 % 4.50 % (1) The variable lease costs for the three and six months ended June 30, 2020 and 2019
Schedule of Future Lease Payments under Noncancelable Leases	Future lease payments under no ncancelable leases as of June 30, 2020 (in thousands): Future Operating Lease Payments 2020 $ 874 2021 1,780 2022 1,829 2023 1,880 2024 1,931 Thereafter 6,825 Total lease payments 15,119 Less: imputed interest (2,486 ) Total operating lease liabilities $ 12,633

Nature of the Business - Additi

Nature of the Business - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Accumulated deficit	$ (355,431)		$ (355,431)		$ (336,660)
Cash, cash equivalents and short-term investments	48,900		48,900
Net loss	$ (8,893)	$ (20,018)	(18,771)	$ (34,436)
Cash in operations			$ 21,389	$ 31,051

Short-Term Investments - Summar

Short-Term Investments - Summary of Short-Term Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 5,998	$ 44,452
Gross Unrealized Gains		9
Gross Unrealized Losses		(2)
Fair Value	5,998	44,459
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,998	23,996
Gross Unrealized Gains		7
Gross Unrealized Losses		(1)
Fair Value	$ 5,998	24,002
U.S Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		20,456
Gross Unrealized Gains		2
Gross Unrealized Losses		(1)
Fair Value		$ 20,457

Short-Term Investments - Additi

Short-Term Investments - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Investments Debt And Equity Securities [Abstract]
Realized gains (losses) on short-term investments	$ 0	$ 0	$ 0	$ 0
Other-than-temporary impairments recognized	$ 0	$ 0	$ 0	$ 0

Fair Value of Financial Asset_3

Fair Value of Financial Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Liabilities:
Derivative liability	$ 3	$ 3
Fair Value, Measurements, Recurring [Member]
Assets:
Total assets	47,869	68,365
Liabilities:
Derivative liability	3	3
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]
Assets:
Cash equivalents	27,873	23,906
Fair Value, Measurements, Recurring [Member] | U.S Government-Sponsored Enterprise Securities [Member]
Assets:
Short-term investments		20,457
Fair Value, Measurements, Recurring [Member] | U.S. Treasury Securities [Member]
Assets:
Cash equivalents	13,998
Short-term investments	5,998	24,002
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Assets:
Total assets	27,873	23,906
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Money Market Funds [Member]
Assets:
Cash equivalents	27,873	23,906
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Assets:
Total assets	19,996	44,459
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S Government-Sponsored Enterprise Securities [Member]
Assets:
Short-term investments		20,457
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | U.S. Treasury Securities [Member]
Assets:
Cash equivalents	13,998
Short-term investments	5,998	24,002
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Liabilities:
Derivative liability	$ 3	$ 3

Fair Value of Financial Asset_4

Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Transfer of assets from level 1 to level 2	$ 0	$ 0
Transfer of assets from level 2 to level 1	0	0
Transfer of liabilities from level 1 to level 2	0	0
Transfer of liabilities from level 2 to level 1	$ 0	0
Fair value determination model	Monte-Carlo simulation analysis
Fair value of derivative liability	$ 0	$ 0

Prepaids and Other Current As_3

Prepaids and Other Current Assets - Schedule of Prepaids and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Prepaid Expense And Other Assets Current [Abstract]
Prepaid clinical, manufacturing and scientific expenses	$ 398	$ 767
Prepaid insurance expenses	1,174	125
Other prepaid expenses and other current assets	392	512
Prepaids and other current assets	$ 1,964	$ 1,404

Accrued Expenses - Schedule of

Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued payroll and related expenses	$ 2,095	$ 3,203
Accrued research and development expenses	1,075	3,186
Accrued professional fees	964	397
Accrued other	23	78
Total accrued expenses	$ 4,157	$ 6,864

Short-Term Borrowings - Additio

Short-Term Borrowings - Additional Information (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2020USD ($)
Short Term Debt [Line Items]
Short-term borrowings	$ 735
Finance And Security Agreement
Short Term Debt [Line Items]
Short-term borrowings	$ 700
Agreement commencement date	Feb. 27, 2020
Debt instrument, term	10 months
Short-term debt, annual interest rate	2.59%
Debt instrument, maturity date	Dec. 11, 2020
Interest on short-term borrowings	$ 100

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail)	Jun. 29, 2020USD ($)Consultant	Feb. 04, 2020	Feb. 03, 2016shares	Jun. 30, 2020USD ($)shares	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)$ / sharesshares	Jun. 30, 2019USD ($)	Jan. 01, 2020shares	Dec. 31, 2019shares	Dec. 31, 2016shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance								1,563,498
Stock-based compensation | $				$ 731,000	$ 1,021,000	$ 1,310,000	$ 1,991,000
Stock option grants						1,663,000
RSUs outstanding				5,639,043		5,639,043			4,364,839
Grant date fair value of options | $						$ 1,800,000
Weighted average grant date fair value | $ / shares						$ 1.09
Requisite service period						4 years
Bonus Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation | $						$ 100,000
RSUs outstanding				4,519		4,519
Vesting of restricted stock units | $	$ 1,200,000
Compensation costs associated with awards | $	$ 0
Award vesting terms						Company shall issue a number of shares of stock equal to the RSU value, divided by the volume-weighted average price per share of the Company’s stock for the 10-day period ending on the Vesting Date. The Company also has the option to issue each Grantee the respective cash equivalent of the Award in part or in full satisfaction of the delivery of the stock in connection with the vesting of each Award.
Number of consultants for services | Consultant	2
Nonemployees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options unvested				83,250		83,250
Nonemployees [Member] | Prior to 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option issued to purchase common stock						203,964
Maximum [Member] | Bonus Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards requisite service period date		Aug. 4, 2020
Minimum [Member] | Bonus Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards requisite service period date		Feb. 4, 2020
2016 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance			1,581,839	1,275,795		1,275,795
Common stock reserved for issuance, percentage of number of shares of common stock outstanding			3.00%
Unrecognized compensation cost related to the unvested stock-based awards | $				$ 4,900,000		$ 4,900,000
Compensation cost not yet recognized, period for recognition						2 years 4 months 24 days
2016 Plan and 2008 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance				6,914,838		6,914,838
2016 ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance			138,757	580,742		580,742
Common stock reserved for issuance, percentage of number of shares of common stock outstanding			1.00%
Common stock available for issuance										138,757
Number of shares issued						31,027
2016 ESPP [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation | $				$ 100,000		$ 100,000

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Detail) - Bonus Restricted Stock Units (RSUs) [Member]	6 Months Ended
	Jun. 30, 2020$ / sharesshares
Number of Shares
Granted	4,519
Unvested balance at June 30, 2020	4,519
Weighted Average Grant Date Fair Value
Granted | $ / shares	$ 1.77

Stock-based Compensation - Su_2

Stock-based Compensation - Summary of Stock-based Compensation Expense, Including Shares Issued to Consultants for Services (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 731	$ 1,021	$ 1,310	$ 1,991
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	266	399	496	769
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Stock-based compensation expense	$ 465	$ 622	$ 814	$ 1,222

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Number of Shares
Outstanding at December 31, 2019	4,364,839
Granted	1,663,000
Forfeited	(388,796)
Outstanding at June 30, 2020	5,639,043	4,364,839
Exercisable at June 30, 2020	2,675,930
Vested and expected to vest at June 30, 2020	5,555,793
Weighted Average Exercise Price Per Share
Outstanding at December 31, 2019	$ 5.30
Granted	1.56
Forfeited	6.11
Outstanding at June 30, 2020	4.14	$ 5.30
Exercisable at June 30, 2020	5.72
Vested and expected to vest at June 30, 2020	$ 4.17
Weighted Average Remaining Contractual Term, Outstanding	7 years 7 months 24 days	7 years 3 months 25 days
Weighted Average Remaining Contractual Term, Exercisable at March 31, 2020	6 years 4 months 2 days
Weighted Average Remaining Contractual Term, Vested and expected to vest at March 31, 2020	7 years 9 months 3 days
Aggregate Intrinsic Value, Outstanding	$ 33	$ 132
Aggregate Intrinsic Value, Exercisable at March 31, 2020	16
Aggregate Intrinsic Value, Vested and expected to vest at March 31, 2020	$ 33

Significant Agreements - Additi

Significant Agreements - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	6 Months Ended
	Feb. 28, 2019	Jun. 30, 2019	Jun. 30, 2020	Dec. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue		$ 5,000
Genentech [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Nonrefundable cash payment			$ 5,000	$ 5,000
Future milestone payment				$ 96,000
Revenue	$ 5,000

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Federal income tax benefit	$ 0	$ 0	$ 0	$ 0
State income tax benefit	$ 0	$ 0	$ 0	$ 0

Net Loss per Share - Schedule o

Net Loss per Share - Schedule of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net loss	$ (8,893)	$ (20,018)	$ (18,771)	$ (34,436)
Denominator:
Weighted average common shares outstanding—basic and diluted	52,147,656	51,097,456	52,147,145	51,037,514
Net loss per share—basic and diluted	$ (0.17)	$ (0.39)	$ (0.36)	$ (0.67)

Net Loss per Share - Schedule_2

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Computation of Diluted Weighted-average Shares Outstanding (Detail) - shares	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	5,643,562	4,598,850
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	5,639,043	4,598,850
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	4,519

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jan. 19, 2018
Leases [Abstract]
Operating lease, initial term			10 years
Operating lease, option to extend additional term			7 years
Operating lease assets	$ 12,002	$ 12,631

Leases - Elements of Lease Expe

Leases - Elements of Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lease cost
Operating lease cost	$ 462	$ 459	$ 925	$ 921
Variable lease cost	158	179	261	316
Total lease cost	$ 620	$ 638	1,186	1,237
Other information
Operating cash flows used for operating leases			$ 859	$ 836
Weighted-average remaining lease term	7 years 10 months 2 days	8 years 10 months 2 days	7 years 10 months 2 days	8 years 10 months 2 days
Weighted-average discount rate	4.50%	4.50%	4.50%	4.50%

Leases - Schedule of Future Lea

Leases - Schedule of Future Lease Payments under Noncancelable Leases (Detail) $ in Thousands	Jun. 30, 2020USD ($)
Leases [Abstract]
2020	$ 874
2021	1,780
2022	1,829
2023	1,880
2024	1,931
Thereafter	6,825
Total lease payments	15,119
Less: imputed interest	(2,486)
Total operating lease liabilities	$ 12,633