Adicet Bio (ACET) 10-Q 5 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 01, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2019
Entity Registrant Name	resTORbio, Inc.
Entity Central Index Key	0001720580
Trading Symbol	TORC
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-38359
Entity Tax Identification Number	81-3305277
Entity Address, Address Line One	500 Boylston Street
Entity Address, Address Line Two	13th Floor
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
City Area Code	(857)
Local Phone Number	315-5528
Entity Common Stock, Shares Outstanding		36,443,631
Security Exchange Name	NASDAQ
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 23,621	$ 7,042
Marketable securities	93,641	100,986
Prepaid expenses	3,998	1,491
Other current assets	21	15
Total current assets	121,281	109,534
Restricted cash	245	84
Property and equipment, net	437	321
Total assets	121,963	109,939
Current liabilities:
Accounts payable	9,973	2,989
Accrued liabilities	2,220	2,727
Total current liabilities	12,193	5,716
Other liabilities	6	19
Total liabilities	12,199	5,735
Commitments and contingencies (Note 10)
Stockholders’ equity:
Common stock, $0.0001 par value, 150,000,000 shares authorized as of September 30, 2019 and December 31, 2018; 36,443,631 and 28,055,344 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively; 36,443,631 and 28,054,344 shares vested as of September 30, 2019 and December 31, 2018, respectively	4	3
Additional paid-in capital	234,893	175,635
Accumulated deficit	(125,242)	(71,393)
Accumulated other comprehensive gain (loss)	109	(41)
Total stockholders’ equity	109,764	104,204
Total liabilities and stockholders’ equity	$ 121,963	$ 109,939

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (unaudited) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares issued	36,443,631	28,055,344
Common stock, shares outstanding	36,443,631	28,055,344
Common stock, shares vested	36,443,631	28,054,344

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Operating expenses:
Research and development	$ 22,118	$ 6,765	$ 47,523	$ 26,716
General and administrative	3,043	2,267	8,498	6,629
Total operating expenses	25,161	9,032	56,021	33,345
Loss from operations	(25,161)	(9,032)	(56,021)	(33,345)
Other income, net	725	625	2,203	1,488
Loss before income taxes	(24,436)	(8,407)	(53,818)	(31,857)
Income tax expense	12		31
Net loss	$ (24,448)	$ (8,407)	$ (53,849)	$ (31,857)
Net loss per share, basic and diluted	$ (0.68)	$ (0.30)	$ (1.51)	$ (1.23)
Weighted-average common shares used in computing net loss per share, basic and diluted	36,217,040	28,046,723	35,585,980	25,895,933
Other comprehensive gain (loss):
Net loss	$ (24,448)	$ (8,407)	$ (53,849)	$ (31,857)
Unrealized (loss) gain on marketable securities	(61)	(46)	150	(76)
Comprehensive loss	$ (24,509)	$ (8,453)	$ (53,699)	$ (31,933)

Condensed Consolidated Statem_2

Condensed Consolidated Statement of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Restricted Shares	Restricted stock units	Public Offering	At-the-Market Offering	Initial Public Offering	Common Stock	Common StockRestricted Shares	Common StockRestricted stock units	Common StockPublic Offering	Common StockAt-the-Market Offering	Common StockInitial Public Offering	Additional Pain In Capital	Additional Pain In CapitalRestricted Shares	Additional Pain In CapitalRestricted stock units	Additional Pain In CapitalPublic Offering	Additional Pain In CapitalAt-the-Market Offering	Additional Pain In CapitalInitial Public Offering	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017	$ (31,929)								$ 1						$ 1,849						$ (33,779)	$ 0
Balance, shares at Dec. 31, 2017									4,562,640
Balance, temporary equity, shares at Dec. 31, 2017		15,527,951	4,792,716
Balance, temporary equity at Dec. 31, 2017		$ 41,674	$ 39,946
Conversion of convertible preferred stock into common stock upon the closing of initial public offering, Shares		(15,527,951)	(4,792,716)						15,870,559
Conversion of convertible preferred stock into common stock upon the closing of initial public offering	81,620	$ (41,674)	$ (39,946)						$ 1						81,619
Issuance of common stock								$ 89,370						$ 1						$ 89,369
Issuance of common stock, Shares														6,516,667
Vesting of restricted shares				$ 865												$ 865
Vesting of restricted shares, shares										1,096,449
Stock-based compensation expense	316														316
Net loss	(9,859)																				(9,859)
Balance at Mar. 31, 2018	130,383								$ 3						174,018						(43,638)	0
Balance, shares at Mar. 31, 2018									28,046,315
Balance, temporary equity, shares at Mar. 31, 2018		0	0
Balance, temporary equity at Mar. 31, 2018		$ 0	$ 0
Balance at Dec. 31, 2017	(31,929)								$ 1						1,849						(33,779)	0
Balance, shares at Dec. 31, 2017									4,562,640
Balance, temporary equity, shares at Dec. 31, 2017		15,527,951	4,792,716
Balance, temporary equity at Dec. 31, 2017		$ 41,674	$ 39,946
Net loss	(31,857)
Unrealized (loss) gain on marketable securities	(76)
Balance at Sep. 30, 2018	109,340								$ 3						175,049						(65,636)	(76)
Balance, shares at Sep. 30, 2018									28,046,815
Balance, temporary equity, shares at Sep. 30, 2018		0	0
Balance, temporary equity at Sep. 30, 2018		$ 0	$ 0
Balance at Mar. 31, 2018	130,383								$ 3						174,018						(43,638)	0
Balance, shares at Mar. 31, 2018									28,046,315
Balance, temporary equity, shares at Mar. 31, 2018		0	0
Balance, temporary equity at Mar. 31, 2018		$ 0	$ 0
Stock-based compensation expense	402														402
Net loss	(13,591)																				(13,591)
Unrealized (loss) gain on marketable securities	(30)																					(30)
Balance at Jun. 30, 2018	117,164								$ 3						174,420						(57,229)	(30)
Balance, shares at Jun. 30, 2018									28,046,315
Balance, temporary equity, shares at Jun. 30, 2018		0	0
Balance, temporary equity at Jun. 30, 2018		$ 0	$ 0
Vesting of restricted shares, shares										500
Stock-based compensation expense	629														629
Net loss	(8,407)																				(8,407)
Unrealized (loss) gain on marketable securities	(46)																					(46)
Balance at Sep. 30, 2018	109,340								$ 3						175,049						(65,636)	(76)
Balance, shares at Sep. 30, 2018									28,046,815
Balance, temporary equity, shares at Sep. 30, 2018		0	0
Balance, temporary equity at Sep. 30, 2018		$ 0	$ 0
Balance at Dec. 31, 2018	$ 104,204								$ 3						175,635						(71,393)	(41)
Balance, shares at Dec. 31, 2018	28,054,344								28,054,344
Issuance of common stock						$ 46,585						$ 1						$ 46,584
Issuance of common stock, Shares												7,200,000
Vesting of restricted shares				$ 1												$ 1
Vesting of restricted shares, shares										500
Stock-based compensation expense	$ 662														662
Net loss	(11,069)																				(11,069)
Unrealized (loss) gain on marketable securities	73																					73
Balance at Mar. 31, 2019	140,456								$ 4						222,882						(82,462)	32
Balance, shares at Mar. 31, 2019									35,254,844
Balance at Dec. 31, 2018	$ 104,204								$ 3						175,635						(71,393)	(41)
Balance, shares at Dec. 31, 2018	28,054,344								28,054,344
Net loss	$ (53,849)
Unrealized (loss) gain on marketable securities	150
Balance at Sep. 30, 2019	$ 109,764								$ 4						234,893						(125,242)	109
Balance, shares at Sep. 30, 2019	36,443,631								36,443,631
Balance at Mar. 31, 2019	$ 140,456								$ 4						222,882						(82,462)	32
Balance, shares at Mar. 31, 2019									35,254,844
Issuance of common stock						$ 3,163	$ 582											$ 3,163	$ 582
Issuance of common stock, Shares												487,934	62,663
Vesting of restricted shares, shares										500
Vesting of restricted stock units, net of shares withheld for taxes					$ (15)												$ (15)
Vesting of restricted stock units, net of shares withheld for taxes, shares											4,423
Exercise of stock options	6														6
Exercise of stock options, Shares									7,029
Stock-based compensation expense	944														944
Net loss	(18,332)																				(18,332)
Unrealized (loss) gain on marketable securities	138																					138
Balance at Jun. 30, 2019	126,941								$ 4						227,561						(100,794)	170
Balance, shares at Jun. 30, 2019									35,817,393
Issuance of common stock							$ 6,135												$ 6,135
Issuance of common stock, Shares													625,137
Vesting of restricted stock units, net of shares withheld for taxes					$ (5)												$ (5)
Vesting of restricted stock units, net of shares withheld for taxes, shares											1,101
Stock-based compensation expense	1,202														1,202
Net loss	(24,448)																				(24,448)
Unrealized (loss) gain on marketable securities	(61)																					(61)
Balance at Sep. 30, 2019	$ 109,764								$ 4						$ 234,893						$ (125,242)	$ 109
Balance, shares at Sep. 30, 2019	36,443,631								36,443,631

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - Common Stock - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2018
Public Offering
Stock issuance cost		$ 228	$ 3,455
At-the-Market Offering
Stock issuance cost	$ 221	$ 64
Initial Public Offering
Stock issuance cost				$ 8,379

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net loss	$ (53,849)	$ (31,857)
Adjustments to reconcile net loss to net cash used in operating activities:
Accretion on marketable securities	(901)	(305)
Depreciation and amortization expense	90	55
Loss on disposal of property and equipment	35
Stock-based compensation expense	2,808	2,212
Changes in operating assets and liabilities:
Restricted cash	(161)	(84)
Prepaid expenses and other current assets	(2,513)	(769)
Accounts payable	6,975	2,807
Accrued liabilities	(507)	(386)
Funding advance		500
Other liabilities	(13)	22
Net cash used in operating activities	(48,036)	(27,805)
Investing activities:
Purchases of property and equipment	(241)	(333)
Maturities of marketable securities	105,500
Purchases of marketable securities	(97,104)	(92,293)
Net cash provided by (used in) investing activities	8,155	(92,626)
Financing activities:
Proceeds from public offering, net of issuance costs	49,748	89,938
Proceeds from at-the-market offering, net of issuance costs	6,726
Taxes paid related to net share settlement of restricted stock units	(20)
Proceeds from exercising stock options	6
Net cash provided by financing activities	56,460	89,938
Net increase (decrease) in cash and cash equivalents	16,579	(30,493)
Cash and cash equivalents at beginning of period	7,042	53,349
Cash and cash equivalents at end of period	23,621	22,856
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable		2
Conversion of redeemable convertible preferred stock into common stock		$ 81,620
Issuance costs associated with at-the-market offering included in accounts payable	$ 9

Organization

Organization	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization resTORbio, Inc. (collectively referred to with its wholly-owned, controlled subsidiary, resTORbio Securities Corp. as “resTORbio” or the “Company”) was incorporated in the State of Delaware on July 5, 2016. The Company is a clinical-stage biopharmaceutical company developing innovative medicines that target the biology of aging to prevent or treat aging-related diseases Since inception, the Company has been primarily involved in research and development activities. The Company devotes substantially all of its efforts to product research and development, initial market development and raising capital. The Company has not generated any product revenue related to its primary business purpose to date and is subject to a number of risks similar to those of other early stage companies, including dependence on key individuals, competition from other companies, the need for development of commercially viable products and the need to obtain adequate additional financing to fund the development of its product candidates. The Company is also subject to a number of risks similar to other companies in the life sciences industry, including regulatory approval of products, uncertainty of market acceptance of products, competition from substitute products and larger companies, the need to obtain additional financing, compliance with government regulations, protection of proprietary technology, product liability, and dependence on third parties and key individuals. Public Offering On March 22, 2019, the Company completed an underwritten public offering, whereby the Company sold 7,200,000 shares of its common stock at a price of $6.95 per share. The aggregate net proceeds received by the Company from the offering were approximately $46.6 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company of $3.5 million. In addition, the Company granted the underwriters a 30-day option to purchase up to an additional 1,080,000 shares of common stock at the public offering price, less underwriting discounts and commissions. On April 10, 2019, the Company sold an additional 487,934 shares of its common stock at a price of $6.95 per share. The aggregate net proceeds received by the Company were approximately $3.2 million, after deducting underwriting discounts and commissions and other offering expenses payable by the Company of $0.2 million. The remainder of the option expired unexercised. At-the-Market Offering On February 1, 2019, the Company filed a Registration Statement on Form S-3 (the “Shelf”) with the Securities and Exchange Commission (the “SEC”) in relation to the registration of common stock, preferred stock, warrants and/or units of any combination thereof (collectively, the “Securities”). The Company also simultaneously entered into a Controlled Equity Offering Sales Agreement (the “Sales Agreement”) with SVB Leerink LLC and Cantor Fitzgerald & Co. (collectively, the “Sales Agents”), to provide for the offering, issuance and sale by the Company of up to an aggregate of $50.0 million of its common stock from time to time in “at-the-market” offerings under the Shelf and subject to the limitations thereof. The Company will pay to the Sales Agents cash commissions of 3.0 percent of the gross proceeds of sales of common stock under the Sales Agreement. Beginning in June 2019 through September 30, 2019, based on settlement date, the Company sold approximately 688,000 shares of common stock at a weighted-average selling price of $10.18 per share in accordance with the Sales Agreement for aggregate net proceeds of $6.7 million, after payment of cash commissions of 3.0 percent of the gross proceeds to the Sales Agent and incurred issuance costs of approximately $75,000 related to legal, accounting, and other fees in connection with the sale. As of September 30, 2019, $43.0 million remained available for sale under the Sales Agreement. Liquidity In the course of its development activities, the Company has sustained operating losses and expects such losses to continue over the next several years. The Company’s ultimate success depends on the outcome of its research and development activities. The Company has incurred net losses from operations since inception and has an accumulated deficit of $125.2 million as of September 30, 2019. As of September 30, 2019, the Company had $117.3 million of cash, cash equivalents, and marketable securities, which the Company believes will be sufficient to fund the Company’s current operating plan through at least the next twelve months from the date of filing this Quarterly Report on Form 10-Q.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements are unaudited. The unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and, in the opinion of management, reflect all adjustments of a normal recurring nature necessary for a fair statement of the Company's financial position as of September 30, 2019 and the results of operations and cash flows for the interim periods ended September 30, 2019 and 2018. The condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 that was filed with the Securities and Exchange Commission (“SEC”) on March 18, 2019 (the “2018 Form 10-K”). Interim results are not necessarily indicative of results for a full year or for any other interim period. The condensed consolidated financial statements include the accounts of resTORbio, Inc. and its wholly owned subsidiary, resTORbio Securities Corp. All inter-company transactions and balances have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities, as of the date of the condensed consolidated financial statements, and the reported amounts of any expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to accrued liabilities, income taxes, and stock-based compensation expense. Management bases its estimates on historical experience, and on various other market-specific relevant assumptions that management believes to be reasonable, under the circumstances. Actual results may differ from those estimates or assumptions. Summary of Significant Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2018, and the notes thereto, which are included in the 2018 Form 10-K. There have been no material changes in the Company’s significant accounting policies during the three and nine months ended September 30, 2019. Fair Value Measurements Fair value is defined as the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. The authoritative accounting guidance describes a fair value hierarchy based on three levels of inputs that may be used to measure fair value, of which the first two are considered observable and the last is considered unobservable. These levels of inputs are as follows: Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3—Unobservable inputs that reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. The following table summarizes assets measured at fair value on a recurring basis at September 30, 2019 (in thousands): Active Observable Unobservable September 30, Markets Inputs Inputs Description 2019 (Level 1) (Level 2) (Level 3) Cash $ 8 $ 8 $ — $ — Money market funds (included in cash and cash equivalents) 23,613 23,613 — — U.S. treasury securities (included in marketable securities) 93,641 93,641 — — Total $ 117,262 $ 117,262 $ — $ — The following table summarizes assets measured at fair value on a recurring basis at December 31, 2018 (in thousands): Active Observable Unobservable December 31, Markets Inputs Inputs Description 2018 (Level 1) (Level 2) (Level 3) Money market funds (included in cash and cash equivalents) $ 6,804 $ 6,804 $ — $ — U.S. treasury securities (included in cash and cash equivalents) 238 238 — — U.S. treasury securities (included in marketable securities) 100,986 100,986 — — Total $ 108,028 $ 108,028 $ — $ — There have been no changes to the valuation methods utilized by the Company during the three and nine months ended September 30, 2019 and 2018. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the three and nine months ended September 30, 2019 and 2018. Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases The adoption of this standard is expected to have an impact on the amount of the Company’s assets and liabilities presented. The Company expects to utilize the new transition method described in ASU No. 2018-11 and use the effective date as the Company’s date of initial application for the new standard. The Company expects to elect the available package of practical expedients in transition which would allow it to not re-assess whether existing or expired arrangements contain a lease, the lease classification of existing or expired leases, or whether previous initial direct costs would qualify for capitalization under the new lease standard. As of September 30, 2019, the Company has not elected to early adopt the guidance or determined the effect that the adoption of this guidance will have on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows In July 2017, the FASB issued ASU 2017-11, Accounting for Certain Financial Instruments with Down Round Features In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting Revenue from Contracts with Customers (“ASC 606”)

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Marketable Securities	3. Marketable Securities As of September 30, 2019, the fair value of marketable securities by type of security was as follows (in thousands): Amortized Unrealized Unrealized Fair Description Cost Gains Losses Value U.S. government agency securities and treasuries $ 93,532 $ 109 $ — $ 93,641 Total $ 93,532 $ 109 $ — $ 93,641 As of December 31, 2018, the fair value of marketable securities by type of security was as follows (in thousands): Amortized Unrealized Unrealized Fair Description Cost Gains Losses Value U.S. government agency securities and treasuries $ 101,027 $ — $ (41) $ 100,986 Total $ 101,027 $ — $ (41) $ 100,986 The estimated fair value and amortized cost of the Company’s available-for-sale securities by contractual maturity are summarized as follows (in thousands): September 30, 2019 Amortized Fair Cost Value Due in one year or less $ 93,532 $ 93,641 Total $ 93,532 $ 93,641 December 31, 2018 Amortized Fair Cost Value Due in one year or less $ 101,027 $ 100,986 Total $ 101,027 $ 100,986

Property and Equipment, Net

Property and Equipment, Net	9 Months Ended
	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, Net	4. Property and equipment, net Property and equipment, net consists of the following: September 30, 2019 December 31, 2018 (In thousands) Leasehold improvements $ — $ 65 Machinery and equipment 38 38 Furniture and fixtures 397 194 Computers 111 76 Office equipment 11 11 Software 22 22 Total property and equipment 579 406 Less: accumulated depreciation and amortization (142 ) (85 ) Property and equipment, net $ 437 $ 321 Depreciation and amortization expense was $34,000 and $90,000 for the three and nine months ended September 30, 2019, respectively. Depreciation and amortization expense was $24,000 and $55,000 for the three and nine months ended September 30, 2018, respectively.

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2019
Payables And Accruals [Abstract]
Accrued Liabilities	5. Accrued Liabilities Accrued liabilities consist of the following: September 30, 2019 December 31, 2018 (In thousands) Accrued payroll and related expenses $ 1,533 $ 1,189 Accrued research and development expenses 514 1,028 Other 173 510 Total accrued liabilities $ 2,220 $ 2,727

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License Agreements	6. License Agreements Novartis License Agreement On March 23, 2017, the Company entered into an exclusive license agreement with Novartis International Pharmaceutical Ltd. (“Novartis”). Under the agreement, Novartis granted the Company an exclusive, field-restricted, worldwide license, to certain intellectual property rights owned or controlled by Novartis, to develop, commercialize and sell one or more therapeutic products comprising RTB101 or RTB101 in combination with everolimus in a fixed dose combination. The exclusive field under the license agreement is for the treatment, prevention and diagnosis of disease and other conditions in all indications in humans and animals. The agreement may be terminated by either party upon a material breach by the other party that is not cured within 60 days after written notice. The Company may terminate the agreement in its entirety or on a product-by-product or country-by-country basis with or without cause with 60 days’ prior written notice. Novartis may terminate the portion of the agreement related to everolimus if the Company fails to use commercially reasonable efforts to research, develop and commercialize a product utilizing everolimus for a period of three years. Novartis may terminate the license agreement upon the Company’s bankruptcy, insolvency, dissolution or winding up. As initial consideration for the license, the Company issued Novartis Institutes for Biomedical Research, Inc., or NIBR, 2,587,992 shares of our Series A preferred Stock. As additional consideration for the license, the Company is required to pay up to an aggregate of $4.3 million upon the satisfaction of clinical milestones, up to an aggregate of $24 million upon the satisfaction of regulatory milestones for the first indication approved, and up to an aggregate of $18 million upon the satisfaction of regulatory milestones for the second indication approved. In addition, the Company is required to pay up to an aggregate of $125 million upon the satisfaction of commercial milestones, based on the amount of annual net sales. The Company is also required to pay tiered royalties ranging from a mid single-digit percentage to a low teen-digit percentage on annual net sales of products. These royalty obligations last on a product-by-product and country-by-country basis until the latest of (i) the expiration of the last valid claim of a Novartis patent covering a subject product, (ii) the expiration of any regulatory exclusivity for the subject product in a country, or (iii) the 10 th Milestone payments to Novartis are recorded as research and development expenses in the condensed consolidated statements of operations once achievement of each associated milestone is considered probable. In May 2017, the Company initiated a Phase 2b clinical trial for a first indication, triggering the first milestone payment under the agreement. Accordingly, the Company paid the related $0.3 million payment in May 2017. In May 2019, the Company initiated a Phase 3 clinical trial for the first indication, triggering another milestone payment of $2.5 million under the agreement. As of September 30, 2019, none of the remaining clinical milestones, regulatory milestones, sales milestones, or royalties is probable.

Research Funding Agreements

Research Funding Agreements	9 Months Ended
	Sep. 30, 2019
Research Funding Agreement [Abstract]
Research Funding Agreement	7. Research Funding Agreement On March 6, 2018, the Company and the Silverstein Foundation for Parkinson’s with GBA (the “Silverstein Foundation”) entered into a research funding agreement (the “Funding Agreement”). One of the Company’s directors is a co-founder and current trustee of the Silverstein Foundation. Under the terms of the Funding Agreement, the Silverstein Foundation will partially fund the preclinical research, development work, and Phase 2 clinical trial expenses (the “Research”) to be conducted and borne by the Company in connection with the development of RTB101, alone or in combination with other products (the “Product”). Upon execution of the Funding Agreement, the Silverstein Foundation paid the Company an upfront sum of $0.5 million (the “Funding Amount”). The Company is entitled to use the Funding Amount solely to conduct the Research and is obligated to repay the Funding Amount in full to the Silverstein Foundation if it successfully conducts a positive Phase 3 clinical trial of the Product for Parkinson’s Disease. The Company is solely responsible for commencing and conducting the Research and will furnish periodic progress updates to the Silverstein Foundation throughout the term of the Funding Agreement. After completing the Research, the Company must provide the Silverstein Foundation with a formal report describing the work performed and the results of the Research. The Company recognizes proceeds received from the Silverstein Foundation as a reduction to research and development expenses, rather than as revenue, in the condensed consolidated statements of operations and comprehensive loss because the corresponding Funding Agreement does not contain specified performance obligations other than to conduct research on a particular program or in a particular field and no obligations to deliver specified products or technology. For funds received under the Funding Agreement, the Company recognizes a reduction in research and development expenses in an amount equal to the qualifying expenses incurred in each period up to the amount funded by the Silverstein Foundation. Funding that has been received by the Company in advance of incurring qualifying expenses is recorded in the condensed consolidated balance sheet as funding advance. No qualifying expenses were incurred during the three and nine months ended September 30, 2019 and 2018. As of September 30, 2019, $0.5 million qualifying expenses have been incurred. Therefore, all amounts received have been recorded as a reduction of the research and development expense.

Preferred Stock and Common Stoc

Preferred Stock and Common Stock	9 Months Ended
	Sep. 30, 2019
Temporary Equity Disclosure [Abstract]
Preferred Stock and Common Stock	8. Preferred Stock and Common Stock As of September 30, 2019, the Company had 10,000,000 shares of preferred stock and 150,000,000 shares of common stock authorized. None of the authorized preferred stock and 36,443,631 shares of common stock were issued and outstanding as of September 30, 2019. Reserve for future issuance The Company has reserved the following number of shares of common stock for future issuance upon the exercise of options, vesting of restricted stock units or grant of equity awards: September 30, 2019 December 31, 2018 Options issued and outstanding 2,285,322 1,122,677 Unvested restricted stock units 17,160 24,960 Options available for future grants 1,303,121 1,350,582 Shares available for issuance under the 2018 ESPP 555,583 275,030 Total 4,161,186 2,773,249

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9. Stock-based Compensation In 2017, the Company adopted the 2017 Stock Incentive Plan (the “2017 Plan”). Under the 2017 Plan, a total of 537,914 shares of the Company’s common stock were reserved for the issuance of stock options to employees, directors, and consultants under terms and provisions established by the Board of Directors (the “Board”). In connection with the Company’s initial public offering completed in January 2018, the Board adopted and the Company’s stockholders approved the 2018 Stock Incentive Plan (“2018 Plan”), which became effective on the date immediately preceding the date on which the Company’s registration statement became effective. The 2018 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock awards, restricted stock units, stock appreciation rights, and other stock-based awards. The Company’s employees, officers, directors, consultants and advisors are eligible to receive awards under the 2018 Plan. The number of shares of common stock that were initially reserved for issuance under the 2018 Plan were 2,200,260 shares. The 2018 Plan provides that the number of shares reserved and available for issuance under the plan will automatically increase each January 1, beginning on January 1, 2019, by 4% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Board. On January 1, 2019, as a result of the foregoing evergreen provision, the number of shares of common stock available for issuance under the 2018 Plan automatically increased from 2,200,260 to 3,322,473 shares. Since the date of effectiveness of the 2018 Plan, the Company has not and will not grant any further awards under the 2017 Plan. However, any shares of common stock subject to awards under the 2017 Plan that expire, terminate, or otherwise are surrendered, canceled, forfeited or repurchased without having been fully exercised or resulting in any common stock being issued will become available for issuance under the 2018 Plan. Stock-based Compensation Expense Total stock-based compensation expense is recognized for stock options granted to employees and non-employees and has been reported in the Company’s condensed consolidated statements of operations as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development $ 633 $ 229 $ 1,409 $ 955 General and administrative 569 400 1,399 1,257 Total stock-based compensation expense $ 1,202 $ 629 $ 2,808 $ 2,212 Stock Options The following table summarizes stock option activity under the Plans: Shares Available for Grant Number of Options Outstanding Weighted- Average Exercise Price per Option Weighted- Average Remaining Contract Term Aggregate Intrinsic Value (In thousands) Outstanding, December 31, 2018 1,350,582 1,122,677 $ 11.63 9.22 Shares reserved for issuance 1,122,213 Options granted (1,286,524 ) 1,286,524 8.66 Options exercised — (7,029 ) 0.79 Options cancelled 116,850 (116,850 ) 10.25 Outstanding, September 30, 2019 1,303,121 2,285,322 10.05 9.05 $ 1,360 Exercisable, September 30, 2019 373,574 11.40 8.33 387 Vested and expected to vest, September 30, 2019 2,285,322 8.63 9.05 1,360 The aggregate intrinsic values of options outstanding, exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock as of September 30, 2019. A total of 7,029 options were exercised for cash proceeds of approximately $6,000 during the nine months ended September 30, 2019. During the nine months ended September 30, 2019, the Company granted options to employees and directors to purchase an aggregate of 1,276,684 common shares with a weighted-average grant date fair value of $6.69 per share. During the nine months ended September 30, 2019, the Company granted options to non-employees to purchase an aggregate of 9,840 common shares with a weighted-average grant date fair value of $7.61 per share. The expense related to options granted to employees and directors for the three and nine months ended September 30, 2019 was $1.2 million and $2.7 million, respectively. The expense related to options granted to non-employees for the three and nine months ended September 30, 2019 was $18,000 and $66,000, respectively. The expense related to options granted to employees and directors was $0.6 million and $1.2 million for the three and nine months ended September 30, 2018, respectively. The expense related to options granted to non-employees was $37,000 and $64,000, for the three and nine months ended September 30, 2018, respectively. As of September 30, 2019, the total unrecognized compensation expense related to unvested options granted to employees and directors was $12.5 million, which the Company expects to recognize over an estimated weighted-average period of 3.00 years. As of September 30, 2019, the total unrecognized compensation expense related to unvested non-employee options was $0.2 million, which the Company expects to recognize over an estimated weighted-average period of 2.39 years. The fair value of stock options for employees and non-employees was estimated using a Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Employees and directors: Fair value of common stock $9.36 - $10.66 $9.03 - $13.94 $6.97 - $10.66 $8.57 - $15.45 Expected term (in years) 6.1 5.9 - 6.1 5.5 - 6.1 5.8 - 6.6 Expected volatility 92.4% - 92.6% 89.8% - 90.6% 92.4% - 104.8% 75.9% - 90.6% Risk-free interest rate 1.4% - 1.8% 2.8% - 2.9% 1.4% - 2.6% 2.4% - 2.9% Expected dividend yield 0.0% 0.0% 0.0% 0.0% Non-employees: Fair value of common stock $8.84 - $10.26 — $6.82 - $10.26 $15.45 Expected term (in years) 7.7 - 9.5 — 7.7 - 10.0 10.0 Expected volatility 89.7% - 90.8% — 89.7% - 94.2% 77.9% Risk-free interest rate 1.7% - 1.9% — 1.7% - 2.6% 2.7% Expected dividend yield 0.0% — 0.0% 0.0% Restricted Stock On April 17, 2018, the Company granted 2,000 shares of restricted stock to a consultant. The restrictions lapsed in four equal quarterly installments and were fully vested on the first anniversary of such grant. Compensation expenses of such unvested shares were remeasured at fair value until vested at each reporting date. The summary of restricted stock activity and related information follows: Number of Restricted Shares Outstanding Unvested shares — December 31, 2018 1,000 Vested (1,000 ) Unvested shares — September 30, 2019 — The Company recognized $0 and $4,000 of stock-based compensation expense related to restricted shares during the three and nine months ended September 30, 2019, respectively. The Company recognized $11,000 and $0.9 million of stock-based compensation expense related to restricted shares during the three and nine months ended September 30, 2018, respectively. As of September 30, 2019, there was no unrecognized stock-based compensation expense related to unvested restricted stock. There were no restricted stock awards issued during the nine months ended September 30, 2019. Restricted Stock Units In May 2018, the Company granted 24,960 restricted stock units to an employee with a grant date fair value of $9.03 per share. The summary of restricted stock unit activity and related information follows: Number of Restricted Stock Units Outstanding Unvested shares — December 31, 2018 24,960 Granted — Vested (7,800 ) Unvested shares — September 30, 2019 17,160 The Company recognized $14,000 and $42,000 of stock-based compensation expense related to restricted stock units during the three and nine months ended September 30, 2019, respectively. As of September 30, 2019, there was $0.1 million of unrecognized stock-based compensation expense related to unvested restricted stock units. This amount is expected to be recognized over a remaining weighted-average period of 2.64 years. There were no restricted stock units granted to employees or non-employees during the three and nine months ended September 30, 2019. The Company recognized $14,000 and $20,000 of stock-based compensation expense related to restricted stock units during the three and nine months ended September 30, 2018, respectively. 2018 Employee Stock Purchase Plan The Board adopted and the Company’s stockholders approved the 2018 Employee Stock Purchase Plan (“2018 ESPP”), which became effective on the date immediately preceding the date on which the Company’s registration statement became effective. The 2018 ESPP enables eligible employees to purchase shares of the Company’s Common Stock at a discount. The number of shares of common stock that are reserved for issuance under the 2018 ESPP are 275,030 shares. The 2018 ESPP provides that the number of shares reserved and available for issuance will automatically increase each January 1, beginning on January 1, 2019 and increasing each January 1 thereafter through January 1, 2028, by the least of (i) 1% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31; (ii) 543,926 shares or (iii) such number of shares as determined by the ESPP administrator. On January 1, 2019, as a result of the foregoing evergreen provision, the number of shares of common stock available for issuance under the 2018 ESPP automatically increased from 275,030 to 555,583 shares.

Commitments and Contingences

Commitments and Contingences	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingences	10. Commitments and Contingences In April 2019, the Company amended its multi-year lease agreement to relocate its office space in Boston, Massachusetts under an operating lease agreement. The amended lease term is for a period of seven years from the date of relocation on August 1, 2019. The initial annual base rent of the relocation premises is $0.6 million per year, increasing 2% annually. In connection with the lease amendment, the Company issued a new cash-collateralized letter of credit for the benefit of the landlord in the amount of $0.2 million. Obligations to make future minimum lease payments are as follows (in thousands): Minimum Lease Payments Remainder of 2019 $ 147 2020 594 2021 606 2022 618 2023 630 Thereafter 1,686 Total $ 4,281 Litigation The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities as of September 30, 2019 and December 31, 2018.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	11. Net Loss per Share The Company computes basic and diluted losses per share using a methodology that gives effect to the impact of outstanding participating securities (the “two-class” method). Basic net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period and excludes any dilutive effects of share-based awards. Diluted net loss per share is computed giving effect to all potential dilutive common shares, including common stock issuable upon exercise of stock options, convertible preferred stock, and unvested restricted common stock. As the Company had net losses for the three and nine months ended September 30, 2019 and 2018, there is no income allocation required under the two-class method or dilution attributed to weighted average shares outstanding in the calculation of diluted loss per share. The following potentially dilutive securities, prior to the use of the treasury stock method, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive effect (in common stock equivalent shares): As of September 30, 2019 2018 Options issued and outstanding 2,285,322 667,590 Unvested restricted stock units 17,160 24,960 Total 2,302,482 692,550

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	12. Related Party Transactions Since the Company’s incorporation in July 2016, the Company has engaged in transactions with related parties. The Company is a party to an intellectual property license agreement with Novartis. In addition, NIBR, an affiliate of Novartis, is a shareholder of the Company (See Note 6). In May 2019, the Company initiated a Phase 3 clinical trial for the first indication, triggering a milestone payment of $2.5 million under the license agreement. No other payments have been made to Novartis during the three and nine months ended September 30, 2019 and 2018. The Company is a party to a Funding Agreement with the Silverstein Foundation, an entity in which one of the Company’s directors is a co-founder and current trustee. The Company received $0 from the Silverstein Foundation during the nine months ended September 30, 2019 and $0 and $0.5 million during the three and nine months ended September 30, 2018, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements are unaudited. The unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial information and, in the opinion of management, reflect all adjustments of a normal recurring nature necessary for a fair statement of the Company's financial position as of September 30, 2019 and the results of operations and cash flows for the interim periods ended September 30, 2019 and 2018. The condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 that was filed with the Securities and Exchange Commission (“SEC”) on March 18, 2019 (the “2018 Form 10-K”). Interim results are not necessarily indicative of results for a full year or for any other interim period. The condensed consolidated financial statements include the accounts of resTORbio, Inc. and its wholly owned subsidiary, resTORbio Securities Corp. All inter-company transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities, as of the date of the condensed consolidated financial statements, and the reported amounts of any expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to accrued liabilities, income taxes, and stock-based compensation expense. Management bases its estimates on historical experience, and on various other market-specific relevant assumptions that management believes to be reasonable, under the circumstances. Actual results may differ from those estimates or assumptions.
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2018, and the notes thereto, which are included in the 2018 Form 10-K. There have been no material changes in the Company’s significant accounting policies during the three and nine months ended September 30, 2019.
Fair Value Measurements	Fair Value Measurements Fair value is defined as the price at which an asset could be exchanged in a current transaction between knowledgeable, willing parties. The authoritative accounting guidance describes a fair value hierarchy based on three levels of inputs that may be used to measure fair value, of which the first two are considered observable and the last is considered unobservable. These levels of inputs are as follows: Level 1—Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active. Level 3—Unobservable inputs that reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. The following table summarizes assets measured at fair value on a recurring basis at September 30, 2019 (in thousands): Active Observable Unobservable September 30, Markets Inputs Inputs Description 2019 (Level 1) (Level 2) (Level 3) Cash $ 8 $ 8 $ — $ — Money market funds (included in cash and cash equivalents) 23,613 23,613 — — U.S. treasury securities (included in marketable securities) 93,641 93,641 — — Total $ 117,262 $ 117,262 $ — $ — The following table summarizes assets measured at fair value on a recurring basis at December 31, 2018 (in thousands): Active Observable Unobservable December 31, Markets Inputs Inputs Description 2018 (Level 1) (Level 2) (Level 3) Money market funds (included in cash and cash equivalents) $ 6,804 $ 6,804 $ — $ — U.S. treasury securities (included in cash and cash equivalents) 238 238 — — U.S. treasury securities (included in marketable securities) 100,986 100,986 — — Total $ 108,028 $ 108,028 $ — $ — There have been no changes to the valuation methods utilized by the Company during the three and nine months ended September 30, 2019 and 2018. The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of financial instruments between levels during the three and nine months ended September 30, 2019 and 2018.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases The adoption of this standard is expected to have an impact on the amount of the Company’s assets and liabilities presented. The Company expects to utilize the new transition method described in ASU No. 2018-11 and use the effective date as the Company’s date of initial application for the new standard. The Company expects to elect the available package of practical expedients in transition which would allow it to not re-assess whether existing or expired arrangements contain a lease, the lease classification of existing or expired leases, or whether previous initial direct costs would qualify for capitalization under the new lease standard. As of September 30, 2019, the Company has not elected to early adopt the guidance or determined the effect that the adoption of this guidance will have on its consolidated financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows Accounting for Certain Financial Instruments with Down Round Features In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting Revenue from Contracts with Customers (“ASC 606”)

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Assets Measured at Fair Value on Recurring Basis	The following table summarizes assets measured at fair value on a recurring basis at September 30, 2019 (in thousands): Active Observable Unobservable September 30, Markets Inputs Inputs Description 2019 (Level 1) (Level 2) (Level 3) Cash $ 8 $ 8 $ — $ — Money market funds (included in cash and cash equivalents) 23,613 23,613 — — U.S. treasury securities (included in marketable securities) 93,641 93,641 — — Total $ 117,262 $ 117,262 $ — $ — The following table summarizes assets measured at fair value on a recurring basis at December 31, 2018 (in thousands): Active Observable Unobservable December 31, Markets Inputs Inputs Description 2018 (Level 1) (Level 2) (Level 3) Money market funds (included in cash and cash equivalents) $ 6,804 $ 6,804 $ — $ — U.S. treasury securities (included in cash and cash equivalents) 238 238 — — U.S. treasury securities (included in marketable securities) 100,986 100,986 — — Total $ 108,028 $ 108,028 $ — $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Schedule of Fair Value Marketable Securities By Type of Security	As of September 30, 2019, the fair value of marketable securities by type of security was as follows (in thousands): Amortized Unrealized Unrealized Fair Description Cost Gains Losses Value U.S. government agency securities and treasuries $ 93,532 $ 109 $ — $ 93,641 Total $ 93,532 $ 109 $ — $ 93,641 As of December 31, 2018, the fair value of marketable securities by type of security was as follows (in thousands): Amortized Unrealized Unrealized Fair Description Cost Gains Losses Value U.S. government agency securities and treasuries $ 101,027 $ — $ (41) $ 100,986 Total $ 101,027 $ — $ (41) $ 100,986
Schedule of Fair Value and Amortized Cost of Company's Available-for-Sale Securities by Contractual Maturity	The estimated fair value and amortized cost of the Company’s available-for-sale securities by contractual maturity are summarized as follows (in thousands): September 30, 2019 Amortized Fair Cost Value Due in one year or less $ 93,532 $ 93,641 Total $ 93,532 $ 93,641 December 31, 2018 Amortized Fair Cost Value Due in one year or less $ 101,027 $ 100,986 Total $ 101,027 $ 100,986

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	9 Months Ended
	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consists of the following: September 30, 2019 December 31, 2018 (In thousands) Leasehold improvements $ — $ 65 Machinery and equipment 38 38 Furniture and fixtures 397 194 Computers 111 76 Office equipment 11 11 Software 22 22 Total property and equipment 579 406 Less: accumulated depreciation and amortization (142 ) (85 ) Property and equipment, net $ 437 $ 321

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2019
Payables And Accruals [Abstract]
Summary of Accrued Liabilities	Accrued liabilities consist of the following: September 30, 2019 December 31, 2018 (In thousands) Accrued payroll and related expenses $ 1,533 $ 1,189 Accrued research and development expenses 514 1,028 Other 173 510 Total accrued liabilities $ 2,220 $ 2,727

Preferred Stock and Common St_2

Preferred Stock and Common Stock (Tables)	9 Months Ended
	Sep. 30, 2019
Temporary Equity Disclosure [Abstract]
Schedule of Number of Shares of Common Stock Reserved for Future Issuance Text Block	The Company has reserved the following number of shares of common stock for future issuance upon the exercise of options, vesting of restricted stock units or grant of equity awards: September 30, 2019 December 31, 2018 Options issued and outstanding 2,285,322 1,122,677 Unvested restricted stock units 17,160 24,960 Options available for future grants 1,303,121 1,350,582 Shares available for issuance under the 2018 ESPP 555,583 275,030 Total 4,161,186 2,773,249

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-Based Compensation Expense	Total stock-based compensation expense is recognized for stock options granted to employees and non-employees and has been reported in the Company’s condensed consolidated statements of operations as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Research and development $ 633 $ 229 $ 1,409 $ 955 General and administrative 569 400 1,399 1,257 Total stock-based compensation expense $ 1,202 $ 629 $ 2,808 $ 2,212
Summary of Stock Option Activity	The following table summarizes stock option activity under the Plans: Shares Available for Grant Number of Options Outstanding Weighted- Average Exercise Price per Option Weighted- Average Remaining Contract Term Aggregate Intrinsic Value (In thousands) Outstanding, December 31, 2018 1,350,582 1,122,677 $ 11.63 9.22 Shares reserved for issuance 1,122,213 Options granted (1,286,524 ) 1,286,524 8.66 Options exercised — (7,029 ) 0.79 Options cancelled 116,850 (116,850 ) 10.25 Outstanding, September 30, 2019 1,303,121 2,285,322 10.05 9.05 $ 1,360 Exercisable, September 30, 2019 373,574 11.40 8.33 387 Vested and expected to vest, September 30, 2019 2,285,322 8.63 9.05 1,360
Schedule of Assumptions to Estimate Fair Value of Stock Options for Employees and Non-Employees Using Black-Scholes Option Pricing Model	The fair value of stock options for employees and non-employees was estimated using a Black-Scholes option pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 Employees and directors: Fair value of common stock $9.36 - $10.66 $9.03 - $13.94 $6.97 - $10.66 $8.57 - $15.45 Expected term (in years) 6.1 5.9 - 6.1 5.5 - 6.1 5.8 - 6.6 Expected volatility 92.4% - 92.6% 89.8% - 90.6% 92.4% - 104.8% 75.9% - 90.6% Risk-free interest rate 1.4% - 1.8% 2.8% - 2.9% 1.4% - 2.6% 2.4% - 2.9% Expected dividend yield 0.0% 0.0% 0.0% 0.0% Non-employees: Fair value of common stock $8.84 - $10.26 — $6.82 - $10.26 $15.45 Expected term (in years) 7.7 - 9.5 — 7.7 - 10.0 10.0 Expected volatility 89.7% - 90.8% — 89.7% - 94.2% 77.9% Risk-free interest rate 1.7% - 1.9% — 1.7% - 2.6% 2.7% Expected dividend yield 0.0% — 0.0% 0.0%
Summary of Restricted Stock Activity	The summary of restricted stock activity and related information follows: Number of Restricted Shares Outstanding Unvested shares — December 31, 2018 1,000 Vested (1,000 ) Unvested shares — September 30, 2019 —
Summary of Restricted Stock Units Activity	The summary of restricted stock unit activity and related information follows: Number of Restricted Stock Units Outstanding Unvested shares — December 31, 2018 24,960 Granted — Vested (7,800 ) Unvested shares — September 30, 2019 17,160

Commitments and Contingences (T

Commitments and Contingences (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Summary of Obligations Future Minimum Lease Payments	Obligations to make future minimum lease payments are as follows (in thousands): Minimum Lease Payments Remainder of 2019 $ 147 2020 594 2021 606 2022 618 2023 630 Thereafter 1,686 Total $ 4,281

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following potentially dilutive securities, prior to the use of the treasury stock method, have been excluded from the calculation of diluted net loss per share because including them would have had an anti-dilutive effect (in common stock equivalent shares): As of September 30, 2019 2018 Options issued and outstanding 2,285,322 667,590 Unvested restricted stock units 17,160 24,960 Total 2,302,482 692,550

Organization - Additional Infor

Organization - Additional Information (Details) - USD ($)	Apr. 10, 2019	Mar. 22, 2019	Feb. 01, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Entity incorporation date							Jul. 5, 2016
Net proceeds received from offering							$ 49,748,000	$ 89,938,000
Accumulated deficit				$ 125,242,000			125,242,000		$ 71,393,000
Cash, cash equivalents and marketable securities				117,300,000			$ 117,300,000
Initial Public Offering
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of common stock shares sold	487,934	7,200,000
Issuance price per shares	$ 6.95	$ 6.95
Net proceeds received from offering	$ 3,200,000	$ 46,600,000
Underwriting discounts and commissions and other offering expenses	$ 200,000	$ 3,500,000
Net proceeds received from offering						$ 89,370,000
Initial Public Offering | Maximum
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Option to purchase of common stock at public offering price		1,080,000
At-the-Market Offering
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Net proceeds received from offering				$ 6,135,000	$ 582,000
At-the-Market Offering | Controlled Equity Offering Sales Agreement | SVB Leerink LLC and Cantor Fitzgerald and Co
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of common stock shares sold							688,000
Issuance price per shares				$ 10.18			$ 10.18
Maximum aggregate value of common stock available for offering At-the-Market price			$ 50,000,000
Sales commission percentage payable to sales agents in cash			3.00%
Net proceeds received from offering							$ 6,700,000
Issuance costs							75,000
Common stock remained available for offering				$ 43,000,000			$ 43,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Summary of Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	$ 117,262	$ 108,028
Cash
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	8
Money Market Funds | Cash and Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	23,613	6,804
U.S. Treasury Securities | Cash and Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis		238
U.S. Treasury Securities | Marketable Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	93,641	100,986
Active Markets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	117,262	108,028
Active Markets (Level 1) | Cash
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	8
Active Markets (Level 1) | Money Market Funds | Cash and Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	23,613	6,804
Active Markets (Level 1) | U.S. Treasury Securities | Cash and Cash Equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis		238
Active Markets (Level 1) | U.S. Treasury Securities | Marketable Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value on a recurring basis	$ 93,641	$ 100,986

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accounting Policies [Abstract]
Fair value assets transferred from level 1 to level 2	$ 0	$ 0	$ 0	$ 0
Fair value assets transferred from level 2 to level 1	0	0	0	0
Fair value liabilities transferred from level 1 to level 2	0	0	0	0
Fair value liabilities transferred from level 2 to level 1	0	0	0	0
Fair value measurement with unobservable inputs reconciliation recurring basis asset transfers net	0	0	0	0
Fair value measurement with unobservable inputs reconciliation recurring basis liabilities transfers net	$ 0	$ 0	$ 0	$ 0

Marketable Securities - Schedul

Marketable Securities - Schedule of Fair Value Marketable Securities By Type of Security (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Marketable Securities [Line Items]
Amortized Cost	$ 93,532	$ 101,027
Unrealized Gains	109
Unrealized Losses		(41)
Fair Value	93,641	100,986
U.S. Government Agency Securities and Treasuries
Marketable Securities [Line Items]
Amortized Cost	93,532	101,027
Unrealized Gains	109
Unrealized Losses		(41)
Fair Value	$ 93,641	$ 100,986

Marketable Securities - Sched_2

Marketable Securities - Schedule of Fair Value and Amortized Cost of Company's Available-for-Sale Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Due in one year or less, Amortized Cost	$ 93,532	$ 101,027
Total, Amortized Cost	93,532	101,027
Due in one year or less, Fair Value	93,641	100,986
Total, Fair Value	$ 93,641	$ 100,986

Property and Equipment, Net - S

Property and Equipment, Net - Summary of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Total property and equipment	$ 579	$ 406
Less: accumulated depreciation and amortization	(142)	(85)
Property and equipment, net	437	321
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment		65
Machinery and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	38	38
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	397	194
Computers
Property Plant And Equipment [Line Items]
Total property and equipment	111	76
Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	11	11
Software
Property Plant And Equipment [Line Items]
Total property and equipment	$ 22	$ 22

Property and Equipment, Net - A

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 34	$ 24	$ 90	$ 55

Accrued Liabilities - Summary o

Accrued Liabilities - Summary of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued payroll and related expenses	$ 1,533	$ 1,189
Accrued research and development expenses	514	1,028
Other	173	510
Total accrued liabilities	$ 2,220	$ 2,727

License Agreements - Additional

License Agreements - Additional Information (Details) - Novartis International Pharmaceutical Ltd. - USD ($)	1 Months Ended		9 Months Ended
	May 31, 2019	May 31, 2017	Sep. 30, 2019	Mar. 23, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License agreement termination description			The agreement may be terminated by either party upon a material breach by the other party that is not cured within 60 days after written notice. The Company may terminate the agreement in its entirety or on a product-by-product or country-by-country basis with or without cause with 60 days’ prior written notice.
Payment for development milestone	$ 2,500,000	$ 300,000
License Agreement | Series A Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Shares issued				2,587,992
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate amount payable upon satisfaction of clinical milestones				$ 4,300,000
Aggregate amount payable upon satisfaction of regulatory milestones for first indication approved				24,000,000
Aggregate amount payable upon satisfaction of regulatory milestones for second indication approved				18,000,000
Aggregate amount payable upon satisfaction of commercial milestones				$ 125,000,000

Research Funding Agreement - Ad

Research Funding Agreement - Additional Information (Details) - USD ($)	Mar. 06, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Research And Development Arrangement Contract To Perform For Others [Line Items]
Amounts received for qualifying expenses incurred recorded as reduction of research and development expense		$ 500,000		$ 500,000
Silverstein Foundation | Funding Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Upfront sum of funding amount	$ 500,000
Qualifying expenses		$ 0	$ 0	$ 0	$ 0

Preferred Stock and Common St_3

Preferred Stock and Common Stock - Additional Information (Details) - shares	Sep. 30, 2019	Dec. 31, 2018
Temporary Equity Disclosure [Abstract]
Preferred stock, shares authorized	10,000,000
Common stock, shares authorized	150,000,000	150,000,000
Preferred stock, shares issued	0
Preferred stock, shares outstanding	0
Common stock, shares issued	36,443,631	28,055,344
Common stock, shares outstanding	36,443,631	28,055,344

Preferred Stock and Common St_4

Preferred Stock and Common Stock -Schedule of Number of Shares of Common Stock Reserved for Future Issuance (Details) - shares	Sep. 30, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Number of shares of common stock reserved for future issuance	4,161,186	2,773,249
Options Issued and Outstanding
Class Of Stock [Line Items]
Number of shares of common stock reserved for future issuance	2,285,322	1,122,677
Restricted stock units
Class Of Stock [Line Items]
Number of shares of common stock reserved for future issuance	17,160	24,960
Options Available for Future Grants
Class Of Stock [Line Items]
Number of shares of common stock reserved for future issuance	1,303,121	1,350,582
Shares Available for Issuance under the 2018 ESPP
Class Of Stock [Line Items]
Number of shares of common stock reserved for future issuance	555,583	275,030

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details)	Apr. 17, 2018Installmentshares	Nov. 29, 2017shares	May 31, 2018$ / sharesshares	Sep. 30, 2019USD ($)shares	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)$ / sharesshares	Sep. 30, 2018USD ($)	Jun. 30, 2019USD ($)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Cash proceeds from stock options exercised | $						$ 6,000
Recognized stock-based compensation expense | $						$ 2,808,000	$ 2,212,000
Restricted stock award issued						0
Options Issued and Outstanding
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of options exercised						7,029
Cash proceeds from stock options exercised | $						$ 6,000
Options Issued and Outstanding | Employees and Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted						1,276,684
Weighted-average grant date fair value of options granted | $ / shares						$ 6.69
Expense related to options granted | $				$ 1,200,000	$ 600,000	$ 2,700,000	1,200,000
Unrecognized compensation expense | $				12,500,000		$ 12,500,000
Unrecognized compensation expense, estimated weighted-average period for recognition						3 years
Options Issued and Outstanding | Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted						9,840
Weighted-average grant date fair value of options granted | $ / shares						$ 7.61
Expense related to options granted | $				18,000	37,000	$ 66,000	64,000
Unrecognized compensation expense | $				200,000		$ 200,000
Unrecognized compensation expense, estimated weighted-average period for recognition						2 years 4 months 20 days
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted	2,000
Number of quarterly installment in which restriction lapse | Installment	4
Recognized stock-based compensation expense | $				0	11,000	$ 4,000	900,000
Unrecognized stock-based compensation expense | $				$ 0		$ 0
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense, estimated weighted-average period for recognition				2 years 7 months 20 days
Shares granted						0
Recognized stock-based compensation expense | $				$ 14,000	$ 14,000	$ 42,000	$ 20,000
Unrecognized stock-based compensation expense | $								$ 100,000
Restricted Stock Units | Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted						0
Restricted Stock Units | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted			24,960	0
Weighted-average grant date fair value | $ / shares			$ 9.03
2017 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance		630,662		537,914		537,914
Number of additional shares reserved for issuance		1,866,009				630,662
2017 Stock Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Terms of stock based options granted						10 years
2018 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of additional shares added on outstanding shares						4.00%
2018 Stock Incentive Plan | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance				2,200,260		2,200,260
2018 Stock Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance				3,322,473		3,322,473
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance				275,030		275,030
Percentage of additional shares added on outstanding shares						1.00%
2018 Employee Stock Purchase Plan | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares reserved for issuance						543,926
2018 Employee Stock Purchase Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares reserved for issuance						555,583

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Details) - Employees And Non Employees - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,202	$ 629	$ 2,808	$ 2,212
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	633	229	1,409	955
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 569	$ 400	$ 1,399	$ 1,257

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Option Activity (Details) - Options Issued and Outstanding - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding, beginning, Shares Available for Grant	1,350,582
Shares reserved for issuance, Shares Available for Grant	1,122,213
Options granted, Shares Available for Grant	(1,286,524)
Options cancelled, Shares Available for Grant	116,850
Outstanding, ending, Shares Available for Grant	1,303,121	1,350,582
Outstanding, beginning, Number of Options	1,122,677
Options granted, Number of Options	1,286,524
Options exercised, Number of Options	(7,029)
Options cancelled, Number of Options	(116,850)
Outstanding, ending, Number of Options	2,285,322	1,122,677
Exercisable, Number of Options	373,574
Vested and expected to vest, Number of Options	2,285,322
Outstanding, beginning, Weighted-Average Exercise Price per Option	$ 11.63
Options granted, Weighted-Average Exercise Price per Option	8.66
Options exercised, Weighted-Average Exercise Price per Option	0.79
Options cancelled, Weighted-Average Exercise Price per Option	10.25
Outstanding, ending, Weighted-Average Exercise Price per Option	10.05	$ 11.63
Exercisable, Weighted-Average Exercise Price per Option	11.40
Vested and expected to vest, Weighted-Average Exercise Price per Option	$ 8.63
Outstanding, beginning, Weighted-Average Remaining Contract Term	9 years 18 days	9 years 2 months 19 days
Exercisable, Weighted-Average Remaining Contract Term	8 years 3 months 29 days
Vested and expected to vest, Weighted-Average Remaining Contract Term	9 years 18 days
Outstanding, ending, Aggregate Intrinsic Value	$ 1,360
Exercisable, Aggregate Intrinsic Value	387
Vested and expected to vest, Aggregate Intrinsic Value	$ 1,360

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Assumptions to Estimate Fair Value of Stock Options for Employees and Non-Employees Using Black-Scholes Option Pricing Model (Details) - Options Issued and Outstanding - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employees and Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days
Expected volatility, minimum	92.40%	89.80%	92.40%	75.90%
Expected volatility, maximum	92.60%	90.60%	104.80%	90.60%
Risk-free interest rate, minimum	1.40%	2.80%	1.40%	2.40%
Risk-free interest rate, maximum	1.80%	2.90%	2.60%	2.90%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock				$ 15.45
Expected term (in years)				10 years
Expected volatility, minimum	89.70%		89.70%
Expected volatility, maximum	90.80%		94.20%
Risk-free interest rate, minimum	1.70%		1.70%
Risk-free interest rate, maximum	1.90%		2.60%
Expected dividend yield	0.00%		0.00%	0.00%
Expected volatility				77.90%
Risk-free interest rate				2.70%
Minimum [Member] | Employees and Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock	$ 9.36	$ 9.03	$ 6.97	$ 8.57
Expected term (in years)		5 years 10 months 24 days	5 years 6 months	5 years 9 months 18 days
Minimum [Member] | Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock	$ 8.84		$ 6.82
Expected term (in years)	7 years 8 months 12 days		7 years 8 months 12 days
Maximum | Employees and Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock	$ 10.66	$ 13.94	$ 10.66	$ 15.45
Expected term (in years)		6 years 1 month 6 days	6 years 1 month 6 days	6 years 7 months 6 days
Maximum | Non-employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Fair value of common stock	$ 10.26		$ 10.26
Expected term (in years)	9 years 6 months		10 years

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2019shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning, Unvested shares	1,000
Number of Shares Outstanding, Vested	(1,000)

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Restricted Stock Units Activity (Details) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2019shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Shares Outstanding, Beginning, Unvested shares	24,960
Number of Shares Outstanding, Granted	0
Number of Shares Outstanding, Vested	(7,800)
Number of Shares Outstanding, Ending, Unvested shares	17,160

Commitment and Contingencies -

Commitment and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended
	Apr. 30, 2019	Sep. 30, 2019	Aug. 01, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Amended lease term from the date of relocation			7 years
Amended base rent per year of the relocation premises	$ 600,000
Percentage increase in operating lease base rent	2.00%
Letters of Credit issued amount	$ 200,000
Estimated Litigation Liability		$ 0		$ 0

Commitments and Contingencies -

Commitments and Contingencies - Commitment and Contingencies - Summary of Obligations Future Minimum Lease Payments (Details) $ in Thousands	Sep. 30, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
Remainder of 2019	$ 147
2020	594
2021	606
2022	618
2023	630
Thereafter	1,686
Total	$ 4,281

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,302,482	692,550
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	17,160	24,960
Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share	2,285,322	667,590

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	May 31, 2019	May 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Novartis International Pharmaceutical Ltd.
Related Party Transaction [Line Items]
Payment for development milestone	$ 2,500,000	$ 300,000
Payments to related parties			$ 0	$ 0	$ 0	$ 0
Silverstein Foundation | Funding Agreement
Related Party Transaction [Line Items]
Fund received from related parties				$ 0	$ 0	$ 500,000