Unity Biotechnology (UBX) 10-Q 9 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Aug. 03, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Trading Symbol	UBX
Entity Registrant Name	Unity Biotechnology, Inc.
Entity Central Index Key	1,463,361
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		42,314,738

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 34,165	$ 7,298
Contribution receivable		1,382
Short-term marketable securities	151,806	79,212
Prepaid expenses and other current assets	1,650	988
Total current assets	187,621	88,880
Property and equipment, net	6,595	6,958
Long-term marketable securities	12,073	5,118
Restricted cash	550	550
Other long-term assets	1,617	518
Total assets	208,456	102,024
Current liabilities:
Accounts payable	1,883	2,378
Accrued compensation	1,941	2,181
Accrued and other current liabilities	4,856	3,338
Contingent consideration liability	725
Total current liabilities	9,405	7,897
Deferred rent, net of current portion	2,867	3,166
Contingent consideration liability, net of current portion	1,033
Other non-current liabilities	82	118
Total liabilities	13,387	11,181
Commitments and contingencies (Note 6)
Convertible preferred stock, $0.0001 par value; 10,000,000 and 91,739,149 shares authorized as of June 30, 2018 and December 31, 2017, respectively; 28,159,724 shares issued and outstanding as of December 31, 2017; aggregate liquidation preference of $190,825 as of December 31, 2017		173,956
Stockholders’ equity (deficit):
Common stock, $0.0001 par value; 300,000,000 and 122,000,000 shares authorized as of June 30, 2018 and December 31, 2017, respectively; 42,314,738 and 4,830,389 shares issued and outstanding as of June 30, 2018 and December 31, 2017, respectively	4	1
Additional paid-in capital	318,758	4,072
Related party promissory notes for purchase of common stock	(201)	(202)
Employee promissory notes for purchase of common stock	(400)
Accumulated other comprehensive loss	(77)	(104)
Accumulated deficit	(123,015)	(86,880)
Total stockholders’ equity (deficit)	195,069	(83,113)
Total liabilities, convertible preferred stock, and stockholders’ equity (deficit)	$ 208,456	$ 102,024

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	10,000,000	91,739,149
Convertible preferred stock, shares issued		28,159,724
Convertible preferred stock, shares outstanding		28,159,724
Convertible preferred stock, liquidation preference		$ 190,825
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	122,000,000
Common stock, shares issued	42,314,738	4,830,389
Common stock, shares outstanding	42,314,738	4,830,389

Condensed Statements of Operati

Condensed Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating expenses:
Research and development	$ 15,198	$ 9,213	$ 28,223	$ 16,183
General and administrative	3,842	2,485	7,299	4,555
Fair value of contingent consideration	1,758		1,758
Total operating expenses	20,798	11,698	37,280	20,738
Loss from operations	(20,798)	(11,698)	(37,280)	(20,738)
Interest income	826	278	1,178	386
Other expense, net	(30)	(8)	(33)	(10)
Net loss	(20,002)	(11,428)	(36,135)	(20,362)
Other comprehensive loss
Unrealized gain (loss) on marketable securities, net of tax	61	(18)	27	(20)
Comprehensive loss	$ (19,941)	$ (11,446)	$ (36,108)	$ (20,382)
Net loss per share, basic and diluted	$ (0.76)	$ (3.62)	$ (2.41)	$ (6.53)
Weighted average number of shares used in computing net loss per share, basic and diluted	26,298,666	3,154,515	15,003,493	3,117,220

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating activities
Net loss	$ (36,135)	$ (20,362)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,023	388
Amortization of premium and discounts on marketable securities	(203)	105
Stock-based compensation	4,208	938
Accretion of tenant improvement allowance	(305)	(302)
Change in fair value of contingent consideration for license agreements	1,758
Changes in operating assets and liabilities:
Contribution receivable	1,382
Prepaid expenses and other current assets	(662)	(513)
Other long-term assets	(1,099)	25
Accounts payable	(633)	1,798
Accrued compensation	(240)	249
Accrued liabilities and other current liabilities	970	(226)
Deferred rent, net of current portion	4	263
Net cash used in operating activities	(29,932)	(17,637)
Investing activities
Purchase of marketable securities	(137,803)	(110,285)
Maturities of marketable securities	58,484	4,750
Purchase of property and equipment	(526)	(984)
Net cash used in investing activities	(79,845)	(106,519)
Financing activities
Proceeds from issuance of convertible preferred stock, net of issuance costs	59,899	42,880
Proceeds from issuance of common stock upon exercise of stock options, net of repurchases	33	(6)
Proceeds from issuance of common stock in initial public offering, net of commissions	79,050
Payment of initial public offering costs	3,199
Proceeds from repayment of recourse notes	895
Payments made on capital lease obligations	(34)
Net cash provided by financing activities	136,644	42,874
Net increase (decrease) in cash, cash equivalents and restricted cash	26,867	(81,282)
Cash, cash equivalents and restricted cash at beginning of year	7,848	89,736
Cash, cash equivalents and restricted cash at end of year	34,715	8,454
Supplemental Disclosures of Non-Cash Investing and Financing Information
Property and equipment included in accounts payable	138	528
Property and equipment acquired under capital leases		$ 96
Receipt of promissory note from related party for purchase of common stock	390
Receipt of promissory note from employees for purchase of common stock	$ 400

Organization and Liquidity Risk

Organization and Liquidity Risks	6 Months Ended
	Jun. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Liquidity Risks	1. Organization Description of Business Unity Biotechnology, Inc. (the “Company” or “we” or “our” or “us”) is a biotechnology company engaged in the research and development of therapeutics to extend human healthspan. The Company devotes substantially all of its time and efforts to performing research and development, raising capital and recruiting personnel. The Company is located in Brisbane, California, was incorporated in the State of Delaware in March 2009 under the name Forge, Inc. and operates in one segment. The Company changed its name to Unity Biotechnology, Inc. in January 2015. Initial Public Offering On May 7, 2018, the Company closed its initial public offering (“IPO”), of 5,000,000 shares of common stock, at an offering price to the public of $17.00 per share. The Company received net proceeds of approximately $75.9 million, after deducting underwriting discounts, commissions and offering related transaction costs of approximately $9.1 million. In connection with the IPO, all of the Company’s outstanding shares of convertible preferred stock were automatically converted into 32,073,149 shares of common stock. In addition, all of our convertible preferred stock warrants were converted into warrants to purchase shares of common stock. In connection with the completion of its IPO, on May 7, 2018, the Company’s certificate of incorporation was amended and restated to provide for 300,000,000 authorized shares of common stock with a par value of $0.0001 per share and 10,000,000 authorized shares of preferred stock with a par value of $0.0001 per share.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) the rules and regulations of United States Securities and Exchange Commission (“SEC”) for interim reporting. The condensed financial statements are unaudited and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation for interim reporting. The results of operations for any interim period are not necessarily indicative of results of operations for any future period. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted. Accordingly, the unaudited condensed financial statements should be read in conjunction with the financial statements as of and for the year ended December 31, 2017, which are included in the Company’s prospectus related to the Company’s initial public offering, filed May 4, 2018 (the “Prospectus”), pursuant to Rule 424 (b) under the Securities Act of 1933, as amended with the SEC. Reverse Stock Split On April 19, 2018, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-2.95 reverse split (“Reverse Split”) of shares of the Company’s common and convertible preferred stock, which was effected on April 20, 2018. The par value and authorized shares of common stock and convertible preferred stock were not adjusted as a result of the Reverse Split. All of the share and per share information included in the accompanying financial statements have been adjusted to reflect the Reverse Split. Accordingly, all share and per share information presented in the condensed financial statements herein, and notes thereto, have been retroactively adjusted to reflect the Reverse Split. Need for Additional Capital The Company has incurred operating losses and has an accumulated deficit as a result of ongoing efforts to develop drug product candidates, including conducting preclinical and clinical trials and providing general and administrative support for these operations. The Company had an accumulated deficit of $123.0 million and $86.9 million as of June 30, 2018 and December 31, 2017, respectively. The Company had net losses of $36.1 million and $20.4 million for the six months ended June 30, 2018 and 2017, respectively, and net cash used in operating activities of $29.9 million and $17.6 million for the six months ended June 30, 2018 and 2017, respectively. To date, none of the Company’s drug candidates have been approved for sale and therefore the Company has not generated any revenue from contracts with customers. The Company has evaluated and concluded there are no conditions or events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern for a period of one year following the date that these financial statements are issued. Management expects operating losses to continue for the foreseeable future. As a result, the Company will need to raise additional capital. If sufficient funds on acceptable terms are not available when needed, the Company could be required to significantly reduce its operating expenses and delay, reduce the scope of, or eliminate one or more of its development programs. Failure to manage discretionary spending or raise additional financing, as needed, may adversely impact the Company’s ability to achieve its intended business objectives. Use of Estimates The condensed financial statements have been prepared in accordance with GAAP, which requires management to make estimates and assumptions that affect the amounts and disclosures reported in the condensed financial statements and accompanying notes. The Company bases its estimates on historical experience and market-specific or other relevant assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company’s balance sheets and the amount of expenses and income reported for each of the periods presented are affected by estimates and assumptions, which are used for, but are not limited to, determining the fair value of assets and liabilities, common stock valuation, contingent consideration and stock-based compensation. Actual results could differ from such estimates or assumptions. Contingent Consideration Liability The Company has entered and may continue to enter into license agreements to access and utilize certain technology. In each case, the Company evaluates if the license agreement results in the acquisition of an asset or a business. To date none of the Company’s license agreements have been considered an acquisition of a business. For asset acquisitions, the upfront payments to acquire such licenses, as well as any future milestone payments made before product approval, are immediately recognized as research and development expense when due, provided there is no alternative future use of the rights in other research and development projects. These license agreements also include contingent consideration in the form of additional issuances of the Company’s common stock based on the achievement of certain milestones. For asset acquisitions, the Company assesses whether such contingent consideration meets the definition of a derivative, until such time that the contingency is met or expires. As of June 30, 2018, the Company has recorded a liability related to contingent consideration as the net settlement criteria of the definition of a derivative had been met. The derivative related to this contingent consideration is measured at fair value as of each balance sheet date with the related change in fair value being reflected in operating expenses. Deferred Offering Costs Deferred offering costs, consisting of direct incremental legal, accounting, filing and other fees incurred related to the preparation of the IPO, have been capitalized and were offset against proceeds upon completion of the offering in May 2018. As of June 30, 2018, there were no deferred offering costs capitalized and included in current assets on the balance sheet. There were no capitalized deferred offering costs at December 31, 2017. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with original maturities of 90 days or less from the date of purchase to be cash equivalents. Cash equivalents primarily include money market funds that invest in U.S. Treasury obligations which are stated at fair value. The Company has issued a letter of credit under a lease agreement which has been collateralized. This cash is classified as noncurrent restricted cash on the balance sheet based on the term of the underlying lease. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the balance sheets that sum to the total of the same amounts shown in the condensed statements of cash flows (in thousands). June 30, 2018 December 31, 2017 Cash and cash equivalents $ 34,165 $ 7,298 Restricted cash 550 550 Total cash, cash equivalents, and restricted cash $ 34,715 $ 7,848 Variable Interest Entities The Company reviews agreements it enters into with third-party entities, pursuant to which the Company may have a variable interest in the entity, in order to determine if the entity is a variable interest entity (“VIE”). If the entity is a VIE, the Company assesses whether or not it is the primary beneficiary of that entity. In determining whether the Company is the primary beneficiary of an entity, the Company applies a qualitative approach that determines whether it has both (i) the power to direct the economically significant activities of the entity and (ii) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. If the Company determines it is the primary beneficiary of a VIE, it consolidates that VIE into the Company’s financial statements. The Company’s determination about whether it should consolidate such VIEs is made continuously as changes to existing relationships or future transactions may result in a consolidation or deconsolidation event. Concentrations of Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash and marketable securities. Substantially all of the Company’s cash and cash equivalents and restricted cash is deposited in accounts with financial institutions that management believes are of high credit quality. Such deposits have and will continue to exceed federally insured limits. The Company maintains its cash with accredited financial institutions and accordingly, such funds are subject to minimal credit risk. The Company has not experienced any losses on its cash deposits. The contribution receivable outstanding as of December 31, 2017 was unsecured and was concentrated with one third-party organization, and accordingly the Company was exposed to credit risk. The Company received the full amount of the contribution receivable in January 2018. The Company’s investment policy limits investments to certain types of securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, restricted cash and marketable securities and issuers of marketable securities to the extent recorded on the balance sheets. As of June 30, 2018, the Company had no off-balance sheet concentrations of credit risk. The Company depends on third-party suppliers for key raw materials used in its manufacturing processes and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate raw materials. Recently Issued Accounting Pronouncements In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business In February 2016, the FASB issued ASU No. 2016-02 (“ASU 2016-02”), Leases (Topic 842) Leases In May 2017, the Financial Accounting Standards Board (FASB) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718)- Scope of Modification Accounting In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230: Classification of Certain Cash Receipts and Cash Payments) In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting On December 22, 2017, the U.S. federal government enacted the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act contains, among other things, significant changes to corporate taxation, including reduction of the corporate tax rate from a top marginal rate of 35% to a flat rate of 21% for tax years beginning after December 31, 2017, limitation of the deduction for net operating losses to 80% of current year taxable income and elimination of net operating loss carrybacks, implementing a territorial tax system, and requiring a mandatory one-time tax on U.S. owned undistributed foreign earnings and profits known as the transition tax. In December 2017, SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The Company determines the fair value of financial and non-financial assets and liabilities based on the assumptions that market participants would use in pricing the asset or liability in an orderly transaction between market participants at the measurement date. The identification of market participant assumptions provides a basis for determining what inputs are to be used for pricing each asset or liability. A fair value hierarchy has been established which gives precedence to fair value measurements calculated using observable inputs over those using unobservable inputs. This hierarchy prioritized the inputs into three broad levels as follows: • Level 1: Quoted prices in active markets for identical instruments • Level 2: Other significant observable inputs (including quoted prices in active markets for similar instruments) • Level 3: Significant unobservable inputs (including assumptions in determining the fair value of certain investments) The carrying amounts of financial instruments such as cash and cash equivalents, restricted cash, contributions receivable, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities approximate the related fair values due to the short maturities of these instruments. The fair value of the Company’s cost method investment is measured when it is deemed to be other-than- temporarily impaired. The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): June 30, 2018 Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 20,142 $ 20,142 $ — $ — U.S. treasuries 1,000 — 1,000 — U.S. government debt securities 10,887 — 10,887 — Total cash equivalents 32,029 20,142 11,887 — Short-term marketable securities: U.S. treasuries 40,077 — 40,077 — U.S. and foreign commercial paper 28,481 — 28,481 — U.S. and foreign corporate debt securities 17,118 — 17,118 — Asset-backed securities 9,865 — 9,865 — U.S. government debt securities 56,265 — 56,265 — Total short-term marketable securities 151,806 — 151,806 — Long-term marketable securities: U.S. treasuries 2,460 — 2,460 U.S. corporate debt securities 1,969 — 1,969 — U.S. government debt securities 7,644 — 7,644 — Total long-term marketable securities 12,073 — 12,073 — Total marketable securities 163,879 — 163,879 — Total assets $ 195,908 $ 20,142 $ 175,766 $ — Liabilities: Contingent consideration 1,758 — — 1,758 Total contingent consideration $ 1,758 $ — $ — $ 1,758 December 31, 2017 Total Level 1 Level 2 Level 3 Money market funds $ 5,709 $ 5,709 $ — $ — Short-term marketable securities: U.S. and foreign commercial paper 6,359 — 6,359 — U.S. and foreign corporate debt securities 16,149 — 16,149 — Asset-backed securities 14,588 — 14,588 — U.S. government debt securities 40,362 — 40,362 — U.S. treasuries 1,754 — 1,754 — Total short-term marketable securities 79,212 — 79,212 — Long-term marketable securities: Asset-backed securities 2,742 — 2,742 — U.S. government debt securities 2,376 — 2,376 — Total long-term marketable securities 5,118 — 5,118 — Total marketable securities 84,330 — 84,330 — Total $ 90,039 $ 5,709 $ 84,330 $ — The Company estimates the fair value of its money market funds, U.S. and foreign commercial paper, U.S. and foreign corporate debt securities, asset-backed securities, U.S. treasuries and U.S. government debt securities by taking into consideration valuations obtained from third-party pricing services. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar securities, issuer credit spreads; benchmark securities; prepayment/default projections based on historical data; and other observable inputs. The fair value of the contingent consideration liability includes inputs not observable in the market and thus represents a Level 3 measurement. The Company has recorded a contingent consideration liability related to two agreements executed in February 2016 with a privately held clinical-stage biopharmaceutical company: (a) a license agreement granting the Company the right to research, develop, and seek and obtain marketing approval for an initial licensed compound, and (b) a compound library and option agreement granting the Company the right to identify and take licenses to additional compounds, in each case for the treatment of indications outside of oncology (collectively, the “Commercial Agreements”). The Commercial Agreements include contingent consideration of up to 666,670 additional shares of common stock to be issued based on achievement of certain specified clinical development and sales milestone events. The Company valued the contingent consideration liability using a probability-weighted valuation approach model which reflects the probability and timing of future issuances of shares. The probability of achieving the defined milestones for each licensed product was estimated by the Company’s management. Total contingent consideration may change significantly as development under the Commercial Agreements progresses and additional data is obtained, impacting the Company’s assumptions regarding probabilities of successful achievement of related development and commercial milestones used to estimate the fair value of the liability and the timing in which they are expected to be achieved. For example, significant increases in the estimated probability of achieving a milestone would result in a significantly higher fair value measurement while significant decreases in the estimated probability of achieving a milestone would result in a significantly lower fair value measurement. The potential contingent consideration value resulting in shares to be issued range from zero if none of the milestones are achieved to a maximum of $11.1 million (using the Company’s stock price as of June 30, 2018). As of June 30, 2018, and December 31, 2017, none of the development and commercial milestones had been achieved and no royalties were due from the sales of licensed products. The following table provides a reconciliation of assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the six months ended June 30, 2018 (in thousands): Amount Balance at December 31, 2017 $ — Additions — Settlements — Change in fair value 1,758 Balance at June 30, 2018 $ 1,758 There were no transfers between the hierarchies during the six months ended June 30, 2018 and the year ended December 31, 2017.

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2018
Investments Debt And Equity Securities [Abstract]
Marketable Securities	4. Marketable Securities Marketable securities, which are classified as available-for-sale, consisted of the following as of June 30, 2018 (in thousands): June 30, 2018 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Short-term marketable securities: U.S. and foreign commercial paper $ 28,487 $ 3 $ (9 ) $ 28,481 U.S. and foreign corporate debt securities 17,142 — (24 ) 17,118 Asset-backed securities 9,885 — (20 ) 9,865 U.S. government debt securities 56,290 3 (28 ) 56,265 U.S. treasuries 40,078 1 (2 ) 40,077 Total short-term marketable securities 151,882 7 (83 ) 151,806 Long-term marketable securities: U.S. corporate debt securities 1,970 — (1 ) 1,969 U.S. government debt securities 7,644 1 (1 ) 7,644 U.S. treasuries 2,460 — — 2,460 Total long-term marketable securities 12,074 1 (2 ) 12,073 Total marketable securities $ 163,956 $ 8 $ (85 ) $ 163,879 Marketable securities, which are classified as available-for-sale, consisted of the following as of December 31, 2017: December 31, 2017 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Short-term marketable securities: U.S. and foreign commercial paper $ 6,369 $ — $ (10 ) $ 6,359 U.S. and foreign corporate debt securities 16,162 — (13 ) 16,149 Asset-backed securities 14,604 — (16 ) 14,588 U.S. government debt securities 40,418 — (56 ) 40,362 U.S. treasuries 1,754 — — 1,754 Total short-term marketable securities 79,307 — (95 ) 79,212 Long-term marketable securities: Asset-backed securities 2,752 — (10 ) 2,742 U.S. government debt securities 2,375 1 — 2,376 Total long-term marketable securities 5,127 1 (10 ) 5,118 Total marketable securities $ 84,434 $ 1 $ (105 ) $ 84,330 At June 30, 2018, the remaining contractual maturities of available-for-sale securities were less than two years

License Agreements

License Agreements	6 Months Ended
	Jun. 30, 2018
Research And Development [Abstract]
License Agreements	5. License Agreements License and Compound Library and Option Agreement The Commercial Agreements referenced above include cash payments of up to $70.3 million as well as the equity payments of up to 666,670 additional shares of common stock, in each case to be issued The Company recognized a $1.8 million contingent consideration liability associated with the potential issuance of common stock related to the Commercial Agreements with the privately held clinical-stage biopharmaceutical company for the three months ended June 30, 2018. In connection with the Commercial Agreements the Company purchased an equity interest in an affiliate of the biopharmaceutical company The Company agreed to provide funding to the biopharmaceutical company for research and development work performed at a cost of up to $2.0 million through February 2020. The research and development expense under the research services agreement was $0.3 million for the six months ended June 30, 2018 and 2017. Under the consolidation guidance, the Company determined that the biopharmaceutical company is a VIE. The Company does not have the power to direct the activities that most significantly affect the economic performance of this entity and as such the Company is not the primary beneficiary and consolidation is not required. As of June 30, 2018, and December 31, 2017, the Company has not provided financial, or other, support to the biopharmaceutical company that was not contractually required. Other License Agreements with Research Institutions The Company has entered into license agreements with various research institutions which have provided the Company with rights to patents, and in certain cases, research “know-how” and proprietary research tools to research, develop and commercialize drug candidates. In addition to upfront consideration paid to these various research institutions in either cash or shares of the Company’s common stock, the Company may be obligated to pay milestone payments in cash or the issuance of the Company’s common stock specific to each agreement upon achievement of certain specified clinical development and/or sales events. The contingent consideration liability considered to be a derivative associated with the potential issuance of common stock related to these license agreements was not significant at June 30, 2018. To date, none of these events has occurred and no contingent consideration, milestone or royalty payments have been recognized.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	6. Commitments and Contingencies Operating Lease The Company has one non-cancelable operating lease consisting of administrative and research and development office space for its Brisbane, California headquarters that expires in October 2022. Future minimum lease payments under our non-cancellable operating lease at June 30, 2018 were as follows (in thousands): Amount 2018 (remaining 6 months) $ 984 2019 2,012 2020 2,072 2021 2,135 2022 1,621 Total future minimum lease payments $ 8,824 Rent expense for the six months ended June 30, 2018 and 2017 was $0.9 million and $0.8 million, respectively. Indemnifications The Company indemnifies each of its officers and directors for certain events or occurrences, subject to certain limits, while the officer or director is or was serving at the Company’s request in such capacity, as permitted under Delaware law and in accordance with the Company’s amended and restated certificate of incorporation and bylaws. The term of the indemnification period lasts as long as an officer or director may be subject to any proceeding arising out of acts or omissions of such officer or director in such capacity. The maximum amount of potential future indemnification is unlimited; however, the Company currently holds director and officer liability insurance. The Company believes that the fair value of these indemnification obligations is minimal. Accordingly, the Company has not recognized any liabilities relating to these obligations for any period presented.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2018
Related Party Transactions [Abstract]
Related-Party Transactions	7. Related-Party Transactions Recourse Notes In December 2015, April 2016, and July 2016, the Company issued three full-recourse promissory notes to two executive officers for an aggregate principal amount of $0.2 million with an interest rate of 2.5% per annum. All of the principal was used to early exercise options for 667,253 shares of the Company’s common stock, in aggregate. All of these related party full-recourse notes were repaid on April 4, 2018 in accordance with the terms of such notes. In October 2017, the Company issued two promissory notes to an executive officer for $1.6 million and $0.5 million, each with an interest rate of 1.85% per annum. The aggregate principal amount of $2.1 million was used to purchase 625,084 shares of restricted stock. The promissory notes were considered to be non-recourse in substance and accordingly, the shares sold subject to such promissory notes are considered an option for accounting purposes. In April 2018, the Company’s board of directors approved the forgiveness of all outstanding principal and accrued interest of the $1.6 million non-recourse promissory note. The non-recourse promissory note outstanding of $0.5 million was repaid on April 4, 2018 in accordance with the terms of the note. The forgiveness of the promissory note was accounted for as a modification of a share-based payment. The Company recorded an incremental $0.8 million charge related to the modification for the three and six months ended June 30, 2018. In January 2018, the Company issued full-recourse promissory notes to an executive and an executive officer of the Company for an aggregate principal amount of $0.4 million with an interest rate of 2.5% per annum. All of the principal was used to early exercise options for 114,406 shares of the Company’s common stock. The full recourse note of $0.2 million for the executive officer was repaid on April 4, 2018 in accordance with the terms of the note. Financing Activities During the six months ended June 30, 2018, the Company issued convertible preferred stock for total proceeds of $3.0 million to shareholders who are considered to be related parties.

Convertible Preferred Stock and

Convertible Preferred Stock and Common Stock	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Convertible Preferred Stock and Common Stock	8. Convertible Preferred Stock and Common Stock Convertible Preferred Stock In March 2018, the Company amended and restated its certificate of incorporation to, among other things, (i) increase its authorized shares of common stock from 122,000,000 to 140,000,000 shares, (ii) increase its authorized shares of preferred stock from 91,739,149 to 103,283,818 shares, of which 11,544,669 shares were designated as Series C convertible preferred stock, and (iii) set forth the rights, preferences and privileges of the Series C convertible preferred stock. In March 2018, the Company sold 3,590,573 shares of Series C convertible preferred stock at $15.3317 per share for net proceeds of $54.9 million and in Each share of Series C convertible preferred stock was convertible into one share of the Company’s common stock. Each share of preferred stock was automatically converted into one share of common stock upon the consummation of a qualified public offering. A qualified public offering was defined as an initial public offering that resulted in listing on a U.S. national securities exchange and at least $30.0 million of gross proceeds at a per share price of not less than the Series C original issue price of $15.3317. The Company evaluated the other rights, preferences and privileges of each series of convertible preferred stock and concluded that there were no freestanding derivative instruments or any embedded derivatives requiring bifurcation. Upon the closing of the IPO, all of the Company’s outstanding shares of convertible preferred stock were converted into 32,073,149 shares of common stock. In addition, all 763,501 of the Company’s convertible preferred stock warrants were converted into warrants to purchase shares of common stock. As of June 30, 2018, the Company had no remaining shares of convertible or preferred stock issued or outstanding. As of December 31, 2017, convertible preferred stock consisted of the following (in thousands, except share amounts): Shares Authorized Shares Issued and Outstanding Liquidation Preference Carrying Value Series A-1 9,085,738 2,887,086 $ 2,495 $ 2,457 Series A-2 32,653,411 10,498,269 9,198 9,214 Series B 50,000,000 14,774,369 179,132 162,285 Total convertible preferred stock 91,739,149 28,159,724 $ 190,825 $ 173,956 Prior to the conversion of the convertible preferred stock upon closing of the IPO, the rights, preferences and privileges of the convertible preferred stock were as follows: Conversion Rights Each share of convertible preferred stock was convertible at the right and option of the stockholder, at any time after the date of issuance, into such number of fully paid and non-assessable shares of common stock on a one for one ratio (1:1 conversion ratio). The Series A-1 conversion price was $0.864 per share, the Series A-2 conversion price was $0.876 per share, the Series B conversion price was $12.125 per share and the Series C conversion price was $15.3317 per share, in each case, subject to certain antidilution adjustments as provided in the Company’s amended and restated certificate of incorporation. Each share of convertible preferred stock was automatically convertible into a fully paid, non-assessable share of common stock at the then-effective conversion rate for such share (i) upon the closing of a firm commitment, underwritten initial public offering of the Company’s common stock with aggregate gross proceeds of not less than $30.0 million and a price per share to the public of not less than $15.3317 per share; or (ii) upon the receipt by the Company of a written request for such conversion from at least 60% of the holders of the convertible preferred stock then outstanding (voting together as a single class and on an as-converted basis), or if later, the effective date for conversion specified in such requests. Liquidation Rights In the event of any voluntary or involuntary liquidation, dissolution or winding up of the Company or a deemed liquidation event, as further defined in the Company’s amended and restated certificate of incorporation, prior to and in preference to any distribution of any of the assets of the Company to the holders of Series B convertible preferred stock and the Series A-1 and Series A-2 convertible preferred stock and common stock, the holders of Series C convertible preferred stock would have been paid, on a pari passu After the payment or setting aside for payment to the holders of the Series C convertible preferred stock of the full amount of the Series C Liquidation Preference, prior to any distribution of any of the assets of the Company to the holders of the Series A-1 and Series A-2 convertible preferred stock and common stock, the holders of Series B convertible preferred stock would have been paid, on a pari passu After the payment or setting aside for payment to the holders of the Series B convertible preferred stock of the full amount of the Series B Liquidation Preference, prior to any distribution of any of the assets of the Company to the holders of the common stock, the holders of Series A-1 and Series A-2 convertible preferred stock would have been paid, on a pari passu basis, an amount per share equal to $0.864 per share for Series A-1 and $0.876 per share for Series A-2, plus, in each case, an amount equal to any dividends declared but unpaid thereon (the “Series A Liquidation Preference”). If upon any such liquidation, dissolution or winding up of the Company or deemed liquidation event, the assets of the Company available for distribution to its stockholders had been insufficient to pay the holders of shares of Series A-1 and Series A-2 convertible preferred stock the full amount to which they shall be entitled, the holders of the Series A-1 and Series A-2 convertible preferred stock would have shared ratably in any distribution of the assets available for distribution in proportion to the respective amounts which would otherwise have been payable in respect of the shares held by them upon such distribution if all amounts payable on or with respect to such shares were paid in full. After the payments or setting aside for payment to the holders of convertible preferred stock of the full amounts specified above, the entire remaining assets of the Company legally available for distribution shall be distributed pro rata to holders of the common stock of the Company in proportion to the number of shares of common stock held by them. Voting Rights The holders of outstanding shares of Series A-1 and Series A-2 convertible preferred stock, voting together as a single class, were entitled to elect two members of the Company’s Board of Directors. The holders of outstanding shares of Series B convertible preferred stock, voting together as a single class, were entitled to elect one member of the Company’s Board of Directors. Additionally, each holder of the Company’s convertible preferred stock was entitled to a vote equal to the number of shares of common stock into which the shares of convertible preferred stock could have been converted as of the record date. The holders of convertible preferred were entitled to vote on all matters on which the common stock shall be entitled to vote. Dividend Rights Holders of the Series A-1, Series A-2, Series B and Series C convertible preferred stock were entitled to receive non-cumulative dividends at a rate of 6% of the original respective series of convertible preferred stock issuance price. Only after payment of the dividends to the holders of Series C convertible preferred stock were the holders of shares of Series B, Series A-1 and Series A-2 convertible preferred stock be entitled to receive dividends, out of any assets legally available therefore, prior and in preference to any declaration or payment of any dividend (other than dividends on the common stock payable solely in common stock) on the common stock. After the payment or setting aside for payment of the dividends described above, any additional dividends (other than dividends on common stock payable solely in common stock) set aside or paid in any fiscal year could have been set aside or paid among the holders of the convertible preferred stock and common stock then outstanding on a pari passu basis in proportion to the greatest whole number of shares of common stock which would have been held by each such holder if all shares of convertible preferred stock were converted at the then-effective conversion rate. Dividends were only payable as and if declared by the Board of Directors. To date, the Company has not declared or paid any dividends. Redemption Rights The convertible preferred stock was not mandatorily redeemable as it did not have a set redemption date or a date after which the shares may be redeemed by the holders. A redemption event would have occurred only upon the occurrence of certain change in control events that are outside the Company’s control, including a sale, lease, transfer, or other disposition of all or substantially all of the Company’s assets. The Company has elected not to adjust the carrying values of the convertible preferred stock to the liquidation preferences of such shares because it is uncertain whether or when an event would have occurred that would obligate the Company to pay the liquidation preferences to holders of shares of convertible preferred stock. Subsequent adjustments to the carrying values of the liquidation preferences will be made only when it becomes probable that such a liquidation event will occur.

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation 2018 Incentive Award Plan In March 2018, the Company’s board of directors adopted the Company’s 2018 Incentive Award Plan (the “2018 Plan”). The 2018 Plan was approved by the Company’s stockholders in April 2018 and became effective on May 2, 2018. The 2018 Plan initially reserved 4,289,936 shares for the issuance of stock options as well as any automatic annual increases in the number of shares of common stock reserved for future issuance under the 2018 Plan. Awards granted under the 2018 Plan expire no later than ten years from the date of grant. For stock options, the option price shall not be less than 100% of the estimated fair value on the day of grant. Options granted typically vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised in connection with an employee’s termination of employment are added back to the 2018 Plan. Following the Company’s IPO and in connection with the effectiveness of the 2018 Plan, the 2013 Equity Incentive Plan (the “2013 Plan”) terminated and no further awards will be granted under that plan. All outstanding awards under the 2013 Plan will continue to be governed by their existing terms and the shares that remained outstanding for issuance under the 2013 Plan were transferred into the 2018 Plan. As of June 30, 2018, there was an aggregate 5,058,434 shares of common stock authorized for issuance under the 2018 Plan. Prior to its termination, the 2013 Plan provided for the granting of incentive stock options (“ISOs”), non-statutory stock options (“NSOs”) and restricted shares to employees, directors, and consultants at the discretion of management and the Board of Directors. The exercise price of an ISO and NSO shall not be less than 100% of the estimated fair value of the shares on the date of grant, and the exercise price of an ISO and NSO granted to a 10% stockholder shall not be less than 110% of the estimated fair value of the shares on the date of grant. For awards granted between September 2017 and June 2018 with an exercise price of $3.42, a deemed fair value ranging from $3.95 to $5.43 per share was used in calculating stock-based compensation expense, which was determined using management hindsight. Options granted under the 2013 Plan expire no later than 10 years from the date of grant and generally vest over a four-year period but may be granted with different vesting terms. Unvested options not exercised in connection with an employee’s termination of employment are added back to the 2018 Plan. Stock Option Activity A summary of the Company’s stock option activity is as follows: Number of Shares Weighted- Average Exercise Price Balances at December 31, 2017 4,196,203 $ 3.06 Granted 1,629,602 $ 13.24 Exercised (401,773 ) $ 3.11 Canceled (48,529 ) $ 7.62 Balances at June 30, 2018 5,375,503 $ 6.10 2018 Employee Stock Purchase Plan In March 2018, the Company’s board of directors adopted the Company’s 2018 Employee Stock Purchase Plan (the “2018 ESPP”). The 2018 ESPP was approved by the Company’s stockholders in April 2018 and became effective on May 2, 2018. The 2018 ESPP reserved 536,242 shares of common stock for issuance pursuant to future awards, as well as any automatic increases in the number of shares of our common stock reserved for future issuance under this plan. Performance Contingent Stock Options Granted to Employees During the six months ended June 30, 2018, the Board of Directors granted performance contingent stock option awards exercisable for 53,575 shares, to certain members of the Company’s executive team. These awards had a weighted average exercise price of $3.42 which was based on the fair market value on the grant date, as determined by the Board of Directors, and vest upon the successful achievement of one or more specified performance goals. The total estimated fair value of employee performance contingent stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model using the same assumptions as the stock options granted to employees with service-based vesting conditions was $0.4 million. As of June 30, 2018, and December 31, 2017, there were 329,498 and 275,922 performance contingent stock option awards outstanding with a total grant date fair value of $0.7 million and $0.3 million respectively. As of June 30, 2018, and December 31, 2017, the Company determined that the achievement of the requisite performance conditions was not probable and, as a result, no compensation cost was recognized for these awards. Performance and Market Contingent Stock Options Granted to Employees During the six months ended June 30, 2018, the Board of Directors granted performance and market contingent stock option awards exercisable for 160,727 shares of common stock to certain members of the Company’s executive team. These awards had a weighted average exercise price of $3.42, which was based on the fair market value on the grant date, as determined by the Board of Directors. The total estimated grant-date fair value of these options was $0.7 million. Key assumptions in the valuation model included expected volatility, a risk-free interest rate, expected dividend yield, and an expected term unique to the terms of these awards. Under the performance and market contingent awards, 53,575 of the shares have three separate market triggers for vesting based upon (i) the closing of a financing where the Company sells shares of its equity securities to institutional investors at a minimum price per share, (ii) a change in control with aggregate proceeds payable to the Company’s common stock at a minimum price per share, or (iii) an initial public offering that becomes effective at a minimum specified price per share. The remaining 107,152 shares have three separate market triggers for vesting based upon (i) the closing of a financing where the Company sells shares of its equity securities to institutional investors at a minimum pre-money valuation, (ii) a change in control with a minimum aggregate proceeds payable to the Company’s common stock, or (iii) an initial public offering that becomes effective or an achievement of a minimum market capitalization, as measured by a trailing 30 day volume-weighted average price. By definition, the market condition in these awards can only be achieved after the performance condition of a liquidity event has been achieved. As such, the requisite service period is based on the estimated period over which the market condition can be achieved. When a performance goal is deemed to be probable of achievement, time-based vesting and recognition of stock-based compensation expense commence. As of June 30, 2018, and December 31, 2017, there were 454,584 and 360,594 performance and market contingent stock option awards outstanding with a grant date total fair value of $1.0 million and $0.4 million respectively. As of June 30, 2018, and December 31, 2017, the Company determined that the achievement of the requisite performance conditions was not probable and, as a result, no compensation cost was recognized for these awards. Restricted Stock A summary of the Company’s restricted stock activity for the six months ended June 30, 2018 : Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2017 478,971 $ 4.57 Granted — $ 4.57 Vested (119,742 ) $ 4.57 Unvested at June 30, 2018 359,229 $ 4.57 Stock-Based Compensation Expense The following table sets forth the total stock-based compensation expense for all options granted to employees and nonemployees, including shares sold through the issuance of non-recourse promissory notes which are considered to be options for accounting purposes, included in the Company’s statement of operations (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Research and development $ 1,969 $ 205 $ 2,943 $ 375 General and administrative 869 320 1,265 563 Total $ 2,838 $ 525 $ 4,208 $ 938

Net Loss per Common Share

Net Loss per Common Share	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Net Loss per Common Share	10. Net Loss per Common Share Basic net loss per share is calculated by dividing net loss by the weighted average number of shares outstanding for the period. Diluted net loss per share is calculated by dividing net loss by the weighted average number of shares of common stock and potential dilutive common stock equivalents outstanding during the period if the effect is dilutive. The calculation of diluted loss per share also requires that, to the extent the presumed issuance of additional shares as contingent consideration is dilutive to earnings (loss) per share for the period, adjustments to net income or net loss used in the calculation are required to remove the change in fair value of the contingent consideration liability for the period. Likewise, adjustments to the denominator are required to reflect the related dilutive shares. A reconciliation of the numerators and denominators used in computing net loss from continuing operations per share is as follows (in thousands, except per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Numerator: Net loss $ (20,002 ) $ (11,428 ) $ (36,135 ) $ (20,362 ) Denominator: Weighted average number of shares outstanding—basic and diluted 26,298,666 3,154,515 15,003,493 3,117,220 Net loss per share—basic and diluted $ (0.76 ) $ (3.62 ) $ (2.41 ) $ (6.53 ) Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: June 30, 2018 2017 Convertible preferred stock — 28,159,724 Options to purchase common stock 5,545,004 2,843,852 Early exercised common stock subject to future vesting 938,545 1,118,047 Restricted stock accounted for as options 359,229 — Warrants to purchase convertible preferred stock — 763,501 Warrants to purchase common stock 850,686 96,610 Total 7,693,464 32,981,734 Up to 739,551 shares may be contingently issued, if certain performance conditions are met under our in-licensing agreements .

Summary of Significant Accoun16

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) the rules and regulations of United States Securities and Exchange Commission (“SEC”) for interim reporting. The condensed financial statements are unaudited and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, necessary for the fair presentation for interim reporting. The results of operations for any interim period are not necessarily indicative of results of operations for any future period. Certain information and footnote disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted. Accordingly, the unaudited condensed financial statements should be read in conjunction with the financial statements as of and for the year ended December 31, 2017, which are included in the Company’s prospectus related to the Company’s initial public offering, filed May 4, 2018 (the “Prospectus”), pursuant to Rule 424 (b) under the Securities Act of 1933, as amended with the SEC.
Reverse Stock Split	Reverse Stock Split On April 19, 2018, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a 1-for-2.95 reverse split (“Reverse Split”) of shares of the Company’s common and convertible preferred stock, which was effected on April 20, 2018. The par value and authorized shares of common stock and convertible preferred stock were not adjusted as a result of the Reverse Split. All of the share and per share information included in the accompanying financial statements have been adjusted to reflect the Reverse Split. Accordingly, all share and per share information presented in the condensed financial statements herein, and notes thereto, have been retroactively adjusted to reflect the Reverse Split.
Need for Additional Capital	Need for Additional Capital The Company has incurred operating losses and has an accumulated deficit as a result of ongoing efforts to develop drug product candidates, including conducting preclinical and clinical trials and providing general and administrative support for these operations. The Company had an accumulated deficit of $123.0 million and $86.9 million as of June 30, 2018 and December 31, 2017, respectively. The Company had net losses of $36.1 million and $20.4 million for the six months ended June 30, 2018 and 2017, respectively, and net cash used in operating activities of $29.9 million and $17.6 million for the six months ended June 30, 2018 and 2017, respectively. To date, none of the Company’s drug candidates have been approved for sale and therefore the Company has not generated any revenue from contracts with customers. The Company has evaluated and concluded there are no conditions or events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern for a period of one year following the date that these financial statements are issued. Management expects operating losses to continue for the foreseeable future. As a result, the Company will need to raise additional capital. If sufficient funds on acceptable terms are not available when needed, the Company could be required to significantly reduce its operating expenses and delay, reduce the scope of, or eliminate one or more of its development programs. Failure to manage discretionary spending or raise additional financing, as needed, may adversely impact the Company’s ability to achieve its intended business objectives.
Use of Estimates	Use of Estimates The condensed financial statements have been prepared in accordance with GAAP, which requires management to make estimates and assumptions that affect the amounts and disclosures reported in the condensed financial statements and accompanying notes. The Company bases its estimates on historical experience and market-specific or other relevant assumptions that it believes are reasonable under the circumstances. The amounts of assets and liabilities reported in the Company’s balance sheets and the amount of expenses and income reported for each of the periods presented are affected by estimates and assumptions, which are used for, but are not limited to, determining the fair value of assets and liabilities, common stock valuation, contingent consideration and stock-based compensation. Actual results could differ from such estimates or assumptions.
Contingent Consideration Liability	Contingent Consideration Liability The Company has entered and may continue to enter into license agreements to access and utilize certain technology. In each case, the Company evaluates if the license agreement results in the acquisition of an asset or a business. To date none of the Company’s license agreements have been considered an acquisition of a business. For asset acquisitions, the upfront payments to acquire such licenses, as well as any future milestone payments made before product approval, are immediately recognized as research and development expense when due, provided there is no alternative future use of the rights in other research and development projects. These license agreements also include contingent consideration in the form of additional issuances of the Company’s common stock based on the achievement of certain milestones. For asset acquisitions, the Company assesses whether such contingent consideration meets the definition of a derivative, until such time that the contingency is met or expires. As of June 30, 2018, the Company has recorded a liability related to contingent consideration as the net settlement criteria of the definition of a derivative had been met. The derivative related to this contingent consideration is measured at fair value as of each balance sheet date with the related change in fair value being reflected in operating expenses.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, consisting of direct incremental legal, accounting, filing and other fees incurred related to the preparation of the IPO, have been capitalized and were offset against proceeds upon completion of the offering in May 2018. As of June 30, 2018, there were no deferred offering costs capitalized and included in current assets on the balance sheet. There were no capitalized deferred offering costs at December 31, 2017.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments with original maturities of 90 days or less from the date of purchase to be cash equivalents. Cash equivalents primarily include money market funds that invest in U.S. Treasury obligations which are stated at fair value. The Company has issued a letter of credit under a lease agreement which has been collateralized. This cash is classified as noncurrent restricted cash on the balance sheet based on the term of the underlying lease. The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the balance sheets that sum to the total of the same amounts shown in the condensed statements of cash flows (in thousands). June 30, 2018 December 31, 2017 Cash and cash equivalents $ 34,165 $ 7,298 Restricted cash 550 550 Total cash, cash equivalents, and restricted cash $ 34,715 $ 7,848
Variable Interest Entities	Variable Interest Entities The Company reviews agreements it enters into with third-party entities, pursuant to which the Company may have a variable interest in the entity, in order to determine if the entity is a variable interest entity (“VIE”). If the entity is a VIE, the Company assesses whether or not it is the primary beneficiary of that entity. In determining whether the Company is the primary beneficiary of an entity, the Company applies a qualitative approach that determines whether it has both (i) the power to direct the economically significant activities of the entity and (ii) the obligation to absorb losses of, or the right to receive benefits from, the entity that could potentially be significant to that entity. If the Company determines it is the primary beneficiary of a VIE, it consolidates that VIE into the Company’s financial statements. The Company’s determination about whether it should consolidate such VIEs is made continuously as changes to existing relationships or future transactions may result in a consolidation or deconsolidation event.
Concentrations of Risk	Concentrations of Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash, cash equivalents, restricted cash and marketable securities. Substantially all of the Company’s cash and cash equivalents and restricted cash is deposited in accounts with financial institutions that management believes are of high credit quality. Such deposits have and will continue to exceed federally insured limits. The Company maintains its cash with accredited financial institutions and accordingly, such funds are subject to minimal credit risk. The Company has not experienced any losses on its cash deposits. The contribution receivable outstanding as of December 31, 2017 was unsecured and was concentrated with one third-party organization, and accordingly the Company was exposed to credit risk. The Company received the full amount of the contribution receivable in January 2018. The Company’s investment policy limits investments to certain types of securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents, restricted cash and marketable securities and issuers of marketable securities to the extent recorded on the balance sheets. As of June 30, 2018, the Company had no off-balance sheet concentrations of credit risk. The Company depends on third-party suppliers for key raw materials used in its manufacturing processes and is subject to certain risks related to the loss of these third-party suppliers or their inability to supply the Company with adequate raw materials.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business In February 2016, the FASB issued ASU No. 2016-02 (“ASU 2016-02”), Leases (Topic 842) Leases In May 2017, the Financial Accounting Standards Board (FASB) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718)- Scope of Modification Accounting In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230: Classification of Certain Cash Receipts and Cash Payments) In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting On December 22, 2017, the U.S. federal government enacted the Tax Cuts and Jobs Act (the “Tax Act”). The Tax Act contains, among other things, significant changes to corporate taxation, including reduction of the corporate tax rate from a top marginal rate of 35% to a flat rate of 21% for tax years beginning after December 31, 2017, limitation of the deduction for net operating losses to 80% of current year taxable income and elimination of net operating loss carrybacks, implementing a territorial tax system, and requiring a mandatory one-time tax on U.S. owned undistributed foreign earnings and profits known as the transition tax. In December 2017, SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act
Fair Value Measurements	Fair Value Measurements The Company determines the fair value of financial and non-financial assets and liabilities based on the assumptions that market participants would use in pricing the asset or liability in an orderly transaction between market participants at the measurement date. The identification of market participant assumptions provides a basis for determining what inputs are to be used for pricing each asset or liability. A fair value hierarchy has been established which gives precedence to fair value measurements calculated using observable inputs over those using unobservable inputs. This hierarchy prioritized the inputs into three broad levels as follows: • Level 1: Quoted prices in active markets for identical instruments • Level 2: Other significant observable inputs (including quoted prices in active markets for similar instruments) • Level 3: Significant unobservable inputs (including assumptions in determining the fair value of certain investments) The carrying amounts of financial instruments such as cash and cash equivalents, restricted cash, contributions receivable, prepaid expenses and other current assets, accounts payable, accrued compensation, accrued and other current liabilities approximate the related fair values due to the short maturities of these instruments. The fair value of the Company’s cost method investment is measured when it is deemed to be other-than- temporarily impaired.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2018
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash within the balance sheets that sum to the total of the same amounts shown in the condensed statements of cash flows (in thousands). June 30, 2018 December 31, 2017 Cash and cash equivalents $ 34,165 $ 7,298 Restricted cash 550 550 Total cash, cash equivalents, and restricted cash $ 34,715 $ 7,848

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis and Level of Inputs Used in Measurements	The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): June 30, 2018 Total Level 1 Level 2 Level 3 Assets: Cash equivalents: Money market funds $ 20,142 $ 20,142 $ — $ — U.S. treasuries 1,000 — 1,000 — U.S. government debt securities 10,887 — 10,887 — Total cash equivalents 32,029 20,142 11,887 — Short-term marketable securities: U.S. treasuries 40,077 — 40,077 — U.S. and foreign commercial paper 28,481 — 28,481 — U.S. and foreign corporate debt securities 17,118 — 17,118 — Asset-backed securities 9,865 — 9,865 — U.S. government debt securities 56,265 — 56,265 — Total short-term marketable securities 151,806 — 151,806 — Long-term marketable securities: U.S. treasuries 2,460 — 2,460 U.S. corporate debt securities 1,969 — 1,969 — U.S. government debt securities 7,644 — 7,644 — Total long-term marketable securities 12,073 — 12,073 — Total marketable securities 163,879 — 163,879 — Total assets $ 195,908 $ 20,142 $ 175,766 $ — Liabilities: Contingent consideration 1,758 — — 1,758 Total contingent consideration $ 1,758 $ — $ — $ 1,758 December 31, 2017 Total Level 1 Level 2 Level 3 Money market funds $ 5,709 $ 5,709 $ — $ — Short-term marketable securities: U.S. and foreign commercial paper 6,359 — 6,359 — U.S. and foreign corporate debt securities 16,149 — 16,149 — Asset-backed securities 14,588 — 14,588 — U.S. government debt securities 40,362 — 40,362 — U.S. treasuries 1,754 — 1,754 — Total short-term marketable securities 79,212 — 79,212 — Long-term marketable securities: Asset-backed securities 2,742 — 2,742 — U.S. government debt securities 2,376 — 2,376 — Total long-term marketable securities 5,118 — 5,118 — Total marketable securities 84,330 — 84,330 — Total $ 90,039 $ 5,709 $ 84,330 $ —
Summary of Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs	The following table provides a reconciliation of assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the six months ended June 30, 2018 (in thousands): Amount Balance at December 31, 2017 $ — Additions — Settlements — Change in fair value 1,758 Balance at June 30, 2018 $ 1,758

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2018
Investments Debt And Equity Securities [Abstract]
Summary of Marketable Securities Classified as Available-for-Sale	Marketable securities, which are classified as available-for-sale, consisted of the following as of June 30, 2018 (in thousands): June 30, 2018 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Short-term marketable securities: U.S. and foreign commercial paper $ 28,487 $ 3 $ (9 ) $ 28,481 U.S. and foreign corporate debt securities 17,142 — (24 ) 17,118 Asset-backed securities 9,885 — (20 ) 9,865 U.S. government debt securities 56,290 3 (28 ) 56,265 U.S. treasuries 40,078 1 (2 ) 40,077 Total short-term marketable securities 151,882 7 (83 ) 151,806 Long-term marketable securities: U.S. corporate debt securities 1,970 — (1 ) 1,969 U.S. government debt securities 7,644 1 (1 ) 7,644 U.S. treasuries 2,460 — — 2,460 Total long-term marketable securities 12,074 1 (2 ) 12,073 Total marketable securities $ 163,956 $ 8 $ (85 ) $ 163,879 Marketable securities, which are classified as available-for-sale, consisted of the following as of December 31, 2017: December 31, 2017 Amortized Cost Basis Unrealized Gains Unrealized Losses Fair Value Short-term marketable securities: U.S. and foreign commercial paper $ 6,369 $ — $ (10 ) $ 6,359 U.S. and foreign corporate debt securities 16,162 — (13 ) 16,149 Asset-backed securities 14,604 — (16 ) 14,588 U.S. government debt securities 40,418 — (56 ) 40,362 U.S. treasuries 1,754 — — 1,754 Total short-term marketable securities 79,307 — (95 ) 79,212 Long-term marketable securities: Asset-backed securities 2,752 — (10 ) 2,742 U.S. government debt securities 2,375 1 — 2,376 Total long-term marketable securities 5,127 1 (10 ) 5,118 Total marketable securities $ 84,434 $ 1 $ (105 ) $ 84,330

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Summary of Future Minimum Lease Payments under Non-cancellable Operating Lease	The Company has one non-cancelable operating lease consisting of administrative and research and development office space for its Brisbane, California headquarters that expires in October 2022. Future minimum lease payments under our non-cancellable operating lease at June 30, 2018 were as follows (in thousands): Amount 2018 (remaining 6 months) $ 984 2019 2,012 2020 2,072 2021 2,135 2022 1,621 Total future minimum lease payments $ 8,824

Convertible Preferred Stock a21

Convertible Preferred Stock and Common Stock (Tables)	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
Summary of Convertible Preferred Stock	As of December 31, 2017, convertible preferred stock consisted of the following (in thousands, except share amounts): Shares Authorized Shares Issued and Outstanding Liquidation Preference Carrying Value Series A-1 9,085,738 2,887,086 $ 2,495 $ 2,457 Series A-2 32,653,411 10,498,269 9,198 9,214 Series B 50,000,000 14,774,369 179,132 162,285 Total convertible preferred stock 91,739,149 28,159,724 $ 190,825 $ 173,956

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity	A summary of the Company’s stock option activity is as follows: Number of Shares Weighted- Average Exercise Price Balances at December 31, 2017 4,196,203 $ 3.06 Granted 1,629,602 $ 13.24 Exercised (401,773 ) $ 3.11 Canceled (48,529 ) $ 7.62 Balances at June 30, 2018 5,375,503 $ 6.10
Summary of Restricted Stock Activity	A summary of the Company’s restricted stock activity for the six months ended June 30, 2018 : Shares Weighted Average Grant Date Fair Value Unvested at December 31, 2017 478,971 $ 4.57 Granted — $ 4.57 Vested (119,742 ) $ 4.57 Unvested at June 30, 2018 359,229 $ 4.57
Summary of Stock-based Compensation Expense	The following table sets forth the total stock-based compensation expense for all options granted to employees and nonemployees, including shares sold through the issuance of non-recourse promissory notes which are considered to be options for accounting purposes, included in the Company’s statement of operations (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Research and development $ 1,969 $ 205 $ 2,943 $ 375 General and administrative 869 320 1,265 563 Total $ 2,838 $ 525 $ 4,208 $ 938

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Schedule of Reconciliation of Numerators and Denominators Used In Computing Net Loss From Continuing Operations Per Share	A reconciliation of the numerators and denominators used in computing net loss from continuing operations per share is as follows (in thousands, except per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Numerator: Net loss $ (20,002 ) $ (11,428 ) $ (36,135 ) $ (20,362 ) Denominator: Weighted average number of shares outstanding—basic and diluted 26,298,666 3,154,515 15,003,493 3,117,220 Net loss per share—basic and diluted $ (0.76 ) $ (3.62 ) $ (2.41 ) $ (6.53 )
Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Per Share	Potentially dilutive securities that were not included in the diluted per share calculations because they would be anti-dilutive were as follows: June 30, 2018 2017 Convertible preferred stock — 28,159,724 Options to purchase common stock 5,545,004 2,843,852 Early exercised common stock subject to future vesting 938,545 1,118,047 Restricted stock accounted for as options 359,229 — Warrants to purchase convertible preferred stock — 763,501 Warrants to purchase common stock 850,686 96,610 Total 7,693,464 32,981,734

Organization - Additional Infor

Organization - Additional Information (Details) $ / shares in Units, $ in Millions	May 07, 2018USD ($)$ / sharesshares	Jun. 30, 2018Segment$ / sharesshares	Mar. 31, 2018shares	Feb. 28, 2018shares	Dec. 31, 2017$ / sharesshares
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of segments | Segment		1
Common stock, shares authorized		300,000,000	140,000,000	122,000,000	122,000,000
Common stock, par value | $ / shares		$ 0.0001			$ 0.0001
Preferred stock, shares authorized			103,283,818	91,739,149
IPO
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of shares issued	5,000,000
Net proceeds from issuance initial public offering after Deducting Underwriting Discounts Commissions and offering related transaction costs | $	$ 75.9
Approximate underwriting discounts commissions and offering related transaction costs | $	$ 9.1
Offering price to public to common stock | $ / shares	$ 17
Common stock, shares authorized	300,000,000
Common stock, par value | $ / shares	$ 0.0001
Preferred stock, shares authorized	10,000,000
Preferred stock, par value | $ / shares	$ 0.0001
IPO | Common Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Common shares issued upon conversion of preferred shares	32,073,149

Summary of Significant Accoun25

Summary of Significant Accounting Policies - Additional Information (Details)	Apr. 20, 2018	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)
Summary Of Significant Accounting Policies [Line Items]
Reverse split of shares of common and convertible preferred stock, conversion ratio	0.33898
Reverse split of shares of common and convertible preferred stock, effective date	Apr. 20, 2018
Accumulated deficit		$ (123,015,000)		$ (123,015,000)		$ (86,880,000)
Net losses		(20,002,000)	$ (11,428,000)	(36,135,000)	$ (20,362,000)
Net cash used in operating activities				(29,932,000)	$ (17,637,000)
Deferred offering costs		0		$ 0
Off-balance sheet concentrations of credit risk description				As of June 30, 2018, the Company had no off-balance sheet concentrations of credit risk.
Off-balance sheet concentrations of credit risk		$ 0		$ 0
Federal statutory income tax rate				21.00%		35.00%
Limitation of net operating loss deduction as percentage of current year taxable income				80.00%
Amended and Restated Certificate of Incorporation
Summary Of Significant Accounting Policies [Line Items]
Reverse split of shares of common and convertible preferred stock	1-for-2.95 reverse split

Summary of Significant Accoun26

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 34,165	$ 7,298
Restricted cash	550	550
Total cash, cash equivalents, and restricted cash	$ 34,715	$ 7,848	$ 8,454	$ 89,736

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis and Level of Inputs Used in Measurements (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Assets:
Short-term marketable securities	$ 151,806	$ 79,212
Long-term marketable securities	12,073	5,118
Total marketable securities	163,879	84,330
Fair Value, Measurements, Recurring
Assets:
Cash equivalents	32,029	5,709
Short-term marketable securities	151,806	79,212
Long-term marketable securities	12,073	5,118
Total marketable securities	163,879	84,330
Total assets	195,908	90,039
Liabilities:
Liabilities fair value disclosure	1,758
Fair Value, Measurements, Recurring | Contingent Consideration
Liabilities:
Liabilities fair value disclosure	1,758
Fair Value, Measurements, Recurring | Level 1
Assets:
Cash equivalents	20,142	5,709
Total assets	20,142	5,709
Fair Value, Measurements, Recurring | Level 2
Assets:
Cash equivalents	11,887
Short-term marketable securities	151,806	79,212
Long-term marketable securities	12,073	5,118
Total marketable securities	163,879	84,330
Total assets	175,766	84,330
Fair Value, Measurements, Recurring | Level 3
Liabilities:
Liabilities fair value disclosure	1,758
Fair Value, Measurements, Recurring | Level 3 | Contingent Consideration
Liabilities:
Liabilities fair value disclosure	1,758
Money market funds | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	20,142
Money market funds | Fair Value, Measurements, Recurring | Level 1
Assets:
Cash equivalents	20,142
U.S. Treasuries | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	1,000
Short-term marketable securities	40,077	1,754
Long-term marketable securities	2,460
U.S. Treasuries | Fair Value, Measurements, Recurring | Level 2
Assets:
Cash equivalents	1,000
Short-term marketable securities	40,077	1,754
Long-term marketable securities	2,460
US Government Debt Securities | Fair Value, Measurements, Recurring
Assets:
Cash equivalents	10,887
Short-term marketable securities	56,265	40,362
Long-term marketable securities	7,644	2,376
US Government Debt Securities | Fair Value, Measurements, Recurring | Level 2
Assets:
Cash equivalents	10,887
Short-term marketable securities	56,265	40,362
Long-term marketable securities	7,644	2,376
Asset-backed Securities | Fair Value, Measurements, Recurring
Assets:
Short-term marketable securities	9,865	14,588
Long-term marketable securities		2,742
Asset-backed Securities | Fair Value, Measurements, Recurring | Level 2
Assets:
Short-term marketable securities	9,865	14,588
Long-term marketable securities		2,742
U.S. and Foreign Commercial Paper | Fair Value, Measurements, Recurring
Assets:
Short-term marketable securities	28,481	6,359
U.S. and Foreign Commercial Paper | Fair Value, Measurements, Recurring | Level 2
Assets:
Short-term marketable securities	28,481	6,359
Corporate Debt Securities | Fair Value, Measurements, Recurring
Assets:
Short-term marketable securities	17,118	16,149
Long-term marketable securities	1,969
Corporate Debt Securities | Fair Value, Measurements, Recurring | Level 2
Assets:
Short-term marketable securities	17,118	$ 16,149
Long-term marketable securities	$ 1,969

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value assets hierarchy levels transfers amount	$ 0	$ 0
Commercial Agreements | Contingent Consideration | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Maximum amount of potential contingent consideration value	$ 11,100,000
Commercial Agreements | Clinical Stage Biopharmaceutical Company | Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration additional common stock issued	666,670

Fair Value Measurements - Sum29

Fair Value Measurements - Summary of Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - Fair Value, Measurements, Recurring - Level 3 $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value	$ 1,758
Balance at June 30, 2018	$ 1,758

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities Classified as Available-for-Sale (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	$ 163,956	$ 84,434
Unrealized Gains	8	1
Unrealized Losses	(85)	(105)
Fair Value	163,879	84,330
Short-Term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	151,882	79,307
Unrealized Gains	7
Unrealized Losses	(83)	(95)
Fair Value	151,806	79,212
Short-Term Marketable Securities | U.S. and Foreign Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	28,487	6,369
Unrealized Gains	3
Unrealized Losses	(9)	(10)
Fair Value	28,481	6,359
Short-Term Marketable Securities | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	17,142	16,162
Unrealized Losses	(24)	(13)
Fair Value	17,118	16,149
Short-Term Marketable Securities | Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	9,885	14,604
Unrealized Losses	(20)	(16)
Fair Value	9,865	14,588
Short-Term Marketable Securities | US Government Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	56,290	40,418
Unrealized Gains	3
Unrealized Losses	(28)	(56)
Fair Value	56,265	40,362
Short-Term Marketable Securities | U S Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	40,078	1,754
Unrealized Gains	1
Unrealized Losses	(2)
Fair Value	40,077	1,754
Long-Term Marketable Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	12,074	5,127
Unrealized Gains	1	1
Unrealized Losses	(2)	(10)
Fair Value	12,073	5,118
Long-Term Marketable Securities | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	1,970
Unrealized Losses	(1)
Fair Value	1,969
Long-Term Marketable Securities | Asset-backed Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis		2,752
Unrealized Losses		(10)
Fair Value		2,742
Long-Term Marketable Securities | US Government Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	7,644	2,375
Unrealized Gains	1	1
Unrealized Losses	(1)
Fair Value	7,644	$ 2,376
Long-Term Marketable Securities | U S Treasuries
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost Basis	2,460
Fair Value	$ 2,460

Marketable Securities - Additio

Marketable Securities - Additional Information (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Investments Debt And Equity Securities [Abstract]
Available-for sale securities maximum remaining contractual maturity	2 years
Realized gains or losses on available-for-sale securities	$ 0

License Agreements - Additional

License Agreements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	May 31, 2018
Research And Development Arrangement Contract To Perform For Others [Line Items]
Research and development expense	$ 15,198,000	$ 9,213,000	$ 28,223,000	$ 16,183,000
Commercial Agreements
Research And Development Arrangement Contract To Perform For Others [Line Items]
Funding provided for the research and development under the agreement in period			2020-02
Research and development expense			$ 300,000	$ 300,000
Commercial Agreements | Clinical Stage Biopharmaceutical Company | Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent consideration additional common stock issued			666,670
Milestone payments			$ 70,300,000
Funding provided for the research and development under the agreement	2,000,000		2,000,000
Commercial Agreements | Affiliate of Clinical-Stage Biopharmaceutical Company
Research And Development Arrangement Contract To Perform For Others [Line Items]
Aggregate purchase price			500,000
Additional amount invested					$ 500,000
Commercial Agreements And Compound Library And Option Agreement | Clinical Stage Biopharmaceutical Company
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent consideration liability	1,800,000		1,800,000
Other Licensing Agreements with Research Institutions
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent consideration, milestone or royalty payments	$ 0		$ 0

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)Lease	Jun. 30, 2017USD ($)
Commitments And Contingencies Disclosure [Abstract]
Number of non-cancelable operating lease | Lease	1
Operating lease, expiration date	Oct. 31, 2022
Rent expense, operating lease | $	$ 0.9	$ 0.8

Commitments and Contingencies34

Commitments and Contingencies - Summary of Future Minimum Lease Payments under Non-cancellable Operating Lease (Details) $ in Thousands	Jun. 30, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
2018 (remaining 6 months)	$ 984
2,019	2,012
2,020	2,072
2,021	2,135
2,022	1,621
Total future minimum lease payments	$ 8,824

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Details) $ in Thousands	Apr. 04, 2018USD ($)	Apr. 30, 2018USD ($)	Jan. 31, 2018USD ($)shares	Oct. 31, 2017USD ($)Promissoryshares	Jul. 31, 2016USD ($)shares	Apr. 30, 2016USD ($)shares	Dec. 31, 2015USD ($)shares	Jun. 30, 2018USD ($)PromissoryNoteExecutive	Jun. 30, 2018USD ($)PromissoryNoteExecutive	Jun. 30, 2017USD ($)
Related Party Transaction [Line Items]
Number of promissory notes | PromissoryNote								3	3
Number of executive officers | Executive								2	2
Proceeds from issuance of convertible preferred stock									$ 59,899	$ 42,880
Executive Officer
Related Party Transaction [Line Items]
Due from related parties				$ 2,100
Restricted stock purchased by related party, shares | shares				625,084
Forgiveness of promissory note accounted as modification of share based payment								$ 800	800
Stockholders | Financing Activities
Related Party Transaction [Line Items]
Proceeds from issuance of convertible preferred stock									$ 3,000
Promissory Note | Executive Officer
Related Party Transaction [Line Items]
Number of promissory notes | Promissory				2
Due from related parties			$ 400		$ 200	$ 200	$ 200
Interest rate			2.50%		2.50%	2.50%	2.50%
Promissory Note | Common Stock | Executive Officer
Related Party Transaction [Line Items]
Early exercise options in aggregate | shares			114,406		667,253	667,253	667,253
Full-recourse Notes | Executive Officer
Related Party Transaction [Line Items]
Repayment of promissory notes	$ 200
Promissory Note One | Executive Officer
Related Party Transaction [Line Items]
Due from related parties				$ 1,600
Interest rate				1.85%
Promissory Note Two | Executive Officer
Related Party Transaction [Line Items]
Due from related parties				$ 500
Interest rate				1.85%
Non-Recourse Promissory Note | Executive Officer
Related Party Transaction [Line Items]
Outstanding principal and accrued interest, forgiveness		$ 1,600
Repayment of promissory notes	$ 500

Convertible Preferred Stock a36

Convertible Preferred Stock and Common Stock - Additional Information (Details)	May 07, 2018$ / sharesshares	Apr. 30, 2018USD ($)$ / sharesshares	Mar. 31, 2018USD ($)$ / sharesshares	Jun. 30, 2018USD ($)$ / sharesshares	Jun. 30, 2017USD ($)	Feb. 28, 2018shares	Dec. 31, 2017shares
Class Of Stock [Line Items]
Common stock, shares authorized			140,000,000	300,000,000		122,000,000	122,000,000
Preferred stock, shares authorized			103,283,818			91,739,149
Number of stock, shares issued							28,159,724
Net proceeds from sale of convertible preferred stock | $				$ 59,899,000	$ 42,880,000
Gross proceeds from public offering | $				$ 79,050,000
Convertible preferred stock warrants converted into warrants	763,501
IPO
Class Of Stock [Line Items]
Common stock, shares authorized	300,000,000
Preferred stock, shares authorized	10,000,000
Share price | $ / shares	$ 17
Common Stock
Class Of Stock [Line Items]
Conversion ratio of preferred to common shares				1
Common Stock | IPO
Class Of Stock [Line Items]
Common shares issued upon conversion of preferred shares	32,073,149
Minimum percentage of preferred shareholders required to request conversion				60.00%
Common Stock | Minimum | IPO
Class Of Stock [Line Items]
Gross proceeds from public offering | $				$ 30,000,000
Share price | $ / shares				$ 15.3317
Series C Convertible Preferred Stock
Class Of Stock [Line Items]
Preferred stock, shares designated			11,544,669
Number of stock, shares issued		322,852	3,590,573
Shares price per share | $ / shares		$ 15.3317	$ 15.3317
Net proceeds from sale of convertible preferred stock | $		$ 5,000,000	$ 54,900,000
Liquidation preference per share | $ / shares				15.3317
Series C Convertible Preferred Stock | U.S. National Securities Exchange | Minimum
Class Of Stock [Line Items]
Gross proceeds from public offering | $			$ 30,000,000
Series C Convertible Preferred Stock | Common Stock
Class Of Stock [Line Items]
Conversion ratio of preferred to common shares			1
Series A-1 Convertible Preferred Stock
Class Of Stock [Line Items]
Number of stock, shares issued							2,887,086
Conversion price of preferred stock | $ / shares				0.864
Liquidation preference per share | $ / shares				0.864
Series A-2 Convertible Preferred Stock
Class Of Stock [Line Items]
Number of stock, shares issued							10,498,269
Conversion price of preferred stock | $ / shares				0.876
Liquidation preference per share | $ / shares				0.876
Series B Convertible Preferred Stock
Class Of Stock [Line Items]
Number of stock, shares issued							14,774,369
Conversion price of preferred stock | $ / shares				12.125
Liquidation preference per share | $ / shares				$ 12.125
Noncumulative Preferred Stock
Class Of Stock [Line Items]
Dividends rate of respective series of convertible preferred stock issuance price				6.00%

Convertible Preferred Stock a37

Convertible Preferred Stock and Common Stock - Summary of Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Temporary Equity [Line Items]
Convertible preferred stock, Shares Authorized	10,000,000	91,739,149
Convertible preferred stock, Shares Issued		28,159,724
Convertible preferred stock, Shares Outstanding		28,159,724
Convertible preferred stock, Liquidation Preference		$ 190,825
Convertible preferred stock, Carrying Value		$ 173,956
Series A-1
Temporary Equity [Line Items]
Convertible preferred stock, Shares Authorized		9,085,738
Convertible preferred stock, Shares Issued		2,887,086
Convertible preferred stock, Shares Outstanding		2,887,086
Convertible preferred stock, Liquidation Preference		$ 2,495
Convertible preferred stock, Carrying Value		$ 2,457
Series A-2
Temporary Equity [Line Items]
Convertible preferred stock, Shares Authorized		32,653,411
Convertible preferred stock, Shares Issued		10,498,269
Convertible preferred stock, Shares Outstanding		10,498,269
Convertible preferred stock, Liquidation Preference		$ 9,198
Convertible preferred stock, Carrying Value		$ 9,214
Series B
Temporary Equity [Line Items]
Convertible preferred stock, Shares Authorized		50,000,000
Convertible preferred stock, Shares Issued		14,774,369
Convertible preferred stock, Shares Outstanding		14,774,369
Convertible preferred stock, Liquidation Preference		$ 179,132
Convertible preferred stock, Carrying Value		$ 162,285

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($)	1 Months Ended		6 Months Ended	10 Months Ended	12 Months Ended
	Mar. 31, 2018	Jun. 30, 2013	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option awards outstanding			5,375,503	5,375,503	4,196,203
Performance Contingent Stock Options Granted to Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Estimated fair value of stock options granted			$ 400,000
Performance Contingent Stock Options Granted to Employees | Executive Officer
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option awards exercisable upon the achievement of performance goals			53,575	53,575
Weighted average exercise price			$ 3.42	$ 3.42
Performance Contingent Stock Options Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option awards outstanding			329,498	329,498	275,922
Stock option awards, grant date fair value			$ 700,000	$ 700,000	$ 300,000
Compensation cost recognized			$ 0		$ 0
Performance and Market Contingent Stock Options Granted to Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option awards outstanding			454,584	454,584	360,594
Stock option awards, grant date fair value			$ 1,000,000	$ 1,000,000	$ 400,000
Compensation cost recognized			$ 0		$ 0
Performance and Market Contingent Stock Options Granted to Employees | Vesting 1
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option awards exercisable upon the achievement of performance goals			53,575	53,575
Vesting rights			(i) the closing of a financing where the Company sells shares of its equity securities to institutional investors at a minimum price per share, (ii) a change in control with aggregate proceeds payable to the Company’s common stock at a minimum price per share, or (iii) an initial public offering that becomes effective at a minimum specified price per share.
Trailing period for Initial public offering that becomes effective or achievement with a minimum market capitalization			30 days
Performance and Market Contingent Stock Options Granted to Employees | Vesting 2
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option awards exercisable upon the achievement of performance goals			107,152	107,152
Vesting rights			(i) the closing of a financing where the Company sells shares of its equity securities to institutional investors at a minimum pre-money valuation, (ii) a change in control with a minimum aggregate proceeds payable to the Company’s common stock, or (iii) an initial public offering that becomes effective or an achievement of a minimum market capitalization, as measured by a trailing 30 day volume-weighted average price.
Performance and Market Contingent Stock Options Granted to Employees | Executive Team
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average exercise price			$ 3.42	$ 3.42
Estimated fair value of stock options granted			$ 700,000
Performance and Market Contingent Stock Options Granted to Employees | Executive Team | Common Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option awards exercisable			160,727	160,727
2018 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance	536,242
2018 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock, capital shares reserved for future issuance	4,289,936
Vesting period, options	4 years
Number of shares of common stock authorized for issuance			5,058,434	5,058,434
2018 Incentive Award Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period from the date of grant, options	10 years
2018 Incentive Award Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price as a percentage of estimated fair value of the shares on the date of grant	100.00%
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period, options		4 years
Exercise price				$ 3.42
Exercise price range, lower range limit				3.95
Exercise price range, upper range limit				$ 5.43
2013 Equity Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period from the date of grant, options		10 years
2013 Equity Incentive Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price as a percentage of estimated fair value of the shares on the date of grant		100.00%
Exercise price as a percentage of estimated grant date fair value of shares for a 10% shareholder		110.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2018$ / sharesshares
Number of Shares
Balances at December 31, 2017 | shares	4,196,203
Granted | shares	1,629,602
Exercised | shares	(401,773)
Canceled | shares	(48,529)
Balances at June 30, 2018 | shares	5,375,503
Weighted-Average Exercise Price
Balances at December 31, 2017 | $ / shares	$ 3.06
Granted | $ / shares	13.24
Exercised | $ / shares	3.11
Canceled | $ / shares	7.62
Balances at June 30, 2018 | $ / shares	$ 6.10

Stock-Based Compensation - Su40

Stock-Based Compensation - Summary of Restricted Stock Activity (Details) - Restricted Stock	6 Months Ended
	Jun. 30, 2018$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares, Unvested at December 31, 2017 | shares	478,971
Shares, Vested | shares	(119,742)
Shares, Unvested at June 30, 2018 | shares	359,229
Weighted Average Grant Date Fair Value, Unvested at December 31, 2017	$ 4.57
Weighted Average Grant Date Fair Value, Granted	4.57
Weighted Average Grant Date Fair Value, Vested	4.57
Weighted Average Grant Date Fair Value, Unvested at June 30, 2018	$ 4.57

Stock-Based Compensation - Su41

Stock-Based Compensation - Summary of Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 2,838	$ 525	$ 4,208	$ 938
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,969	205	2,943	375
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 869	$ 320	$ 1,265	$ 563

Net Loss per Common Share - Sch

Net Loss per Common Share - Schedule of Reconciliation of Numerators and Denominators Used In Computing Net Loss From Continuing Operations Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net loss	$ (20,002)	$ (11,428)	$ (36,135)	$ (20,362)
Denominator:
Weighted average number of shares used in computing net loss per share, basic and diluted	26,298,666	3,154,515	15,003,493	3,117,220
Net loss per share, basic and diluted	$ (0.76)	$ (3.62)	$ (2.41)	$ (6.53)

Net Loss per Common Share - Sum

Net Loss per Common Share - Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	7,693,464	32,981,734
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share		28,159,724
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	5,545,004	2,843,852
Early Exercised Common Stock Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	938,545	1,118,047
Restricted Stock Accounted For as Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	359,229
Warrants to Purchase Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share		763,501
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of diluted net loss per share	850,686	96,610

Net Loss per Common Share - Add

Net Loss per Common Share - Additional Information (Details)	6 Months Ended
	Jun. 30, 2018shares
Maximum
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Shares contingently issued	739,551