Aptinyx (APTX) 10-Q 13 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 13, 2018
Document and Entity Information
Entity Registrant Name	Aptinyx Inc.
Entity Central Index Key	1,674,365
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		33,497,344
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 165,578	$ 92,136
Restricted cash	252
Accounts receivable	593	937
Prepaid expenses and other current assets	1,169	1,960
Total current assets	167,592	95,033
Other assets	674	473
Property and equipment, net	1,813	1,816
Total assets	170,079	97,322
Current liabilities:
Accounts payable	1,208	1,537
Accrued expenses and other current liabilities	6,465	2,835
Total current liabilities	7,673	4,372
Other long-term liabilities	435	282
Total liabilities	8,108	4,654
Commitments and contingencies (see Note 10)
Stockholders' equity (deficit):
Preferred stock, $0.01 par value, 10,000 and no shares authorized as of September 30, 2018 and December 31, 2017, respectively; no shares issued and outstanding as of September 30, 2018 and December 31, 2017, respectively
Common stock, $0.01 par value, 150,000 shares authorized, 33,229 issued and outstanding as of September 30, 2018 and 900,000 shares authorized, 5,342 issued and outstanding as of December 31, 2017	332	53
Additional paid-in capital	253,084	12,486
Accumulated deficit	(91,445)	(52,257)
Total stockholders’ equity (deficit)	161,971	(39,718)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 170,079	97,322
Series A-1
Convertible preferred stock:
Convertible preferred stock		22,650
Series A-2
Convertible preferred stock:
Convertible preferred stock		39,979
Series B
Convertible preferred stock:
Convertible preferred stock		$ 69,757

Condensed Balance Sheets (Paren

Condensed Balance Sheets (Parenthetical) - $ / shares shares in Thousands	Sep. 30, 2018	Dec. 31, 2017
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	150,000	900,000
Common stock, shares issued	33,229	5,342
Common stock, shares outstanding	33,229	5,342
Series A-1
Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Convertible preferred stock, shares authorized	0	151,773
Convertible preferred stock, shares issued	0	151,773
Convertible preferred stock, shares outstanding	0	151,773
Series A-2
Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Convertible preferred stock, shares authorized	0	173,453
Convertible preferred stock, shares issued	0	173,453
Convertible preferred stock, shares outstanding	0	173,453
Series B
Convertible preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Convertible preferred stock, shares authorized	0	234,955
Convertible preferred stock, shares issued	0	234,955
Convertible preferred stock, shares outstanding	0	234,955

Condensed Statements of Operati

Condensed Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Condensed Statements of Operations
Collaboration and grant revenue	$ 943	$ 1,205	$ 5,535	$ 3,778
Type of Revenue [Extensible List]	aptx:CollaborationAndGrantMember	aptx:CollaborationAndGrantMember	aptx:CollaborationAndGrantMember	aptx:CollaborationAndGrantMember
Operating expenses:
Research and development	$ 11,950	$ 8,067	$ 37,860	$ 24,930
General and administrative	3,782	1,318	7,853	3,819
Total operating expenses	15,732	9,385	45,713	28,749
Loss from operations	(14,789)	(8,180)	(40,178)	(24,971)
Other income	608	35	990	129
Net loss and comprehensive loss	$ (14,181)	$ (8,145)	$ (39,188)	$ (24,842)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (0.43)	$ (1.56)	$ (2.48)	$ (4.82)
Weighted-average number of common shares outstanding, basic and diluted (in shares)	33,191	5,232	15,789	5,159

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (39,188)	$ (24,842)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	336	225
Stock-based compensation expense	1,984	653
Changes in operating assets and liabilities:
Prepaid expenses and other assets	356	(613)
Accounts receivable	344	(262)
Accounts payable	(263)	839
Accrued expenses and other liabilities	3,966	(336)
Net cash used in operating activities	(32,465)	(24,336)
Cash flows from investing activities:
Purchases of property and equipment	(391)	(1,338)
Net cash used in investing activities	(391)	(1,338)
Cash flows from financing activities:
Proceeds from issuance of Series A-2 convertible preferred stock, net issuance of costs		39,979
Payment of deferred issuance costs associated with Series B convertible preferred stock financing	(232)
Proceeds from stock options exercised	2
Proceeds from initial public offering, net of underwriters discounts	109,517
Payment of deferred offering costs	(2,971)
Net cash provided by financing activities	106,316	39,979
Net increase in cash, cash equivalents, and restricted cash	73,460	14,305
Cash, cash equivalents and restricted cash at beginning of period	92,609	16,953
Cash, cash equivalents and restricted cash at end of period	166,069	31,258
Supplemental disclosure of non-cash investing and financing activities:
Property and equipment purchases not yet paid		$ 34
Deferred initial public offering costs not yet paid	$ 41

Statements of Convertible Prefe

Statements of Convertible Preferred Stock - USD ($) shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Series A-1
Convertible Preferred Stock Rollforward
Convertible preferred stock beginning balance	$ 22,650	$ 22,650
Convertible preferred stock shares beginning balance	151,773	151,773
Conversion of preferred stock upon IPO	$ (22,650)
Conversion of preferred stock upon IPO (in shares)	(151,773)
Convertible preferred stock shares ending balance	0	151,773
Convertible preferred stock ending balance		$ 22,650
Series A-2
Convertible Preferred Stock Rollforward
Convertible preferred stock beginning balance	$ 39,979
Convertible preferred stock shares beginning balance	173,453
Issuance of convertible preferred stock, net of issuance costs		$ 39,979
Issuance of convertible preferred stock, net of issuance costs (in shares)		173,453
Conversion of preferred stock upon IPO	$ (39,979)
Conversion of preferred stock upon IPO (in shares)	(173,453)
Convertible preferred stock shares ending balance	0	173,453
Convertible preferred stock ending balance		$ 39,979
Series B
Convertible Preferred Stock Rollforward
Convertible preferred stock beginning balance	$ 69,757
Convertible preferred stock shares beginning balance	234,955
Issuance of convertible preferred stock, net of issuance costs		$ 69,757
Issuance of convertible preferred stock, net of issuance costs (in shares)		234,955
Conversion of preferred stock upon IPO	$ (69,757)
Conversion of preferred stock upon IPO (in shares)	(234,955)
Convertible preferred stock shares ending balance	0	234,955
Convertible preferred stock ending balance		$ 69,757

Statements of Convertible Pre_2

Statements of Convertible Preferred Stock (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)
Series A-2
Stock issuance costs capitalized	$ 21
Series B
Stock issuance costs capitalized	$ 243

Statements of Stockholders' (De

Statements of Stockholders' (Deficit) Equity - USD ($) shares in Thousands, $ in Thousands	Common stock	Additional paid-in capital	Accumulated deficit	Total
Stockholders' (deficit) equity beginning balance at Dec. 31, 2016	$ 50	$ 11,588	$ (20,189)	$ (8,551)
Stockholders' (deficit) equity shares beginning balance at Dec. 31, 2016	5,049
Stockholders' (Deficit) Equity Rollforward
Issuance of common stock upon vesting of restricted stock awards	$ 3	(3)
Issuance of common stock upon vesting of restricted stock awards (in shares)	293
Stock-based compensation		901		901
Net loss			(32,068)	$ (32,068)
Stockholders' (deficit) equity shares ending balance at Dec. 31, 2017	5,342			5,342
Stockholders' (deficit) equity ending balance at Dec. 31, 2017	$ 53	12,486	(52,257)	$ (39,718)
Stockholders' (Deficit) Equity Rollforward
Issuance of common stock upon vesting of restricted stock awards	$ 2	(2)
Issuance of common stock upon vesting of restricted stock awards (in shares)	220
Stock-based compensation		1,984		1,984
Conversion of preferred stock upon IPO	$ 203	132,183		132,386
Conversion of preferred stock upon IPO (in shares)	20,306
Issuance of common stock upon IPO, net of underwriters' discount and other offering costs of $2,902	$ 74	106,431		106,505
Issuance of common stock upon IPO, net of underwriters' discount and other offering costs of $2,902 (in shares)	7,360
Issuance of common stock upon exercise of stock options		2		2
Issuance of common stock upon exercise of stock options (in shares)	1
Net loss			(39,188)	$ (39,188)
Stockholders' (deficit) equity shares ending balance at Sep. 30, 2018	33,229			33,229
Stockholders' (deficit) equity ending balance at Sep. 30, 2018	$ 332	$ 253,084	$ (91,445)	$ 161,971

Statements of Stockholders' (_2

Statements of Stockholders' (Deficit) Equity (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2018USD ($)
Statements of Stockholders' (Deficit) Equity
Stock issuance costs capitalized	$ 2,902

Organization

Organization	9 Months Ended
	Sep. 30, 2018
Organization
Organization	1. Organization Description of business Aptinyx Inc. (the “Company” or “Aptinyx”) was incorporated in Delaware on June 24, 2015 and maintains its headquarters in Evanston, Illinois. Aptinyx is a clinical‑stage biopharmaceutical company focused on the discovery, development, and commercialization of novel, proprietary, synthetic small molecules for the treatment of brain and nervous system disorders. Aptinyx has a platform for discovering proprietary compounds that work through a novel mechanism: modulation of N‑methyl‑D‑aspartate receptors (“NMDAr”), which are vital to normal and effective brain and nervous system functions. This mechanism has applicability across a number of brain and nervous system disorders. Initial public offering On June 20, 2018, the Company’s registration statement on Form S ‑ 1 (File No. 333‑225150) relating to the initial public offering (“IPO”) of its common stock became effective and on June 25, 2018, the IPO closed. Pursuant to the IPO, the Company issued and sold 7,359,998 shares of common stock at a public offering price of $16.00 per share, which included 959,999 shares sold pursuant to the exercise of the underwriters’ option to purchase additional shares. The Company received net proceeds of $106.5 million after deducting underwriting discounts and commissions and other offering costs of $3.0 million. The shares began trading on the Nasdaq Global Select Market on June 21, 2018. Upon the closing of the IPO, all of the Company’s outstanding shares of convertible preferred stock automatically converted into 20,306,497 shares of common stock at the applicable conversion ratio. The Company is also authorized to issue 10 million shares of undesignated preferred stock, par value $0.01, in one or more series. As of September 30, 2018, no shares of preferred stock were issued or outstanding. Liquidity and capital resources As of September 30, 2018, the Company had cash and cash equivalents of $165.6 million which the Company believes will be sufficient to funds its planned operations for a period of at least twelve months from the date of issuance of these condensed financial statements.

Summary of significant accounti

Summary of significant accounting policies	9 Months Ended
	Sep. 30, 2018
Summary of significant accounting policies
Summary of significant accounting policies	2. Basis of presentation The condensed financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. The accompanying condensed financial statements reflect all adjustments consisting of normal, recurring adjustments that are necessary for a fair presentation of the financial position results of operations and cash flows for the interim periods presented. Interim results are not necessarily indicative of results for a full year. Accordingly, these financial statements should be read in conjunction with the financial statements as of and for the year ended December 31, 2017, and notes thereto, included in the Company’s final prospectus for the IPO filed with the SEC pursuant to Rule 424(b)(4) dated June 20, 2018 (the “Prospectus”). From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards, which delays the adoption of these accounting standards until they would apply to private companies. Reverse stock split On June 7, 2018, the Company effected a one-for‑27.58621 reverse stock split of the Company’s issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for the Company’s convertible preferred stock. The par value per share and authorized shares of common and convertible preferred stock were not adjusted as a result of the reverse stock split. All common stock and common stock per share amounts within the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital. Use of estimates The financial statements are prepared in conformity with GAAP. This process requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates. Significant accounting policies The Company’s significant accounting policies are described in Note 3, “Summary of significant accounting policies,” in the Prospectus. There have been no material changes to the significant accounting policies during the period ended September 30, 2018. Recently issued accounting pronouncements In February 2016, the FASB issued ASU No. 2016‑02, Leases (“ASU 2016‑02”), which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short‑term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. The new standard will be effective for the Company beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the potential impact ASU 2016‑02 may have on its financial statements. In May 2014, the FASB issued ASU No. 2014‑09, Revenue from Contracts with Customers (“ASU 2014‑09”), which supersedes nearly all existing revenue recognition guidance. The core principle of ASU 2014‑09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled for those goods or services. ASU 2014‑09 defines a five step process to achieve this core principle and, in doing so, more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP. The standard is effective for annual periods beginning after December 15, 2018, using either of the following transition methods: (i) a full retrospective approach reflecting the application of the standard in each prior reporting period with the option to elect certain practical expedients, or (ii) a retrospective approach with the cumulative effect of initially adopting ASU 2014‑09 recognized at the date of adoption (which includes additional footnote disclosures). The Company is evaluating the impact of the pending adoption of ASU 2014‑09 on the financial statements and has not yet determined the method by which the Company will adopt the standard when required.

Supplemental financial informat

Supplemental financial information	9 Months Ended
	Sep. 30, 2018
Supplemental financial information
Supplemental financial information	3. Supplemental financial information Cash, cash equivalents and restricted cash Cash and cash equivalents consist of cash and, if applicable, highly liquid investments with an original maturity of three months or less when purchased. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). As of As of September 30, December 31, Cash and cash equivalents $ 165,578 $ 92,136 Short-term and long-term restricted cash 491 473 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 166,069 $ 92,609 Prepaid expenses and other current assets Prepaid expenses and other current assets consist of the following (in thousands): As of As of September 30, December 31, Prepaid clinical $ 173 $ 1,718 Prepaid insurance 791 137 Other prepaid expenses and current assets 205 105 Total prepaid expenses and other current assets $ 1,169 $ 1,960 Accrued expenses and other current liabilities Accrued expenses and other current liabilities consist of the following (in thousands): As of As of September 30, December 31, Employee-related expenses $ 2,056 $ 1,435 Development costs and sponsored research 1,805 737 Clinical trials 2,282 69 Other 322 594 Total accrued expenses and other current liabilities $ 6,465 $ 2,835

Research collaboration agreemen

Research collaboration agreement with Allergan	9 Months Ended
	Sep. 30, 2018
Research collaboration agreement with Allergan
Research collaboration agreement with Allergan	4. Research collaboration agreement with Allergan On July 24, 2015, the Company entered into a Research Collaboration Agreement (“RCA”) with Naurex Inc., a subsidiary of Allergan plc (“Allergan”), focused on the research and discovery of small molecules that modulate NMDArs. The collaboration is supervised by a Joint Steering Committee (“JSC”) comprising an equal number of representatives from both the Company and Allergan. Under the terms of the agreement, Allergan will pay the Company $1.0 million for each option exercised by Allergan. Under the terms of the agreement, the RCA will terminate upon the earlier of a predetermined anniversary of the RCA or on the date on which Allergan exercises three options to acquire molecules from a pool of eligible compounds. On May 16, 2018, Allergan exercised its option to acquire exclusive rights to develop and commercialize AGN-241751 within a predefined set of indications. For the nine months ended September 30, 2018, the Company recognized the $1.0 million non-refundable milestone payment within collaboration and grant revenue in the statements of operations as there were no remaining performance obligations associated with the optioned compound. The Company accounts for the agreement as a joint risk-sharing collaboration in accordance with ASC 808, Collaboration Arrangements. Costs between the Company and Allergan with respect to each party’s share of development costs that have been incurred pursuant to the RCA are substantially recorded within research and development in the accompanying statements of operations. Reimbursable expenses under the RCA include chemistry, discovery, screening, and profiling efforts around novel NMDAr modulators from the Company’s discovery platform as well as salary of full-time employees at a fixed annual rate for each individual assigned to those efforts, consistent with oversight and guidance of the JSC. Such costs for each compound are considered reimbursable up until the point that the compound is selected by one of the collaboration parties. As such, none of the costs reimbursed by Allergan in any period presented were directly related to the Company’s lead product candidates, NYX-2925, NYX-783, and NYX-458, which the Company selected under the collaboration. During the three months ended September 30, 2018 and 2017, the Company recorded expenses of $1.9 million and $1.9 million, respectively, for certain development activities in accordance with the terms of the RCA of which 50% was reimbursed by Allergan. The Company received reimbursements of $0.9 million and $1.0 million during the three months ended September 30, 2018 and 2017, respectively. During the nine months ended September 30, 2018 and 2017, the Company recorded expenses of $5.8 million and $5.8 million, respectively, for certain development activities in accordance with the terms of the RCA of which 50% was reimbursed by Allergan. The Company received reimbursements of $2.9 and $2.9 million during the nine months ended September 30, 2018 and 2017, respectively. Such reimbursements were reported within collaboration and grant revenue in the statements of operations.

Fair value measurements

Fair value measurements	9 Months Ended
	Sep. 30, 2018
Fair value measurements
Fair value measurements	5. Fair value measurements ASC 820, Fair Value Measurement (“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). ASC 820 identifies fair value as the exchange price, or exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tier fair value hierarchy that distinguishes between the following: · Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities; · Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly; and · Level 3 inputs are unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying values reported in the Company’s balance sheets for cash and cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued expenses are reasonable estimates of their fair values due to the short-term nature of these items. Assets measured at fair value as of September 30, 2018 are as follows (in thousands): September 30, Level 1 Level 2 Level 3 Assets Money market funds, included in cash and cash equivalents $ 163,705 $ 163,705 $ — $ — Money market funds, included in restricted cash 252 252 — — Money market funds, included in other assets 67 67 — — $ 164,024 $ 164,024 $ — $ — Assets measured at fair value as of December 31, 2017 are as follows (in thousands): December 31, Level 1 Level 2 Level 3 Assets Money market funds, included in cash and cash equivalents $ 89,553 $ 89,553 $ — $ — Money market funds, included in other assets 317 317 — — $ 89,870 $ 89,870 $ — $ —

Property and equipment

Property and equipment	9 Months Ended
	Sep. 30, 2018
Property and equipment
Property and equipment	6 . Property and equipment Property and equipment are as follows (in thousands): As of As of September 30, December 31, Computer software and equipment $ 15 $ 15 Office equipment and furniture 160 92 Laboratory equipment 1,571 1,529 Leasehold improvements 1,051 748 Construction in progress — 22 Less accumulated depreciation (984) (590) Property and equipment, net $ 1,813 $ 1,816 Depreciation expense was $0.1 million for each of the three months ended September 30, 2018 and 2017, and $0.4 million and $0.2 million for the nine months ended September 30, 2018 and 2017, respectively.

Stock incentive plans

Stock incentive plans	9 Months Ended
	Sep. 30, 2018
Stock incentive plans
Stock incentive plans	7. Stock incentive plans On June 5, 2018, the Company’s stockholders approved the 2018 Stock Option and Incentive Plan (the “2018 Plan”), which became effective on June 20, 2018. The number of shares available for grant under the Company’s 2018 Plan as of September 30, 2018 was 3,878,940, which includes 505,046 shares of the Company’s common stock reserved under the Company’s 2015 Stock Option and Grant Plan (the “2015 Plan”) that became available for issuance upon the effectiveness of the 2018 Plan. No future issuance will be made under the 2015 Plan. Stock‑based compensation expense Non-cash stock-based compensation expense recognized in the accompanying statements of operations relating to both stock options and restricted stock awards for the three and nine months ended September 30, 2018 and 2017 was as follows (in thousands): Three months ended Nine months ended September 30, September 30, Research and development $ 242 $ 91 $ 616 $ 233 General and administrative 478 151 1,368 420 Total stock‑based compensation expense $ 720 $ 242 $ 1,984 $ 653 Stock options The table below summarizes activity related to stock options (in thousands, except per share amounts): Weighted‑ Weighted‑ average average remaining Aggregate exercise contractual intrinsic Options Shares price term value Outstanding, December 31, 2017 1,498 $ 2.48 8.93 $ 4,146 Granted 2,443 9.95 Exercised 1 1.82 Forfeited and canceled (5) 2.77 Outstanding, September 30, 2018 3,937 $ 7.07 8.94 $ 86,148 Vested and expected to vest at September 30, 2018 3,937 $ 7.07 8.94 $ 86,148 Exercisable at September 30, 2018 702 $ 2.28 8.08 $ 18,739 During the nine months ended September 30, 2018 and 2017, the Company granted 2.4 million and 1.2 million stock options, respectively and these options had a weighted-average grant-date fair value of $9.95 and $2.59 per share, respectively. As of September 30, 2018, there was $15.3 million of total unrecognized stock-based compensation expense related to non-vested stock options which is expected to be recognized over a weighted-average period of 3.16 years. The options have a ten-year life and generally vest over a period of four years, subject to continuous employment. Restricted stock awards Non-cash restricted stock award expense recognized in the accompanying statements of operations was $0.1 million for each of the three months ended September 30, 2018 and 2017 and $0.3 million for each of the nine months ended September 30, 2018 and 2017. The total fair value of shares that vested in the nine months ended September 30, 2018 was $1.4 million. At September 30, 2018, there was $0.3 million of unrecognized compensation cost related to 268,000 unvested restricted stock awards that will be recognized as expense over a weighted-average period of 0.91 years.

Net loss per share

Net loss per share	9 Months Ended
	Sep. 30, 2018
Net loss per share
Net loss per share	8. Net loss per share Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the three and nine months ended September 30, 2018 and 2017 (in thousands, except per share data): Three months ended Nine months ended September 30, September 30, Numerator: Net loss attributable to common stockholders $ (14,181) $ (8,145) $ (39,188) $ (24,842) Denominator: Weighted-average common shares outstanding—basic and diluted 33,191 5,232 15,789 5,159 Net loss per share attributable to common stockholders—basic and diluted $ (0.43) $ (1.56) $ (2.48) $ (4.82) The following common stock equivalents outstanding as of September 30, 2018 and 2017, were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti‑dilutive (in thousands): As of September 30, Series A-1 convertible preferred stock — 5,502 Series A-2 convertible preferred stock — 6,288 Stock options issued and outstanding 3,937 1,497 Unvested restricted stock 268 655 Total 4,205 13,942

Income taxes

Income taxes	9 Months Ended
	Sep. 30, 2018
Income taxes
Income taxes	9. Income taxes Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax bases of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Valuation allowances are provided if based upon the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, including its net operating losses. Based on its history of operating losses, the Company believes that it is more likely than not that the benefit of its deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance for deferred tax assets as of September 30, 2018 and December 31, 2017. On December 22, 2017, the President of the United States signed into law the Tax Cuts and Jobs Act (“TCJA”). The TCJA makes significant changes in U.S. tax law including a reduction in the corporate tax rates, changes to net operating loss carryforwards and carrybacks, and a reduction of the amount of the orphan drug credit. As a result of the TCJA, the Company remeasured its ending deferred tax assets and liabilities at December 31, 2017 to the newly enacted U.S. federal corporate tax rate of 21%. The Company recognized the provisional tax impacts related to the remeasurement of the deferred tax assets and liabilities pursuant to SEC Staff Accounting Bulletin No. 118 and included these amounts in its financial statements for the year ended December 31, 2017. The Company did not record any adjustments to this provisional amount during the period ended September 30, 2018 and will continue to analyze and refine its calculations related to the remeasurement as the impact of TCJA is finalized.

Commitments and contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and contingencies
Commitments and contingencies	10. Commitments and contingencies Contingencies From time to time, the Company is subject to occasional lawsuits, investigations and claims arising out of the normal conduct of business. The Company has no significant pending or threatened litigation as of September 30, 2018. Indemnifications In the normal course of business, the Company enters into contracts that contain a variety of indemnifications with its employees, licensors, suppliers and service providers. Further, the Company indemnifies its directors and officers who are, or were, serving at the Company’s request in such capacities. The Company’s maximum exposure under these arrangements is unknown at September 30, 2018. The Company does not anticipate recognizing any significant losses relating to these arrangements. Leases The Company enters into various non-cancelable, operating lease agreements for its facilities and equipment in order to conduct its operations. The Company expenses rent on a straight-line basis over the life of the lease and has recorded deferred rent on the Company’s balance sheets within both accrued expenses and other current liabilities and other long-term liabilities. On July 18, 2018, the Company entered into a sublease agreement for additional office space adjacent to the Company’s existing headquarters in Evanston, Illinois, totaling approximately 6,172 square feet. The term of the lease commenced on July 18, 2018 and continues through September 30, 2022. The total aggregate estimated base rent payments over the term of the sublease approximate $0.9 million. Total rent expense, inclusive of lease incentives, under all the operating lease agreements amounted to $0.2 million for each of the three months ended September 30, 2018 and 2017, and $0.5 million for each of the nine months ended September 30, 2018 and 2017.

Related party transactions

Related party transactions	9 Months Ended
	Sep. 30, 2018
Related party transactions
Related party transactions	11. Related party transactions The Company received consulting services from PharmaKey, LLC (“PharmaKey”) during the three and nine months ended September 30, 2018 and 2017, where the Company’s Chief Development Officer is founder, owner, chairman, and former president. The transactions engaged between the Company and PharmaKey have been reviewed and approved by the Company’s Board of Directors and transacted on an arm’s length basis. As of September 30, 2018, the Company had a balance of approximately $1,000 recorded within accounts payable. The Company incurred consulting services from PharmaKey totaling approximately $1,000 and $34,000 for the three months ended September 30, 2018 and 2017, respectively, and approximately $13,000 and $76,000 for the nine months ended September 30, 2018 and 2017, respectively, which are included within research and development expenses in the statements of operations.

Summary of significant accoun_2

Summary of significant accounting policies (Policies)	9 Months Ended
	Sep. 30, 2018
Summary of significant accounting policies
Basis of presentation	Basis of presentation The condensed financial statements of the Company included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) have been condensed or omitted from this report, as is permitted by such rules and regulations. The accompanying condensed financial statements reflect all adjustments consisting of normal, recurring adjustments that are necessary for a fair presentation of the financial position results of operations and cash flows for the interim periods presented. Interim results are not necessarily indicative of results for a full year. Accordingly, these financial statements should be read in conjunction with the financial statements as of and for the year ended December 31, 2017, and notes thereto, included in the Company’s final prospectus for the IPO filed with the SEC pursuant to Rule 424(b)(4) dated June 20, 2018 (the “Prospectus”). From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”), or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the impact of recently issued standards that are not yet effective will not have a material impact on the Company’s financial statements upon adoption. Under the Jumpstart Our Business Startups Act of 2012, as amended (the “JOBS Act”), the Company meets the definition of an emerging growth company, and has elected the extended transition period for complying with new or revised accounting standards, which delays the adoption of these accounting standards until they would apply to private companies.
Reverse stock split	Reverse stock split On June 7, 2018, the Company effected a one-for‑27.58621 reverse stock split of the Company’s issued and outstanding shares of common stock and a proportional adjustment to the existing conversion ratios for the Company’s convertible preferred stock. The par value per share and authorized shares of common and convertible preferred stock were not adjusted as a result of the reverse stock split. All common stock and common stock per share amounts within the financial statements and notes thereto have been retroactively adjusted for all periods presented to give effect to this reverse stock split, including reclassifying an amount equal to the reduction in par value of common stock to additional paid-in capital.
Use of estimates	Use of estimates The financial statements are prepared in conformity with GAAP. This process requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of expenses during the reporting period. Actual results could differ from those estimates.
Recent issued accounting pronouncements	Recently issued accounting pronouncements In February 2016, the FASB issued ASU No. 2016‑02, Leases (“ASU 2016‑02”), which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short‑term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. The new standard will be effective for the Company beginning after December 15, 2019, and early adoption is permitted. The Company is currently evaluating the potential impact ASU 2016‑02 may have on its financial statements. In May 2014, the FASB issued ASU No. 2014‑09, Revenue from Contracts with Customers (“ASU 2014‑09”), which supersedes nearly all existing revenue recognition guidance. The core principle of ASU 2014‑09 is to recognize revenues when promised goods or services are transferred to customers in an amount that reflects the consideration to which an entity expects to be entitled for those goods or services. ASU 2014‑09 defines a five step process to achieve this core principle and, in doing so, more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP. The standard is effective for annual periods beginning after December 15, 2018, using either of the following transition methods: (i) a full retrospective approach reflecting the application of the standard in each prior reporting period with the option to elect certain practical expedients, or (ii) a retrospective approach with the cumulative effect of initially adopting ASU 2014‑09 recognized at the date of adoption (which includes additional footnote disclosures). The Company is evaluating the impact of the pending adoption of ASU 2014‑09 on the financial statements and has not yet determined the method by which the Company will adopt the standard when required.

Supplemental financial inform_2

Supplemental financial information (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental financial information
Schedule of cash, cash equivalents and restricted cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows (amounts in thousands). As of As of September 30, December 31, Cash and cash equivalents $ 165,578 $ 92,136 Short-term and long-term restricted cash 491 473 Total cash, cash equivalents, and restricted cash shown in the statements of cash flows $ 166,069 $ 92,609
Schedule of prepaid expenses and other current assets	Prepaid expenses and other current assets consist of the following (in thousands): As of As of September 30, December 31, Prepaid clinical $ 173 $ 1,718 Prepaid insurance 791 137 Other prepaid expenses and current assets 205 105 Total prepaid expenses and other current assets $ 1,169 $ 1,960
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): As of As of September 30, December 31, Employee-related expenses $ 2,056 $ 1,435 Development costs and sponsored research 1,805 737 Clinical trials 2,282 69 Other 322 594 Total accrued expenses and other current liabilities $ 6,465 $ 2,835

Fair value measurements (Tables

Fair value measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair value measurements
Schedule of assets measured at fair value	Assets measured at fair value as of September 30, 2018 are as follows (in thousands): September 30, Level 1 Level 2 Level 3 Assets Money market funds, included in cash and cash equivalents $ 163,705 $ 163,705 $ — $ — Money market funds, included in restricted cash 252 252 — — Money market funds, included in other assets 67 67 — — $ 164,024 $ 164,024 $ — $ — Assets measured at fair value as of December 31, 2017 are as follows (in thousands): December 31, Level 1 Level 2 Level 3 Assets Money market funds, included in cash and cash equivalents $ 89,553 $ 89,553 $ — $ — Money market funds, included in other assets 317 317 — — $ 89,870 $ 89,870 $ — $ —

Property and equipment (Tables)

Property and equipment (Tables)	9 Months Ended
	Sep. 30, 2018
Property and equipment
Schedule of property and equipment	Property and equipment are as follows (in thousands): As of As of September 30, December 31, Computer software and equipment $ 15 $ 15 Office equipment and furniture 160 92 Laboratory equipment 1,571 1,529 Leasehold improvements 1,051 748 Construction in progress — 22 Less accumulated depreciation (984) (590) Property and equipment, net $ 1,813 $ 1,816

Stock incentive plans (Tables)

Stock incentive plans (Tables)	9 Months Ended
	Sep. 30, 2018
Stock incentive plans
Allocation of stock-based compensation expenses	Non-cash stock-based compensation expense recognized in the accompanying statements of operations relating to both stock options and restricted stock awards for the three and nine months ended September 30, 2018 and 2017 was as follows (in thousands): Three months ended Nine months ended September 30, September 30, Research and development $ 242 $ 91 $ 616 $ 233 General and administrative 478 151 1,368 420 Total stock‑based compensation expense $ 720 $ 242 $ 1,984 $ 653
Summary of stock option activity	The table below summarizes activity related to stock options (in thousands, except per share amounts): Weighted‑ Weighted‑ average average remaining Aggregate exercise contractual intrinsic Options Shares price term value Outstanding, December 31, 2017 1,498 $ 2.48 8.93 $ 4,146 Granted 2,443 9.95 Exercised 1 1.82 Forfeited and canceled (5) 2.77 Outstanding, September 30, 2018 3,937 $ 7.07 8.94 $ 86,148 Vested and expected to vest at September 30, 2018 3,937 $ 7.07 8.94 $ 86,148 Exercisable at September 30, 2018 702 $ 2.28 8.08 $ 18,739

Net loss per share (Tables)

Net loss per share (Tables)	9 Months Ended
	Sep. 30, 2018
Net loss per share
Schedule of basic and diluted net loss per share attributable to common stockholders calculation	Basic and diluted net loss per share attributable to common stockholders was calculated as follows for the three and nine months ended September 30, 2018 and 2017 (in thousands, except per share data): Three months ended Nine months ended September 30, September 30, Numerator: Net loss attributable to common stockholders $ (14,181) $ (8,145) $ (39,188) $ (24,842) Denominator: Weighted-average common shares outstanding—basic and diluted 33,191 5,232 15,789 5,159 Net loss per share attributable to common stockholders—basic and diluted $ (0.43) $ (1.56) $ (2.48) $ (4.82)
Schedule of anti-dilutive securities excluded from computation of diluted net loss per share	The following common stock equivalents outstanding as of September 30, 2018 and 2017, were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti‑dilutive (in thousands): As of September 30, Series A-1 convertible preferred stock — 5,502 Series A-2 convertible preferred stock — 6,288 Stock options issued and outstanding 3,937 1,497 Unvested restricted stock 268 655 Total 4,205 13,942

Organization (Details)

Organization (Details) - USD ($) $ / shares in Units, $ in Thousands	Jun. 25, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Organization
Payment of offering costs		$ 2,971
Preferred stock, shares authorized		10,000,000		0
Preferred stock, par value (in dollars per share)		$ 0.01		$ 0.01
Preferred stock, shares issued		0		0
Preferred stock, shares outstanding		0		0
Cash proceeds, net of issuance cost			$ 39,979
Cash and cash equivalents		$ 165,578		$ 92,136
Expected period of sufficient funds for planned operations		12 months
IPO
Organization
Common stock issued and sold in initial public offering	7,359,998
Public offering price of the shares sold	$ 16
Net proceeds from issuance of common stock	$ 106,500
Payment of offering costs	$ 3,000
Number of preferred stock converted into common stock	20,306,497
Underwriters' option
Organization
Common stock issued and sold in initial public offering	959,999

Summary of significant accoun_3

Summary of significant accounting policies (Details)	Jun. 07, 2018
Summary of significant accounting policies
Reverse stock split ratio	0.03625

Supplemental financial inform_3

Supplemental financial information - Cash, cash equivalents, and restricted cash (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Supplemental financial information
Cash and cash equivalents	$ 165,578	$ 92,136
Short-term and long-term restricted cash	491	473
Total cash, cash equivalents, and restricted cash shown in the statements of cash flows	$ 166,069	$ 92,609	$ 31,258	$ 16,953

Supplemental financial inform_4

Supplemental financial information - Prepaid expenses and other current assets (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Supplemental financial information
Prepaid clinical	$ 173	$ 1,718
Prepaid insurance	791	137
Other prepaid expenses and current assets	205	105
Total prepaid expenses and other current assets	$ 1,169	$ 1,960

Supplemental financial inform_5

Supplemental financial information - Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Supplemental financial information
Employee-related expenses	$ 2,056	$ 1,435
Development costs and sponsored research	1,805	737
Clinical trials	2,282	69
Other	322	594
Total accrued expenses and other current liabilities	$ 6,465	$ 2,835

Research collaboration agreem_2

Research collaboration agreement with Allergan (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Jul. 24, 2015USD ($)Option
Research collaboration agreement with Allergan
Collaboration and grant revenue	$ 943	$ 1,205	$ 5,535	$ 3,778
Research and development	11,950	8,067	37,860	24,930
RCA
Research collaboration agreement with Allergan
Payment of option exercise fee					$ 1,000
Number of options to acquire molecules | Option					3
Collaboration and grant revenue			1,000
Research and development	$ 1,900	$ 1,900	$ 5,800	$ 5,800
Development activities reimbursement percentage	50.00%	50.00%	50.00%	50.00%
Development activities expenses reimbursed	$ 900	$ 1,000	$ 2,900	$ 2,900

Fair value measurements (Detail

Fair value measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Money Market Funds Included In Other Assets
Fair value measurements
Money market funds	$ 67
Level 1 | Money Market Funds Included In Other Assets
Fair value measurements
Money market funds	67
Recurring
Fair value measurements
Assets measured at fair value	164,024	$ 89,870
Recurring | Money Market Funds In Cash And Cash Equivalents
Fair value measurements
Money market funds	163,705	89,553
Recurring | Money Market Funds Included In Restricted Cash
Fair value measurements
Money market funds	252
Recurring | Money Market Funds Included In Other Assets
Fair value measurements
Money market funds		317
Recurring | Level 1
Fair value measurements
Assets measured at fair value	164,024	89,870
Recurring | Level 1 | Money Market Funds In Cash And Cash Equivalents
Fair value measurements
Money market funds	163,705	89,553
Recurring | Level 1 | Money Market Funds Included In Restricted Cash
Fair value measurements
Money market funds	$ 252
Recurring | Level 1 | Money Market Funds Included In Other Assets
Fair value measurements
Money market funds		$ 317

Property and equipment (Details

Property and equipment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Property and equipment
Less accumulated depreciation	$ (984)		$ (984)		$ (590)
Property and equipment, net	1,813		1,813		1,816
Depreciation and amortization	100	$ 100	336	$ 225
Computer software and equipment
Property and equipment
Property and equipment, gross	15		15		15
Office equipment and furniture
Property and equipment
Property and equipment, gross	160		160		92
Laboratory equipment
Property and equipment
Property and equipment, gross	1,571		1,571		1,529
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 1,051		$ 1,051		748
Construction in progress
Property and equipment
Property and equipment, gross					$ 22

Stock incentive plans (Details)

Stock incentive plans (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance					3,878,940
Stock-based compensation expense	$ 720	$ 242	$ 1,984	$ 653
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	242	91	616	233
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	478	151	1,368	420
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 100	$ 100	$ 300	$ 300
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	505,046		505,046

Stock incentive plans - Activit

Stock incentive plans - Activity related to stock options (Details) - Stock options - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Shares
Outstanding, at the beginning of the period	1,498
Granted	2,443	1,200
Exercised	1
Forfeited and canceled	(5)
Outstanding, at the end of the period	3,937		1,498
Vested and expected to vest	3,937
Exercisable	702
Weighted-average exercise price
Outstanding, at the beginning of the period	$ 2.48
Granted	9.95
Exercised	1.82
Forfeited and canceled	2.77
Outstanding, at the end of the period	7.07		$ 2.48
Vested and expected to vest	7.07
Exercisable at the beginning	$ 2.28
Weighted-average remaining contractual term
Weighted-average remaining contractual term	8 years 11 months 9 days		8 years 11 months 5 days
Vested and expected to vest	8 years 11 months 9 days
Exercisable	8 years 29 days
Aggregate intrinsic value
Outstanding, at the beginning of the period	$ 4,146
Outstanding, at the end of the period	86,148		$ 4,146
Vested and expected to vest at the beginning of the period	86,148
Exercisable	$ 18,739
Weighted-average grant date fair value per share	$ 9.95	$ 2.59
Unrecognized stock-based compensation related to non-vested stock options	$ 15,300
Term in which unrecognized compensation expenses will be recognized	3 years 1 month 28 days
Term of award	10 years
Vesting period	4 years

Stock incentive plans - Restric

Stock incentive plans - Restricted stock awards (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Shares
Stock-based compensation expense	$ 720	$ 242	$ 1,984	$ 653
Restricted stock awards
Shares
Outstanding, at the end of the period	268,000		268,000
Stock-based compensation expense	$ 100	$ 100	$ 300	$ 300
Fair value of shares vested			1,400
Compensation expenses not yet recognized	$ 300		$ 300
Term in which unrecognized compensation expenses will be recognized			10 months 28 days

Net loss per share (Details)

Net loss per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net loss attributable to common stockholders	$ (14,181)	$ (8,145)	$ (39,188)	$ (24,842)
Denominator:
Weighted-average common shares outstanding—basic and diluted	33,191	5,232	15,789	5,159
Net loss per share attributable to common stockholders—basic and diluted	$ (0.43)	$ (1.56)	$ (2.48)	$ (4.82)

Net loss per share - Anti-dilut

Net loss per share - Anti-dilutive securities (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	4,205	13,942
Series A-1 convertible preferred stock
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share		5,502
Series A-2 convertible preferred stock
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share		6,288
Stock options
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	3,937	1,497
Unvested restricted stock
Common stock equivalents outstanding excluded from the computation of diluted net loss per share attributable to common stockholders
Outstanding anti-dilutive securities excluded from computation of diluted net loss per share	268	655

Income taxes (Details)

Income taxes (Details)	Jan. 01, 2018
Income taxes
Federal effective tax rate	21.00%

Commitments and contingencies (

Commitments and contingencies (Details) $ in Millions	Jul. 18, 2018USD ($)ft²	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)
Operating leases
Leased space (in square feet) | ft²	6,172
Rent expense inclusive of lease incentives | $	$ 0.9	$ 0.2	$ 0.2	$ 0.5	$ 0.5

Related party transactions (Det

Related party transactions (Details) - PharmaKey - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Related party transactions
Accounts payable	$ 1,000		$ 1,000
Research and development
Related party transactions
Consulting services	$ 1,000	$ 34,000	$ 13,000	$ 76,000