Entasis Therapeutics (ETTX) 10-Q 14 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 09, 2019
Document And Entity Information Abstract
Entity Registrant Name	Entasis Therapeutics Holdings Inc.
Entity Central Index Key	0001724344
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
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	true
Entity Common Stock, Shares Outstanding		13,132,004
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 13,535	$ 49,360
Short-term investments	61,020	35,732
Grants receivable	1,728	1,706
Prepaid expenses and other current assets	2,593	1,994
Total current assets	78,876	88,792
Property and equipment, net	379	419
Operating lease right-of-use assets	1,949
Other assets	63	63
Total assets	81,267	89,274
Current liabilities:
Accounts payable	4,080	1,370
Accrued expenses and other current liabilities	4,896	4,846
Total current liabilities	8,976	6,216
Operating lease liabilities, net of current portion	1,717
Deferred rent		175
Total liabilities	10,693	6,391
Commitments (Notes 5 and 11)
Shareholders' equity (deficit):
Common stock, par value $0.001; 125,000,000 shares authorized and 13,127,128 and 13,124,842 shares issued and outstanding as of March 31, 2019 and December 31, 2018, respectively	13	13
Additional paid-in capital	173,577	172,988
Accumulated other comprehensive income (loss)	34	(9)
Accumulated deficit	(103,050)	(90,109)
Total stockholders' equity	70,574	82,883
Total liabilities and stockholders' equity	$ 81,267	$ 89,274

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2019	Dec. 31, 2018
Common stock par value (in dollar per share)	$ 0.001	$ 0.001
Common stock authorized (in shares)	125,000,000	125,000,000
Common stock issued (in shares)	13,127,128	13,124,842
Common stock outstanding (in shares)	13,127,128	13,124,842

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating expenses:
Research and development	$ 11,002	$ 8,550
General and administrative	3,189	3,218
Total operating expenses	14,191	11,768
Loss from operations	(14,191)	(11,768)
Other income:
Grant income	829	1,089
Interest income	492	12
Total other income	1,321	1,101
Loss before income taxes	(12,870)	(10,667)
Provision for income taxes	71
Net loss	$ (12,941)	$ (10,667)
Net Loss per Share
Net loss per share attributable to common stockholders—basic and diluted (in dollar per share)	$ (0.99)	$ (844.01)
Weighted average common stock outstanding—basic and diluted (in shares)	13,126,595	12,639
Other comprehensive loss
Net loss	$ (12,941)	$ (10,667)
Net unrealized loss on investments held	43
Foreign currency translation adjustments		(44)
Comprehensive loss	$ (12,898)	$ (10,711)

CONSOLIDATED STATEMENTS OF REDE

CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Series A Redeemable Convertible Preferred Stock	Series B Redeemable Convertible Preferred Stock	Series B‑1 Tranche A Redeemable Convertible Preferred Stock	Series B‑1 Tranche B Redeemable Convertible Preferred Stock	Common Stock	Additional Paid-in CapitalASU 2018-07	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Retained EarningsASU 2018-07	Retained Earnings	Total
Balance at Dec. 31, 2017	$ 23,866	$ 24,550	$ 24,423	$ 31,874
Balance (in shares) at Dec. 31, 2017	33,499,900	25,000,000	42,372,882	54,067,796
Balance at Mar. 31, 2018	$ 23,866	$ 24,550	$ 24,423	$ 31,874
Balance (in shares) at Mar. 31, 2018	33,499,900	25,000,000	42,372,882	54,067,796
Balance at Dec. 31, 2017					$ 3		$ 1,377			$ (57,170)	$ (55,790)
Balance (in shares) at Dec. 31, 2017					12,639
Increase (Decrease) in Temporary Equity and Stockholders' Equity (Deficit)
Stock-based compensation expense							200				200
Unrealized loss on foreign currency translation								$ (44)			(44)
Net loss										(10,667)	(10,667)
Balance at Mar. 31, 2018					$ 3		1,564	(44)		(67,824)	(66,301)
Balance (in shares) at Mar. 31, 2018					12,639
Increase (Decrease) in Temporary Equity and Stockholders' Equity (Deficit)
ASU 2018‑07 modified retrospective adjustment						$ (13)			$ 13
Balance at Dec. 31, 2018					$ 13		172,988	(9)		(90,109)	82,883
Balance (in shares) at Dec. 31, 2018					13,124,842
Increase (Decrease) in Temporary Equity and Stockholders' Equity (Deficit)
Stock-based compensation expense							578				578
Exercise of stock options							11				11
Exercise of stock options (in shares)					2,286
Unrealized gain on investments held								43			43
Net loss										(12,941)	(12,941)
Balance at Mar. 31, 2019					$ 13		$ 173,577	$ 34		$ (103,050)	$ 70,574
Balance (in shares) at Mar. 31, 2019					13,127,128

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (12,941)	$ (10,667)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	40	56
Stock-based compensation expense	578	200
Amortization and accretion of investments	(195)
Changes in operating assets and liabilities:
Grants receivable	(22)	(722)
Prepaid expenses and other assets	(2,548)	(318)
Accounts payable	2,747	596
Accrued expenses and other current liabilities	1,917	(2,278)
Deferred rent	(175)	41
Net cash used in operating activities	(10,599)	(13,092)
Cash flows from investing activities:
Purchase of property and equipment	(37)	(137)
Purchase of short-term investments	(25,050)
Net cash used in investing activities	(25,087)	(137)
Cash flows from financing activities:
Proceeds from exercise of stock options	11
Payments of initial public offering costs	(150)	(1,706)
Net cash used in financing activities	(139)	(1,706)
Effect of exchange rate changes on cash and cash equivalents		(44)
Net decrease in cash and cash equivalents	(35,825)	(14,979)
Cash and cash equivalents at beginning of the period	49,360	55,101
Cash and cash equivalents at end of the period	$ 13,535	40,122
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable		110
Deferred offering costs included in accounts payable and accrued expenses		$ 413

Organization and Description of

Organization and Description of Business	3 Months Ended
	Mar. 31, 2019
Organization and Description of Business
Organization and Description of Business	1. Organization and Description of Business Entasis Therapeutics Holdings Inc. (“Entasis” or the “Company”) is a clinical‑stage biopharmaceutical company focused on the discovery, development and commercialization of novel antibacterial products to treat serious infections caused by multidrug-resistant Gram‑negative bacteria. The Company has three subsidiaries: Entasis Therapeutics Limited; Entasis Therapeutics Inc.; and Entasis Therapeutics Security Corporation. The Company was initially formed as Entasis Therapeutics Limited (“Entasis Limited”) on March 6, 2015 in the United Kingdom (“U.K.”) as a wholly owned subsidiary of AstraZeneca AB (“AstraZeneca”). In connection with the spin‑out of Entasis Limited from AstraZeneca in May 2015, Entasis Limited issued 4 ordinary shares to AstraZeneca. Additionally, pursuant to a business transfer and subscription agreement with AstraZeneca (the “A Subscription Agreement”), Entasis Limited also issued 33,499,900 shares of A redeemable convertible preference shares (“A Preferred Stock”) to AstraZeneca in May 2015. In March 2016, Entasis Limited issued 25,000,000 shares of B redeemable convertible preference shares (“B Preferred Stock”) to third‑party investors, at which point AstraZeneca no longer held a controlling interest in Entasis Limited. On April 23, 2018, Entasis Limited completed a corporate reorganization (the “Reorganization”). As part of the Reorganization, Entasis Limited formed Entasis Therapeutics Holdings Inc., a Delaware corporation, in March 2018 with nominal assets and liabilities for the purpose of consummating the Reorganization. In connection with the Reorganization, the existing shareholders of Entasis Limited exchanged each of their classes of shares of Entasis Limited for the same number and classes of common stock and preferred stock of Entasis Therapeutics Holdings Inc. on a one‑to‑one basis. The newly issued stock of Entasis Therapeutics Holdings Inc. have substantially identical rights to the exchanged shares of Entasis Limited. As a result of the exchange, Entasis Therapeutics Holdings Inc. became the sole shareholder of Entasis Limited. Upon the completion of the Reorganization on April 23, 2018, the historical consolidated financial statements of Entasis Limited became the historical consolidated financial statements of Entasis Therapeutics Holdings Inc. On September 28, 2018, the Company completed an initial public offering of its common stock, in which the Company issued and sold 5,000,000 shares of common stock at a price to the public of $15.00 per share. The aggregate net proceeds to the Company from the initial public offering were approximately $65.6 million after deducting underwriting discounts and commissions and offering expenses payable by the Company. Upon the completion of the Company’s initial public offering, all of the outstanding shares of redeemable convertible preferred stock of the Company, including accrued dividends, automatically converted into 8,084,414 shares of the Company’s common stock. Risks and Uncertainties As of March 31, 2019, the Company had $74.6 million in cash, cash equivalents and short-term investments and an accumulated deficit of $103.1 million. Since its inception through March 31, 2019, the Company has funded its operations primarily with proceeds from the sale of redeemable convertible preferred stock and the sale of its common stock. The Company has also either directly received funding or financial commitments from, or has had its program activities conducted and funded by, United States (“U.S.”) government agencies and non-profit entities. In the absence of positive cash flows from operations, the Company is highly dependent on its ability to find additional sources of funding in the form of debt or equity financing. The Company believes its existing cash, cash equivalents and short-term investments will enable it to fund its operating expenses and capital requirements into the fourth quarter of 2020. As an early-stage company, the Company is subject to a number of risks common to other life science companies, including, but not limited to, raising additional capital, development by its competitors of new technological innovations, risk of failure in preclinical and clinical studies, safety and efficacy of its product candidates in clinical trials, the risk of relying on external parties such as contract research organizations (“CROs”) and contract manufacturing organizations (“CMOs”), the regulatory approval process, market acceptance of the Company’s products once approved, lack of marketing and sales history, dependence on key personnel and protection of proprietary technology. The Company’s therapeutic programs are currently pre-commercial, spanning discovery through late development and will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval, prior to commercialization of any product candidates. These efforts require significant amounts of additional capital, adequate personnel, infrastructure, and extensive compliance-reporting capabilities. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that any products developed will obtain necessary regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate revenue from product sales. The Company may never achieve profitability, and unless and until it does, it will continue to need to raise additional capital or obtain financing from other sources, such as strategic collaborations or partnerships.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Significant Accounting Policies The Company’s significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2018 and the notes thereto, which are included in the Company’s most recent Annual Report on Form 10-K. Since the date of those consolidated financial statements, there have been no material changes to its significant accounting policies, with the exception of significant accounting policies related to the adoption of FASB ASC Topic 842, Leases , effective January 1, 2019, as described below. Basis of Presentation and Consolidation The accompanying consolidated financial statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and pursuant to the instructions to Form 10-Q and Article 10 of Regulation S-X. The December 31, 2018 consolidated balance sheet was derived from audited consolidated financial statements. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements, which are contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the Securities and Exchange Commission (“SEC”) on March 29, 2019. The interim consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all normal and recurring adjustments necessary for a fair statement of the Company’s financial position and results of operations. The accompanying consolidated financial statements include the Company’s accounts and those of the Company’s wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The results for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019, any other interim periods, or any future year or period. Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates, judgments and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the recognition of revenue, the recognition of research and development expenses and the valuation of common stock used in the determination of stock-based compensation expense. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from the Company’s estimates. Recently Adopted Accounting Pronouncements Effective January 1, 2019, the Company adopted the requirements under the Financial Accounting Standards Board (“FASB”), Accounting Standards Codification (“ASC”) 842, Leases (“ASC 842”) using the cumulative effect adjustment transition option. Comparative periods have not been restated. This standard requires entities that lease assets to recognize the assets and liabilities for the rights and obligations created by those leases on the balance sheet. The Company elected the available package of practical expedients which allows it to not reassess previous accounting conclusions around whether arrangements are or contain leases, the classification of its leases, and the treatment of initial direct costs. The Company has made an accounting policy election to keep leases with an initial term of 12 months or less off of the balance sheet. ASC 842 was issued in order to increase transparency and comparability of financial reporting related to leasing arrangements. The main difference between previous U.S. GAAP (“ASC 840”) and ASC 842 is the recognition of right-of-use lease assets and lease liabilities by lessees for those leases that were classified as operating leases under ASC 840. At January 1, 2019, the Company recorded right-of-use assets of $2.1 million and operating lease liabilities of $2.2 million. Adoption of the standard did not have a material impact on the consolidated statements of operations. For additional information regarding how the Company is accounting for leases under ASC 842, refer to Note 5, Leases. Recently Issued Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement , which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The guidance is effective for all entities for fiscal years beginning after December 15, 2019 and for interim periods within those fiscal years, but entities are permitted to early adopt either the entire standard or only the provisions that eliminate or modify the requirements. The Company does not expect the adoption of the new guidance to have a material effect on its consolidated financial statements. In November 2018, the FASB issued ASU 2018-18 — Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 . This update clarifies the interaction between Topic 808, Collaborative Arrangements, and Topic 606, Revenue from Contracts with Customers. The standard is effective for fiscal years and the interim periods within those fiscal years beginning after December 15, 2019. The guidance is required to be applied retrospectively to the date of initial application of Topic 606. An entity should recognize the cumulative effect of initially applying the amendments as an adjustment to the opening balance of retained earnings of the later of the earliest annual period presented and the annual period that includes the date of the entity’s initial application of Topic 606. The Company is currently assessing the impact that adoption of this guidance will have on its consolidated financial statements.

Short-term Investments

Short-term Investments	3 Months Ended
	Mar. 31, 2019
Short-term Investment
Short-term Investments	3. Short-Term Investments The following table summarizes the amortized cost and estimated fair value of the Company’s marketable securities, which are considered to be available-for-sale investments and were included in short-term investments on the consolidated balance sheets: Amortized Unrealized Unrealized Cost Gains Losses Fair Value (in thousands) Balance at March 31, 2019: U.S. government-sponsored enterprise securities $ 11,821 $ 7 $ — $ 11,828 U.S. Treasury securities 49,170 22 — 49,192 Total $ 60,991 $ 29 $ — $ 61,020 Amortized Unrealized Unrealized Cost Gains Losses Fair Value (in thousands) Balance at December 31, 2018: U.S. government-sponsored enterprise securities $ 6,059 $ — $ — $ 6,059 U.S. Treasury securities 29,680 — (7) 29,673 Total $ 35,739 $ — $ (7) $ 35,732 Certain short-term debt securities with original maturities of less than 90 days are included in cash and cash equivalents on the consolidated balance sheets and are not included in the tables above. As of March 31, 2019, and December 31, 2018, all investments have contractual maturities within one year.

Fair Value of Instruments

Fair Value of Instruments	3 Months Ended
	Mar. 31, 2019
Fair Value of Instruments
Fair Value of Instruments	4. Fair Value of Instruments The following tables set forth the Company’s assets that were accounted for at fair value on a recurring basis: March 31, 2019 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 10,814 $ — $ — $ 10,814 U.S. Treasury securities — — — — Short-term investments: U.S. government-sponsored enterprise securities — 11,828 — 11,828 U.S. Treasury securities 49,192 — — 49,192 Total $ 60,006 $ 11,828 $ — $ 71,834 December 31, 2018 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 18,609 $ — $ — $ 18,609 U.S. Treasury securities 19,964 — — 19,964 Short-term investments: U.S. government-sponsored enterprise securities — 6,059 — 6,059 U.S. Treasury securities 29,673 — — 29,673 Total $ 68,246 $ 6,059 $ — $ 74,305 The Company classifies its money market funds and U.S. Treasury securities as Level 1 assets under the fair value hierarchy, as these assets have been valued using quoted market prices in active markets without any valuation adjustment. The Company classifies its corporate and municipal notes as Level 2 assets under the fair value hierarchy, as these assets have been valued using information obtained through a third-party pricing service at each balance sheet date, using observable market inputs that may include trade information, broker or dealer quotes, bids, offers, or a combination of these data sources. The carrying amounts of the Company’s cash equivalents, grants receivable, accounts payable and accrued expenses approximate their fair value due to the short-term nature of these amounts.

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases
Leases	5. Leases The Company adopted ASC 842 on January 1, 2019. ASC 842 allows the Company to elect a package of practical expedients, which include: (i) an entity need not reassess whether any expired or existing contracts are or contain leases; (ii) an entity need not reassess the lease classification for any expired or existing leases; and (iii) an entity need not reassess any initial direct costs for any existing leases. Another practical expedient allows the Company to use hindsight in determining the lease term when considering lessee options to extend or terminate the lease and to purchase the underlying asset. The Company has elected to utilize this package of practical expedients and has not elected the hindsight methodology in its implementation of ASC 842. The Company determined that it held one significant operating lease as of January 1, 2019, consisting of 20,062 square feet of office and laboratory space in Waltham, Massachusetts that expires in December 2022 pursuant to a May 2015 lease with AstraZeneca (“AZ lease”), as amended in February 2018. During the three months ended March 31, 2019 and 2018, the Company recorded lease expense of $0.2 million and $0.1 million, respectively, related to this lease. The Company has two additional operating leases that are included in its lease accounting but are not considered significant. During the three months ended March 31, 2019 and 2018, the Company recorded lease expense of $0.2 million and $0.1 million, respectively related to all leases. In calculating the present value of future lease payments, the Company utilized its incremental borrowing rate based on the remaining lease term at the date of adoption. The AZ lease contains a renewal option that can extend the lease for three years. Because the Company is not reasonably certain to exercise this renewal option, the option is not considered in determining the lease term, and associated potential additional payments are excluded from lease payments. The Company has elected to account for each lease component and its associated non-lease components as a single lease component and has allocated all of the contract consideration across lease components only. The Company has existing net leases in which the non-lease components (e.g. common area maintenance) are paid separately from rent based on actual costs incurred and therefore are not included in the operating lease right-of-use assets and lease liabilities and are reflected as an expense in the period incurred. The following table summarizes the presentation in the Company’s consolidated balance sheet of its operating leases (in thousands): As of March 31, 2019 Assets Operating lease right-of-use assets $ 1,949 Liabilities Operating lease liabilities $ 417 Operating lease liabilities, net of current portion 1,717 Total operating lease liabilities $ 2,134 The operating lease right-of-use assets balance primarily relates to amounts associated with the AZ lease. Of the $2.1 million operating lease liabilities, $2.1 million represents amounts associated with the AZ lease. During the three months ended March 31, 2019, the Company made cash payments of $0.1 million for operating leases. Future minimum lease payments under non-cancelable leases as of March 31, 2019, were as detailed below (in thousands): Fiscal Year As of March 31, 2019 2019 (remaining 9 months) $ 454 2020 663 2021 717 2022 737 2023 1 Total undiscounted lease payments 2,572 Less: imputed interest (438) Total operating lease liabilities $ 2,134 As of March 31, 2019, the weighted average remaining lease term was 3.8 years and the weighted average incremental borrowing rate used to determine the operating lease right-of-use assets was 9.1%. ASC 840 Disclosures Future minimum lease payments under non-cancelable leases as of December 31, 2018, were as detailed below (in thousands): Fiscal Year As of 2019 597 2020 656 2021 710 2022 730 Total future minimum lease payments $ 2,693

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	3 Months Ended
	Mar. 31, 2019
Accrued Expenses and Other Current Liabilities.
Accrued Expenses and Other Current Liabilities	6. Accrued Expenses and Other Current Liabilities Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, December 31, 2019 2018 Accrued compensation and benefits $ 671 $ 1,526 Accrued contract manufacturing 1,584 1,003 Accrued clinical costs 628 752 Accrued professional services 788 672 Accrued research costs 229 364 Other 996 529 Total accrued expenses and other current liabilities $ 4,896 $ 4,846

Funding Arrangements

Funding Arrangements	3 Months Ended
	Mar. 31, 2019
Funding Arrangements
Funding Arrangements	7. Funding Arrangements In December 2016, the Company entered into a funding arrangement with the U.S. Army Medical Research Acquisition Activity (the “USAMRAA grant”) that covers up to $1.1 million of specified research expenditures of the Company incurred from December 2016 through June 2019 (the “performance period”). The Company has until September 2022 to obtain the reimbursements from USAMRAA for the specified research expenditures incurred and paid by the Company during the performance period. The Company recognized grant income of $37,000 for the three months ended March 31, 2019 and $0.1 million for the three months ended March 31, 2018. The Company received $0.2 million of funding under the grant for the three months ended March 31, 2019 and $0.5 million of funding under the grant for the three months ended March 31, 2018. The Company recorded a receivable to reflect unreimbursed, eligible costs incurred under the grant in the amount of $45,000 and $0.2 million as of March 31, 2019 and December 31, 2018, respectively. In March 2017 and October 2017, the Company entered into funding arrangements with the Trustees of Boston University to utilize funds from the U.S. government through the Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator (CARB‑X) program. These funding arrangements will cover up to $16.4 million of specified research expenditures of the Company from April 2017 through September 2021. The Company recognized grant income in connection with the CARB-X agreements of $0.8 million and $1.0 million for the three months ended March 31, 2019 and 2018, respectively. The Company received $0.6 million and $0.2 million of funding under the grant for the three months ended March 31, 2019 and 2018, respectively. The Company recorded a receivable to reflect unreimbursed, eligible costs incurred under the CARB-X agreements in the amount of $1.7 million and $1.5 million as of March 31, 2019 and December 31, 2018, respectively. Collaboration Agreement In July 2017, the Company entered into a collaboration agreement (the “Agreement”) with the Global Antibiotic Research and Development Partnership (“GARDP”) for the development, manufacture and commercialization of the product candidate zoliflodacin in certain countries. The Phase 3 clinical trial has not commenced and there have been no material transactions with respect to the agreement as of March 31, 2019. The Company also had zoliflodacin program activities conducted and funded by the U.S. government through its arrangements with the U.S. National Institute of Allergy and Infectious Diseases, or NIAID.

License and Collaboration Agree

License and Collaboration Agreement with Zai Lab	3 Months Ended
	Mar. 31, 2019
License and Collaboration Agreement with Zai Lab
License and Collaboration Agreement with Zai Lab	8. License and Collaboration Agreement with Zai Lab In April 2018, the Company entered into a license and collaboration agreement with Zai Lab, pursuant to which Zai Lab licensed exclusive rights to ETX2514 and ETX2514SUL in the Asia‑Pacific region (the “Zai Agreement”). Under the terms of the Zai Agreement, Zai Lab will fund most of the Company’s clinical trial costs in China for ETX2514SUL, including all costs in China for the Company’s Phase 3 clinical trial of ETX2514SUL, with the exception of patient drug supply. Zai Lab will conduct development activities, plan and obtain regulatory approval in a specified number of countries in the Asia‑Pacific region beyond China after regulatory approval of a licensed product in China. Zai Lab is also solely responsible for commercializing licensed products in the Asia‑Pacific region and will commercialize licensed products for which it has obtained regulatory approval. The Company is obligated to conduct specified development activities for the Asia‑Pacific region. The Company is also obligated to supply Zai Lab with the licensed products for clinical development, although Zai Lab may take over manufacturing responsibilities for its own commercialization activities within a specified time period following the effective date of the Zai Agreement. Both parties are prohibited from developing and commercializing products in the Asia‑Pacific region that would compete with the licensed products. In addition, under the Zai Agreement, either party may propose that Zai Lab pursue a combination of imipenem together with ETX2514SUL in the territory. If the parties decide to pursue an imipenem combination, Zai Lab would provide the Company with limited research and development support for the combination. The Company received an upfront, non‑refundable payment of $5.0 million, less applicable taxes of $0.8 million, and $0.3 million of research support funding, less applicable taxes from Zai Lab in 2018. The Company is eligible to receive up to an aggregate of $98.3 million in additional research and development support payments and development, regulatory and sales milestone payments related to ETX2514SUL, imipenem and other combinations with the licensed products. In the event the China Food and Drug Administration requires a modification or supplement to the trial protocol, and the Company delays Zai Lab from proceeding with such modified protocol and subsequently obtaining regulatory approval for the pivotal study of ETX2514SUL in China, then the sales‑based milestone payments that become due to the Company will be reduced by an agreed upon amount that increases with the length of the delay. Zai Lab will pay the Company a tiered royalty equal to a high‑single digit to low‑double digit percentage based on annual net sales of licensed products in the territory, subject to specified reductions for the market entry of competing products, loss of patent coverage of licensed products and for payments owed to third parties for additional rights necessary to commercialize licensed products in the territory. The Company evaluated the Zai Agreement under Topic 606 and identified two material promises: (1) an exclusive license to develop, manufacture and commercialize products containing ETX2514 or ETX2514SUL in the territory and (2) the initial technology transfer of licensed know‑how. The Company determined that the exclusive license and initial technology transfer were not distinct from one another, as the license has limited value without the transfer of the Company’s technology and Zai Lab would incur additional costs to recreate the Company’s know‑how. Therefore, the license and initial technology transfer were combined as a single performance obligation. The Company determined the $5.0 million non‑refundable upfront payment is the entire transaction price at the outset of the Zai Agreement. All other future potential milestone payments were excluded from the transaction price as they are fully constrained as the risk of significant reversal has not yet been resolved. The achievement of the future potential milestones is not within the Company’s control and is subject to certain research and development success, regulatory approvals or commercial success and therefore carry significant uncertainty. The Company will reevaluate the likelihood of achieving future milestones at the end of each reporting period. Future development milestone revenue from the arrangement will be recognized as revenue in the period when it is no longer probable that revenue attributable to the milestone will result in a significant reversal of cumulative revenue. Through March 31, 2019, the Company had recognized revenue of $5.0 million in the Company’s consolidated statements of operations and comprehensive loss under the Zai Agreement. During the three months ended March 31, 2019 and March 31, 2018, the Company recognized no revenue under the Zai Agreement.

Stock-Based Compensation Expens

Stock-Based Compensation Expense	3 Months Ended
	Mar. 31, 2019
Stock-Based Compensation Expense
Stock-Based Compensation Expense	9. Stock‑Based Compensation Expense Stock Incentive Plan In connection with the Reorganization, Entasis Therapeutics Holdings Inc. assumed the Entasis Limited amended and restated stock incentive plan, and each outstanding share option to purchase ordinary shares of Entasis Limited was assumed by Entasis Therapeutics Holdings Inc. and converted into an option to purchase the same number of shares of common stock of Entasis Therapeutics Holdings Inc. at the same exercise price per share and on the same vesting schedule. Each new option has and is subject to the same terms and conditions as were in effect immediately prior to the assumption and conversion. No share options of Entasis Limited are outstanding following the assumption and conversion. In September 2018, the Company’s board of directors adopted, and its stockholders approved the 2018 Equity Incentive Plan (the “2018 Plan”), which became effective on September 25, 2018, at which point no further grants will be made under the 2015 Stock Incentive Plan (the “2015 Plan”). Under the 2018 Plan, the Company may grant incentive stock options (“ISOs”), non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. As of March 31, 2019, options to purchase an aggregate of 844,306 shares had been granted and 878,850 shares were available for future issuance under the 2018 Plan. Initially, subject to adjustment as provided in the 2018 Plan, the aggregate number of shares of the Company’s common stock available for issuance under the 2018 Plan was 1,181,972. The number of shares of the Company’s common stock reserved for issuance under the 2018 Plan will automatically increase on January 1 of each year, for a period of 10 years, from January 1, 2019 continuing through January 1, 2028, by 4% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, or a lesser number of shares as may be determined by the Company’s board of directors. Accordingly, on January 1, 2019, 524,993 shares were added to the number of available shares. The maximum number of shares that may be issued pursuant to the exercise of ISOs under the 2018 Plan is 7,500,000. The maximum number of shares of the Company’s common stock subject to awards granted under the 2018 Plan or otherwise during a single calendar year to any nonemployee directors, taken together with any cash fees paid by the Company to such nonemployee director during the calendar year for serving on the Company’s board of directors, will not exceed $500,000 in total value, or, with respect to the calendar year in which a nonemployee director is first appointed or elected to the Company’s board of directors, $800,000. All options and awards granted under the 2015 Plan consisted of the Company’s common stock. As of September 25, 2018, no additional stock awards have been or will be granted under the 2015 plan. Although the 2015 Plan was terminated as to future awards in September 2018, it continues to govern the terms of options that remain outstanding under the 2015 Plan. Stock Option Activity Stock option activity under both plans for the three months ended March 31, 2019 is summarized as follows: Weighted- Weighted- Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Options Price Term (Years) Value (in thousands) Outstanding as of December 31, 2018 1,375,730 $ 6.54 8.66 $ 426 Granted 601,200 5.67 Exercised (2,286) 4.55 Cancelled or forfeited (7,668) 7.19 Outstanding as of March 31, 2019 1,966,976 $ 6.28 8.84 $ 2,973 Vested or expected to vest as of March 31, 2019 1,966,976 $ 6.28 8.84 $ 2,973 Exercisable as of March 31, 2019 563,190 $ 4.57 7.69 $ 1,243 The aggregate intrinsic value of options is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock for those options that had exercise prices lower than the fair value of the Company’s common stock. During the three months ended March 31, 2019, the weighted-average grant date fair value per granted option was $3.89. There were no stock option awards granted in the three months ended March 31, 2018. Employee Stock Purchase Plan In September 2018, the Company’s board of directors and its stockholders approved the 2018 Employee Stock Purchase Plan (the “ESPP”), which became effective as of September 25, 2018. The ESPP is intended to qualify as an “employee stock purchase plan” within the meaning of Section 423 of the U.S. Internal Revenue Code of 1986, as amended. The number of shares of common stock initially reserved for issuance under the ESPP was 140,000 shares. The ESPP provides for an annual increase on the first day of each year beginning in 2019 and ending in 2028, in each case subject to the approval of the board of directors, equal to the lesser of (i) 1% of the shares of common stock outstanding on the last day of the prior fiscal year or (ii) 250,000 shares; provided, that prior to the date of any such increase, the board of directors may determine that such increase will be less than the amount set forth in clauses (i) and (ii). Pursuant to the terms of the 2018 Employee Stock Purchase Plan, an additional 131,248 shares were added to the number of available shares effective January 1, 2019. As of March 31, 2019, no shares of common stock had been issued under the ESPP and 271,248 shares remained available for future issuance under the ESPP. No offering period under the ESPP has been set by the Company’s board of directors. Stock‑Based Compensation Stock‑based compensation expense was classified in the consolidated statement of operations as follows (in thousands): Three Months Ended March 31, 2019 2018 Research and development $ 232 $ 72 General and administrative 346 128 Total stock-based compensation expense $ 578 $ 200 As of March 31, 2019, total unrecognized stock‑based compensation expense related to unvested options was $6.1 million, which is expected to be recognized over the weighted average period of approximately 2.9 years. The total unrecognized stock-based compensation expense will be adjusted for actual forfeitures as they occur. The following weighted-average assumptions were used to calculate the fair value of each stock-based option award granted during the three months ended March 31, 2019, under the Black-Scholes option-pricing model: expected stock price volatility 78.0%; risk free interest rate 2.7%; expected life of options 6.0 years and a dividend yield of zero. There were no stock option awards granted during the three months ended March 31, 2018.

Net Loss per Share

Net Loss per Share	3 Months Ended
	Mar. 31, 2019
Net Loss per Share
Net Loss per Share	10. Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding for the period, without consideration for common stock equivalents. The Company’s potentially dilutive shares, which include outstanding stock options, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The amounts in the table below were excluded from the calculation of net loss per share, due to their anti-dilutive effect: As of March 31, 2019 2018 Options to purchase shares of common stock 1,966,976 811,386 Redeemable convertible preferred stock (as converted to common stock) — 7,474,930 1,966,976 8,286,316

Commitments

Commitments	3 Months Ended
	Mar. 31, 2019
Commitments
Commitments	11. Commitments Lease Commitments The Company has an operating lease agreement for its office and laboratory space with AstraZeneca. See Note 5 for additional information. A Subscription Agreement In connection with the A Subscription Agreement, the Company agreed to pay AstraZeneca a one‑time milestone payment of $5.0 million within three months of achieving a specified cumulative net sales milestone for ETX2514. This milestone payment will be automatically waived should the Company’s common stock trade on Nasdaq at or above a specified price at the time it achieves such specified cumulative net sales milestone for ETX2514. The Company is also obligated to pay AstraZeneca a one‑time milestone payment of $10.0 million within two years of achieving the first commercial sale of zoliflodacin. At the Company’s election, either milestone payment may be paid in cash, common stock, or a combination of cash and common stock. Additionally, the Company is obligated to pay AstraZeneca tiered, single‑digit, per‑country royalties on the annual worldwide net sales of ETX2514 and zoliflodacin.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2019
Related Party Transactions
Related Party Transactions	12. Related Party Transactions The Company was formed in May 2015 as a wholly owned subsidiary of AstraZeneca, which maintained a controlling interest in the Company until March 2016. Prior to the closing of the initial public offering on September 28, 2018, AstraZeneca was the sole A Preferred Stockholder. Upon the closing of the initial public offering, all shares of preferred stock converted into shares of common stock. Lease Commitments The Company has an operating lease agreement for its office and laboratory space with AstraZeneca. See Note 5, Leases, for additional information. Pharmaron Beijing Co., Ltd. (China) The Company contracts with Pharmaron Beijing Co., Ltd. (China), or Pharmaron, to provide various medicinal chemistry research and manufacturing development services related to our ongoing product candidates. The Company began utilizing Pharmaron as a service provider prior to the spin-out in 2015 (see Note 1), and this relationship has continued into 2019. In 2019, the Senior Vice President of Strategic Partnerships at Pharmaron began sharing a household with the Company’s Chief Executive Officer, and as a result the Company now considers the agreements between the Company and Pharmaron to be related-party transactions. In the three months ended March 31, 2019, the Company recorded expense of $2.2 million for services rendered pursuant to multiple Pharmaron agreements. Amounts due to Pharmaron were $0.8 million as of March 31, 2019.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Summary of Significant Accounting Policies
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying consolidated financial statements are unaudited and have been prepared in accordance with accounting principles generally accepted in the United States (“U.S. GAAP”) and pursuant to the instructions to Form 10-Q and Article 10 of Regulation S-X. The December 31, 2018 consolidated balance sheet was derived from audited consolidated financial statements. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements, which are contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the Securities and Exchange Commission (“SEC”) on March 29, 2019. The interim consolidated financial statements have been prepared on the same basis as the annual audited consolidated financial statements and, in the opinion of management, reflect all normal and recurring adjustments necessary for a fair statement of the Company’s financial position and results of operations. The accompanying consolidated financial statements include the Company’s accounts and those of the Company’s wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The results for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019, any other interim periods, or any future year or period.
Use of Estimates	Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with U.S. GAAP requires management to make estimates, judgments and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the recognition of revenue, the recognition of research and development expenses and the valuation of common stock used in the determination of stock-based compensation expense. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from the Company’s estimates.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Effective January 1, 2019, the Company adopted the requirements under the Financial Accounting Standards Board (“FASB”), Accounting Standards Codification (“ASC”) 842, Leases (“ASC 842”) using the cumulative effect adjustment transition option. Comparative periods have not been restated. This standard requires entities that lease assets to recognize the assets and liabilities for the rights and obligations created by those leases on the balance sheet. The Company elected the available package of practical expedients which allows it to not reassess previous accounting conclusions around whether arrangements are or contain leases, the classification of its leases, and the treatment of initial direct costs. The Company has made an accounting policy election to keep leases with an initial term of 12 months or less off of the balance sheet. ASC 842 was issued in order to increase transparency and comparability of financial reporting related to leasing arrangements. The main difference between previous U.S. GAAP (“ASC 840”) and ASC 842 is the recognition of right-of-use lease assets and lease liabilities by lessees for those leases that were classified as operating leases under ASC 840. At January 1, 2019, the Company recorded right-of-use assets of $2.1 million and operating lease liabilities of $2.2 million. Adoption of the standard did not have a material impact on the consolidated statements of operations. For additional information regarding how the Company is accounting for leases under ASC 842, refer to Note 5, Leases.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement , which eliminates, adds and modifies certain disclosure requirements for fair value measurements. The guidance is effective for all entities for fiscal years beginning after December 15, 2019 and for interim periods within those fiscal years, but entities are permitted to early adopt either the entire standard or only the provisions that eliminate or modify the requirements. The Company does not expect the adoption of the new guidance to have a material effect on its consolidated financial statements. In November 2018, the FASB issued ASU 2018-18 — Collaborative Arrangements (Topic 808): Clarifying the Interaction between Topic 808 and Topic 606 . This update clarifies the interaction between Topic 808, Collaborative Arrangements, and Topic 606, Revenue from Contracts with Customers. The standard is effective for fiscal years and the interim periods within those fiscal years beginning after December 15, 2019. The guidance is required to be applied retrospectively to the date of initial application of Topic 606. An entity should recognize the cumulative effect of initially applying the amendments as an adjustment to the opening balance of retained earnings of the later of the earliest annual period presented and the annual period that includes the date of the entity’s initial application of Topic 606. The Company is currently assessing the impact that adoption of this guidance will have on its consolidated financial statements.

Short-term Investments (Tables)

Short-term Investments (Tables)	3 Months Ended
	Mar. 31, 2019
Short-term Investment
Summary of amortized cost and estimated fair value of Company’s marketable securities	Amortized Unrealized Unrealized Cost Gains Losses Fair Value (in thousands) Balance at March 31, 2019: U.S. government-sponsored enterprise securities $ 11,821 $ 7 $ — $ 11,828 U.S. Treasury securities 49,170 22 — 49,192 Total $ 60,991 $ 29 $ — $ 61,020 Amortized Unrealized Unrealized Cost Gains Losses Fair Value (in thousands) Balance at December 31, 2018: U.S. government-sponsored enterprise securities $ 6,059 $ — $ — $ 6,059 U.S. Treasury securities 29,680 — (7) 29,673 Total $ 35,739 $ — $ (7) $ 35,732

Fair Value of Instruments (Tabl

Fair Value of Instruments (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value of Instruments
Schedule of assets that were accounted for at fair value on recurring basis	March 31, 2019 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 10,814 $ — $ — $ 10,814 U.S. Treasury securities — — — — Short-term investments: U.S. government-sponsored enterprise securities — 11,828 — 11,828 U.S. Treasury securities 49,192 — — 49,192 Total $ 60,006 $ 11,828 $ — $ 71,834 December 31, 2018 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 18,609 $ — $ — $ 18,609 U.S. Treasury securities 19,964 — — 19,964 Short-term investments: U.S. government-sponsored enterprise securities — 6,059 — 6,059 U.S. Treasury securities 29,673 — — 29,673 Total $ 68,246 $ 6,059 $ — $ 74,305

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases
Schedule of operating lease balance sheet information	The following table summarizes the presentation in the Company’s consolidated balance sheet of its operating leases (in thousands): As of March 31, 2019 Assets Operating lease right-of-use assets $ 1,949 Liabilities Operating lease liabilities $ 417 Operating lease liabilities, net of current portion 1,717 Total operating lease liabilities $ 2,134
Schedule of future lease payments	Future minimum lease payments under non-cancelable leases as of March 31, 2019, were as detailed below (in thousands): Fiscal Year As of March 31, 2019 2019 (remaining 9 months) $ 454 2020 663 2021 717 2022 737 2023 1 Total undiscounted lease payments 2,572 Less: imputed interest (438) Total operating lease liabilities $ 2,134
Schedule of future minimum lease payments for the combined spaces	Future minimum lease payments under non-cancelable leases as of December 31, 2018, were as detailed below (in thousands): Fiscal Year As of 2019 597 2020 656 2021 710 2022 730 Total future minimum lease payments $ 2,693

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	3 Months Ended
	Mar. 31, 2019
Accrued Expenses and Other Current Liabilities.
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following (in thousands): March 31, December 31, 2019 2018 Accrued compensation and benefits $ 671 $ 1,526 Accrued contract manufacturing 1,584 1,003 Accrued clinical costs 628 752 Accrued professional services 788 672 Accrued research costs 229 364 Other 996 529 Total accrued expenses and other current liabilities $ 4,896 $ 4,846

Stock-Based Compensation Expe_2

Stock-Based Compensation Expense (Tables)	3 Months Ended
	Mar. 31, 2019
Stock-Based Compensation Expense
Summary of Stock option activity under the 2015 and 2018 Plan	Weighted- Weighted- Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Options Price Term (Years) Value (in thousands) Outstanding as of December 31, 2018 1,375,730 $ 6.54 8.66 $ 426 Granted 601,200 5.67 Exercised (2,286) 4.55 Cancelled or forfeited (7,668) 7.19 Outstanding as of March 31, 2019 1,966,976 $ 6.28 8.84 $ 2,973 Vested or expected to vest as of March 31, 2019 1,966,976 $ 6.28 8.84 $ 2,973 Exercisable as of March 31, 2019 563,190 $ 4.57 7.69 $ 1,243
Schedule of stock-based compensation expense	Stock‑based compensation expense was classified in the consolidated statement of operations as follows (in thousands): Three Months Ended March 31, 2019 2018 Research and development $ 232 $ 72 General and administrative 346 128 Total stock-based compensation expense $ 578 $ 200

Net Loss per Share (Tables)

Net Loss per Share (Tables)	3 Months Ended
	Mar. 31, 2019
Net Loss per Share
Schedule of anti-dilutive securities	As of March 31, 2019 2018 Options to purchase shares of common stock 1,966,976 811,386 Redeemable convertible preferred stock (as converted to common stock) — 7,474,930 1,966,976 8,286,316

Organization and Description _2

Organization and Description of Business (Details) $ / shares in Units, $ in Thousands	Sep. 28, 2018USD ($)$ / sharesshares	Apr. 23, 2018	Mar. 31, 2016shares	May 31, 2015shares	Mar. 31, 2019USD ($)subsidiary	Dec. 31, 2018USD ($)
Number of subsidiaries | subsidiary					3
Shares issued (in shares)				4
Shares exchange ratio (as a percent)		100
Risks and Uncertainties
Cash, cash equivalents and short-term investments | $					$ 74,600
Accumulated deficit | $					$ (103,050)	$ (90,109)
Initial Public Offering
Shares issued (in shares)	5,000,000
Share price (in dollars per share) | $ / shares	$ 15
Proceeds from initial public offering, net | $	$ 65,600
Preferred stock including accrued dividends, converted into common stock	8,084,414
Series A Redeemable Convertible Preferred Stock
Shares issued (in shares)				33,499,900
Series B Redeemable Convertible Preferred Stock
Shares issued (in shares)			25,000,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Recently Adopted Accounting Pronouncements
Operating lease right-of-use assets	$ 1,949
Operating lease liability	$ 2,134
Accounting Standards Update 2016-02 | Adjustment
Recently Adopted Accounting Pronouncements
Operating lease right-of-use assets		$ 2,100
Operating lease liability		$ 2,200

Short-term Investments (Details

Short-term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Table summarizes the amortized cost and estimated fair value of the Company’s marketable securities
Amortized Cost	$ 60,991	$ 35,739
Unrealized Gains	29
Unrealized Losses		(7)
Fair Value	61,020	35,732
U.S. government-sponsored enterprise securities
Table summarizes the amortized cost and estimated fair value of the Company’s marketable securities
Amortized Cost	11,821	6,059
Unrealized Gains	7
Fair Value	11,828	6,059
U.S. Treasury securities
Table summarizes the amortized cost and estimated fair value of the Company’s marketable securities
Amortized Cost	49,170	29,680
Unrealized Gains	22
Unrealized Losses		(7)
Fair Value	$ 49,192	$ 29,673

Fair Value of Instruments (Deta

Fair Value of Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Company’s assets that were accounted for at fair value on a recurring basis
Short-term investments	$ 61,020	$ 35,732
Recurring
Company’s assets that were accounted for at fair value on a recurring basis
Total	71,834	74,305
Recurring | Level 1
Company’s assets that were accounted for at fair value on a recurring basis
Total	60,006	68,246
Recurring | Level 2
Company’s assets that were accounted for at fair value on a recurring basis
Total	11,828	6,059
Recurring | Money market funds
Company’s assets that were accounted for at fair value on a recurring basis
Cash equivalents	10,814	18,609
Recurring | Money market funds | Level 1
Company’s assets that were accounted for at fair value on a recurring basis
Cash equivalents	10,814	18,609
Recurring | U.S. Treasury securities
Company’s assets that were accounted for at fair value on a recurring basis
Cash equivalents		19,964
Short-term investments	49,192	29,673
Recurring | U.S. Treasury securities | Level 1
Company’s assets that were accounted for at fair value on a recurring basis
Cash equivalents		19,964
Short-term investments	49,192	29,673
Recurring | U.S. government-sponsored enterprise securities
Company’s assets that were accounted for at fair value on a recurring basis
Short-term investments	11,828	6,059
Recurring | U.S. government-sponsored enterprise securities | Level 2
Company’s assets that were accounted for at fair value on a recurring basis
Short-term investments	$ 11,828	$ 6,059

Leases - Lease Commitments (Det

Leases - Lease Commitments (Details) $ in Millions	Jan. 01, 2019ft²item	Mar. 31, 2019USD ($)	Mar. 31, 2018USD ($)
Operating leases
Lease, Practical Expedients, Package	true
Lease, Practical Expedient, Use of Hindsight	false
Operating lease expense | $		$ 0.2	$ 0.1
Number of other non-significant operating leases | item	2
Lessee, Operating Lease, Existence of Option to Extend	true
Renewal term	3 years
Waltham, Massachusetts lease
Operating leases
Number of significant operating leases | item	1
Significant operating lease space | ft²	20,062
Operating lease expense | $		$ 0.2	$ 0.1

Leases - Lease Balance Sheet (D

Leases - Lease Balance Sheet (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)
Operating lease right-of-use assets	$ 1,949
Operating lease liabilities	417
Operating lease liabilities, net of current portion	1,717
Total operating lease liabilities	2,134
Cash payments for operating leases	100
Waltham, Massachusetts lease
Total operating lease liabilities	$ 2,100

Leases -Operating Lease Maturit

Leases -Operating Lease Maturity (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases
2019 (remaining 9 months)	$ 454
2020	663
2021	717
2022	737
2023	1
Total undiscounted lease payments	2,572
Less: imputed interest	(438)
Total operating lease liabilities	$ 2,134
Weighted average remaining lease term	3 years 9 months 18 days
weighted average incremental borrowing rate (as a percent)	9.10%

Leases - Future minimum lease p

Leases - Future minimum lease payments (Details) $ in Thousands	Dec. 31, 2018USD ($)
Future minimum lease payments for the combined spaces
2019	$ 597
2020	656
2021	710
2022	730
Total future minimum lease payments	$ 2,693

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accrued Expenses and Other Current Liabilities.
Accrued compensation and benefits	$ 671	$ 1,526
Accrued contract manufacturing	1,584	1,003
Accrued clinical costs	628	752
Accrued professional services	788	672
Accrued research costs	229	364
Other	996	529
Total accrued expenses and other current liabilities	$ 4,896	$ 4,846

Funding Arrangements (Details)

Funding Arrangements (Details) - USD ($)	1 Months Ended	3 Months Ended		8 Months Ended
	Dec. 31, 2016	Mar. 31, 2019	Mar. 31, 2018	Oct. 31, 2017	Dec. 31, 2018
USAMRAA grant
Funding Arrangements
Maximum reimbursable research expenditures	$ 1,100,000
Grant income recognized		$ 37,000	$ 100,000
Funds received during the period		200,000	500,000
Grants receivable		45,000			$ 200,000
CARB-X program
Funding Arrangements
Maximum reimbursable research expenditures				$ 16,400,000
Grant income recognized		800,000	1,000,000
Funds received during the period		600,000	$ 200,000
Grants receivable		$ 1,700,000			$ 1,500,000

License and Collaboration Agr_2

License and Collaboration Agreement with Zai Lab (Details) - License and collaboration agreement with Zai Lab - USD ($)	1 Months Ended	3 Months Ended		12 Months Ended
	Apr. 30, 2018	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019
License and Collaboration Agreement with Zai Lab
Upfront, non-refundable payment received, net of tax	$ 5,000,000			$ 5,000,000
Upfront, non-refundable payment received, tax expense	800,000
Upfront, non-refundable research support funding, net of tax	300,000
Eligible amount receivable in research and development support payments and development, regulatory and sales milestone payments	$ 98,300,000
Revenue		$ 0	$ 0

Stock-Based Compensation Expe_3

Stock-Based Compensation Expense - Stock Incentive Plan (Details) - USD ($)	Jan. 01, 2019	Sep. 25, 2018	Sep. 30, 2018	Mar. 31, 2019	Sep. 26, 2018
Stock Options
Stock-Based Compensation
Number of options granted (in shares)				0
Incentive stock options
Stock-Based Compensation
Annual increase in the number of shares to the shares of common stock (in shares)	524,993
2015 Stock Incentive Plan
Stock-Based Compensation
Number of options granted (in shares)		0
Number of shares available for future issuance (in shares)					0
2018 Stock Incentive Plan | Non-employee directors
Stock-Based Compensation
Maximum cash fee paid			$ 500,000
2018 Stock Incentive Plan | Board of directors
Stock-Based Compensation
Maximum cash fee paid			$ 800,000
2018 Stock Incentive Plan | Stock Options
Stock-Based Compensation
Number of options granted (in shares)				844,306
Number of shares available for future issuance (in shares)				878,850
Number of shares available for grant (in shares)			1,181,972
Period of options			10 years
Percentage of annual increase to the total number of common stock outstanding (as a percent)			4.00%
2018 Stock Incentive Plan | Incentive stock options
Stock-Based Compensation
Maximum number of shares issued (in shares)			7,500,000

Stock-Based Compensation Expe_4

Stock-Based Compensation Expense - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 01, 2019	Sep. 25, 2018	Sep. 30, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Sep. 26, 2018
Employee Stock Purchase Plan
Aggregate Intrinsic Value
Number of shares available for future issuance (in shares)			140,000	271,248
Percentage of annual increase to the total number of common stock outstanding (as a percent)			1.00%
Annual increase in the number of shares to the shares of common stock (in shares)	131,248		250,000
Maximum number of shares issued (in shares)				0
2015 Stock Incentive Plan
Number of Options
Granted (in shares)		0
Aggregate Intrinsic Value
Number of shares available for future issuance (in shares)							0
2015 and 2018 Stock Incentive Plan
Number of Options
Outstanding, as of beginning of period (in shares)	1,375,730			1,375,730
Granted (in shares)				601,200	0
Exercised (in shares)				(2,286)
Cancelled or forfeited (in shares)				(7,668)
Outstanding, as of end of period (in shares)				1,966,976		1,375,730
Vested or expected to vest (in shares)				1,966,976
Exerciseable (in shares)				563,190
Weighted Average Exercise Price
Outstanding, as of beginning of period (in dollar per share)	$ 6.54			$ 6.54
Granted (in dollar per share)				5.67
Exercised (in dollar per share)				4.55
Cancelled or forfeited (in dollar per share)				7.19
Outstanding, as of end of period (in dollar per share)				6.28		$ 6.54
Vested or expected to vest (in dollar per share)				6.28
Exercisable (in dollar per share)				$ 4.57
Weighted Average Remaining Contractual Term (Years)
Options outstanding				8 years 10 months 2 days		8 years 7 months 28 days
Vested or expected to vest				8 years 10 months 2 days
Exercisable				7 years 8 months 9 days
Aggregate Intrinsic Value
Options outstanding				$ 2,973		$ 426
Vested or expected to vest				2,973
Exercisable				$ 1,243
Weighted average grant date fair value per share of options granted (in dollar per share)				$ 3.89

Stock-Based Compensation Expe_5

Stock-Based Compensation Expense - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Stock-Based Compensation
Total stock-based compensation expense	$ 578	$ 200
Unrecognized compensation cost	$ 6,100
Period for recognition	2 years 10 months 24 days
Research and development.
Stock-Based Compensation
Total stock-based compensation expense	$ 232	72
General and administrative
Stock-Based Compensation
Total stock-based compensation expense	$ 346	$ 128

Stock-Based Compensation Expe_6

Stock-Based Compensation Expense - Black-Scholes option pricing model (Details) - Stock Options	3 Months Ended
	Mar. 31, 2019shares
Stock-Based Compensation
Expected stock price volatility (as a percent)	78.00%
Risk-free interest rate (as a percent)	2.70%
Expected life of options	6 years
Expected annual dividend yield	0.00%
Number of options granted (in shares)	0

Net Loss per Share - Antidiluti

Net Loss per Share - Antidilutive Securities Excluded from Computation (Details) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net Loss per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	1,966,976	8,286,316
Stock Options
Net Loss per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	1,966,976	811,386
Redeemable convertible preferred stock
Net Loss per Share
Antidilutive securities excluded from computation of earnings per share (in shares)		7,474,930

Commitments - A Subscription Ag

Commitments - A Subscription Agreement (Details) - AstraZeneca $ in Millions	1 Months Ended
	Apr. 30, 2018USD ($)
Commitments and Contingencies
Subscription agreement one-time milestone payment on net sales	$ 5
Term of the milestone payment on net sales	3 months
Subscription agreement one-time milestone payment on first commercial sale	$ 10
Term of the milestone payment on first commercial sale	2 years

Related Party Transactions (Det

Related Party Transactions (Details) - Pharmaron Beijing Co., Ltd. $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)
Related Party Transactions
Expenses recorded	$ 2.2
Owed to related party	$ 0.8