Entasis Therapeutics (ETTX) 10-K3 Mar 222021 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2021	Feb. 25, 2022	Jun. 30, 2021
Cover Abstract
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Document Transition Report	false
Entity File Number	001-38670
Entity Registrant Name	Entasis Therapeutics Holdings Inc.
Entity Central Index Key	0001724344
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-4592913
Entity Address, Address Line One	35 Gatehouse Drive
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	781
Local Phone Number	810-0120
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	ETTX
Security Exchange Name	NASDAQ
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$ 28.6
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		47,851,779
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Auditor Name	KPMG LLP
Auditor Firm ID	185
Auditor Location	Boston, MA

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 32,307	$ 53,247
Grants receivable	1,258	1,890
Prepaid expenses	5,754	4,160
Other current assets	496	835
Total current assets	39,815	60,132
Property and equipment, net	198	222
Operating lease right-of-use assets	604	1,141
Other assets	303	63
Total assets	40,920	61,558
Current liabilities:
Accounts payable	1,183	660
Accrued expenses and other current liabilities	8,525	7,905
Total current liabilities	9,708	8,565
Operating lease liabilities, net of current portion		704
Total liabilities	9,708	9,269
Commitments (Notes 4 and 10)
Stockholders' equity:
Common stock, par value $0.001; 125,000,000 shares authorized and 47,851,779 and 36,637,357 shares issued and outstanding as of December 31, 2021 and December 31, 2020, respectively	48	37
Additional paid-in capital	262,760	236,707
Accumulated deficit	(231,596)	(184,455)
Total stockholders' equity	31,212	52,289
Total liabilities and stockholders' equity	$ 40,920	$ 61,558

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED BALANCE SHEETS
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)	47,851,779	36,637,357
Common stock outstanding (in shares)	47,851,779	36,637,357

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating expenses:
Research and development	$ 37,105	$ 41,022
General and administrative	15,212	13,209
Total operating expenses	52,317	54,231
Loss from operations	(52,317)	(54,231)
Other income:
Grant income	5,163	3,562
Interest income	13	173
Total other income	5,176	3,735
Net loss	(47,141)	(50,496)
Comprehensive loss	$ (47,141)	$ (50,496)
Net loss per share - basic (in dollars per share)	$ (1.09)	$ (2.10)
Net loss per share - diluted (in dollars per share)	$ (1.09)	$ (2.10)
Weighted average common stock outstanding-basic (in shares)	43,340,826	24,060,615
Weighted average common stock outstanding-diluted (in shares)	43,340,826	24,060,615

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2019	$ 13	$ 176,103	$ (133,959)	$ 42,157
Balance (in shares) at Dec. 31, 2019	13,291,563
Stock-based compensation expense		2,951		2,951
Sale of common stock and warrants in Private Placement, net of issuance costs	$ 22	57,653		57,675
Sale of common stock and warrants in Private Placement, net of issuance costs (in shares)	22,183,878
Exercise of warrants	$ 2			2
Exercise of warrants (in shares)	1,161,916
Net loss			(50,496)	(50,496)
Balance at Dec. 31, 2020	$ 37	236,707	(184,455)	52,289
Balance (in shares) at Dec. 31, 2020	36,637,357
Stock-based compensation expense		4,023		4,023
Sale of common stock and warrants in Private Placement, net of issuance costs	$ 10	19,941		19,951
Sale of common stock and warrants in Private Placement, net of issuance costs (in shares)	10,000,000
Exercise of warrants	$ 1	1,799		1,800
Exercise of warrants (in shares)	672,897
Sale of common stock related to at-the-market offerings, net of issuance costs		290		290
Sale of common stock related to at-the-market offerings, net of issuance costs (in shares)	200,000
Issuance of common stock upon the vesting of restricted stock units (in shares)	341,525
Net loss			(47,141)	(47,141)
Balance at Dec. 31, 2021	$ 48	$ 262,760	$ (231,596)	$ 31,212
Balance (in shares) at Dec. 31, 2021	47,851,779

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (47,141)	$ (50,496)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	104	141
Stock-based compensation expense	4,023	2,951
Amortization and accretion of investments		(37)
Changes in operating assets and liabilities:
Grants receivable	632	(658)
Prepaid expenses	(1,594)	400
Other assets	636	1,881
Accounts payable	513	(644)
Accrued expenses and other liabilities	(145)	1,036
Net cash used in operating activities	(42,972)	(45,426)
Cash flows from investing activities:
Purchases of property and equipment	(70)	(18)
Proceeds from maturities of short-term investments		25,000
Net cash (used in) provided by investing activities	(70)	24,982
Cash flows from financing activities:
Proceeds from the sale of common stock and warrants in private placements, net of issuance costs	19,951	57,657
Proceeds from the exercise of warrants	1,800
Proceeds from the sale of common stock related to at-the-market offering, net of issuance costs	351
Net cash provided by financing activities	22,102	57,657
Net (decrease) increase in cash and cash equivalents	(20,940)	37,213
Cash and cash equivalents at beginning of the year	53,247	16,034
Cash and cash equivalents at end of the year	32,307	$ 53,247
Supplemental disclosure of non-cash investing and financing activities:
Financing costs included in accrued expenses	61
Purchases of property and equipment in accounts payable	$ 10

Organization and Description of

Organization and Description of Business	12 Months Ended
Organization and Description of Business	Dec. 31, 2021
Organization and Description of Business
Organization and Description of Business	ENTASIS THERAPEUTICS HOLDINGS INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS 1. Organization and Description of Business Entasis Therapeutics Holdings Inc., or Entasis, or the Company, is an advanced, late clinical-stage biopharmaceutical company focused on the discovery, development and commercialization of targeted antibacterial products that address high unmet medical needs to treat serious infections caused by multidrug-resistant pathogens. The Company has four subsidiaries: Entasis Therapeutics Limited; Entasis Therapeutics Inc.; Entasis Therapeutics Security Corporation; and Entasis Therapeutics (Ireland) Limited. On April 12, 2020, the Company entered into a securities purchase agreement, or the First Securities Purchase Agreement, with Innoviva Inc., or Innoviva, pursuant to which the Company issued and sold to Innoviva, in a private placement, 14,000,000 newly issued shares of common stock of the Company at $2.50 per share, and warrants to purchase up to 14,000,000 shares of common stock with an exercise price per share of $2.50, resulting in an aggregate gross purchase price of approximately $35.0 million, collectively, the First Private Placement. As a result of the transaction, Innoviva acquired control of the Company, owning approximately 51.3% of the Company’s common stock without giving effect to the potential exercise of its warrants. On August 27, 2020, the Company entered into another securities purchase agreement, or the Second Securities Purchase Agreement, with the purchasers named therein, or the Investors, which included existing stockholder Innoviva. Pursuant to the Second Securities Purchase Agreement, the Company issued and sold to the Investors in a private placement (i) 8,183,878 newly issued shares of common stock of the Company at $2.675 per share, (ii) warrants to purchase an aggregate of 9,345,794 shares of common stock with an exercise price of $2.675, and (iii) pre-funded warrants, in lieu of common stock, to purchase an aggregate of 1,161,916 shares of common stock with an exercise price of $0.001 per share, resulting in aggregate gross proceeds of approximately $25.0 million, which is referred to collectively as the Second Private Placement. The closing of the Second Private Placement occurred on September 1, 2020. As a result of the transaction, Innoviva owned approximately 52.6% of the Company’s common stock without giving effect to the potential exercise of its warrants. On May 3, 2021, the Company entered into a securities purchase agreement, or the Third Securities Purchase Agreement, with a subsidiary of Innoviva, pursuant to which the Company agreed to issue and sell to Innoviva, in a private placement up to 10,000,000 newly issued shares of common stock of the Company at $2.00 per share and warrants to purchase up to 10,000,000 shares of common stock with an exercise price per share of $2.00, collectively, the Third Private Placement. The warrants were exercisable immediately and have a five-year term. The Third Private Placement occurred in two tranches. At the closing of the first tranche, or the First Closing, which occurred on May 3, 2021, Innoviva purchased 3,731,025 shares of common stock and warrants to purchase up to 3,731,025 shares of common stock, for an aggregate purchase price of approximately $7.5 million. At the closing of the second tranche, or the Second Closing, which occurred on June 11, 2021, Innoviva purchased the remaining 6,268,975 shares of common stock and warrants to purchase up to 6,268,975 shares of common stock, for an aggregate purchase price of approximately $12.5 million. As a result of these transactions, as of December 31, 2021, Innoviva owned approximately 59.9% of the Company’s common stock without giving effect to the potential exercise of the warrants. If Innoviva were to exercise all of its warrants, as of December 31, 2021 Innoviva would have held approximately 74.9% of the Company’s outstanding common stock. On February 17, 2022, the Company entered into a securities purchase agreement, or Fourth Securities Purchase Agreement with a subsidiary of Innoviva, pursuant to which the Company issued and sold to Innoviva, in a private placement which closed on February 18, 2022, a convertible promissory note having a principal amount of $15.0 million. This transaction is described in further detail in Note 16 – Subsequent Events Going Concern Since its inception, the Company has incurred recurring net losses and negative cash flows from its operations. The Company has financed its operations primarily with proceeds from the sale of preferred stock, common stock, warrants and pre-funded warrants The Company follows the provisions of Financial Accounting Standards Board, or FASB, Accounting Standards Codification, or ASC, Topic 205-40 , Presentation of Financial Statements Going Concern Based on the Company’s available cash resources, the Company believes its existing cash and cash equivalents, including the $15.0 million received from Innoviva as part of the Fourth Securities Purchase Agreement, will enable it to fund its operating expenses and capital requirements through the end of the third quarter of 2022. Accordingly, The consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates continuity of operations, the realization of assets and the satisfaction of liabilities and commitments in the normal course of business. The consolidated financial statements do not include any adjustments that might result from the outcome of this uncertainty. Risks and Uncertainties As of December 31, 2021, the Company had $32.3 million in cash and cash equivalents, and an accumulated deficit of $231.6 million. Since its inception through December 31, 2021, the Company has funded its operations primarily with proceeds from the sale of preferred stock, common stock, warrants and pre-funded warrants. The Company also has either directly received funding or financial commitments from, or has had its program activities conducted and funded by, United States government agencies, non-profit entities and the collaboration agreement with Zai Lab (Shanghai), Co., Ltd., or Zai Lab. 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, equity financing, strategic collaborations, or partnerships. If the Company raises additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, it may be required to relinquish valuable rights to its technologies, future revenue streams, research programs or product candidates or to grant licenses on terms that may not be favorable. If the Company is unable to raise additional funds through equity or debt financings when needed, it may be required to delay, limit, reduce or terminate drug development or future commercialization efforts or grant rights to a third party to develop and market product candidates. The Company’s failure to raise capital as and when needed would compromise its ability to pursue its business strategy. As a late clinical-stage company, Entasis 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 and contract manufacturing organizations, 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-stage development and will require additional research and development efforts, including the completion of Phase 3 registration trials 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. The COVID-19 pandemic has, and will likely continue to have, a significant impact on the U.S. economy and businesses. The social distancing and stay-at-home orders issued by national, state and local governments have resulted in closures of offices and factories and disrupted supply chains. The pandemic also has taxed healthcare systems both in the U.S. and around the world, resulting in disruption to or temporary suspension of clinical trials. The nature, extent and duration of the COVID-19 pandemic remains uncertain and the time needed for businesses and healthcare systems to recover remains unknown. The full impact of the pandemic on the economy, including the capital markets, also remains unknown. The continuation of prolonged adverse economic conditions (including due to any resurgence of COVID-19 infections) could limit the Company’s access to financial resources from the capital markets and other sources. It is not possible to predict the full impact of the COVID-19 pandemic on the Company’s business and access to capital in the future. Despite these challenges, the Company and its contract research organization, or CRO, partner were able to keep the ATTACK Phase 3 registration trial enrolling throughout the pandemic and announced positive top-line data in October 2021. Furthermore, the Company has observed an increase in the enrollment rate during the past two quarters in the zoliflodacin Phase 3 registration trial.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2021
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP. The consolidated financial statements include the Company’s accounts and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. 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 and the recognition of research and development expenses. 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. Fair Value Measurements The accounting standard for fair value measurements defines fair value, establishes a framework for measuring fair value in accordance with U.S. GAAP, and requires detailed disclosures about fair value measurements. Under this standard, fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The valuation techniques are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect the Company’s assumptions. This standard classifies these inputs into the following hierarchy: Level 1 Inputs Level 2 Inputs Level 3 Inputs The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between Level 1, Level 2 or Level 3 during the years ended December 31, 2021 and 2020. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks, money market instruments, corporate and municipal notes, U.S. Treasury securities and federal agency securities. Cash equivalents are stated at fair value. The amount of cash equivalents included in cash and cash equivalents was approximately $28.1 million and $49.1 million as of December 31, 2021 and 2020, respectively. Concentrations of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and short-term investments. The Company maintains each of its cash balances with high-quality, accredited, financial institutions and, accordingly, such funds are not exposed to significant credit risk. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company is dependent on third-party manufacturers to supply active pharmaceutical ingredient, or API, and drug product for research and development activities for its programs, including clinical trial testing. These programs could be adversely affected by a significant interruption in the supply of API or drug product. Deferred Financing Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statement of operations. Property and Equipment Property and equipment is recorded at cost and depreciated over the estimated useful lives of the related assets using the straight-line method. Upon disposal of an asset, the related cost and accumulated depreciation are removed from the asset accounts and any resulting gain or loss is included in the consolidated statement of operations. Repair and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment. The estimated useful lives of the Company’s respective assets are as follows: Estimated Useful Life Laboratory equipment 3 Computer software 3 years Computer equipment 3 years Furniture and fixtures 5 years Impairment of Long-Lived Assets Long-lived assets are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Whenever such events occur, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. Segment Information The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. As of December 31, 2021 and 2020, all of the Company’s long-lived assets were domiciled in the United States. Revenue Recognition The Company enters into collaboration agreements for research, development, manufacturing and commercial services, under which the Company licenses certain rights to its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, upfront license fees; reimbursement of certain costs; customer option exercise fees; development, regulatory and commercial milestone payments; and royalties on net sales of licensed products. The amount of variable consideration is constrained until it is probable that the revenue is not at a significant risk of reversal in a future period. The contracts into which the Company enters generally do not include significant financing components. As part of the accounting for these arrangements, the Company may be required to use significant judgment to determine: (a) the performance obligations in the contract, (b) the transaction price and (c) the timing of revenue recognition, including the appropriate measure of progress. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price, as described further below. The transaction price is allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. If a milestone or other variable consideration relates specifically to the Company’s efforts to satisfy a single performance obligation or to a specific outcome from satisfying the performance obligation, the Company generally allocates the milestone amount entirely to that performance obligation once it is probable that a significant revenue reversal would not occur. Amounts received prior to revenue recognition are recorded as deferred revenue. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date would be classified as current portion of deferred revenue in the consolidated balance sheet. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date would be classified as deferred revenue, net of current portion. Licenses of intellectual property In assessing whether a license is distinct from the other promises, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from a license for its intended purpose without the receipt of the remaining promise(s), whether the value of the license is dependent on the unsatisfied promise(s), whether there are other vendors that could provide the remaining promise(s), and whether it is separately identifiable from the remaining promise(s). For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Customer options If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the goods and services underlying the customer options are not considered to be performance obligations at the outset of the arrangement, as they are contingent upon option exercise. The Company evaluates the customer options for material rights, or options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent or include a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the relative standalone selling price, which is determined based on the identified discount and the probability that the customer will exercise. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised. Milestone payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur, the associated milestone value is included in the transaction price. Milestone payments based on events that are not within the Company’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant reversal of cumulative revenue would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue and earnings in the period of adjustment. Government Contracts and Grant Agreements Income from grants is recognized in the period during which the related specified expenses are incurred, provided that the conditions under which the grants or incentives were provided have been met. Grant funding that is received by the Company in advance of incurring specified expenses is recorded in the consolidated balance sheet as a liability. Grant income recognized upon incurring specified expenses in advance of receipt of grant funding is recorded in the consolidated balance sheet as a receivable. Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses include employee costs, such as salaries, equity-based compensation and benefits, as well as consulting, contract research, third-party license fees, depreciation, rent and other corporate or operational costs attributable to the Company’s research and development activities. These costs include allocated facility-related expenses and external costs of outside vendors engaged to conduct both preclinical studies and clinical trials. Non-refundable pre-payments for goods or services that will be used or rendered for future research and development activities are deferred. Such amounts are recognized as expense as the goods or services are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered. The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. Patent Costs The Company expenses patent costs as incurred and records such costs within general and administrative expenses. Stock-Based Compensation The Company measures stock-based awards based on the estimated fair value of the award on the date of the grant and recognizes compensation expense for those awarded to employees and directors over the requisite service period, which is generally the vesting period of the respective award, and for those awarded to nonemployees over the period during which services are rendered by nonemployees until completed. Forfeitures are accounted for as they occur. The Company has historically issued stock-based awards with only service-based vesting conditions and records the expense for these awards using the straight-line method. The Company classifies stock-based compensation expense in its consolidated statement of operations in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model. The Company lacks company-specific historical and implied volatility information for its stock. The Company estimates its expected stock price volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method. The “simplified” method estimates the expected term of stock options as the mid-point between the weighted average time to vesting and the contractual maturity. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. There is no expected dividend yield since the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future. Income Taxes The Company accounts for income taxes using the asset and liability method which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of assets and liabilities. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax asset to a level which, more likely than not, will be realized. See Note 11 for further discussion of income taxes. Accounting for income taxes requires a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if, based on the technical merits, it is more likely than not that the position will be sustained upon audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50 percent likely of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Basic and Diluted Net Loss Per Share Net earnings or loss per share is calculated in accordance with the applicable accounting guidance provided in ASC 260, Earnings per Share. Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) is computed by adjusting net income (loss) to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share is computed by dividing the diluted net income (loss) by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents. Recently Adopted Accounting Pronouncements Effective January 1, 2021, the Company adopted the provisions of FASB ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes Recently Issued Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
Fair Value of Financial Instruments	Dec. 31, 2021
Fair Value of Financial Instruments
Fair Value of Financial Instruments	3. Fair Value of Financial Instruments The following tables set forth the Company’s assets that were accounted for at fair value on a recurring basis: December 31, 2021 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 28,137 $ — $ — $ 28,137 Total $ 28,137 $ — $ — $ 28,137 December 31, 2020 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 49,125 $ — $ — $ 49,125 Total $ 49,125 $ — $ — $ 49,125 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 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.

Property and Equipment, net

Property and Equipment, net	12 Months Ended
Property and Equipment, net	Dec. 31, 2021
Property and Equipment, net
Property and Equipment, net	4. Property and Equipment, net Property and equipment, net consisted of the following (in thousands): As of December 31, 2021 2020 Laboratory equipment $ 1,039 $ 1,001 Computer software 87 71 Computer equipment 44 38 Furniture and fixtures 22 6 Total 1,192 1,116 Less: accumulated depreciation (994) (894) Property and equipment, net $ 198 $ 222 Depreciation expense was $0.1 million for each of the years ended December 31, 2021 and 2020.

Leases

Leases	12 Months Ended
Leases	Dec. 31, 2021
Leases
Leases	5. Leases The Company has one significant operating lease, 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, or the AZ lease, as amended in February 2018. During each of the years ended December 31, 2021 and December 31, 2020, the Company recorded lease expense of $0.6 million related to this lease. The Company has two additional operating leases that are included in its lease accounting which are not considered significant. 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. As of December 31, 2021, the Company was not reasonably certain to exercise this renewal option. In February 2022, the Company made the decision to exercise this renewal option which will extend the lease term for an additional three years. Therefore, 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 of the Company’s operating leases in its consolidated balance sheet (in thousands): As of December 31, 2021 2020 Assets Operating lease right-of-use assets $ 604 $ 1,141 Liabilities Operating lease liabilities, current $ 704 $ 617 Operating lease liabilities, net of current portion — 704 Total operating lease liabilities $ 704 $ 1,321 The operating lease right-of-use assets and operating lease liabilities balances relate primarily to amounts associated with the AZ lease. Future minimum lease payments under non-cancelable leases were as detailed below (in thousands): Fiscal Year As of December 31, 2021 2022 $ 737 2023 1 Total undiscounted lease payments 738 Less: imputed interest (34) Total operating lease liabilities $ 704 As of December 31, 2021, the weighted-average remaining lease term was 1.0 years and the weighted-average incremental borrowing rate used to determine the operating lease right-of-use assets was 9.1%.

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	12 Months Ended
Accrued Expenses and Other Current Liabilities	Dec. 31, 2021
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): As of December 31, 2021 2020 Accrued compensation and benefits $ 3,668 $ 2,935 Accrued contract manufacturing 2,678 2,959 Current portion of operating lease liabilities 704 617 Accrued clinical 691 504 Accrued professional services 375 435 Accrued research 292 349 Other 117 106 Total accrued expenses and other current liabilities $ 8,525 $ 7,905

Funding Arrangements

Funding Arrangements	12 Months Ended
Funding Arrangements	Dec. 31, 2021
Funding Arrangements
Funding Arrangements	7. Funding Arrangements NIH In June 2020, the Company entered into a contract with the National Institute of Allergy and Infectious Diseases, or NIAID, part of the National Institutes of Health, or NIH, the NIH Contract, which was effective beginning July 1, 2020 and provides the Company with reimbursement of certain qualified expenses incurred The initial award consisted of approximately , with the potential to increase up to , and will be used to develop novel molecules from the Company’s non-β-lactam inhibitor, or NBP, platform. Funding from the contract will support research towards developing molecules with expanded Gram-negative spectrum against antibiotic resistant bacterial pathogens including E. coli, Acinetobacter, Pseudomonas and Klebsiella . I Through December 31, 2021, the Company has received $3.2 million in payments and recorded $3.9 million of grant income under this contract. The Company recognized grant income in connection with the NIH contract of $2.6 million during the year ended December 31, 2021 and $1.3 million during the year ended December 31, 2020. As of December 31, 2021, and December 31, 2020 the Company’s receivables for unreimbursed, eligible costs incurred under the NIH contract totaled $0.6 million, including both billed and unbilled amounts. CARB-X 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, or CARB-X, program, in support of the Company’s ETX0282CPDP and ETX0462 programs. The amount of specified research expenditures of the Company that could be covered is $18.5 million from April 2017 through May 2023. Through December 31, 2021, the Company had received $12.6 million in payments and recorded $12.9 million of grant income under these funding arrangements. The remaining $5.6 million that could be received is related to the Company’s ETX0462 program. The Company recognized grant income in connection with the CARB-X agreements of $2.6 million during the year ended December 31, 2021, and $2.3 million during the year ended December 31, 2020. As of December 31, 2021 and 2020, the Company’s receivables for unreimbursed, eligible costs incurred under the CARB-X agreements totaled $0.7 million and $1.1 million, respectively, including both billed and unbilled amounts.

License and Collaboration Agree

License and Collaboration Agreements	12 Months Ended
License and Collaboration Agreements	Dec. 31, 2021
License and Collaboration Agreements
License and Collaboration Agreements	8. License and Collaboration Agreements GARDP In July 2017, the Company entered into a collaboration agreement with the Global Antibiotic Research and Development Partnership, or GARDP, for the development, manufacture and commercialization of the product candidate zoliflodacin in certain countries. Under the terms of the collaboration agreement, GARDP will use commercially reasonable endeavors to perform and fully fund the Phase 3 registration trial, including the manufacture and supply of the product candidate containing zoliflodacin, in uncomplicated gonorrhea. The Phase 3 registration trial was initiated in September 2019 with activation of U.S. sites. The trial was negatively impacted by the COVID-19 pandemic, resulting in a 4-month pause in enrollment in mid-2020. Although GARDP resumed patient enrollment into the Phase 3 registration trial after the pause, any future impact by the continued COVID-19 pandemic at clinical trial sites cannot be estimated at this time. The Company has observed an increase in the enrollment rate during the past two quarters and now anticipates the Phase 3 trial to be fully enrolled in 2023. In addition, under the collaboration agreement, the Company has granted GARDP a worldwide, fully paid, exclusive and royalty-free license, with the right to sublicense, to use its zoliflodacin technology in connection with GARDP’s development, manufacture and commercialization of zoliflodacin in low-income and specified middle-income countries. The Company has retained commercial rights in all other countries worldwide, including the major markets in North America, Europe and Asia-Pacific. The Company has also retained the right to use and grant licenses to its zoliflodacin technology to perform its obligations under the collaboration agreement and for any purpose other than gonorrhea or community-acquired indications. If the Company believes that the results of the Phase 3 registration trial of zoliflodacin would be supportive of an application for marketing approval, it is obligated to use its best efforts to file an application for marketing approval with the FDA within six months of the completion of the trial and to use commercially reasonable endeavors to file an application for marketing approval with the EMA. Each party is responsible for using commercially reasonable efforts to obtain marketing authorizations for the product candidate in their respective territories. Zai Lab In April 2018, the Company entered into a license and collaboration agreement with Zai Lab (Shanghai) Co., Ltd., or Zai Lab, pursuant to which Zai Lab licensed exclusive rights to durlobactam and sulbactam-durlobactam, or SUL-DUR, in the Asia-Pacific region, or 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 SUL-DUR, including all costs in China for the Company’s Phase 3 registration trial of SUL-DUR, with the exception of Phase 3 patient drug supply. Zai Lab will conduct development activities and plan and obtain regulatory approval in a specified number of countries in the Asia-Pacific region beyond China after receipt of 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 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. The Company received an upfront, non-refundable payment of $5.0 million, milestone payments of $7.0 million, research support funding of $0.6 million and certain other reimbursable registration trial costs of $5.4 million, less applicable taxes of $2.2 million, from Zai Lab through December 31, 2021. During the years ended December, 2021 and 2020, the Company recognized no revenue under the Zai Agreement. The Company is eligible to receive up to an aggregate of $91.0 million in additional research and development support payments and development, regulatory and sales milestone payments related to SUL-DUR, imipenem and other combinations with the licensed products. Zai Lab will pay the Company a tiered royalty ranging from 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. Payments received for research support and reimbursable clinical trial costs are recorded as an offset to research and development expense during the period in which the qualifying expenses are incurred. Future potential milestone payments were excluded from the initial transaction price as they were fully constrained as the risk of significant reversal of revenue had not yet been resolved. At the outset of the Zai Agreement, the achievement of the future potential milestones was not within the Company’s control and was subject to certain research and development success, regulatory approvals or commercial success and therefore carried significant uncertainty. The Company reevaluates the likelihood of achieving the 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.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2021
Stockholders' Equity
Stockholders' Equity	9. Stockholders’ Equity Common Stock Each holder of common stock shall be entitled to one vote for each share of common stock held of record by such holder on all matters on which stockholders generally are entitled to vote. Common stockholders are entitled to receive dividends when and if declared by the board of directors, out of any funds legally available. As of December 31, 2021, no dividends have been declared or paid. Third Private Placement On May 3, 2021, the Company entered into the Third Securities Purchase Agreement, with a subsidiary of Innoviva, pursuant to which the Company agreed to issue and sell to Innoviva up to 10,000,000 newly issued shares of common stock of the Company at $2.00 per share and warrants to purchase up to 10,000,000 shares of common stock, each with an exercise price per share of $2.00. Third Private Placement occurred in two tranches. At the First Closing, which occurred on May 3, 2021, Innoviva purchased 3,731,025 shares of common stock and warrants to purchase 3,731,025 shares of common stock, for aggregate gross proceeds of $7.5 million. At the Second Closing, which occurred on June 11, 2021, Innoviva purchased the remaining 6,268,975 shares of common stock and warrants to purchase 6,268,975 shares of common stock, for aggregate gross proceeds of $12.5 million. Second Private Placement On August 27, 2020, the Company entered into the Second Securities Purchase Agreement with the Investors, including existing stockholder Innoviva, pursuant to which the Company issued and sold to the Investors in a private placement (i) 8,183,878 newly issued shares of common stock of the Company at $2.675 per share, (ii) warrants to purchase an aggregate of 9,345,794 shares of common stock with and exercise price of $2.675, and (iii) pre-funded warrants, in lieu of common stock, to purchase an aggregate of 1,161,916 shares of common stock, with an exercise price of $0.001 per share, resulting in aggregate gross proceeds of approximately $25.0 million. The closing of the Second Private Placement occurred on September 1, 2020. The exercise price and the number of shares of common stock issuable upon exercise of each warrant is subject to appropriate adjustments in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting the Company’s common stock. Each warrant is exercisable from the date of issuance and has a term of five years. First Private Placement On April 12, 2020, the Company entered into the First Securities Purchase Agreement, with Innoviva, pursuant to which the Company issued and sold to Innoviva 14,000,000 newly issued shares of common stock of the Company at $2.50 per share, and warrants to purchase up to 14,000,000 shares of common stock with an exercise price per share of $2.50. Under the First Securities Purchase Agreement, the First Private Placement occurred in two tranches. At the closing of the first tranche, which occurred on April 22, 2020, or the First Closing, Innoviva purchased 1,322,510 shares of common stock and warrants to purchase 1,322,510 shares of common stock, for an aggregate gross purchase price of approximately $3.3 million. At the closing of the second tranche, which occurred on June 11, 2020, or the Second Closing, Innoviva purchased the remaining 12,677,490 shares of common stock and warrants to purchase 12,677,490 shares of the common stock for an aggregate gross purchase price of approximately $31.7 million. As of December 31, 2021, Innoviva owned approximately 59.9% of the Company’s outstanding common stock without giving effect to the potential exercise of the warrants. At-the-Market Facility In August 2021, the Company entered into a Controlled Equity Offering Sales Agreement, or Sales Agreement, with Cantor Fitzgerald & Co, or Cantor, for the offer and sale of up to $17.5 million of its common stock at the then current market prices in amounts to be determined from time to time. On October 21, 2021, the Company sold an aggregate of 200,000 shares of common stock at a sale price of $3.25 per share, for gross proceeds of $0.7 million. Proceeds, net of fees, were $0.6 million. Warrants As of December 31, 2021, outstanding warrants to purchase shares of the Company’s common stock are as follows: Shares Underlying Outstanding Warrants Exercise Price Expiration Date 1,322,510 $ 2.50 April 22, 2025 12,677,490 $ 2.50 June 11, 2025 8,672,897 $ 2.675 September 1, 2025 10,000,000 $ 2.00 May 3, 2026 32,672,897

Stock-Based Compensation Expens

Stock-Based Compensation Expense	12 Months Ended
Stock-Based Compensation Expense	Dec. 31, 2021
Stock-Based Compensation Expense
Stock-Based Compensation Expense	10. Stock-Based Compensation Expense Stock Incentive Plan In September 2018, the Company’s board of directors adopted and its stockholders approved the 2018 Equity Incentive Plan, or 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, or the 2015 Plan, previously in effect. Under the 2018 Plan, the Company may grant incentive stock options, or ISOs, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. As of December 31, 2021, options to purchase an aggregate of 5,213,285 shares had been granted, restricted stock units, or RSUs, of 992,600 had been awarded, and 1,604,834 shares were available for future issuance under the 2018 Plan. The options issued under the 2018 Plan expire after 10 years from the date of grant. At its inception, the aggregate number of shares of the Company’s common stock available for issuance under the 2018 Plan was 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 directors 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 year ended December 31, 2021 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, 2020 3,112,704 $ 5.58 7.76 $ 44 Granted 1,492,776 2.45 Forfeited and expired (1,710,100) 6.86 Outstanding as of December 31, 2021 2,895,380 $ 3.21 8.33 $ 30 Exercisable as of December 31, 2021 978,915 $ 3.84 6.57 $ 7 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 years ended December 31, 2021 and 2020 the weighted-average grant-date fair value per granted option was $4.03 and $2.95, respectively. As described below, on July 16, 2021, the Company completed a stock option exchange program that resulted in the termination of options to purchase 1,562,752 shares of the Company’s common stock with a weighted-average exercise price of $7.17 per share and the issuance of stock options to purchase 1,148,572 shares of the Company’s common stock with an exercise price of $2.44 per share. Stock Option Exchange On June 17, 2021, the Company commenced a voluntary stock option exchange program, or the Exchange Program, to permit the Company’s eligible employees, directors and certain consultants to exchange some or all of their eligible outstanding options, or the Original Options, to purchase the Company’s common stock with an exercise price greater than or equal to $4.98 per share, whether vested or unvested, for a lesser number of new stock options, or the New Options. The New Options will be granted under the 2018 Plan on the date on which the Original Options accepted for exchange are cancelled. Participants must remain continuously employed by the Company or in continuous service to the Company through the New Option grant date. New Options will have a per share exercise price equal to the per share closing price of the Company’s common stock on the New Option grant date. The New Options will have the same vesting schedule as the Original Options for options with a remaining vesting period exceeding 12 months. For Original Options with a remaining vesting period of 12 months or less, including full vesting options, the replacement options will vest in full 12 months from the New Option grant date. In accordance with the terms and conditions of the Exchange Program, the Company closed the exchange program and accepted all exchanged outstanding options on July 16, 2021, at which time the Company’s common stock price per share was $2.44. The stock option exchange program was approved at the Company’s annual shareholder meeting on June 10, 2021. Pursuant to the Exchange Program, 44 eligible participants elected to exchange, and the Company accepted for cancellation Original Options to purchase an aggregate of 1,562,752 shares of the Company’s common stock, representing approximately 97% of the total shares of common stock underlying the eligible Original Options. On July 16, 2021, immediately following the expiration of the exchange offer, the Company granted New Options to purchase 1,148,572 shares of common stock, pursuant to the terms of the exchange offer and the Company’s 2018 Plan. In addition to the grant date fair value of the original awards, the Company will recognize incremental expense of approximately $0.3 million over the remaining service periods of the replacement awards. Restricted Stock Unit Activity Restricted stock unit activity for the year ended December 31, 2021 is summarized as follows: Weighted- Average Number of Grant Date Units Fair Value Outstanding as of December 31, 2020 395,100 $ 1.65 Granted 597,500 2.57 Released (427,975) 2.24 Forfeited (73,650) 1.99 Outstanding as of December 31, 2021 490,975 $ 2.20 Employee Stock Purchase Plan In September 2018, the Company’s board of directors and its stockholders approved the 2018 Employee Stock Purchase Plan, or 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 250,000 shares were added to the number of available shares effective January 1, 2022 and 2021. As of December 31, 2021, no shares of common stock had been issued under the ESPP and 654,163 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): Year Ended December 31, 2021 2020 Research and development $ 1,932 $ 1,397 General and administrative 2,091 1,554 Total stock-based compensation expense $ 4,023 $ 2,951 The following table summarizes stock-based compensation expense by type of award (in thousands): Year Ended December 31, 2021 2020 Stock options $ 2,714 $ 2,898 Restricted stock units 1,309 53 Total stock-based compensation expense $ 4,023 $ 2,951 The following table summarizes unrecognized stock-based compensation expense as of December 31, 2021, by type of awards, and the weighted-average period over which that expense is expected to be recognized. The total unrecognized stock-based compensation expense will be adjusted for actual forfeitures as they occur. As of December 31, 2021 Unrecognized Expense Weighted-average Remaining Recognition Period (in thousands) (in years) Stock options $ 1,945 1.69 Restricted stock units $ 679 0.72 The following weighted average assumptions were used to calculate the fair value of each stock option award under the Black-Scholes option pricing model: Year Ended December 31, 2021 2020 Expected stock price volatility 80.7 % 82.0 % Risk-free interest rate 0.9 % 0.5 % Expected annual dividend yield — — Expected life of options 6.1 years 6.3 years

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2021
Income Taxes
Income Taxes	11. Income Taxes During the years ended December 31, 2021 and 2020, the Company recorded no income tax benefits for the net operating losses incurred due to its uncertainty of realizing a benefit from those items. The Company’s losses before income taxes were generated in the United States and the United Kingdom. Net loss before the provision for income taxes for the years ended December 31, 2021 and 2020, consisted of the following (in thousands): Year Ended December 31, 2021 2020 United Kingdom $ 28,411 $ 38,280 United States 18,730 12,216 $ 47,141 $ 50,496 A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows: Year Ended December 31, 2021 2020 Income tax benefit computed at U.S. statutory tax rate 21.0 % 21.0 % State taxes, net of federal benefit 6.4 6.6 Foreign rate differential (1.2) (1.5) Disregarded entity 12.7 15.9 Research and development tax credits 1.4 1.4 Permanent difference (1.2) (0.6) Valuation allowances (58.9) (45.7) Rate change 20.0 3.6 Other (0.2) (0.7) Effective income tax rate (0.0) % (0.0) % Net deferred tax assets consisted of the following (in thousands): As of December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 84,786 $ 57,265 Tax credit carryforwards 5,261 4,345 Accrued expenses and other 2,275 3,099 Total deferred tax assets 92,322 64,709 Deferred tax liabilities: Right-of-use asset (165) (312) Total deferred tax liabilities (165) (312) Valuation allowance (92,157) (64,397) Net deferred tax assets $ — $ — Net operating losses generated in years ending after December 31, 2018 will be carried forward indefinitely and can no longer be carried back, and net operating losses generated in years beginning after December 31, 2017, can only reduce taxable income by 80% when utilized in a future period. As of December 31, 2021, the Company had federal and state net operating loss carryforwards, or NOLs, of $166.3 million and $167.4 million, respectively, which begin to expire in 2035. Included in the $166.3 million of federal net operating losses are losses of $153.6 million that will carry forward indefinitely as a result of the Tax Cuts and Jobs Act. As of December 31, 2021, the Company had federal and state research and development tax credits carryforwards of $4.1 million and $1.4 million, respectively, which begin to expire in 2035 and 2026, respectively. Utilization of the NOLs and research and development tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three-year period. During 2020, Innoviva purchased over 50% of the Company’s common stock. This ownership change may result in a limitation of the Company’s NOLs. The Company has not conducted a study to assess whether there have been multiple changes of control since inception due to the significant complexity and cost associated with such a study. Ownership changes may limit the amount of NOLs and tax credit carryforwards that could be utilized annually to offset future taxable income. The amount of the annual limitation is determined based on the Company’s value immediately prior to the ownership change. Subsequent significant changes in ownership could affect the limitations in future years. Any limitation may result in expiration of a portion of the net operating loss carryforwards or tax credit carryforwards before utilization. As of December 31, 2021, the Company had NOLs in the United Kingdom of $157.2 million to offset future taxable income. The NOLs in the United Kingdom can be carried forward indefinitely. The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s history of cumulative net losses incurred since inception and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the federal, state and foreign deferred tax assets. Accordingly, a full valuation allowance of $92.2 million has been established against the deferred tax assets as of December 31, 2021. Management reevaluates the positive and negative evidence at each reporting period. Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2021 and 2020 related primarily to the increases in NOLs and research and development tax credit carryforwards and were as follows (in thousands): Year Ended December 31, 2021 2020 Valuation allowance at beginning of year $ (64,397) $ (41,253) Increases recorded to income tax provision (27,760) (23,144) Valuation allowance at end of year $ (92,157) $ (64,397) The Company has not recorded an amount for unrecognized tax benefits or related interest and penalties accrued as of December 31, 2021. The Company files income tax returns in the United States, Massachusetts and the United Kingdom. The federal and state returns are generally subject to tax examinations for the tax years ended December 31, 2015 to the present. The statute of limitations for assessment by the United Kingdom is open for the tax years since 2015. There are currently no pending tax examinations. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service and state tax authorities to the extent utilized in a future or prior period. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision.

Net Loss per Share

Net Loss per Share	12 Months Ended
Net Loss per Share	Dec. 31, 2021
Net Loss per Share
Net Loss per Share	12. Net Loss per Share Basic and diluted net loss per share of the Company was calculated as follows (in thousands, except share and per share amounts): Year Ended December 31, 2021 2020 Numerator: Net loss $ (47,141) $ (50,496) Net loss attributable to common stockholders—basic and diluted $ (47,141) $ (50,496) Denominator: Weighted average common stock outstanding — 43,340,826 24,060,615 Net loss per share attributable to common stockholders — $ (1.09) $ (2.10) The following outstanding securities have been excluded from the computation of diluted weighted average shares outstanding for the year ended December 31, 2021 and 2020, respectively, as they would have been anti-dilutive: As of December 31, 2021 2020 Options to purchase shares of common stock 2,895,380 3,112,704 Warrants to purchase shares of common stock 32,672,897 23,345,794 Unvested restricted stock units 490,975 395,100 36,059,252 26,853,598

Commitments

Commitments	12 Months Ended
Commitments	Dec. 31, 2021
Commitments
Commitments	13. Commitments Lease Commitments The Company has an operating lease agreement for its office and laboratory space with AstraZeneca. See Note 5, Leases AstraZeneca Subscription Agreement In connection with the Company’s spin-out from AstraZeneca in 2015, the Company entered into a business transfer and subscription agreement with AstraZeneca, or the AstraZeneca Subscription Agreement, pursuant to which 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 durlobactam. 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 durlobactam. 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 durlobactam and zoliflodacin.

Related Party Transactions

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2021
Related Party Transactions
Related Party Transactions	14. Related Party Transactions AstraZeneca The Company was formed in May 2015 as a wholly owned subsidiary of AstraZeneca. Prior to the closing of the initial public offering on September 28, 2018, AstraZeneca was the sole holder of Series A preferred stock. Upon the closing of the initial public offering, all shares of preferred stock converted into shares of common stock. AstraZeneca continues to maintain an ownership interest in the Company. The Company has an operating lease agreement for its office and laboratory space with AstraZeneca. See Note 5, Leases Pharmaron Beijing Co., Ltd. (China) The Company contracts with Pharmaron Beijing Co., Ltd. (China), or Pharmaron, to provide various medicinal chemistry research, manufacturing development and clinical services related to the Company’s ongoing product candidates. The Company began utilizing Pharmaron as a service provider prior to the spin-out in 2015, and this relationship has continued through 2020. 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 considers the agreements between the Company and Pharmaron to be related-party transactions. The Company recorded expense of $3.7 million and $5.0 million during the years ended December 31, 2021 and December 31, 2020, respectively, for services pursuant to multiple Pharmaron agreements. Amounts due to Pharmaron were $0.1 million and $2.0 million as of December 31, 2021 and December 31, 2020, respectively.

Benefit Plans

Benefit Plans	12 Months Ended
Benefit Plans	Dec. 31, 2021
Benefits Plans
Benefit Plans	15. Benefit Plans The Company has a tax-qualified employee savings and retirement 401(k) plan, covering all qualified employees. Participants may elect a salary deferral up to the statutorily prescribed annual limit for tax-deferred contributions. The Company made matching contributions of $0.3 million for the years ended December 31, 2021 and 2020.

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2021
Subsequent Events
Subsequent Events	16. Subsequent Events Securities Purchase Agreement On February 17, 2022, the Company entered into a securities purchase agreement, or Fourth Securities Purchase Agreement with a subsidiary of Innoviva, pursuant to which the Company issued and sold to Innoviva, in a private placement which closed on February 18, 2022, a convertible promissory note having a principal amount of $15.0 million, or the Convertible Note. The Convertible Note is convertible at maturity at the election of the Company or Innoviva into shares of the Company’s common stock at a conversion price of $1.48 per share of common stock and warrants to purchase an equal number of shares of common stock with an exercise price of $1.48 per share of common stock, or the Warrants. The Convertible Note will also be convertible at the option of Innoviva if the Company engages in certain capital markets transactions, asset sales or royalty transactions. If the Company is acquired prior to the maturity date of the Convertible Note, the Convertible Note will be payable in cash at the time of such acquisition. The Convertible Note will mature on August 18, 2022 and bears interest at a rate of 0.59% per annum to, but excluding, the date of repayment or conversion of the Convertible Note. From and including the date of maturity, if not converted, the Convertible Note will bear interest at a rate of 10.00% per annum to, but excluding, the date of repayment or conversion of the Convertible Note. The Convertible Note and the Warrants will have provisions that preclude conversion or exercise, respectively, if such conversion or exercise would result in the issuance of more than 19.99% of the Company’s currently outstanding common stock in the aggregate prior to obtaining stockholder approval. Registration Rights Agreement On February 18, 2022, the Company and Innoviva entered into a registration rights agreement, or the Registration Rights Agreement, pursuant to which, among other things, the Company must prepare and file with the Securities and Exchange Commission, or the SEC, a registration statement with respect to the resale of shares of common stock and the warrants issuable upon conversion of the Convertible Note and shares of common stock issuable upon exercise of the Warrants. AZ Lease

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2021
Summary of Significant Accounting Policies
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States, or U.S. GAAP. The consolidated financial statements include the Company’s accounts and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
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 and the recognition of research and development expenses. 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.
Fair Value Measurements	Fair Value Measurements The accounting standard for fair value measurements defines fair value, establishes a framework for measuring fair value in accordance with U.S. GAAP, and requires detailed disclosures about fair value measurements. Under this standard, fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The valuation techniques are based on observable and unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, while unobservable inputs reflect the Company’s assumptions. This standard classifies these inputs into the following hierarchy: Level 1 Inputs Level 2 Inputs Level 3 Inputs The Company evaluates transfers between levels at the end of each reporting period. There were no transfers of assets or liabilities between Level 1, Level 2 or Level 3 during the years ended December 31, 2021 and 2020.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of 90 days or less at acquisition to be cash equivalents. Cash and cash equivalents include cash held in banks, money market instruments, corporate and municipal notes, U.S. Treasury securities and federal agency securities. Cash equivalents are stated at fair value. The amount of cash equivalents included in cash and cash equivalents was approximately $28.1 million and $49.1 million as of December 31, 2021 and 2020, respectively.
Concentrations of Credit Risk and of Significant Suppliers	Concentrations of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash and short-term investments. The Company maintains each of its cash balances with high-quality, accredited, financial institutions and, accordingly, such funds are not exposed to significant credit risk. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company is dependent on third-party manufacturers to supply active pharmaceutical ingredient, or API, and drug product for research and development activities for its programs, including clinical trial testing. These programs could be adversely affected by a significant interruption in the supply of API or drug product.
Deferred Financing Costs	Deferred Financing Costs The Company capitalizes certain legal, professional accounting and other third-party fees that are directly associated with in-process equity financings as deferred offering costs until such financings are consummated. After consummation of the equity financing, these costs are recorded in stockholders’ equity as a reduction of proceeds generated as a result of the offering. Should a planned equity financing be abandoned, the deferred offering costs would be expensed immediately as a charge to operating expenses in the consolidated statement of operations.
Property and Equipment	Property and Equipment Property and equipment is recorded at cost and depreciated over the estimated useful lives of the related assets using the straight-line method. Upon disposal of an asset, the related cost and accumulated depreciation are removed from the asset accounts and any resulting gain or loss is included in the consolidated statement of operations. Repair and maintenance costs are expensed as incurred, whereas major improvements are capitalized as additions to property and equipment. The estimated useful lives of the Company’s respective assets are as follows: Estimated Useful Life Laboratory equipment 3 Computer software 3 years Computer equipment 3 years Furniture and fixtures 5 years
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Whenever such events occur, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows.
Segment Information	Segment Information The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. As of December 31, 2021 and 2020, all of the Company’s long-lived assets were domiciled in the United States.
Revenue Recognition	Revenue Recognition The Company enters into collaboration agreements for research, development, manufacturing and commercial services, under which the Company licenses certain rights to its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, upfront license fees; reimbursement of certain costs; customer option exercise fees; development, regulatory and commercial milestone payments; and royalties on net sales of licensed products. The amount of variable consideration is constrained until it is probable that the revenue is not at a significant risk of reversal in a future period. The contracts into which the Company enters generally do not include significant financing components. As part of the accounting for these arrangements, the Company may be required to use significant judgment to determine: (a) the performance obligations in the contract, (b) the transaction price and (c) the timing of revenue recognition, including the appropriate measure of progress. The Company uses judgment to determine whether milestones or other variable consideration, except for royalties, should be included in the transaction price, as described further below. The transaction price is allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenue as or when the performance obligations under the contract are satisfied. If a milestone or other variable consideration relates specifically to the Company’s efforts to satisfy a single performance obligation or to a specific outcome from satisfying the performance obligation, the Company generally allocates the milestone amount entirely to that performance obligation once it is probable that a significant revenue reversal would not occur. Amounts received prior to revenue recognition are recorded as deferred revenue. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date would be classified as current portion of deferred revenue in the consolidated balance sheet. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date would be classified as deferred revenue, net of current portion. Licenses of intellectual property In assessing whether a license is distinct from the other promises, the Company considers factors such as the research, development, manufacturing and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from a license for its intended purpose without the receipt of the remaining promise(s), whether the value of the license is dependent on the unsatisfied promise(s), whether there are other vendors that could provide the remaining promise(s), and whether it is separately identifiable from the remaining promise(s). For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Customer options If an arrangement is determined to contain customer options that allow the customer to acquire additional goods or services, the goods and services underlying the customer options are not considered to be performance obligations at the outset of the arrangement, as they are contingent upon option exercise. The Company evaluates the customer options for material rights, or options to acquire additional goods or services for free or at a discount. If the customer options are determined to represent or include a material right, the material right is recognized as a separate performance obligation at the outset of the arrangement. The Company allocates the transaction price to material rights based on the relative standalone selling price, which is determined based on the identified discount and the probability that the customer will exercise. Amounts allocated to a material right are not recognized as revenue until, at the earliest, the option is exercised. Milestone payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur, the associated milestone value is included in the transaction price. Milestone payments based on events that are not within the Company’s control, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant reversal of cumulative revenue would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenue and earnings in the period of adjustment.
Government Contracts and Grant Agreements	Government Contracts and Grant Agreements Income from grants is recognized in the period during which the related specified expenses are incurred, provided that the conditions under which the grants or incentives were provided have been met. Grant funding that is received by the Company in advance of incurring specified expenses is recorded in the consolidated balance sheet as a liability. Grant income recognized upon incurring specified expenses in advance of receipt of grant funding is recorded in the consolidated balance sheet as a receivable.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses include employee costs, such as salaries, equity-based compensation and benefits, as well as consulting, contract research, third-party license fees, depreciation, rent and other corporate or operational costs attributable to the Company’s research and development activities. These costs include allocated facility-related expenses and external costs of outside vendors engaged to conduct both preclinical studies and clinical trials. Non-refundable pre-payments for goods or services that will be used or rendered for future research and development activities are deferred. Such amounts are recognized as expense as the goods or services are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered. The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.
Patent Costs	Patent Costs The Company expenses patent costs as incurred and records such costs within general and administrative expenses.
Stock-Based Compensation	Stock-Based Compensation The Company measures stock-based awards based on the estimated fair value of the award on the date of the grant and recognizes compensation expense for those awarded to employees and directors over the requisite service period, which is generally the vesting period of the respective award, and for those awarded to nonemployees over the period during which services are rendered by nonemployees until completed. Forfeitures are accounted for as they occur. The Company has historically issued stock-based awards with only service-based vesting conditions and records the expense for these awards using the straight-line method. The Company classifies stock-based compensation expense in its consolidated statement of operations in the same manner in which the award recipients’ payroll costs are classified or in which the award recipients’ service payments are classified. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model. The Company lacks company-specific historical and implied volatility information for its stock. The Company estimates its expected stock price volatility based on the historical volatility of publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method. The “simplified” method estimates the expected term of stock options as the mid-point between the weighted average time to vesting and the contractual maturity. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. There is no expected dividend yield since the Company has never paid cash dividends on common stock and does not expect to pay any cash dividends in the foreseeable future.
Income Taxes	Income Taxes The Company accounts for income taxes using the asset and liability method which requires recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of assets and liabilities. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. A valuation allowance is provided to reduce the deferred tax asset to a level which, more likely than not, will be realized. See Note 11 for further discussion of income taxes. Accounting for income taxes requires a two-step approach to recognize and measure uncertain tax positions. The first step is to evaluate the tax position for recognition by determining if, based on the technical merits, it is more likely than not that the position will be sustained upon audit, including resolution of related appeals or litigation processes, if any. The second step is to measure the tax benefit as the largest amount that is more than 50 percent likely of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Basic and Diluted Net Loss Per Share	Basic and Diluted Net Loss Per Share Net earnings or loss per share is calculated in accordance with the applicable accounting guidance provided in ASC 260, Earnings per Share. Basic net income (loss) per share is computed by dividing the net income (loss) by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) is computed by adjusting net income (loss) to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share is computed by dividing the diluted net income (loss) by the weighted average number of common shares outstanding for the period, including potential dilutive common shares assuming the dilutive effect of common stock equivalents.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Effective January 1, 2021, the Company adopted the provisions of FASB ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In November 2021, the FASB issued ASU 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2021
Summary of Significant Accounting Policies
Schedule of estimated useful lives of property and equipment	Estimated Useful Life Laboratory equipment 3 Computer software 3 years Computer equipment 3 years Furniture and fixtures 5 years

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	12 Months Ended
Fair Value of Financial Instruments (Tables)	Dec. 31, 2021
Fair Value of Financial Instruments
Schedule of assets that were accounted for at fair value on recurring basis	December 31, 2021 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 28,137 $ — $ — $ 28,137 Total $ 28,137 $ — $ — $ 28,137 December 31, 2020 Fair Value Measurement Using Level 1 Level 2 Level 3 Total (in thousands) Cash equivalents: Money market funds $ 49,125 $ — $ — $ 49,125 Total $ 49,125 $ — $ — $ 49,125

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
Property and Equipment, net (Tables)	Dec. 31, 2021
Property and Equipment, net
Schedule of property and equipment, net	Property and equipment, net consisted of the following (in thousands): As of December 31, 2021 2020 Laboratory equipment $ 1,039 $ 1,001 Computer software 87 71 Computer equipment 44 38 Furniture and fixtures 22 6 Total 1,192 1,116 Less: accumulated depreciation (994) (894) Property and equipment, net $ 198 $ 222

Leases (Tables)

Leases (Tables)	12 Months Ended
Leases (Tables)	Dec. 31, 2021
Leases
Schedule of operating lease balance sheet information	The following table summarizes the presentation of the Company’s operating leases in its consolidated balance sheet (in thousands): As of December 31, 2021 2020 Assets Operating lease right-of-use assets $ 604 $ 1,141 Liabilities Operating lease liabilities, current $ 704 $ 617 Operating lease liabilities, net of current portion — 704 Total operating lease liabilities $ 704 $ 1,321
Schedule of future lease payments	The operating lease right-of-use assets and operating lease liabilities balances relate primarily to amounts associated with the AZ lease. Future minimum lease payments under non-cancelable leases were as detailed below (in thousands): Fiscal Year As of December 31, 2021 2022 $ 737 2023 1 Total undiscounted lease payments 738 Less: imputed interest (34) Total operating lease liabilities $ 704

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	12 Months Ended
Accrued Expenses and Other Current Liabilities (Tables)	Dec. 31, 2021
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): As of December 31, 2021 2020 Accrued compensation and benefits $ 3,668 $ 2,935 Accrued contract manufacturing 2,678 2,959 Current portion of operating lease liabilities 704 617 Accrued clinical 691 504 Accrued professional services 375 435 Accrued research 292 349 Other 117 106 Total accrued expenses and other current liabilities $ 8,525 $ 7,905

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
Stockholders' Equity (Tables)	Dec. 31, 2021
Stockholders' Equity
Summary of outstanding warrants to purchase shares of common stock	As of December 31, 2021, outstanding warrants to purchase shares of the Company’s common stock are as follows: Shares Underlying Outstanding Warrants Exercise Price Expiration Date 1,322,510 $ 2.50 April 22, 2025 12,677,490 $ 2.50 June 11, 2025 8,672,897 $ 2.675 September 1, 2025 10,000,000 $ 2.00 May 3, 2026 32,672,897

Stock-Based Compensation Expe_2

Stock-Based Compensation Expense (Tables)	12 Months Ended
Stock-Based Compensation Expense (Tables)	Dec. 31, 2021
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, 2020 3,112,704 $ 5.58 7.76 $ 44 Granted 1,492,776 2.45 Forfeited and expired (1,710,100) 6.86 Outstanding as of December 31, 2021 2,895,380 $ 3.21 8.33 $ 30 Exercisable as of December 31, 2021 978,915 $ 3.84 6.57 $ 7
Summary of Restricted Stock Unit activity	Weighted- Average Number of Grant Date Units Fair Value Outstanding as of December 31, 2020 395,100 $ 1.65 Granted 597,500 2.57 Released (427,975) 2.24 Forfeited (73,650) 1.99 Outstanding as of December 31, 2021 490,975 $ 2.20
Schedule of stock-based compensation expense	Stock-based compensation expense was classified in the consolidated statement of operations as follows (in thousands): Year Ended December 31, 2021 2020 Research and development $ 1,932 $ 1,397 General and administrative 2,091 1,554 Total stock-based compensation expense $ 4,023 $ 2,951 The following table summarizes stock-based compensation expense by type of award (in thousands): Year Ended December 31, 2021 2020 Stock options $ 2,714 $ 2,898 Restricted stock units 1,309 53 Total stock-based compensation expense $ 4,023 $ 2,951
Schedule of unrecognized stock-based compensation expense	As of December 31, 2021 Unrecognized Expense Weighted-average Remaining Recognition Period (in thousands) (in years) Stock options $ 1,945 1.69 Restricted stock units $ 679 0.72
Schedule of Black-Scholes option-pricing model	Year Ended December 31, 2021 2020 Expected stock price volatility 80.7 % 82.0 % Risk-free interest rate 0.9 % 0.5 % Expected annual dividend yield — — Expected life of options 6.1 years 6.3 years

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2021
Income Taxes
Schedule of net loss before provision for income taxes	Net loss before the provision for income taxes for the years ended December 31, 2021 and 2020, consisted of the following (in thousands): Year Ended December 31, 2021 2020 United Kingdom $ 28,411 $ 38,280 United States 18,730 12,216 $ 47,141 $ 50,496
Schedule of reconciliation of the federal statutory income tax rate to the Company's effective income tax rate	Year Ended December 31, 2021 2020 Income tax benefit computed at U.S. statutory tax rate 21.0 % 21.0 % State taxes, net of federal benefit 6.4 6.6 Foreign rate differential (1.2) (1.5) Disregarded entity 12.7 15.9 Research and development tax credits 1.4 1.4 Permanent difference (1.2) (0.6) Valuation allowances (58.9) (45.7) Rate change 20.0 3.6 Other (0.2) (0.7) Effective income tax rate (0.0) % (0.0) %
Schedule of net deferred tax assets	Net deferred tax assets consisted of the following (in thousands): As of December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 84,786 $ 57,265 Tax credit carryforwards 5,261 4,345 Accrued expenses and other 2,275 3,099 Total deferred tax assets 92,322 64,709 Deferred tax liabilities: Right-of-use asset (165) (312) Total deferred tax liabilities (165) (312) Valuation allowance (92,157) (64,397) Net deferred tax assets $ — $ —
Schedule of changes in valuation allowance for deferred tax assets	Changes in the valuation allowance for deferred tax assets during the years ended December 31, 2021 and 2020 related primarily to the increases in NOLs and research and development tax credit carryforwards and were as follows (in thousands): Year Ended December 31, 2021 2020 Valuation allowance at beginning of year $ (64,397) $ (41,253) Increases recorded to income tax provision (27,760) (23,144) Valuation allowance at end of year $ (92,157) $ (64,397)

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
Net Loss per Share (Tables)	Dec. 31, 2021
Net Loss per Share
Schedule of computation of basic and diluted net loss per share	Basic and diluted net loss per share of the Company was calculated as follows (in thousands, except share and per share amounts): Year Ended December 31, 2021 2020 Numerator: Net loss $ (47,141) $ (50,496) Net loss attributable to common stockholders—basic and diluted $ (47,141) $ (50,496) Denominator: Weighted average common stock outstanding — 43,340,826 24,060,615 Net loss per share attributable to common stockholders — $ (1.09) $ (2.10)
Schedule of anti-dilutive securities	As of December 31, 2021 2020 Options to purchase shares of common stock 2,895,380 3,112,704 Warrants to purchase shares of common stock 32,672,897 23,345,794 Unvested restricted stock units 490,975 395,100 36,059,252 26,853,598

Organization and Description _2

Organization and Description of Business - General (Details) $ in Thousands	Feb. 18, 2022USD ($)	Feb. 17, 2022USD ($)	Dec. 31, 2021USD ($)subsidiary	Dec. 31, 2020USD ($)
Number of subsidiaries \| subsidiary			4
Going Concern
Cash and cash equivalents			$ 32,307	$ 53,247
Private Placement
Going Concern
Convertible notes payable	$ 15,000
Private Placement \| Subsequent Events. \| Securities purchase agreement
Going Concern
Convertible notes payable		$ 15,000

Organization and Description _3

Organization and Description of Business - Securities Purchase Agreement (Details) $ / shares in Units, $ in Thousands	Jun. 11, 2021USD ($)shares	May 03, 2021USD ($)item$ / sharesshares	Aug. 27, 2020USD ($)$ / sharesshares	Jun. 11, 2020USD ($)shares	Apr. 22, 2020USD ($)shares	Apr. 12, 2020USD ($)item$ / sharesshares	Dec. 31, 2021USD ($)$ / sharesshares	Feb. 18, 2022USD ($)	Dec. 31, 2020$ / shares
Common Stock
Common stock par value (in dollar per share) \| $ / shares							$ 0.001		$ 0.001
Warrants to purchase common stock							32,672,897
Proceeds from the sale of common stock \| $							$ 351
Number of tranches \| item						2
Private Placement
Common Stock
Convertible notes payable \| $								$ 15,000
Securities purchase agreement \| Private Placement
Common Stock
Price per share \| $ / shares						$ 2.50
Warrant exercise price \| $ / shares						$ 2.50
Percentage of outstanding shares of common stock						51.30%
Pro forma percentage of outstanding shares of common stock	74.90%
Securities purchase agreement \| Second Private Placement
Common Stock
Shares issued (in shares)			8,183,878
Price per share \| $ / shares			$ 2.675
Warrants to purchase common stock			9,345,794
Term of warrant			5 years
Warrant exercise price \| $ / shares			$ 2.675
Proceeds from the sale of common stock \| $			$ 25,000
Percentage of outstanding shares of common stock			52.60%
Securities purchase agreement \| Pre-funded Warrants
Common Stock
Shares issued (in shares)			1,161,916
Warrant exercise price \| $ / shares			$ 0.001
Securities purchase agreement \| Third Private Placement
Common Stock
Price per share \| $ / shares		$ 2
Term of warrant		5 years
Warrant exercise price \| $ / shares		$ 2
Number of tranches \| item		2
Percentage of outstanding shares of common stock		59.90%					59.90%
Securities purchase agreement \| Closing of first tranche \| Third Private Placement
Common Stock
Shares issued (in shares)		3,731,025
Aggregate purchase price of warrants \| $		$ 7,500
Warrants to purchase common stock		3,731,025
Securities purchase agreement \| Closing of second tranche \| Third Private Placement
Common Stock
Shares issued (in shares)	6,268,975
Aggregate purchase price of warrants \| $	$ 12,500
Warrants to purchase common stock	6,268,975
Securities purchase agreement \| Minimum \| Private Placement
Common Stock
Aggregate purchase price of warrants \| $						$ 35,000
Securities purchase agreement \| Minimum \| Closing of first tranche \| Private Placement
Common Stock
Shares issued (in shares)					1,322,510
Aggregate purchase price of warrants \| $					$ 3,300
Warrants to purchase common stock					1,322,510
Securities purchase agreement \| Minimum \| Closing of second tranche \| Private Placement
Common Stock
Shares issued (in shares)				12,677,490
Aggregate purchase price of warrants \| $				$ 31,700
Warrants to purchase common stock				12,677,490
Securities purchase agreement \| Maximum \| Private Placement
Common Stock
Shares issued (in shares)						14,000,000
Warrants to purchase common stock						14,000,000
Securities purchase agreement \| Maximum \| Third Private Placement
Common Stock
Shares issued (in shares)		10,000,000
Warrants to purchase common stock		10,000,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details)	12 Months Ended
Summary of Significant Accounting Policies (Details)	Dec. 31, 2021USD ($)segment	Dec. 31, 2020USD ($)segment
Fair Value Measurements
Transfers between level 1 and level 2	$ 0	$ 0
Transfers between level 2 and level 1	0	0
Asset transfers into level 3	0	0
Asset transfers out of level 3	0	0
Cash and Cash Equivalents
Cash equivalents	$ 28,100,000	$ 49,100,000
Segment Information
Number of operating segments \| segment	1	1
Laboratory equipment \| Minimum
Property and Equipment
Estimated useful lives (in years)	3 years
Laboratory equipment \| Maximum
Property and Equipment
Estimated useful lives (in years)	5 years
Computer software
Property and Equipment
Estimated useful lives (in years)	3 years
Computer equipment
Property and Equipment
Estimated useful lives (in years)	3 years
Furniture and fixtures
Property and Equipment
Estimated useful lives (in years)	5 years

Fair Value of Financial Instr_3

Fair Value of Financial Instruments (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Company's assets that were accounted for at fair value on a recurring basis
Total	$ 28,137	$ 49,125
Level 1
Company's assets that were accounted for at fair value on a recurring basis
Total	28,137	49,125
Money market funds
Company's assets that were accounted for at fair value on a recurring basis
Cash equivalents	28,137	49,125
Money market funds \| Level 1
Company's assets that were accounted for at fair value on a recurring basis
Cash equivalents	$ 28,137	$ 49,125

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property and equipment, net
Total	$ 1,192	$ 1,116
Less: accumulated depreciation	(994)	(894)
Property and equipment, net	198	222
Depreciation expense	104	141
Laboratory equipment
Property and equipment, net
Total	1,039	1,001
Computer software
Property and equipment, net
Total	87	71
Computer equipment
Property and equipment, net
Total	44	38
Furniture and fixtures
Property and equipment, net
Total	$ 22	$ 6

Leases - Lease Commitments (Det

Leases - Lease Commitments (Details) $ in Millions	Jan. 01, 2019ft²item	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Feb. 28, 2022
Leases
Number of other non-significant operating leases	2
Lessee, Operating Lease, Existence of Option to Extend	true
Renewal term				3 years
AstraZeneca
Leases
Renewal term	3 years
Waltham, Massachusetts lease
Leases
Number of significant operating leases	1
Significant operating lease space \| ft²	20,062
Operating lease expense \| $		$ 0.6	$ 0.6

Leases - Lease Balance Sheet (D

Leases - Lease Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases
Operating lease right-of-use assets	$ 604	$ 1,141
Operating lease liabilities, current	$ 704	$ 617
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued Expenses And Other Current Liabilities	Accrued Expenses And Other Current Liabilities
Operating lease liabilities, net of current portion		$ 704
Total operating lease liabilities	$ 704	$ 1,321

Leases - Operating Lease Maturi

Leases - Operating Lease Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases
2022	$ 737
2023	1
Total undiscounted lease payments	738
Less: imputed interest	(34)
Total operating lease liabilities	$ 704	$ 1,321
Weighted average remaining lease term	1 year
weighted average incremental borrowing rate (as a percent)	9.10%

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accrued Expenses and Other Current Liabilities.
Accrued compensation and benefits	$ 3,668	$ 2,935
Accrued contract manufacturing	2,678	2,959
Current portion of operating lease liabilities	704	617
Accrued clinical	691	504
Accrued professional services	375	435
Accrued research	292	349
Other	117	106
Total accrued expenses and other current liabilities	$ 8,525	$ 7,905

Funding Arrangements (Details)

Funding Arrangements (Details) - USD ($) $ in Millions	Aug. 01, 2021	Jul. 01, 2020	Jun. 30, 2020	Dec. 31, 2021	Dec. 31, 2020	Jul. 31, 2021	Dec. 31, 2021	Dec. 31, 2021
CARB-X program
Funding Arrangements
Funds received during the period								$ 12.6
Grant income recognized				$ 2.6	$ 2.3			12.9
Grants receivable				0.7	1.1		$ 0.7	0.7
ETX0462 program
Funding Arrangements
Grants receivable				5.6			5.6	5.6
National Institute of Allergy and Infectious Diseases
Funding Arrangements
Eligible amount receivable in research and development support payments and development, regulatory and sales milestone payments	$ 2.9	$ 3				$ 5.9
Funds received during the period							3.2
Grant income recognized				2.6	1.3		3.9
Grants receivable				$ 0.6	$ 0.6		$ 0.6	$ 0.6
Maximum \| CARB-X program
Funding Arrangements
Reimbursable research expenditures			$ 18.5
Maximum \| National Institute of Allergy and Infectious Diseases
Funding Arrangements
Eligible amount receivable in research and development support payments and development, regulatory and sales milestone payments		$ 15.5

License and Collaboration Agr_2

License and Collaboration Agreements (Details) - License and collaboration agreement with Zai Lab - USD ($) $ in Millions	12 Months Ended		45 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021
License and Collaboration Agreement with Zai Lab
Upfront, non-refundable payment received			$ 5
Research support funding			0.6
Certain other reimbursable registration trial costs			5.4
Tax expense withheld			2.2
Eligible amount receivable in research and development support payments and development, regulatory and sales milestone payments			91
Revenue	$ 0	$ 0	$ 7

Stockholders' Equity (Details)

Stockholders' Equity (Details) $ / shares in Units, $ in Thousands	Oct. 21, 2021USD ($)$ / sharesshares	Jun. 11, 2021USD ($)shares	May 03, 2021USD ($)item$ / sharesshares	Aug. 27, 2020USD ($)$ / sharesshares	Jun. 11, 2020USD ($)shares	Apr. 22, 2020USD ($)shares	Apr. 12, 2020USD ($)item$ / sharesshares	Dec. 31, 2021USD ($)$ / sharesshares	Dec. 31, 2021USD ($)Vote$ / sharesshares	Dec. 31, 2020USD ($)shares
Common Stock
Dividend declared or paid \| $								$ 0	$ 0
Warrants to purchase common stock								32,672,897	32,672,897
Proceeds from the sale of common stock related to at-the-market offering, net of issuance costs \| $									$ 351
Net proceeds after deducting underwriting discounts and commissions and offering costs \| $									$ 19,951	$ 57,675
Number of tranches \| item							2
Common Stock
Common Stock
Number of votes per share \| Vote									1
Shares issued (in shares)									10,000,000	22,183,878
Net proceeds after deducting underwriting discounts and commissions and offering costs \| $									$ 10	$ 22
Issuance of common stock upon the vesting of restricted stock units (in shares)									341,525
April 22, 2025 Expiration Date
Common Stock
Warrants to purchase common stock								1,322,510	1,322,510
Warrant exercise price \| $ / shares								$ 2.50	$ 2.50
June 11, 2025 Expiration Date
Common Stock
Warrants to purchase common stock								12,677,490	12,677,490
Warrant exercise price \| $ / shares								$ 2.50	$ 2.50
September 1, 2025 Expiration Date
Common Stock
Warrants to purchase common stock								8,672,897	8,672,897
Warrant exercise price \| $ / shares								$ 2.675	$ 2.675
Warrant May 3 ,2026 Expiration Date
Common Stock
Warrants to purchase common stock								10,000,000	10,000,000
Warrant exercise price \| $ / shares								$ 2	$ 2
Securities purchase agreement \| Private Placement
Common Stock
Price per share \| $ / shares							$ 2.50
Warrant exercise price \| $ / shares							$ 2.50
Percentage of Outstanding Shares Of Common Stock							51.30%
Securities purchase agreement \| Second Private Placement
Common Stock
Shares issued (in shares)				8,183,878
Price per share \| $ / shares				$ 2.675
Warrants to purchase common stock				9,345,794
Warrant exercise price \| $ / shares				$ 2.675
Proceeds from the sale of common stock related to at-the-market offering, net of issuance costs \| $				$ 25,000
Term of warrant				5 years
Percentage of Outstanding Shares Of Common Stock				52.60%
Securities purchase agreement \| Pre-funded Warrants
Common Stock
Shares issued (in shares)				1,161,916
Warrant exercise price \| $ / shares				$ 0.001
Securities purchase agreement \| Third Private Placement
Common Stock
Price per share \| $ / shares			$ 2
Warrant exercise price \| $ / shares			$ 2
Term of warrant			5 years
Percentage of Outstanding Shares Of Common Stock			59.90%						59.90%
Number of tranches \| item			2
Securities purchase agreement \| Closing of first tranche \| Third Private Placement
Common Stock
Shares issued (in shares)			3,731,025
Warrants to purchase common stock			3,731,025
Aggregate purchase price of warrants \| $			$ 7,500
Securities purchase agreement \| Closing of second tranche \| Third Private Placement
Common Stock
Shares issued (in shares)		6,268,975
Warrants to purchase common stock		6,268,975
Aggregate purchase price of warrants \| $		$ 12,500
Securities purchase agreement \| Maximum \| Private Placement
Common Stock
Shares issued (in shares)							14,000,000
Warrants to purchase common stock							14,000,000
Securities purchase agreement \| Maximum \| Third Private Placement
Common Stock
Shares issued (in shares)			10,000,000
Warrants to purchase common stock			10,000,000
Securities purchase agreement \| Minimum \| Private Placement
Common Stock
Aggregate purchase price of warrants \| $							$ 35,000
Securities purchase agreement \| Minimum \| Closing of first tranche \| Private Placement
Common Stock
Shares issued (in shares)						1,322,510
Warrants to purchase common stock						1,322,510
Aggregate purchase price of warrants \| $						$ 3,300
Securities purchase agreement \| Minimum \| Closing of second tranche \| Private Placement
Common Stock
Shares issued (in shares)					12,677,490
Warrants to purchase common stock					12,677,490
Aggregate purchase price of warrants \| $					$ 31,700
Cantor Fitzgerald & Co \| Controlled Equity Offering Sale Agreement
Common Stock
Shares issued (in shares)	200,000
Price per share \| $ / shares	$ 3.25
Gross proceeds \| $	$ 700
Proceeds from sale of shares \| $	$ 600
Cantor Fitzgerald & Co \| Controlled Equity Offering Sale Agreement \| Maximum
Common Stock
Maximum number of shares that can be purchased under purchase notice								17,500,000

Stock-Based Compensation Expe_3

Stock-Based Compensation Expense - Other (Details) - USD ($)	Sep. 25, 2018	Sep. 30, 2018	Dec. 31, 2021	Jan. 01, 2022	Jan. 01, 2021
2015 Stock Incentive Plan
Stockholders' Equity and Stock-Based Compensation Expense
Number of options granted (in shares)	0
2018 Stock Incentive Plan \| Non-employee directors
Stockholders' Equity and Stock-Based Compensation Expense
Maximum cash fee paid		$ 500,000
2018 Stock Incentive Plan \| Board of directors
Stockholders' Equity and Stock-Based Compensation Expense
Maximum cash fee paid		$ 800,000
2018 Stock Incentive Plan \| Options to purchase shares of common stock
Stockholders' Equity and Stock-Based Compensation Expense
Number of options granted (in shares)			5,213,285
Number of shares available for future issuance (in shares)			1,604,834
Number of shares available for grant (in shares)		2,350,000
Increase in number of shares available for grant (in shares)				1,914,071	1,465,494
Period of options		10 years	10 years
Percentage of annual increase to the total number of common stock outstanding (as a percent)		4.00%
2018 Stock Incentive Plan \| Unvested restricted stock units
Stockholders' Equity and Stock-Based Compensation Expense
Number of options granted (in shares)			992,600
2018 Stock Incentive Plan \| Incentive stock options
Stockholders' Equity and Stock-Based Compensation Expense
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	Jul. 16, 2021	Sep. 30, 2018	Dec. 31, 2021	Dec. 31, 2020	Jan. 01, 2022	Jan. 01, 2021
Employee Stock Purchase Plan
Stockholders' Equity and Stock-Based Compensation Expense
Increase in number of shares available for grant (in shares)					250,000	250,000
Number of shares available for future issuance (in shares)		140,000	654,163
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)		250,000
Maximum number of shares issued (in shares)			0
2015 and 2018 Stock Incentive Plan
Number of Options
Outstanding, as of beginning of period (in shares)			3,112,704
Granted (in shares)	1,148,572		1,492,776
Forfeited (in shares)			(1,710,100)
Cancelled (in shares)	1,562,752
Outstanding, as of end of period (in shares)			2,895,380	3,112,704
Exercisable (in shares)			978,915
Weighted Average Exercise Price
Outstanding, as of beginning of period (in dollar per share)			$ 5.58
Granted (in dollar per share)	$ 2.44		2.45
Forfeited (in dollars per share)			6.86
Cancelled (in dollar per share)	$ 7.17
Outstanding, as of end of period (in dollar per share)			3.21	$ 5.58
Exercisable (in dollar per share)			$ 3.84
Weighted Average Remaining Contractual Term (Years)
Options outstanding			8 years 3 months 29 days	7 years 9 months 3 days
Exercisable			6 years 6 months 25 days
Aggregate Intrinsic Value
Options outstanding			$ 30	$ 44
Exercisable			$ 7
Weighted average grant date fair value per share of options granted (in dollar per share)			$ 4.03	$ 2.95

Stock-Based Compensation Expe_5

Stock-Based Compensation Expense - Restricted Stock (Details) - Unvested restricted stock units	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Number of Units
Outstanding, beginning balance (in shares) \| shares	395,100
Granted (in shares) \| shares	597,500
Released (in shares) \| shares	(427,975)
Forfeited (in shares) \| shares	(73,650)
Outstanding, ending balance (in shares) \| shares	490,975
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in dollars per share) \| $ / shares	$ 1.65
Granted (in dollars per share) \| $ / shares	2.57
Release (in dollars per share) \| $ / shares	2.24
Forfeited (in dollars per share) \| $ / shares	1.99
Outstanding, ending balance (in dollars per share) \| $ / shares	$ 2.20

Stock-Based Compensation Expe_6

Stock-Based Compensation Expense - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Stockholders' Equity and Stock-Based Compensation Expense
Total stock-based compensation expense	$ 4,023	$ 2,951
Research and development.
Stockholders' Equity and Stock-Based Compensation Expense
Total stock-based compensation expense	1,932	1,397
General and administrative
Stockholders' Equity and Stock-Based Compensation Expense
Total stock-based compensation expense	2,091	1,554
Options to purchase shares of common stock
Stockholders' Equity and Stock-Based Compensation Expense
Total stock-based compensation expense	2,714	2,898
Unrecognized compensation cost	$ 1,945
Period for recognition	1 year 8 months 8 days
Unvested restricted stock units
Stockholders' Equity and Stock-Based Compensation Expense
Total stock-based compensation expense	$ 1,309	$ 53
Unrecognized compensation cost	$ 679
Period for recognition	8 months 19 days

Stock-Based Compensation Expe_7

Stock-Based Compensation Expense - Black-Scholes option pricing model (Details) - Options to purchase shares of common stock	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Stockholders' Equity and Stock-Based Compensation Expense
Expected stock price volatility (as a percent)	80.70%	82.00%
Risk-free interest rate (as a percent)	0.90%	0.50%
Expected annual dividend yield	0.00%	0.00%
Expected life of options	6 years 1 month 6 days	6 years 3 months 18 days

Stock-Based Compensation Expe_8

Stock-Based Compensation Expense - Stock Option Exchange (Details) - Stock Option Exchange Program $ / shares in Units, $ in Millions	Jul. 16, 2021USD ($)item$ / sharesshares
Stockholders' Equity and Stock-Based Compensation Expense
Stock Option Exchange Program minimum price per-share that is eligible for exchange \| $ / shares	$ 4.98
Price per share \| $ / shares	$ 2.44
Number of eligible participants \| item	44
Aggregate number of shares cancelled \| shares	1,562,752
Percentage of shares underlying eligible original options	97.00%
Aggregate number of shares to purchase the common stock \| shares	1,148,572
Incremental expense to be recognized over the remaining service period \| $	$ 0.3

Income Taxes - Net Loss Before

Income Taxes - Net Loss Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes
United Kingdom	$ 28,411	$ 38,280
United States	18,730	12,216
Net loss before the provision for income taxes	$ (47,141)	$ (50,496)

Income Taxes - Reconciliation (

Income Taxes - Reconciliation (Details)	12 Months Ended
Income Taxes - Reconciliation (Details)	Dec. 31, 2021	Dec. 31, 2020
Income Taxes
Income tax benefit computed at statutory tax rate (as a percent)	21.00%	21.00%
State taxes, net of federal benefit (as a percent)	6.40%	6.60%
Foreign rate differential (as a percent)	(1.20%)	(1.50%)
Disregarded entity (as a percent)	12.70%	15.90%
Research and development tax credits (as a percent)	1.40%	1.40%
Permanent difference (as a percent)	(1.20%)	(0.60%)
Valuation allowances (as a percent)	(58.90%)	(45.70%)
Rate changes (as a percent)	20.00%	3.60%
Other (as a percent)	(0.20%)	(0.70%)
Effective income tax rate (as a percent)	0.00%	0.00%

Income Taxes - Net Deferred Tax

Income Taxes - Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carryforwards	$ 84,786	$ 57,265
Tax credit carryforwards	5,261	4,345
Accrued expenses and other	2,275	3,099
Total deferred tax assets	92,322	64,709
Deferred tax liabilities:
ASC 842 right-of-use asset	(165)	(312)
Total deferred tax liabilities	(165)	(312)
Valuation allowance	$ (92,157)	$ (64,397)	$ (41,253)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
TCJA, NOL and Tax Credit
Maximum percent of net operating losses utilized in future periods (as a percent)	80.00%
Valuation allowance	$ 92,157	$ 64,397	$ 41,253
U.K.
TCJA, NOL and Tax Credit
Net operating loss carryforwards	157,200
U.S. federal
TCJA, NOL and Tax Credit
Net operating loss carryforwards	166,300
Federal indefinite net operating loss carry forwards from JOBS act	153,600
U.S. federal \| Research and development
TCJA, NOL and Tax Credit
Tax credits carryforwards	4,100
State
TCJA, NOL and Tax Credit
Net operating loss carryforwards	167,400
State \| Research and development
TCJA, NOL and Tax Credit
Tax credits carryforwards	$ 1,400

Income Taxes - Valuation Allowa

Income Taxes - Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Taxes
Valuation allowance at beginning of year	$ (64,397)	$ (41,253)
Increases recorded to income tax provision	(27,760)	(23,144)
Valuation allowance at end of year	$ (92,157)	$ (64,397)

Net Loss per Share - Calculatio

Net Loss per Share - Calculation (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net loss	$ (47,141)	$ (50,496)
Net loss attributable to common stockholders-basic and diluted	$ (47,141)	$ (50,496)
Denominator:
Weighted average common stock outstanding-basic (in shares)	43,340,826	24,060,615
Weighted average common stock outstanding-diluted (in shares)	43,340,826	24,060,615
Net loss per share - basic (in dollars per share)	$ (1.09)	$ (2.10)
Net loss per share - diluted (in dollars per share)	$ (1.09)	$ (2.10)

Net Loss per Share (Details)

Net Loss per Share (Details) - shares	12 Months Ended
Net Loss per Share (Details) - shares	Dec. 31, 2021	Dec. 31, 2020
Net Loss per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	36,059,252	26,853,598
Options to purchase shares of common stock
Net Loss per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	2,895,380	3,112,704
Warrants to purchase shares of common stock
Net Loss per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	32,672,897	23,345,794
Unvested restricted stock units
Net Loss per Share
Antidilutive securities excluded from computation of earnings per share (in shares)	490,975	395,100

Commitments (Details)

Commitments (Details) - AstraZeneca $ in Millions	1 Months Ended
Commitments (Details) - AstraZeneca $ in Millions	Apr. 30, 2018USD ($)
Commitments
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. - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Related Party Transactions
Expenses recorded	$ 3.7	$ 5
Owed to related party	$ 0.1	$ 2

Benefit Plans (Details)

Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
Benefit Plans (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Benefits Plans
Company's matching contributions	$ 0.3	$ 0.3

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions	Aug. 18, 2022	Apr. 12, 2020	Feb. 28, 2022	Feb. 18, 2022	Feb. 17, 2022
Subsequent Event
Renewal term			3 years
Private Placement
Subsequent Event
Convertible notes payable				$ 15
Securities purchase agreement \| Private Placement
Subsequent Event
Percentage of outstanding shares of common stock		51.30%
Price of warrants		$ 2.50
Subsequent Events.
Subsequent Event
Renewal term			3 years
Subsequent Events. \| Securities purchase agreement \| Private Placement
Subsequent Event
Convertible notes payable					$ 15
Conversion price					$ 1.48
Interest rate percentage	0.59%
Debt interest rate	10.00%
Percentage of outstanding shares of common stock	19.99%
Price of warrants					$ 1.48