0001169245-21-000078 | 10-Q | XBRL Viewer | Phasebio Pharmaceuticals INC

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Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2021	Aug. 09, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-38697
Entity Registrant Name	PhaseBio Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	03-0375697
Entity Address, Address Line One	1 Great Valley Parkway
Entity Address, Address Line Two	Suite 30
Entity Address, City or Town	Malvern
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	19355
City Area Code	610
Local Phone Number	981-6500
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	PHAS
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		48,042,483
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001169245
Current Fiscal Year End Date	--12-31

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 64,456	$ 28,122
Receivable from sublicense	18,400	0
Prepaid expenses and other assets	5,644	12,027
Total current assets	88,500	40,149
Property and equipment, net	10,379	8,224
Operating lease right-of-use assets	1,701	1,927
Other assets	57	57
Total assets	100,637	50,357
Current liabilities:
Current portion of long-term debt	5,384	5,355
Current portion of deferred sublicense revenue	1,424	0
Accounts payable	2,958	3,674
Accrued expenses and other current liabilities	6,408	5,931
Total current liabilities	16,174	14,960
Long-term debt, net	4,073	6,773
Operating lease liabilities, net	1,306	1,548
Deferred sublicense revenue, net	8,238	0
Development derivative liability	89,329	51,719
Other long-term liabilities	692	559
Total liabilities	119,812	75,559
Commitments and contingencies (Note 9)
Stockholders’ deficit:
Preferred stock, $0.001 par value; 10,000,000 shares authorized; zero shares issued and outstanding at June 30, 2021 and December 31, 2020	0	0
Common stock, $0.001 par value; 200,000,000 shares authorized; 48,057,720 shares issued and 48,027,753 shares outstanding at June 30, 2021; 29,471,854 shares issued and 29,441,887 shares outstanding at December 31, 2020	48	29
Treasury stock, at cost, 29,967 shares as of June 30, 2021 and December 31, 2020	(24)	(24)
Additional paid-in capital	297,561	235,516
Accumulated deficit	(316,760)	(260,723)
Total stockholders’ deficit	(19,175)	(25,202)
Total liabilities and stockholders' deficit	$ 100,637	$ 50,357

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	48,057,720	29,471,854
Common stock, shares outstanding (in shares)	48,027,753	29,441,887
Treasury stock, shares (in shares)	29,967	29,967

CONDENSED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
CONDENSED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenue	$ 10,338	$ 0	$ 10,338	$ 320
Operating expenses:
Research and development	27,366	20,856	49,686	32,305
General and administrative	4,025	3,242	7,352	6,401
Total operating expenses	31,391	24,098	57,038	38,706
Loss from operations	(21,053)	(24,098)	(46,700)	(38,386)
Other income (expense):
Loss from remeasurement of development derivative liability	(5,777)	(3,708)	(7,203)	(4,162)
Interest income	5	21	7	232
Interest expense	(254)	(379)	(539)	(757)
Foreign exchange gain (loss)	0	22	(2)	26
Total other expense	(6,026)	(4,044)	(7,737)	(4,661)
Net loss before income taxes	(27,079)	(28,142)	(54,437)	(43,047)
Provision for income taxes	1,600	0	1,600	0
Net loss	$ (28,679)	$ (28,142)	$ (56,037)	$ (43,047)
Net loss per common share, basic (in usd per share)	$ (0.60)	$ (0.98)	$ (1.41)	$ (1.50)
Net loss per common share, diluted (in usd per share)	$ (0.60)	$ (0.98)	$ (1.41)	$ (1.50)
Weighted average common shares outstanding, basic (in shares)	47,985,871	28,805,238	39,680,408	28,789,256
Weighted average common shares outstanding, diluted (in shares)	47,985,871	28,805,238	39,680,408	28,789,256
Sublicense revenue
Revenue	$ 10,338	$ 0	$ 10,338	$ 0
Grant revenue
Revenue	$ 0	$ 0	$ 0	$ 320

CONDENSED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2019		28,796,371	(29,967)
Beginning balance at Dec. 31, 2019	$ 59,978	$ 29	$ (24)	$ 222,131	$ (162,158)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock warrants	7,925			7,925
Exercises of stock options (in shares)		14,236
Exercise of stock options	17			17
Stock-based compensation	471			471
Net loss	(14,905)				(14,905)
Ending balance (in shares) at Mar. 31, 2020		28,810,607	(29,967)
Ending balance at Mar. 31, 2020	53,486	$ 29	$ (24)	230,544	(177,063)
Beginning balance (in shares) at Dec. 31, 2019		28,796,371	(29,967)
Beginning balance at Dec. 31, 2019	59,978	$ 29	$ (24)	222,131	(162,158)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(43,047)
Ending balance (in shares) at Jun. 30, 2020		28,891,534	(29,967)
Ending balance at Jun. 30, 2020	26,393	$ 29	$ (24)	231,593	(205,205)
Beginning balance (in shares) at Mar. 31, 2020		28,810,607	(29,967)
Beginning balance at Mar. 31, 2020	53,486	$ 29	$ (24)	230,544	(177,063)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net (in shares)		80,523
Issuance of common stock in public offering, net	473			473
Exercises of stock options (in shares)		404
Exercise of stock options	1			1
Stock-based compensation	575			575
Net loss	(28,142)				(28,142)
Ending balance (in shares) at Jun. 30, 2020		28,891,534	(29,967)
Ending balance at Jun. 30, 2020	$ 26,393	$ 29	$ (24)	231,593	(205,205)
Beginning balance (in shares) at Dec. 31, 2020	29,441,887	29,471,854	(29,967)
Beginning balance at Dec. 31, 2020	$ (25,202)	$ 29	$ (24)	235,516	(260,723)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net (in shares)		18,400,000
Issuance of common stock in public offering, net	60,084	$ 19		60,065
Exercises of stock options (in shares)		110,146
Exercise of stock options	217			217
Stock-based compensation	670			670
Net loss	(27,358)				(27,358)
Ending balance (in shares) at Mar. 31, 2021		47,982,000	(29,967)
Ending balance at Mar. 31, 2021	$ 8,411	$ 48	$ (24)	296,468	(288,081)
Beginning balance (in shares) at Dec. 31, 2020	29,441,887	29,471,854	(29,967)
Beginning balance at Dec. 31, 2020	$ (25,202)	$ 29	$ (24)	235,516	(260,723)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net (in shares)		18,400,000
Net loss	$ (56,037)
Ending balance (in shares) at Jun. 30, 2021	48,027,753	48,057,720	(29,967)
Ending balance at Jun. 30, 2021	$ (19,175)	$ 48	$ (24)	297,561	(316,760)
Beginning balance (in shares) at Mar. 31, 2021		47,982,000	(29,967)
Beginning balance at Mar. 31, 2021	8,411	$ 48	$ (24)	296,468	(288,081)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in public offering, net	157			157
Exercises of stock options (in shares)		3,615
Exercise of stock options	6			6
Issuance of common stock through employee share purchase plan (in shares)		72,105
Issuance of common stock through employee share purchase plan	202			202
Stock-based compensation	728			728
Net loss	$ (28,679)				(28,679)
Ending balance (in shares) at Jun. 30, 2021	48,027,753	48,057,720	(29,967)
Ending balance at Jun. 30, 2021	$ (19,175)	$ 48	$ (24)	$ 297,561	$ (316,760)

CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net loss	$ (56,037)	$ (43,047)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,057	111
Stock-based compensation	1,398	1,046
Loss from remeasurement of development derivative liability	7,203	4,162
Non-cash interest expense	173	261
Non-cash research and development expense	23,705	5,735
Other non-cash transactions	0	100
Changes in operating assets and liabilities:
Receivable from sublicense	(18,400)	0
Other receivables	0	1,233
Prepaid expenses and other assets	8,855	(7,107)
Accounts payable	(585)	4,302
Accrued expenses and other current liabilities	1,679	419
Deferred sublicense revenue	9,662	0
Net cash used in operating activities	(21,290)	(32,785)
Investing activities
Purchases of property and equipment	(385)	(1,079)
Acquisition of intellectual property rights	0	(100)
Net cash used in investing activities	(385)	(1,179)
Financing activities
Proceeds from development derivative liability	0	12,649
Proceeds from issuance of common stock in public offering, net	60,351	472
Payments of deferred stock offering costs	(40)	(175)
Proceeds from exercise of stock options	223	18
Issuance of common stock through employee share purchase plan	202	0
Repayments of long-term debt	(2,727)	0
Net cash provided by financing activities	58,009	12,964
Net increase (decrease) in cash and cash equivalents	36,334	(21,000)
Cash and cash equivalents at the beginning of the period	28,122	74,025
Cash and cash equivalents at the end of the period	64,456	53,025
Supplemental disclosure for cash flow
Cash paid for interest	366	496
Supplemental disclosure of non-cash investing and financing activities
Issuance of warrants in conjunction with development derivative liability	0	7,925
Initial recognition of operating lease right-of-use assets and operating lease liabilities	0	564
Purchases of property and equipment by incurring development derivative liability	4,160	0
Purchases of property and equipment included in accounts payable and accrued expenses	$ 44	$ 2,741

Organization and Description of Business	6 Months Ended
Organization and Description of Business	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Description of Business PhaseBio Pharmaceuticals, Inc. (the “Company”) was incorporated as a Delaware corporation on January 10, 2002. The Company is a clinical-stage biopharmaceutical company focused on the development and commercialization of novel therapies for cardiopulmonary diseases. The Company’s lead product candidate, bentracimab (also known as PB2452), is a novel reversal agent for the antiplatelet drug ticagrelor, which the Company is developing for the reversal of the antiplatelet effects of ticagrelor in patients with uncontrolled major or life-threatening bleeding or requiring urgent surgery or an invasive procedure. The Company’s second product candidate, pemziviptadil (also known as PB1046), is in Phase 2 development for the treatment of pulmonary arterial hypertension ("PAH"). Pemziviptadil utilizes the Company’s proprietary half-life extending elastin-like polypeptide technology, which also serves as an engine for the Company’s preclinical pipeline. The Company is also developing its preclinical product candidate, PB6440, for treatment-resistant hypertension. Liquidity The Company has experienced net losses and negative cash flows from operations and, as of June 30, 2021, had an accumulated deficit of $316.8 million. The Company expects to continue to incur net losses for at least the next several years. As of June 30, 2021, the Company had cash and cash equivalents of $64.5 million and working capital of $72.3 million. In January 2020, the Company entered into a co-development agreement ("SFJ Agreement") with SFJ Pharmaceuticals X, Ltd., an SFJ Pharmaceuticals Group company ("SFJ"), pursuant to which SFJ provides funding and operational support for the clinical development of bentracimab. Management believes that its existing cash and cash equivalents as of June 30, 2021, in addition to the $12.5 million in clinical trial costs and other expenses that the Company expects SFJ will fund or reimburse pursuant to the SFJ Agreement and the $20.0 million received from Alfasigma S.p.A. ("Alfasigma") in July 2021 pursuant to the Alfasigma Sublicense (as described below), will be sufficient to fund operating expenses and capital requirements through the fourth quarter of 2022. In July 2021, the Company received a $20.0 million upfront payment upon entering into an exclusive sublicense agreement ("Alfasigma Sublicense") with Alfasigma for the commercialization of any product composed of or containing bentracimab (the "Licensed Products") in the European Union and European Economic Area, as well as the United Kingdom, Russia, Ukraine and certain other countries within the Commonwealth of Independent States, Europe and central Asia (the "Sublicense Territory"). The Company plans to address its future liquidity needs through the pursuit of additional funding through a combination of equity or debt financings, or other third-party financing, marketing and distribution arrangements and other collaborations, strategic alliances and licensing arrangements. However, there is no assurance that these funding efforts will be successful. The Company currently has an effective shelf registration statement on Form S-3 ("2019 Shelf Registration Statement") on file with the Securities and Exchange Commission ("SEC"), which expires in January 2023. The 2019 Shelf Registration Statement currently permits (i) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $200.0 million of common stock, preferred stock, debt securities and warrants in one or more offerings and in any combination and (ii) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $60.0 million of common stock that may be issued and sold under the "at-the-market" sales agreement with Citigroup Global Markets Inc. and William Blair & Company, L.L.C. (the "ATM Program"). As of June 30, 2021, the Company has sold 561,848 shares of common stock pursuant to the ATM Program for net proceeds of $2.9 million. During the six months ended June 30, 2021, the Company sold 18,400,000 shares of common stock in an underwritten offering pursuant to the 2019 Shelf Registration Statement for net proceeds of $60.2 million, after deducting underwriting discounts and commissions and other offering costs. As of June 30, 2021, the Company had $132.6 million of common stock remaining that can be sold under the 2019 Shelf Registration Statement, of which $57.0 million may be sold under the ATM Program. The Company is continuing to assess the effect that the COVID-19 pandemic may have on its business and operations. The extent to which COVID-19 may impact the Company's business and operations will depend on future developments that are highly uncertain and cannot be predicted with confidence, such as the geographic distribution of the disease and its variants over time, the efficacy, availability and pace of administration of vaccines and antiviral agents against the disease, the continued duration of the outbreak, the duration and effect of business disruptions and the short-term effects and ultimate effectiveness of the travel restrictions, quarantines, social distancing requirements and business closures in the United States and other countries to contain and treat the disease. While the potential economic impact brought by, and the continued duration of, the COVID-19 pandemic may be difficult to assess or predict, a continued and growing pandemic could result in significant disruption of global financial markets, reducing the Company's ability to access capital, which could in the future negatively affect its liquidity. In addition, a recession or market correction resulting from the spread of COVID-19 could materially affect the Company's business and the value of its common stock. Basis of Presentation The accompanying condensed financial statements have been prepared in accordance with United States generally accepted accounting principles (“GAAP”) for interim financial reporting and the rules and regulations of the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. All adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the accompanying condensed financial statements have been made. Although these interim condensed financial statements do not include all of the information and footnotes required for complete annual financial statements, management believes the disclosures are adequate to make the information presented not misleading. The unaudited interim results of operations and cash flows for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the full year. The unaudited interim condensed financial statements and footnotes should be read in conjunction with the audited financial statements and footnotes for the year ended December 31, 2020, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 15, 2021, wherein a more complete discussion of significant accounting policies and certain other information can be found. Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board (“FASB”). The Company manages its operations as a single reportable segment for the purposes of assessing performance and making operating decisions.

Significant Accounting Policies

6 Months Ended

Jun. 30, 2021

Accounting Policies [Abstract]

Significant Accounting Policies

Use of Estimates

The preparation of the Company’s condensed financial statements requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s condensed financial statements and accompanying notes. The most significant estimates in the Company’s condensed financial statements relate to the valuation of the development derivative liability, the deferral and recognition of revenue under the Alfasigma Sublicense and the clinical trial accruals. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results could differ materially from those estimates and assumptions.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains certain deposit accounts and money market funds in federally insured financial institutions in excess of federally insured limits. The Company could experience losses on the money market funds in the future.

Cash and Cash Equivalents

The Company considers all highly liquid investments with an original maturity from the date of purchase of three months or less to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts.

Receivable from Sublicense

Receivable from sublicense relates to amounts due from Alfasigma under the Alfasigma Sublicense. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional.

Fair Value of Financial Instruments

The carrying amounts of other receivables, prepaid expenses and other assets, accounts payable and accrued expenses and other current liabilities are reasonable estimates of their fair value because of the short maturity of these items. Based on the borrowing rates currently available to the Company for loans with similar terms, the Company believes the fair values of the term loan and operating lease liabilities and corresponding right-of-use assets approximate their respective carrying values.

Deferred Sublicense Revenue

When consideration is received, or such consideration is unconditionally due, from a customer prior to the Company completing its performance obligation to the customer under the terms of a contract, a contract liability is recorded as deferred revenue. Deferred revenues expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current liabilities. Deferred revenues not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as long-term liabilities.

Development Derivative Liability

Development derivative liability is recorded based on the present value of the estimated consideration to be received and the estimated consideration to be paid pursuant to contractual terms of the SFJ Agreement, which was determined to have been fair value. The liability is remeasured quarterly, as a Level 3 derivative, with any change in fair value recorded in the form of a gain (loss) from remeasurement of development derivative liability on the condensed statements of operations.

Property and Equipment

Property and equipment are recorded at cost and depreciated over the estimated useful lives of the assets (three to five years) using the straight-line method. Leasehold improvements are amortized over the shorter of their estimated useful lives or the lease term.

Leases

At lease commencement, the Company records a lease liability based on the present value of lease payments over the expected lease term including any options to extend the lease that the Company is reasonably certain to exercise. The Company calculates the present value of lease payments using an incremental borrowing rate as the Company’s leases do not provide an implicit interest rate. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. At the lease commencement date, the Company records a corresponding right-of-use lease asset based on the lease liability, adjusted for any lease incentives received and any initial direct costs paid to the lessor prior to the lease commencement date. The Company may enter into leases with an initial term of 12 months or less (“Short-Term Leases”). For any Short-Term Leases, the Company records the rent expense on a straight-line basis and does not record the leases on the condensed balance sheet. The Company had no Short-Term Leases as of June 30, 2021 or December 31, 2020.

After lease commencement, the Company measures its leases as follows: (i) the lease liability based on the present value of the remaining lease payments using the discount rate determined at lease commencement and (ii) the right-of-use lease asset based on the remeasured lease liability, adjusted for any unamortized lease incentives received, any unamortized initial direct costs and the cumulative difference between rent expense and amounts paid under the lease agreement. Any lease incentives received and any initial direct costs are amortized on a straight-line basis over the expected lease term. Rent expense is recorded on a straight-line basis over the expected lease term.

Long-Lived Assets

The Company regularly reviews the carrying value and estimated lives of all of its long-lived assets, including property and equipment and right-of-use assets to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. The determinants used for this evaluation include management’s estimate of the asset’s ability to generate net positive cash flow in future periods as well as the strategic significance of the assets to the Company’s business objectives. Should an impairment exist, the impairment loss would be measured based on the extent that the estimated fair value is less than its carrying value. The Company did not recognize any impairment losses in either the six months ended June 30, 2021 or the year ended December 31, 2020.

Preclinical and Clinical Trial Accruals

The Company accrues and expenses amounts incurred in connection with preclinical studies and clinical trial activities performed by third parties based upon estimates of the proportion of work completed over the life of the individual trial and subject enrollment rates in accordance with agreements with clinical research organizations, contract manufacturing organizations and clinical trial sites. The Company determines the estimates by reviewing contracts, vendor agreements and purchase orders, and through discussions with internal clinical personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services. However, actual costs and timing of clinical trials are highly uncertain, subject to risks and may change depending upon a number of factors, including the Company’s clinical development plan.

Management makes estimates of the Company’s accrued expenses as of each balance sheet date in the Company’s condensed financial statements based on facts and circumstances known to the Company at that time. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Nonrefundable advance payments for goods and services, including fees for process development or manufacturing and distribution of clinical supplies that will be used in future research and development activities, are deferred and recognized as expense in the period that the related goods are consumed or services are performed.

Revenue Recognition

Sublicense Revenue

Sublicensing arrangements may contain multiple components, which may include (i) sublicenses; (ii) research and development activities; and (iii) the manufacturing and supply of certain materials. Payments pursuant to these arrangements may include non-refundable payments, upfront payments, milestone payments upon the achievement of significant regulatory and development events or sales of product at certain agreed-upon amounts, sales milestones and royalties on product sales. 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.

In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under a sublicense agreement, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are capable of being distinct; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue as the Company satisfies each performance obligation.

The Company must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation, which determines how the transaction price is allocated among the performance obligations. The estimation of the stand-alone selling price may include such estimates as forecasted revenues and costs, development timelines, discount rates and probabilities of regulatory and commercial success. The Company also applies significant judgment when evaluating whether contractual obligations represent distinct performance obligations, allocating transaction price to performance obligations within a contract, determining when performance obligations have been met, assessing the recognition and future reversal of variable consideration and determining and applying appropriate methods of measuring progress for performance obligations satisfied over time.

Grant Revenue

Grant revenue is derived from government grants that support the Company’s efforts on specific research projects. The Company has determined that the government agencies providing grants to the Company are not customers. The Company recognizes grant revenue when there is reasonable assurance of compliance with the conditions of the grant and reasonable assurance that the grant revenue will be received.

Research and Development Expense

Research and development costs are expensed as incurred. Costs incurred in obtaining technology licenses are charged to research and development expense if the technology has no alternative future use.

Stock-Based Compensation

The Company measures and recognizes compensation expense for all stock-based compensation based on the estimated fair value at the date of grant. Currently, the Company’s stock-based awards consist only of stock options; however, future grants under the Company’s equity compensation plan may also consist of shares of restricted stock, restricted stock units, stock appreciation rights, performance awards and performance units. The Company also maintains the 2018 Employee Stock Purchase Plan ("ESPP") under which it may issue shares of common stock. The Company estimates the fair value of stock options and shares that will be issued under the ESPP using the Black-Scholes option-pricing model, which requires the use of estimates. The Company recognizes stock-based compensation cost for ratably vesting stock options and for shares that it will issue under the ESPP on a straight-line basis over the requisite service period of the award and records forfeitures in the period in which they occur.

The Black-Scholes option-pricing model requires the input of subjective assumptions, including the risk-free interest rate, the expected dividend yield of the Company’s common stock, the expected volatility of the price of the Company’s common stock, and the expected term of the option. These estimates involve inherent uncertainties and the application of management’s judgment. If factors change and different assumptions are used, the Company’s stock-based compensation expense could be materially different in the future.

Income Taxes

The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the condensed financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the condensed financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date.

The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes.

The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits, if any, within income tax expense, and any accrued interest and penalties are included within the related tax liability line.

Net Loss Per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and common share equivalents outstanding for the period. Common stock equivalents are only included when their effect is dilutive. The Company’s potentially dilutive securities, which include outstanding options under the Company's stock option plan, warrants issued from time to time and shares of common stock to be potentially issued under the ESPP, have been excluded from the computation of diluted net loss per share as they would be anti-dilutive. For all periods presented, there is no difference in the number of shares used to compute basic and diluted shares outstanding due to the Company’s net loss position.

The following table sets forth the outstanding, potentially dilutive securities that have been excluded in the calculation of diluted net loss per share because their inclusion would be anti-dilutive:


	As of June 30,
	2021	2020
Common stock options	4,359,395	3,740,815
Warrants to purchase common stock	2,349,595	2,349,595
Employee stock purchase plan	275,077	271,012
Total	6,984,067	6,361,422

Recent Accounting Pronouncements

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which among other things, eliminates certain exceptions in the current rules regarding the approach for intraperiod tax allocations and the methodology for calculating income taxes in an interim period, and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. The standard became effective for the Company in the first quarter of 2021. Adoption of this new standard did not have a material impact on the Company's condensed financial statements and related disclosures.

Fair Value Measurement

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Fair Value Measurement

Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability.

The Company classifies fair value measurements in one of the following three categories for disclosure purposes:

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Inputs other than Level 1 prices for similar assets or liabilities that are directly or indirectly observable in the marketplace.

Level 3: Unobservable inputs that are supported by little or no market activity and values determined using pricing models, discounted cash flow methodologies, or similar techniques, as well as instruments for which the determination of fair value requires significant judgment or estimation.

The Company’s cash equivalents are classified using Level 1 inputs within the fair value hierarchy because they are valued using quoted market prices, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. None of the Company’s non-financial assets or liabilities are recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented.

The fair value of the Company's financial commitment to SFJ in conjunction with the SFJ Agreement is presented as a development derivative liability based on Level 3 inputs.

The following table summarizes the Company’s assets and liabilities that require fair value measurements on a recurring basis and their respective input levels based on the fair value hierarchy (in thousands):


	Total		Fair Value Measurements at Reporting Date
			Level 1		Level 2		Level 3
As of June 30, 2021:
Assets
Cash equivalents	$	64,236	$	64,236	$	—	$	—
Liabilities
Development derivative liability (Note 8)	$	89,329	$	—	$	—	$	89,329
As of December 31, 2020:
Assets
Cash equivalents	$	27,872	$	27,872	$	—	$	—
Liabilities
Development derivative liability (Note 8)	$	51,719	$	—	$	—	$	51,719

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Property and Equipment

6 Months Ended

Jun. 30, 2021

Property, Plant and Equipment [Abstract]

Property and Equipment

The following table presents the composition of property and equipment, net as of June 30, 2021 and December 31, 2020 (in thousands):


	As of June 30, 2021		As of December 31, 2020
Lab equipment	$	12,244	$	8,994
Computer hardware, software and telephone	140		140
Furniture and fixtures	114		107
Leasehold improvements	77		67
Construction in progress	986		1,042
	13,561		10,350
Less accumulated depreciation	(3,182)		(2,126)
Property and equipment, net	$	10,379	$	8,224

Depreciation expense was $0.6 million and $0.1 million for the three months ended June 30, 2021 and 2020, respectively, and $1.1 million and $0.1 million for the six months ended June 30, 2021 and 2020, respectively.

Accrued Expenses and Other Current Liabilities

6 Months Ended

Jun. 30, 2021

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

Accrued Expenses and Other Current LiabilitiesThe following table presents the composition of accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 (in thousands):


	As of June 30, 2021		As of December 31, 2020
Accrued clinical and related costs	$	3,921	$	2,753
Accrued compensation and related costs	1,483		2,260
Accrued interest	52		69
Current portion of operating lease liability	476		459
Accrued other	476		390
Accrued expenses and other current liabilities	$	6,408	$	5,931

Deferred Sublicense Revenue

6 Months Ended

Jun. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Deferred Sublicense Revenue

In June 2021, the Company entered into the Alfasigma Sublicense with Alfasigma, under which the Company granted to Alfasigma exclusive rights to develop, use, sell, have sold, offer for sale and import the Licensed Products in the Sublicense Territory. Under the terms of the Alfasigma Sublicense, the Company received a $20.0 million upfront payment from Alfasigma in July 2021 and will be eligible to receive up to $35.0 million upon the achievement of certain pre-revenue regulatory milestones, up to $190.0 million upon the achievement of certain commercial milestones and tiered royalty payments based on net sales, with percentages starting in the low double digits and escalating up to the mid-twenties. Also, as part of the overall arrangement, the Company has agreed to supply the Licensed Products to Alfasigma at the lower of cost or a price not to exceed certain agreed amounts.

Under the Alfasigma Sublicense, the Company is responsible for developing the Licensed Products and securing regulatory approval with the European Medicines Agency (the “EMA”), and the Medicines and Healthcare products Regulatory Agency (the “MHRA”), including in accordance with the SFJ Agreement, after which any marketing authorizations will be assigned to Alfasigma. Alfasigma is obligated to obtain and maintain any regulatory approvals necessary to market and sell the Licensed Products (including pricing approvals and post-marketing commitments) and is also responsible for securing regulatory approval in the countries within the Sublicense Territory outside of the European Union and the United Kingdom.

The Company first assessed the Alfasigma Sublicense under ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether the Alfasigma Sublicense or units of accounts within the Alfasigma Sublicense represent a collaborative arrangement based on the risks and rewards and activities of the parties. The Company concluded that Alfasigma represented a customer and applied relevant guidance from ASC 606, Revenue from Contracts with Customers (“ASC 606”) to evaluate the appropriate accounting under the Alfasigma Sublicense. In accordance with this guidance, the Company identified the following commitments under the arrangement: (i) exclusive sublicense rights to develop, use, sell, have sold, offer for sale and import Licensed Products (the “License”); (ii) development and regulatory activities (“Development and Regulatory Activities”); and (iii) the requirement to supply Alfasigma with the Licensed Product at the lower of cost or a price not to exceed certain agreed amounts (the “Supply of Licensed Product”). The Company determined that these three commitments represent distinct performance obligations for purposes of recognizing revenue and will recognize revenue as it fulfills these performance obligations.

The Company determined that the upfront payment of $20.0 million constitutes the transaction price as of the outset of the Alfasigma Sublicense. Future potential regulatory and development milestone payments were fully constrained as the risk of significant revenue reversal related to these amounts has not yet been resolved. The achievement of the future potential milestones is not within the Company’s control and is subject to certain research and development success or regulatory approvals and therefore carry significant uncertainty. The Company will reevaluate the likelihood of achieving these milestones at the end of each reporting period and adjust the transaction price in the period the risk is resolved. In addition, the Company will recognize any consideration related to sales-based milestones and royalties when the subsequent sales occur since those payments relate primarily to the License, which was delivered by the Company to Alfasigma upon entering into the Alfasigma Sublicense.

The transaction price was allocated to the three performance obligations based on the estimated stand-alone selling prices at contract inception. The stand-alone selling price of the License was based on a discounted cash flow approach and considered several factors including, but not limited to, discount rate, development timeline, regulatory risks, estimated market demand and future revenue potential using an adjusted market approach. The stand-alone selling price of the Development and Regulatory Activities and the Supply of Licensed Product was estimated using the expected cost-plus margin approach. The Company allocated the upfront portion of the transaction price to the performance obligations as of June 30, 2021 as follows (in thousands):


	Transaction Price		Cumulative Sublicense Revenue Recognized		Deferred Sublicense Revenue
License	$	10,223	$	10,223	$	—
Development and Regulatory Services	2,647		115		2,532
Supply of License Product	7,130		—		7,130
	$	20,000	$	10,338	9,662
Less current portion of long-term deferred sublicense revenue					(1,424)
Total long-term deferred sublicense revenue					$	8,238

The Company reevaluates the transaction price and the total estimated costs expected to be incurred to satisfy the performance obligations and adjusts the deferred sublicense revenue at the end of each reporting period. Such changes will result in a change to the amount of sublicense revenue recognized and deferred sublicense revenue.

Debt

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Debt

March 2019 Loan Agreement with Silicon Valley Bank and WestRiver Innovation Lending Fund VIII, L.P.

In March 2019, the Company entered into a loan (the "2019 Loan") with SVB and WestRiver Innovation Lending Fund VIII, L.P. (“WestRiver”), pursuant to which the Company could borrow up to $15.0 million, issuable in three separate tranches (“Advances”), of $7.5 million (“Tranche 1”), which was issued upon execution of the 2019 Loan, $2.5 million, which was issued in May 2019 (“Tranche 2”) and $5.0 million, which was issued in October 2019 (“Tranche 3”), which the Company was required to draw upon the achievement of certain regulatory milestones (the “Tranche 3 Milestones”).

The maturity date of the 2019 Loan is March 1, 2023. Under the terms of the 2019 Loan, the Company made interest-only payments through June 30, 2020 with respect to Tranche 1, Tranche 2 and Tranche 3 at a rate equal to the greater of the Prime Rate plus 1.00%, as defined in the 2019 Loan, or 6.5%, followed by an amortization period of 33 months of equal monthly payments of principal plus interest until paid in full. In addition to and not in substitution for the Company’s regular monthly payments of principal plus accrued interest, the Company is required to make a final payment equal to 6% of the aggregate principal amount of the advances (“Final Payment”) on the maturity date.

Upon execution of the 2019 Loan and the draw of Tranche 1, the Company issued to SVB and WestRiver warrants to purchase an aggregate of 37,606 shares of common stock with an exercise price of $4.73 per share. In May 2019, upon the draw of Tranche 2, the Company issued to SVB and WestRiver warrants to purchase an aggregate of 12,130 shares of common stock with an exercise price of $10.86 per share. In October 2019, upon the draw of Tranche 3, the Company issued to SVB and WestRiver warrants to purchase an aggregate of 24,262 shares of common stock with an exercise price of $3.88 per share. All warrants are immediately exercisable and expire ten years from the date of issuance.

Upon execution of the 2019 Loan, the Company drew $7.5 million from Tranche 1 and repaid the outstanding principal balance and the accrued portion of the Final Payment of the SVB Loan.

The Company’s obligations under the 2019 Loan are secured by a first-priority security interest in substantially all of the Company’s current and future assets. The Company is also obligated to comply with various other customary covenants, including restrictions on the Company’s ability to encumber its intellectual property assets. The Company was in compliance with all covenants under the 2019 Loan as of December 31, 2020.

The Company recorded a debt discount of $0.4 million for the estimated fair value of warrants and debt issuance costs upon the borrowings of Tranches 1, 2 and 3. The balance of the Final Payment liability was $0.7 million as of June 30, 2021 and is included in other long-term liabilities on the condensed balance sheet. The debt discount and Final Payment liability are being amortized to interest expense over the term of the 2019 Loan using the effective-interest method. Interest expense, including amortization of the debt discount related to the term debt and the Final Payment liability, totaled $0.3 million and $0.4 million for the three months ended June 30, 2021 and 2020, respectively, and $0.5 million and $0.8 million for the six months ended June 30, 2021 and 2020, respectively.

The following table sets forth by year the Company’s required future principal payments as of June 30, 2021 (in thousands):


Years Ending December 31,
2021 (remaining six months)	$	2,727
2022	5,455
2023	1,363
Thereafter	—
Total principal payments	9,545
Less unamortized loan fees	(88)
Total term loan borrowings	$	9,457

Development Derivative Liability

6 Months Ended

Jun. 30, 2021

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Development Derivative Liability

In January 2020, the Company entered into the SFJ Agreement, pursuant to which SFJ has agreed to provide up to $120.0 million in funding and project management services in connection with the REVERSE-IT trial, a global Phase 3 clinical trial of bentracimab. During the term of the SFJ Agreement, the Company will have primary responsibility for clinical development and regulatory activities for bentracimab in the United States and the European Union, while SFJ will have primary responsibility for clinical development and regulatory activities for bentracimab in China and Japan and will provide clinical trials operational support in the European Union.

From the inception of the SFJ Agreement through June 30, 2021, SFJ has provided funding and paid for amounts on the Company's behalf in the aggregate amount of $77.5 million under the SFJ Agreement. In addition, the Company expects that SFJ will fund or reimburse an additional $12.5 million of clinical trial costs and other expenses. SFJ will also provide up to an additional $30.0 million upon the achievement of specified milestones with respect to the Company's clinical development of bentracimab.

If the United States Food and Drug Administration ("FDA") approves a Biologics License Application for bentracimab, the Company has agreed to pay to SFJ an initial payment of $5.0 million and an additional $325.0 million in the aggregate in seven additional annual payments (the “U.S. Approval Payments”). If the EMA or the national regulatory authorities in certain European countries provide marketing approval of bentracimab, the Company will pay SFJ an initial payment of $5.0 million and an additional $205.0 million in the aggregate in seven additional annual payments (the “EU Approval Payments”). The majority of the U.S. Approval Payments and the EU Approval Payments will be made from the third anniversary to the seventh anniversary of marketing approval in the applicable jurisdiction. If either the Pharmaceuticals and Medical Devices Agency (the “PMDA”) of Japan or the National Medical Products Administration (the “NMPA”) of China provides marketing approval of bentracimab, the Company will pay SFJ an initial payment of $1.0 million and then an additional $59.0 million in the aggregate in eight additional annual payments (the “Japan/China Approval Payments”), with the majority of the payments to be made from the fifth anniversary to the eighth anniversary of marketing approval. The Japan/China Approval Payments will only be paid once regardless of receipt of marketing approval in both Japan and China. The U.S. Approval Payments, EU Approval Payments and Japan/China Approval Payments will be proportionately adjusted in the event that the actual funding from SFJ is lower or greater than $120.0 million. The Company will not be obligated to make the U.S. Approval Payments if it does not receive marketing approval for bentracimab from the FDA, the EU Approval Payments if it does not receive marketing approval for bentracimab from the EMA or the national regulatory authority in certain European countries or the Japan/China Approval Payments if it does not receive marketing approval for bentracimab from either the PMDA or the NMPA.

Upon execution of the SFJ Agreement, the Company issued to SFJ a warrant to purchase an aggregate of 2,200,000 shares of common stock at an exercise price of $6.50 per share with a contractual term of ten years. The warrant is exercisable in two tranches: Tranche A and Tranche B. Tranche A represents 1,100,000 shares that are immediately exercisable by SFJ. Tranche B represents 1,100,000 shares that are exercisable at the earlier of (i) the achievement of certain development milestones or (ii) the consummation of an Acquisition, as defined in the SFJ Agreement. The warrants are equity-classified and were valued at $7.9 million at issuance using a probability adjusted Black-Scholes valuation technique.

The Company accounts for the SFJ Agreement as a derivative instrument that increases and decreases as consideration is received and repayments are made, respectively. The derivative is further adjusted at each reporting period to its estimated fair value. At June 30, 2021, the derivative is presented as a liability in the Company's condensed balance sheet. Any

changes in fair value are recorded within the Company's condensed statements of operations. The liability was initially recorded at a value of $2.1 million, which incorporates the $10.0 million upfront payment from SFJ and the issuance of the Company's common stock warrants to SFJ. During the six months ended June 30, 2021, SFJ provided additional funding and paid for amounts on the Company's behalf in the aggregate amount of $30.4 million, and the development derivative liability was subsequently remeasured at June 30, 2021, as a Level 3 derivative. The change in fair value was $5.8 million and $3.7 million for the three months ended June 30, 2021 and 2020, respectively, and $7.2 million and $4.2 million for the six months ended June 30, 2021 and 2020, respectively.

The development derivative liability is valued using a scenario-based discounted cash flow method, whereby each scenario makes assumptions about the probability and timing of cash flows, and such cash flows are present valued using a risk-adjusted discount rate. The valuation method incorporates certain unobservable Level 3 key inputs including (i) the probability and timing of funding, (ii) the probability and timing of achieving regulatory approvals, (iii) the Company's cost of borrowing (16.00% plus the risk free borrowing rate) and (iv) SFJ's cost of borrowing (2.50% plus the risk free borrowing rate).

The following table presents activity for the development derivative liability during the six months ended June 30, 2021 (in thousands):


	Development Derivative Liability
Balance at December 31, 2020	$	51,719
Funding during the period	30,407
Change in fair value	7,203
Balance at June 30, 2021	$	89,329

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings The Company is not currently a party to any litigation, nor is management aware of any pending or threatened litigation against the Company, that it believes would materially affect the Company’s business, operating results, financial condition or cash flows.

Leases

6 Months Ended

Jun. 30, 2021

Leases [Abstract]

Leases

The Company leases office and research and development facilities and equipment under various non-cancellable operating lease agreements.

In January 2010, the Company entered into a lease for office and laboratory space in Malvern, Pennsylvania (the “Malvern Lease”). The Malvern Lease commenced in March 2010 and was amended to extend its term to July 2018 and again to September 2023, with an option to extend the lease for an additional three years. This lease contains escalating rent payments. In December 2018, the Company entered into a lease for office space in San Diego, California, which expires in October 2022. In June 2020, the Company entered into a lease for additional office space in Malvern, Pennsylvania, which expires in September 2023. As of June 30, 2021, the weighted average remaining lease term for the Company’s leases was 4.2 years, and the weighted average discount rate used to determine the right-of-use assets and corresponding operating lease liabilities was 5.8%.

Maturities of operating lease liabilities as of June 30, 2021 are as follows (in thousands):


Year Ending December 31,
2021 (remaining six months)	$	283
2022	555
2023	419
2024	279
2025	283
Thereafter	215
Total future minimum lease payments	2,034
Less: Present value adjustment	(252)
Operating lease liabilities	$	1,782

The Company recognizes rent expense for the operating leases on a straight-line basis. Rent expense was $0.2 million and $0.1 million for the three months ended June 30, 2021 and 2020, respectively, and $0.4 million and $0.2 million for the six months ended June 30, 2021 and 2020, respectively.

Stockholders’ Equity	6 Months Ended
Stockholders’ Equity	Jun. 30, 2021
Stockholders' Equity Note [Abstract]
Stockholders’ Equity	Stockholders’ Equity Shelf Registration Statement In December 2019, the Company filed the 2019 Shelf Registration Statement on Form S-3, which became effective in January 2020. The 2019 Shelf Registration Statement, which expires in January 2023, permits: (i) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $200.0 million of common stock, preferred stock, debt securities and warrants in one or more offerings and in any combination; and (ii) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $60.0 million of the Company's common stock that may be issued and sold in "at-the-market" sales under the ATM Program. As of June 30, 2021, the Company has $132.6 million of common stock remaining that can be sold under the 2019 Shelf Registration Statement, of which $57.0 million may be sold under the ATM Program. Shares Sold Under the ATM Program As of June 30, 2021, the Company has sold 561,848 shares of common stock pursuant to the ATM Program for gross proceeds of $2.9 million. March 2021 Offering In March 2021, pursuant to the 2019 Shelf Registration Statement, the Company completed an underwritten public offering of its common stock, which resulted in the issuance and sale of an aggregate of 18,400,000 shares of common stock at a public offering price of $3.50 per share, generating net proceeds of $60.2 million, after deducting underwriting discounts and commissions and other offering costs.

Stock-Based Compensation

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Stock-Based CompensationStock-based compensation expense has been reported in the Company’s condensed statements of operations for the three and six months ended June 30, 2021 and 2020 as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
General and administrative	$	510	$	402	$	984	$	742
Research and development	219		173		414		304
Total stock-based compensation	$	729	$	575	$	1,398	$	1,046

As of June 30, 2021, the total unrecognized compensation expense related to unvested employee and non-employee stock options was $5.6 million, which is expected to be recognized over a weighted-average period of approximately 2.5 years.

In October 2018, the Company's board of directors and stockholders approved the ESPP, which became effective on October 17, 2018. The ESPP is intended to qualify as an "employee stock purchase plan" within the meaning of Section 423 of the Internal Revenue Code.

Under the ESPP, eligible employees are granted rights to purchase shares of common stock, which are funded through payroll deductions that cannot exceed 15% of each employee’s compensation. The ESPP generally provides for a 24-month offering period, which includes four six-month purchase periods. At the end of each purchase period, eligible employees are permitted to purchase shares of common stock at 85% of the lower of fair market value at the beginning of the offering period or fair market value at the end of the purchase period. The ESPP is considered a compensatory plan, and the Company recorded stock-based compensation expense of $0.1 million and $21,000 for the three months ended June 30, 2021 and 2020, respectively, and $0.1 million and $21,000 for the six months ended June 30, 2021 and 2020, respectively. The Company issued 72,105 and zero shares of common stock under the ESPP for the six months ended June 30, 2021 and 2020, respectively.

As of June 30, 2021, the total unrecognized compensation expense related to the ESPP was $0.2 million, which is expected to be recognized over a weighted-average period of approximately 0.8 years.

Licenses and Other Agreements	6 Months Ended
Licenses and Other Agreements	Jun. 30, 2021
License Agreements [Abstract]
Licenses and Other Agreements	License and Other Agreements MedImmune Limited License Agreement In November 2017, the Company entered into a license agreement (“MedImmune License”) with MedImmune Limited (“MedImmune”). MedImmune is a wholly-owned subsidiary of AstraZeneca plc (“AstraZeneca”). Pursuant to the terms of the MedImmune License, MedImmune granted the Company exclusive global rights for the purpose of developing and commercializing products under the MedImmune License (“MedImmune licensed product”). The Company has made contingent milestone payments of $3.0 million and is obligated to make remaining contingent milestone payments totaling up to an aggregate of $15.0 million upon the achievement of clinical development and regulatory milestones. In addition, the Company will pay MedImmune tiered royalties ranging from mid-single-digit to low-teen percentages of net sales of any MedImmune licensed products and additional payments of up to $50.0 million in aggregate commercial milestones. The Company incurred no royalty costs under the MedImmune License in the three and six months ended June 30, 2021 and 2020. The Company also must pay quarterly fees relating to technical services provided by MedImmune. The MedImmune License requires the Company to cooperate with MedImmune on commercial messaging of bentracimab and provides MedImmune with the return of rights to bentracimab if certain commercial diligence requirements are not achieved by the Company. In addition, the MedImmune License offers an option for third-party product storage costs. The Company incurred no third-party product storage costs in the three and six months ended June 30, 2021 and 2020. AstraZeneca is a stockholder of the Company. Duke License Agreement In October 2006, the Company entered into a license agreement with Duke University (“Duke”) (as amended, the “Duke License”). Pursuant to the Duke License, Duke granted to the Company an exclusive, worldwide license under certain patent rights and a non-exclusive license to know-how owned or controlled by Duke to develop and commercialize any products or processes covered under the Duke License (the “Duke licensed products”). The Duke License was amended in February 2016 to allow Duke to use the Company’s technology in the area of small-molecule oncologics. The Duke License is a worldwide, sublicensable agreement and remains in full effect for the life of the last-to-expire patents included in the patent rights, which is estimated to be 2030. The Company is required to apply for, prosecute and maintain all United States and foreign patent rights under the Duke License. The Company is obligated to pay up to $2.2 million upon the achievement of clinical development and regulatory milestones and up to $0.4 million upon the achievement of commercial milestones. The Duke License may be terminated by Duke if the Company fails to meet certain clinical development and regulatory milestones within specified timeframes. As of June 30, 2021, the Company was in compliance with its development obligations. The Company is required to use commercially reasonable efforts to develop one or more products or processes and introduce them into commercial markets. Duke will receive low single-digit royalty percentages on net sales of Duke licensed products by the Company or its sublicensee, with minimum aggregate royalties of $0.2 million payable following the Company’s achievement of certain commercial milestones. No sales of Duke licensed products or services have occurred since the effective date through June 30, 2021. Certain alliance fee payments up to the greater of $0.3 million or a low double-digit percentage of the fees the Company receives from a third party in consideration of forming a strategic alliance may be required depending upon how the patent rights are commercialized. The Company must pay Duke the first $1.0 million of non-royalty payments it receives from a sublicensee, and thereafter a specified percentage of any additional non-royalty payments it receives, subject to certain conditions. If Duke receives revenue as a result of a license or sublicense to a third party in the field of small-molecule oncologics, it will pay the Company a specified percentage of the amount of such revenue in excess of $1.0 million. The Company incurred no costs under the Duke License in the three and six months ended June 30, 2021 and 2020. Alfasigma Sublicense In June 2021, the Company entered into the Alfasigma Sublicense with Alfasigma under which the Company granted to Alfasigma exclusive rights to develop, use, sell, have sold, offer for sale and import the Licensed Products in the Sublicense Territory. Under the terms of the Alfasigma Sublicense, in July 2021, the Company received a $20.0 million upfront payment from Alfasigma and will be eligible to receive up to $35.0 million upon the achievement of certain pre-revenue regulatory milestones, up to $190.0 million upon the achievement of certain commercial milestones and tiered royalty payments on net sales, with percentages starting in the low double digits and escalating up to the mid-twenties. With respect to the up to $35.0 million of regulatory milestone payments: (i) $10.0 million is payable following acceptance by the EMA of the filing of the first drug approval application for a Licensed Product; (ii) $12.5 million is payable following achievement of conditional regulatory approval from the EMA; and (iii) the remaining $12.5 million is payable following achievement of unconditional regulatory approval from the EMA allowing for prescribing of a Licensed Product for the reversal of the antiplatelet effects of ticagrelor in both (a) patients with uncontrolled major or life-threatening bleeding and (b) patients requiring urgent surgery or an invasive procedure. Under the Alfasigma Sublicense, the Company is responsible for developing the Licensed Products and securing regulatory approval with the EMA and the MHRA, including in accordance with the SFJ Agreement, after which any marketing authorizations will be assigned to Alfasigma. Alfasigma is obligated to obtain and maintain any regulatory approvals necessary to market and sell the Licensed Products (including pricing approvals and post-marketing commitments) and is also responsible for securing regulatory approval in countries outside of Europe and the United Kingdom. Alfasigma will purchase its requirements from the Company for a set period, after which the Company is obligated to supply a lesser amount of Alfasigma's requirements, for Licensed Product at the lower of cost or a price not to exceed certain agreed amounts. Unless earlier terminated, the Alfasigma Sublicense automatically expires, with respect to each Licensed Product and each country in the Sublicense Territory, on the latest of (1) the tenth anniversary of the first commercial sale of such Licensed Product in such country, (2) the expiration of the last out-licensed patent of such Licensed Product in such country and (3) the expiration of regulatory exclusivity, if any, of such Licensed Product in such country. In connection with the Alfasigma Sublicense, the Company and Alfasigma also entered into an Acknowledgement of Grant of Sublicense with MedImmune (the “Acknowledgement of Grant”), which provides for, among other things, (i) a potential assignment of the Alfasigma Sublicense from the Company to MedImmune or (ii) a potential assignment of the Medimmune License from the Company to Alfasigma, in either case in the event that the Company breaches certain obligations under the Medimmune License that are not cured or remedied and SFJ has grounds to execute a “Program Transfer” (as defined in the SFJ Agreement) but elects not to do so. Wacker License Agreement In April 2019, the Company entered into a license agreement (“Wacker License Agreement”), with Wacker Biotech GmbH (“Wacker”), pursuant to which Wacker granted the Company an exclusive license under certain of Wacker’s intellectual property rights to use Wacker’s proprietary E. coli strain for the manufacture of bentracimab worldwide outside of specified Asian countries, and to commercialize bentracimab, if approved, manufactured by the Company or on the Company’s behalf using Wacker’s proprietary E. coli strain throughout the world. The Company has the right to grant sublicenses under the license, subject to certain conditions as specified in the Wacker License Agreement. Under the terms of the agreement, the Company is required to pay a fixed, nominal per-unit royalty, which is subject to adjustment, and an annual license fee in a fixed Euro amount in the low to mid six digits. The agreement will be in force for an indefinite period of time, and upon the expiration of the Company’s royalty obligations, the license will be considered fully paid and will convert to a non-exclusive license. Either party may terminate the Wacker License Agreement for breach if such breach is not cured within a specified number of days. The Company incurred $0.1 million and $0.1 million under the Wacker License Agreement for the three months ended June 30, 2021 and 2020, respectively, and $0.2 million and $0.2 million for the six months ended June 30, 2021 and 2020, respectively. Viamet Asset Purchase Agreement In January 2020, the Company entered into a purchase agreement ("PB6440 Agreement") with Viamet Pharmaceuticals Holdings, LLC and its wholly-owned subsidiary, Selenity Therapeutics (Bermuda), Ltd. (the "Sellers"), pursuant to which the Company acquired all of the assets and intellectual property rights related to the Sellers’ proprietary CYP11B2 inhibitor compound, formerly known as SE-6440 or VT-6440, and certain other CYP11B2 inhibitor compounds that are covered by the patent rights acquired by the Company under the PB6440 Agreement (together, "Compounds"). Under the terms of the PB6440 Agreement, the Company paid the Sellers an upfront fee of $0.1 million upon the closing of the transaction, and are required to pay the Sellers up to $5.1 million upon the achievement of certain development and intellectual property milestones with respect to certain product candidates that contain a Compound, up to $142.5 million upon the achievement of certain commercial milestones with respect to any approved product that contains a Compound and low- to mid-single digit royalty percentages on the net sales of approved products that contain a Compound, subject to customary reductions and offsets in specified circumstances. The Company incurred zero in costs under the PB6440 Agreement for the three months ended June 30, 2021 and 2020, and zero and $0.1 million for the six months ended June 30, 2021 and 2020, respectively. BioVectra Supply Agreement In March 2021, the Company entered into a supply agreement, ("BioVectra Agreement"), with BioVectra Inc. ("BioVectra") for the manufacture and supply by BioVectra of bulk drug substance for bentracimab for commercial distribution following regulatory approval, if obtained. Under the terms of the BioVectra Agreement, BioVectra has committed to maintaining capacity to manufacture an agreed number of batches of product each year, and the Company has committed to purchase a specified minimum number of batches of product per year (the "Minimum Annual Commitment"), although it is free to contract with third parties for the manufacture of bentracimab. The Company will pay a supply price per batch of bentracimab to be determined after the manufacturing process for the bentracimab is validated in accordance with the BioVectra Agreement, plus the cost of certain consumables, raw materials, and third-party testing. Pursuant to the Minimum Annual Commitments, the Company is obligated to purchase a minimum of (i) approximately $14.0 million of batches of bentracimab in years 2022 through 2023, (ii) approximately $37.0 million of batches of bentracimab in 2024, and (iii) approximately $48.0 million of batches of bentracimab in each of years 2025 through 2031. In the event the Company does not purchase the applicable Minimum Annual Commitment in a given year, it will be obligated to make a payment to BioVectra in an amount equal to the then-applicable supply price per batch multiplied by the difference between the Minimum Annual Commitment for such year and the number of batches of product it actually purchased in such year, except in the event that BioVectra was unable to deliver the number of batches ordered by the Company in such year. The Company will have the right to reduce the Minimum Annual Commitments for the year 2026 and subsequent years by up to a specified maximum percentage per year. Further, if the Company is only able to obtain regulatory approval for products incorporating bentracimab in only one of the United States or Europe, BioVectra and the Company have agreed to discuss in good faith an amendment to the BioVectra Agreement to reflect decreased requirements for product and impacts to the supply price to reflect lower volume commitments.

Revenue	6 Months Ended
Revenue	Jun. 30, 2021
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Sublicense revenue Sublicense revenue relates to the revenue that the Company recognized in relation to the Alfasigma Sublicense. The Company recognized sublicense revenue of $10.3 million and zero in the three months ended June 30, 2021 and 2020 and $10.3 million and zero for the six months ended June 30, 2021 and 2020, respectively. Grant revenue In February 2018, the Company received Small Business Innovation Research (“SBIR”) grants from the National Institutes of Health in an aggregate amount of $2.8 million to support the clinical development of pemziviptadil for the treatment of pulmonary arterial hypertension for the period from February 17, 2018 to July 31, 2020. In connection with the SBIR grants, the United States government will receive a non-exclusive, royalty-free license to use any technology the Company develops under such grants. As of March 31, 2020, the Company had received all $2.8 million in funding available under the SBIR grant. The Company recognized zero revenue under the SBIR grants in the three months ended June 30, 2021 and 2020, and zero and $0.3 million for the six months ended June 30, 2021 and 2020, respectively.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130554-203045

+ Details

Related Party Transactions	6 Months Ended
Related Party Transactions	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Related Party TransactionsAs described above in Note 13, the Company is party to the MedImmune License. AstraZeneca, the parent company of MedImmune, is a related party of the Company.

Significant Accounting Policies (Policies)	6 Months Ended
Significant Accounting Policies (Policies)	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed financial statements have been prepared in accordance with United States generally accepted accounting principles (“GAAP”) for interim financial reporting and the rules and regulations of the SEC. Certain information and note disclosures normally included in annual financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to those rules and regulations. All adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the accompanying condensed financial statements have been made. Although these interim condensed financial statements do not include all of the information and footnotes required for complete annual financial statements, management believes the disclosures are adequate to make the information presented not misleading. The unaudited interim results of operations and cash flows for the three and six months ended June 30, 2021 are not necessarily indicative of the results that may be expected for the full year. The unaudited interim condensed financial statements and footnotes should be read in conjunction with the audited financial statements and footnotes for the year ended December 31, 2020, included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020, filed with the SEC on March 15, 2021, wherein a more complete discussion of significant accounting policies and certain other information can be found. Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board (“FASB”). The Company manages its operations as a single reportable segment for the purposes of assessing performance and making operating decisions.
Use of Estimates	Use of Estimates The preparation of the Company’s condensed financial statements requires management to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s condensed financial statements and accompanying notes. The most significant estimates in the Company’s condensed financial statements relate to the valuation of the development derivative liability, the deferral and recognition of revenue under the Alfasigma Sublicense and the clinical trial accruals. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results could differ materially from those estimates and assumptions.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company maintains certain deposit accounts and money market funds in federally insured financial institutions in excess of federally insured limits. The Company could experience losses on the money market funds in the future.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with an original maturity from the date of purchase of three months or less to be cash equivalents. Cash and cash equivalents include cash in readily available checking and money market accounts.
Receivable from Sublicense	Receivable from SublicenseReceivable from sublicense relates to amounts due from Alfasigma under the Alfasigma Sublicense. The Company records amounts as accounts receivable when the right to consideration is deemed unconditional.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of other receivables, prepaid expenses and other assets, accounts payable and accrued expenses and other current liabilities are reasonable estimates of their fair value because of the short maturity of these items. Based on the borrowing rates currently available to the Company for loans with similar terms, the Company believes the fair values of the term loan and operating lease liabilities and corresponding right-of-use assets approximate their respective carrying values.
Revenue Recognition	Deferred Sublicense Revenue When consideration is received, or such consideration is unconditionally due, from a customer prior to the Company completing its performance obligation to the customer under the terms of a contract, a contract liability is recorded as deferred revenue. Deferred revenues expected to be recognized as revenue within the 12 months following the balance sheet date are classified as current liabilities. Deferred revenues not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as long-term liabilities. Revenue Recognition Sublicense Revenue Sublicensing arrangements may contain multiple components, which may include (i) sublicenses; (ii) research and development activities; and (iii) the manufacturing and supply of certain materials. Payments pursuant to these arrangements may include non-refundable payments, upfront payments, milestone payments upon the achievement of significant regulatory and development events or sales of product at certain agreed-upon amounts, sales milestones and royalties on product sales. 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. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under a sublicense agreement, the Company performs the following steps: (i) identification of the promised goods or services in the contract; (ii) determination of whether the promised goods or services are performance obligations, including whether they are capable of being distinct; (iii) measurement of the transaction price, including the constraint on variable consideration; (iv) allocation of the transaction price to the performance obligations; and (v) recognition of revenue as the Company satisfies each performance obligation. The Company must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation, which determines how the transaction price is allocated among the performance obligations. The estimation of the stand-alone selling price may include such estimates as forecasted revenues and costs, development timelines, discount rates and probabilities of regulatory and commercial success. The Company also applies significant judgment when evaluating whether contractual obligations represent distinct performance obligations, allocating transaction price to performance obligations within a contract, determining when performance obligations have been met, assessing the recognition and future reversal of variable consideration and determining and applying appropriate methods of measuring progress for performance obligations satisfied over time. Grant Revenue Grant revenue is derived from government grants that support the Company’s efforts on specific research projects. The Company has determined that the government agencies providing grants to the Company are not customers. The Company recognizes grant revenue when there is reasonable assurance of compliance with the conditions of the grant and reasonable assurance that the grant revenue will be received.
Development Derivative Liabilities	Development Derivative LiabilityDevelopment derivative liability is recorded based on the present value of the estimated consideration to be received and the estimated consideration to be paid pursuant to contractual terms of the SFJ Agreement, which was determined to have been fair value. The liability is remeasured quarterly, as a Level 3 derivative, with any change in fair value recorded in the form of a gain (loss) from remeasurement of development derivative liability on the condensed statements of operations.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost and depreciated over the estimated useful lives of the assets (three to five years) using the straight-line method. Leasehold improvements are amortized over the shorter of their estimated useful lives or the lease term.
Leases	Leases At lease commencement, the Company records a lease liability based on the present value of lease payments over the expected lease term including any options to extend the lease that the Company is reasonably certain to exercise. The Company calculates the present value of lease payments using an incremental borrowing rate as the Company’s leases do not provide an implicit interest rate. The Company’s incremental borrowing rate for a lease is the rate of interest it would have to pay on a collateralized basis to borrow an amount equal to the lease payments under similar terms. At the lease commencement date, the Company records a corresponding right-of-use lease asset based on the lease liability, adjusted for any lease incentives received and any initial direct costs paid to the lessor prior to the lease commencement date. The Company may enter into leases with an initial term of 12 months or less (“Short-Term Leases”). For any Short-Term Leases, the Company records the rent expense on a straight-line basis and does not record the leases on the condensed balance sheet. The Company had no Short-Term Leases as of June 30, 2021 or December 31, 2020. After lease commencement, the Company measures its leases as follows: (i) the lease liability based on the present value of the remaining lease payments using the discount rate determined at lease commencement and (ii) the right-of-use lease asset based on the remeasured lease liability, adjusted for any unamortized lease incentives received, any unamortized initial direct costs and the cumulative difference between rent expense and amounts paid under the lease agreement. Any lease incentives received and any initial direct costs are amortized on a straight-line basis over the expected lease term. Rent expense is recorded on a straight-line basis over the expected lease term.
Long-Lived Assets	Long-Lived Assets The Company regularly reviews the carrying value and estimated lives of all of its long-lived assets, including property and equipment and right-of-use assets to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. The determinants used for this evaluation include management’s estimate of the asset’s ability to generate net positive cash flow in future periods as well as the strategic significance of the assets to the Company’s business objectives. Should an impairment exist, the impairment loss would be measured based on the extent that the estimated fair value is less than its carrying value. The Company did not recognize any impairment losses in either the six months ended June 30, 2021 or the year ended December 31, 2020.
Preclinical and Clinical Trial Accruals	Preclinical and Clinical Trial Accruals The Company accrues and expenses amounts incurred in connection with preclinical studies and clinical trial activities performed by third parties based upon estimates of the proportion of work completed over the life of the individual trial and subject enrollment rates in accordance with agreements with clinical research organizations, contract manufacturing organizations and clinical trial sites. The Company determines the estimates by reviewing contracts, vendor agreements and purchase orders, and through discussions with internal clinical personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services. However, actual costs and timing of clinical trials are highly uncertain, subject to risks and may change depending upon a number of factors, including the Company’s clinical development plan. Management makes estimates of the Company’s accrued expenses as of each balance sheet date in the Company’s condensed financial statements based on facts and circumstances known to the Company at that time. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Nonrefundable advance payments for goods and services, including fees for process development or manufacturing and distribution of clinical supplies that will be used in future research and development activities, are deferred and recognized as expense in the period that the related goods are consumed or services are performed.
Research and Development Expense	Research and Development Expense Research and development costs are expensed as incurred. Costs incurred in obtaining technology licenses are charged to research and development expense if the technology has no alternative future use.
Stock-Based Compensation	Stock-Based Compensation The Company measures and recognizes compensation expense for all stock-based compensation based on the estimated fair value at the date of grant. Currently, the Company’s stock-based awards consist only of stock options; however, future grants under the Company’s equity compensation plan may also consist of shares of restricted stock, restricted stock units, stock appreciation rights, performance awards and performance units. The Company also maintains the 2018 Employee Stock Purchase Plan ("ESPP") under which it may issue shares of common stock. The Company estimates the fair value of stock options and shares that will be issued under the ESPP using the Black-Scholes option-pricing model, which requires the use of estimates. The Company recognizes stock-based compensation cost for ratably vesting stock options and for shares that it will issue under the ESPP on a straight-line basis over the requisite service period of the award and records forfeitures in the period in which they occur. The Black-Scholes option-pricing model requires the input of subjective assumptions, including the risk-free interest rate, the expected dividend yield of the Company’s common stock, the expected volatility of the price of the Company’s common stock, and the expected term of the option. These estimates involve inherent uncertainties and the application of management’s judgment. If factors change and different assumptions are used, the Company’s stock-based compensation expense could be materially different in the future.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the condensed financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the condensed financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits, if any, within income tax expense, and any accrued interest and penalties are included within the related tax liability line.
Net Loss Per Share	Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and common share equivalents outstanding for the period. Common stock equivalents are only included when their effect is dilutive. The Company’s potentially dilutive securities, which include outstanding options under the Company's stock option plan, warrants issued from time to time and shares of common stock to be potentially issued under the ESPP, have been excluded from the computation of diluted net loss per share as they would be anti-dilutive. For all periods presented, there is no difference in the number of shares used to compute basic and diluted shares outstanding due to the Company’s net loss position.
Recent Accounting Pronouncements	Recent Accounting PronouncementsIn December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, which among other things, eliminates certain exceptions in the current rules regarding the approach for intraperiod tax allocations and the methodology for calculating income taxes in an interim period, and clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. The standard became effective for the Company in the first quarter of 2021. Adoption of this new standard did not have a material impact on the Company's condensed financial statements and related disclosures.

Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2021

Accounting Policies [Abstract]

Schedule of Outstanding Potentially Dilutive Securities Excluded in Calculation of Diluted Net Loss Per Share


	As of June 30,
	2021	2020
Common stock options	4,359,395	3,740,815
Warrants to purchase common stock	2,349,595	2,349,595
Employee stock purchase plan	275,077	271,012
Total	6,984,067	6,361,422

Fair Value Measurement (Tables)

6 Months Ended

Jun. 30, 2021

Fair Value Disclosures [Abstract]

Summary of Assets and Liabilities that Require Fair Value Measurements on a Recurring Basis


	Total		Fair Value Measurements at Reporting Date
			Level 1		Level 2		Level 3
As of June 30, 2021:
Assets
Cash equivalents	$	64,236	$	64,236	$	—	$	—
Liabilities
Development derivative liability (Note 8)	$	89,329	$	—	$	—	$	89,329
As of December 31, 2020:
Assets
Cash equivalents	$	27,872	$	27,872	$	—	$	—
Liabilities
Development derivative liability (Note 8)	$	51,719	$	—	$	—	$	51,719

Property and Equipment (Tables)

6 Months Ended

Jun. 30, 2021

Property, Plant and Equipment [Abstract]

Composition of Property and Equipment, Net

The following table presents the composition of property and equipment, net as of June 30, 2021 and December 31, 2020 (in thousands):


	As of June 30, 2021		As of December 31, 2020
Lab equipment	$	12,244	$	8,994
Computer hardware, software and telephone	140		140
Furniture and fixtures	114		107
Leasehold improvements	77		67
Construction in progress	986		1,042
	13,561		10,350
Less accumulated depreciation	(3,182)		(2,126)
Property and equipment, net	$	10,379	$	8,224

Accrued Expenses and Other Current Liabilities (Tables)

6 Months Ended

Jun. 30, 2021

Payables and Accruals [Abstract]

Schedule of Composition of Accrued Expenses

The following table presents the composition of accrued expenses and other current liabilities as of June 30, 2021 and December 31, 2020 (in thousands):


	As of June 30, 2021		As of December 31, 2020
Accrued clinical and related costs	$	3,921	$	2,753
Accrued compensation and related costs	1,483		2,260
Accrued interest	52		69
Current portion of operating lease liability	476		459
Accrued other	476		390
Accrued expenses and other current liabilities	$	6,408	$	5,931

Deferred Sublicense Revenue (Tables)

6 Months Ended

Jun. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Transaction Price to Performance Obligations

The Company allocated the upfront portion of the transaction price to the performance obligations as of June 30, 2021 as follows (in thousands):


	Transaction Price		Cumulative Sublicense Revenue Recognized		Deferred Sublicense Revenue
License	$	10,223	$	10,223	$	—
Development and Regulatory Services	2,647		115		2,532
Supply of License Product	7,130		—		7,130
	$	20,000	$	10,338	9,662
Less current portion of long-term deferred sublicense revenue					(1,424)
Total long-term deferred sublicense revenue					$	8,238

Debt (Tables)

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Summary of Future Principal Payments

The following table sets forth by year the Company’s required future principal payments as of June 30, 2021 (in thousands):


Years Ending December 31,
2021 (remaining six months)	$	2,727
2022	5,455
2023	1,363
Thereafter	—
Total principal payments	9,545
Less unamortized loan fees	(88)
Total term loan borrowings	$	9,457

Development Derivative Liability (Tables)

6 Months Ended

Jun. 30, 2021

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Development Derivative Liability

The following table presents activity for the development derivative liability during the six months ended June 30, 2021 (in thousands):


	Development Derivative Liability
Balance at December 31, 2020	$	51,719
Funding during the period	30,407
Change in fair value	7,203
Balance at June 30, 2021	$	89,329

Leases (Tables)

6 Months Ended

Jun. 30, 2021

Leases [Abstract]

Schedule of Maturities of Operating Lease Liabilities

Maturities of operating lease liabilities as of June 30, 2021 are as follows (in thousands):


Year Ending December 31,
2021 (remaining six months)	$	283
2022	555
2023	419
2024	279
2025	283
Thereafter	215
Total future minimum lease payments	2,034
Less: Present value adjustment	(252)
Operating lease liabilities	$	1,782

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Stock-based Compensation Expense

Stock-based compensation expense has been reported in the Company’s condensed statements of operations for the three and six months ended June 30, 2021 and 2020 as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
General and administrative	$	510	$	402	$	984	$	742
Research and development	219		173		414		304
Total stock-based compensation	$	729	$	575	$	1,398	$	1,046

Organization and Description of Business - Additional Information (Details) $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended
	Jul. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 shares	Jun. 30, 2020 shares	Jun. 30, 2021 USD ($) segment shares	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Organization and Description of Business [Line Item]
Accumulated deficit		$ 316,760			$ 316,760		$ 260,723
Cash and cash equivalents		64,456			64,456		$ 28,122
Working capital		72,300			72,300
Aggregate offering price		200,000			200,000
Proceeds from issuance of common stock					60,351	$ 472
Proceeds from issuance of common stock, deducting underwriting discounts, commissions, and other offering costs					60,200
Aggregate offering price, remaining		132,600			$ 132,600
Reportable segment \| segment					1
Common Stock
Organization and Description of Business [Line Item]
Issuance of common stock in public offering, net (in shares) \| shares			18,400,000	80,523	18,400,000
SFJ Pharmaceuticals X, Ltd.
Organization and Description of Business [Line Item]
Proceeds from partnership contribution					$ 12,500
Equity Distribution Agreement with Citigroup Global Markets Inc. and William Blair & Company, L.L.C.
Organization and Description of Business [Line Item]
Aggregate offering price		60,000			60,000
Proceeds from issuance of common stock					2,900
Aggregate offering price, remaining		57,000			$ 57,000
Equity Distribution Agreement with Citigroup Global Markets Inc. and William Blair & Company, L.L.C. \| Common Stock
Organization and Description of Business [Line Item]
Issuance of common stock in public offering, net (in shares) \| shares					561,848
Alfasigma S.p.A.
Organization and Description of Business [Line Item]
Upfront payment from sublicense agreement		$ 20,000
Alfasigma S.p.A. \| Subsequent Event [Member]
Organization and Description of Business [Line Item]
Upfront payment from sublicense agreement	$ 20,000

Significant Accounting Policies - Additional Information (Details)	6 Months Ended
	Jun. 30, 2021
Minimum
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives (in years)	3 years
Maximum
Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives (in years)	5 years

Significant Accounting Policies - Schedule of Outstanding Potentially Dilutive Securities Excluded In Calculation Of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Significant Accounting Policies [Line Items]
Outstanding potentially dilutive securities excluded in calculation of diluted net loss per share (in shares)	6,984,067	6,361,422
Common stock options
Significant Accounting Policies [Line Items]
Outstanding potentially dilutive securities excluded in calculation of diluted net loss per share (in shares)	4,359,395	3,740,815
Warrants to purchase common stock
Significant Accounting Policies [Line Items]
Outstanding potentially dilutive securities excluded in calculation of diluted net loss per share (in shares)	2,349,595	2,349,595
Employee stock purchase plan
Significant Accounting Policies [Line Items]
Outstanding potentially dilutive securities excluded in calculation of diluted net loss per share (in shares)	275,077	271,012

Fair Value Measurement - Summary of Assets and Liabilities that Require Fair Value Measurements on a Recurring Basis (Details) - Fair Value Measurements on Recurring Basis - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Assets
Cash equivalents	$ 64,236	$ 27,872
Liabilities
Development derivative liability (Note 8)	89,329	51,719
Level 1
Assets
Cash equivalents	64,236	27,872
Liabilities
Development derivative liability (Note 8)	0	0
Level 2
Assets
Cash equivalents	0	0
Liabilities
Development derivative liability (Note 8)	0	0
Level 3
Assets
Cash equivalents	0	0
Liabilities
Development derivative liability (Note 8)	$ 89,329	$ 51,719

Property and Equipment - Composition of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 13,561	$ 10,350
Less accumulated depreciation	(3,182)	(2,126)
Property and equipment, net	10,379	8,224
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	12,244	8,994
Computer hardware, software and telephone
Property, Plant and Equipment [Line Items]
Property and equipment, gross	140	140
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	114	107
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	77	67
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 986	$ 1,042

Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Property, Plant and Equipment [Abstract]
Depreciation	$ 0.6	$ 0.1	$ 1.1	$ 0.1

Accrued Expenses and Other Current Liabilities - Schedule of Composition of Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Accrued clinical and related costs	$ 3,921	$ 2,753
Accrued compensation and related costs	1,483	2,260
Accrued interest	52	69
Current portion of operating lease liability	476	459
Accrued other	476	390
Accrued expenses and other current liabilities	$ 6,408	$ 5,931

Deferred Sublicense Revenue - Additional Information (Details) $ in Millions	1 Months Ended
	Jun. 30, 2021 USD ($)
Alfasigma S.p.A. \| Achievement Of Certain Pre-Revenue Regulatory Milestones
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment	$ 35.0
Alfasigma S.p.A. \| Achievement Of Certain Commercial Milestones And Tiered Royalty Payments On Net Sales
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment	190.0
Alfasigma S.p.A. \| EMA Approval Of Application For Licensed Product
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment	10.0
Alfasigma S.p.A. \| Achievement Of Conditional Regulatory Approval From EMA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment	12.5
Alfasigma S.p.A. \| Achievement Of Unconditional Regulatory Approval From EMA
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestones payment	12.5
Alfasigma S.p.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment from sublicense agreement	$ 20.0

Deferred Sublicense Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cumulative Sublicense Revenue Recognized	$ 10,338	$ 0	$ 10,338	$ 320
Less current portion of long-term deferred sublicense revenue	(1,424)		(1,424)		$ 0
Total long-term deferred sublicense revenue	8,238		8,238		$ 0
Alfasigma S.p.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction Price			20,000
Cumulative Sublicense Revenue Recognized			10,338
Deferred Sublicense Revenue	9,662		9,662
Less current portion of long-term deferred sublicense revenue	(1,424)		(1,424)
Total long-term deferred sublicense revenue	8,238		8,238
License \| Alfasigma S.p.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction Price			10,223
Cumulative Sublicense Revenue Recognized			10,223
Deferred Sublicense Revenue	0		0
Development and Regulatory Services \| Alfasigma S.p.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction Price			2,647
Cumulative Sublicense Revenue Recognized			115
Deferred Sublicense Revenue	2,532		2,532
Supply of License Product \| Alfasigma S.p.A.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Transaction Price			7,130
Cumulative Sublicense Revenue Recognized			0
Deferred Sublicense Revenue	$ 7,130		$ 7,130

Debt - Additional Information (Details)	1 Months Ended	3 Months Ended		6 Months Ended
Debt - Additional Information (Details)	Mar. 31, 2019 USD ($) tranche $ / shares shares	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Oct. 31, 2019 $ / shares shares	Jun. 30, 2019	May 31, 2019 $ / shares shares
SVB and WestRiver
Debt Instrument [Line Items]
Expiration term	10 years
Long-term debt		$ 9,545,000		$ 9,545,000
SVB and WestRiver \| Tranche 1
Debt Instrument [Line Items]
Number of warrants issued (in shares) \| shares	37,606
Exercise price of warrant (in usd per share) \| $ / shares	$ 4.73
Proceeds from lines of credit	$ 7,500,000
SVB and WestRiver \| Tranche 2
Debt Instrument [Line Items]
Number of warrants issued (in shares) \| shares								12,130
Exercise price of warrant (in usd per share) \| $ / shares								$ 10.86
SVB and WestRiver \| Tranche 3
Debt Instrument [Line Items]
Number of warrants issued (in shares) \| shares						24,262
Exercise price of warrant (in usd per share) \| $ / shares						$ 3.88
Silicon Valley Bank
Debt Instrument [Line Items]
Percentage of final payment on principal amount of refinanced advances							6.00%
Long-term debt		700,000		700,000
Silicon Valley Bank \| Tranche 1, 2, and 3
Debt Instrument [Line Items]
Interest rate	6.50%
Amortization period of payments of principal plus interest amounts	33 months
Silicon Valley Bank \| Tranche 1, 2, and 3 \| Prime Rate
Debt Instrument [Line Items]
Interest rate, percentage point added to reference rate	1.00%
Term Loan \| SVB and WestRiver
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 15,000,000.0
Number of tranches \| tranche	3
Term Loan \| SVB and WestRiver \| Tranche 1
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 7,500,000
Term Loan \| Silicon Valley Bank
Debt Instrument [Line Items]
Interest expense		300,000	$ 400,000	500,000	$ 800,000
Term Loan \| Silicon Valley Bank \| Tranche 1, 2, and 3
Debt Instrument [Line Items]
Debt discount		$ 400,000		$ 400,000
Term Loan \| Silicon Valley Bank \| Tranche 2
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	2,500,000
Term Loan \| Silicon Valley Bank \| Tranche 3
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000,000.0