0000950170-22-004774 | 10-K | XBRL Viewer

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Aileron Therapeutics, Inc. (“Aileron” or the “Company”) is a clinical stage chemoprotection oncology company focused on fundamentally transforming the experience of chemotherapy for cancer patients. ALRN-6924, the Company’s first-in-class MDM2/MDMX dual inhibitor, is designed to activate p53, which in turn upregulates p21, a known inhibitor of the cell replication cycle. ALRN-6924 is the only reported chemoprotective agent in clinical development to employ a biomarker strategy, in which the Company exclusively focuses on treating patients with p53-mutated cancers. The Company’s targeted strategy is designed to selectively protect multiple healthy cell types throughout the body from chemotherapy without protecting cancer cells.

The Company is subject to risks common to companies in the biotechnology industry, including but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations, uncertainties in the clinical development of product candidates and in the ability to obtain needed additional financing. ALRN-6924 will require significant additional research and development efforts, including preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance-reporting capabilities.

There can be no assurance that the Company’s research and development of ALRN-6924 will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained, that ALRN-6924 will obtain necessary governmental regulatory approval or that if approved, will be commercially viable. Even if the Company’s drug development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its key employees and consultants.

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”).

Liquidity

In accordance with Accounting Standards Update (“ASU”) No. 2014-15, Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern (Subtopic 205-40), management must evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the company’s ability to continue as a going concern within one year after the date that the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists, management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the company’s ability to continue as a going concern. The mitigating effect of management’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued, and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. Generally, to be considered probable of being effectively implemented, the plans must have been approved before the date that the financial statements are issued.

The Company’s financial statements have been prepared on a going concern basis, which contemplates the continuity of operations, realization of assets and the satisfaction of liabilities in the ordinary course of business. Through December 31, 2021, the Company has financed operations primarily through $145,467 in net proceeds from sales of common stock and warrants, $131,211 from sales of preferred stock prior to its IPO, and $34,910 from a collaboration agreement in 2010.

As of December 31, 2021, the Company had cash, cash equivalents and investments of $45,933. The Company has incurred losses and negative cash flows from operations and had an accumulated deficit of $245,456 as of December 31, 2021. The Company expects to continue to generate losses for the foreseeable future.

The Company believes that, based on its current operating plan, its cash, cash equivalents and investments of $45,933 as of December 31, 2021 will enable the Company to fund its operating expenses for greater than twelve months from the date of issuance of these financial statements.

The Company will need substantial funding to support its continuing operations and pursue its growth strategy. Until such time as the Company can generate significant revenue from product sales, if ever, it expects to finance its operations through the sale of common stock in public offerings and/or private placements, debt financings or other capital sources, including collaborations with other companies or other strategic transactions. The Company may not be able to obtain financing when needed, on acceptable terms or at all. The terms of any financing may adversely affect the holdings or the rights of the Company’s stockholders. If the Company is unable to obtain funding, the Company could be forced to delay, reduce or eliminate some or all of its clinical programs, product portfolio expansion plans or commercialization efforts, which could adversely affect its business prospects. The financial statements do not include any adjustments that might result from the outcome of this uncertainty.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2021

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, the accrual of research and development expenses and the valuation of common stock and stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from the Company’s estimates.

Cash Equivalents

The Company considers all short-term, highly liquid investments with original maturities of 90 days or less at acquisition date to be cash equivalents. Cash equivalents, which consist of money market accounts, corporate notes and commercial paper are stated at fair value.

Restricted Cash

As of December 31, 2021, restricted cash of $25 consisted of cash deposited in a separate restricted bank account as a security deposit for the Company’s corporate credit cards. As of December 31, 2020, restricted cash consisted of $568 of cash deposited in a separate restricted bank account as a security deposit for the lease of the Company’s facility and $25 of cash deposited in a separate restricted bank account as a security deposit for the Company’s corporate credit cards.

Investments

The Company classifies its available-for-sale debt security investments as current assets on the balance sheet if they mature within one year from the balance sheet date.

The Company classifies all of its investments as available-for-sale securities. The Company’s investments are measured and reported at fair value using quoted prices in active markets for similar securities or using other inputs that are observable or can be corroborated by observable market data. Unrealized gains and losses on available-for-sale securities are reported as accumulated other comprehensive income (loss), which is a separate component of stockholders’ equity (deficit). The cost of securities sold is determined on a specific identification basis, and realized gains and losses are included in other income (expense) within the statements of operations and comprehensive loss.

The Company evaluates its investments with unrealized losses for other-than-temporary impairment. When assessing investments for other-than-temporary declines in value, the Company considers such factors as, among other things, how significant the decline in value is as a percentage of the original cost, how long the market value of the investment has been less than its original cost, the Company’s ability and intent to retain the investment for a period of time sufficient to allow for any anticipated recovery in fair value and market conditions in general. If any adjustment to fair value reflects a decline in the value of the investment that the Company considers to be “other than temporary”, the Company reduces the investment to fair value through a charge to the statements of operations and comprehensive loss. No such adjustments were necessary during the periods presented.

Concentration of Credit Risk and of Significant Suppliers

Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and investments. From time to time, the Company has maintained all of its cash, cash equivalents and investment balances at three accredited financial institutions, in amounts that exceed federally insured limits. The Company generally invests its excess cash in money market funds, commercial paper and corporate notes that are subject to minimal credit and market risks. Management has established guidelines relative to credit ratings and maturities intended to safeguard principal balances and maintain liquidity. The investment portfolio is maintained in accordance with the Company’s investment policy, which defines allowable investments, specifies credit quality standards and limits the credit exposure of any single issuer.

The Company is dependent on third-party manufacturers to supply products for research and development activities of its programs, including preclinical and clinical testing. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients and formulated drugs related to these programs. These programs could be adversely affected by a significant interruption in the supply of active pharmaceutical ingredients and formulated drugs.

Fair Value Measurements

Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable.

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

•

Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities, or other inputs that are observable or can be corroborated by observable market data.

•

Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques.

The Company’s cash equivalents and investments are carried at fair value, determined according to the fair value hierarchy described above (see Note 3). The carrying values of the Company’s accounts payable and accrued expenses approximate their fair value due to the short-term nature of these liabilities.

Property and Equipment

Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization expense is recognized using the straight-line method over the following estimated useful lives:

Laboratory equipment

5 years

Computer equipment and software

Furniture and fixtures

3 to 5 years

7 years

Expenditures for repairs and maintenance of assets are charged to expense as incurred. Upon retirement or sale, the cost and related accumulated depreciation and amortization of assets disposed of are removed from the accounts and any resulting gain or loss is included in the statements of operations and comprehensive loss.

Leases

On January 1, 2019, the Company adopted a new U.S. GAAP accounting standard which requires that all lessees recognize the assets and liabilities that arise from leases on the balance sheet and disclose qualitative and quantitative information about its leasing arrangements (ASC 842). The new standard was adopted using the modified retrospective transition method, which requires the Company to apply the standard as of the effective date and does not require restatement of prior periods. The Company elected to apply the package of practical expedients, which allowed the Company to not reassess: (i) whether expired or existing contracts contain leases; (ii) lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases.

The Company has an operating lease of office space, which has a remaining lease term of less than 2 years and includes one or more options to renew or terminate early. The Company determines if an arrangement contains a lease at inception. Operating lease right-of-use assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. Certain adjustments to the right-of-use asset may be required for items such as prepaid or accrued lease payments, initial direct costs paid or incentives received. The Company’s leases do not contain an implicit rate, and therefore the Company uses an estimated incremental borrowing rate based on the information available at the lease commencement date in determining the present value of lease payments. Options to extend or terminate the lease are reflected in the calculation when it is reasonably certain that the option will be exercised. The Company has elected to account for lease and non-lease components as a single lease component, however non-lease components that are variable, such as common area maintenance and utilities, are generally paid separately from rent based on actual costs incurred and therefore are not included in the right-of-use asset and operating lease liability and are reflected as an expense in the period incurred. Leases with an initial term of 12 months or less are not recorded on the balance sheet.

Impairment of Long-Lived Assets

Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. To date, the Company has not recorded any impairment losses on long-lived assets.

Research and Development Costs

Research and development expenditures are expensed as incurred. Research and development expenses are comprised of salaries, stock-based compensation and benefits of employees, third-party license fees and other operational costs related to the Company’s research and development activities, including allocated facility-related expenses and external costs of outside vendors engaged to conduct both preclinical studies and clinical trials.

Research Contract Costs and Accruals

The Company has entered into various research and development contracts with research institutions and other companies. These agreements are cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. This process involves reviewing open contracts and purchase orders, communicating with personnel to identify services that have been performed and estimating level of service performed and the associated costs incurred for the services for which the Company has not yet been invoiced. Significant judgment and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.

Patent Costs

All patent-related costs incurred in connection with filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.

Accounting for Stock-Based Compensation

The Company measures all stock options and other stock-based awards granted to employees and directors based on the fair value on the date of the grant and recognizes compensation expense of those awards, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award. The Company applies the straight-line method of expense recognition to all awards with only service-based vesting conditions and applies the graded vesting method to all awards with performance-based vesting conditions or both service-based and performance-based vesting conditions.

The Company recognizes compensation expense for only the portion of awards that are expected to vest. In developing a forfeiture rate estimate, the Company has considered its historical experience to estimate pre-vesting forfeitures for awards with service-based vesting conditions. The impact of a forfeiture rate adjustment will be recognized in full in the period of adjustment, and if the actual forfeiture rate is materially different from the Company’s estimate, the Company may be required to record adjustments to stock-based compensation expense in future periods.

The Company classifies share-based compensation expense in its statement of operations and comprehensive loss in the same manner in which the award recipient's payroll costs are classified or in which the award recipient's service payments are classified.

The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions, the expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The expected term of stock options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the financial statements or in the Company’s tax returns. Deferred taxes are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect in the years in which the differences are expected to reverse.

The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weight of available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Changes in valuation allowances from period to period are included in the Company’s tax provision in the period of change. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected and considering prudent and feasible tax planning strategies.

The Company accounts for uncertainty in income taxes recognized in the financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Segment Data

The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on developing a novel class of therapeutics for the treatment of cancer and other diseases. All of the Company’s tangible assets are held in the United States.

Comprehensive Loss

Comprehensive loss includes net loss as well as other changes in stockholders’ equity (deficit) that result from transactions and economic events other than those with stockholders. The Company’s only element of other comprehensive loss in all periods presented was unrealized gains (losses) on available-for-sale investments.

Net Income (Loss) per Share

Basic net income (loss) per share attributable to common stockholders is computed by dividing the net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net income (loss) attributable to common stockholders is computed by adjusting income (loss) per share attributable to common stockholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to common stockholders is computed by dividing the diluted net income (loss) attributable to common stockholders by the weighted average number of shares of common stock outstanding for the period, including potential dilutive common shares. For purpose of this calculation, outstanding options to purchase common stock are considered potential dilutive common shares.

Risks and Uncertainties

The ongoing COVID-19 pandemic and government measures taken in response have had a significant impact, both direct and indirect, on businesses and commerce. The future progression of the pandemic and its effects on our business and operations are uncertain.

Potential impacts to the Company’s business include disruptions in supply of the Company’s product candidate and/or procuring items that are essential for the Company’s research and development activities, including, for example, raw materials used in the manufacturing of ALRN-6924, medical and laboratory supplies used in the Company’s clinical trials or preclinical studies or animals that are used for preclinical testing, in each case, for which there may be shortages because of ongoing efforts to address the COVID-19 pandemic. While the Company believes that it currently has sufficient supply of its product candidate to continue the Company’s ongoing and planned clinical trials, its product candidate, or materials contained therein, come from facilities located in areas impacted by the COVID-19 pandemic.

Additionally, the Company has enrolled, and is seeking to enroll, cancer patients in the Company’s clinical trials at sites located both in the United States and Europe, which are areas that continue to be impacted by the COVID-19 pandemic. Enrollment at clinical trial sites may be disrupted as the effects of the COVID-19 pandemic persist. In the event that clinical trial sites close to enrollment in the Company’s trials or shift resources to address COVID-19, this could have a material adverse impact on the Company’s clinical trial plans and timelines. The Company may face difficulties recruiting or retaining patients in its ongoing and planned clinical trials if patients are affected by the virus or are fearful of visiting or traveling to our clinical trial sites because of the COVID-19 pandemic.

Any negative impact that the COVID-19 pandemic has on the ability of the Company’s suppliers to provide materials necessary for the Company’s product candidate or on recruiting or retaining patients in the Company’s clinical trials could cause costly delays to clinical trial activities, which could adversely affect the Company’s ability to obtain regulatory approval for and to commercialize the Company’s product candidate, increase the Company’s operating expenses, affect the Company’s ability to raise additional capital, and impact the Company’s operating and financial results. The capital markets have also experienced significant volatility as a result of the pandemic. Future disruptions in the capital markets could negatively impact the Company’s ability to raise capital in the future.

Recently Issued Accounting Pronouncements

In December 2019, the FASB issued ASU 2019-12, Income Taxes, or ASC 740, which simplifies the accounting for income taxes. The ASU was effective for the Company in the first quarter of fiscal 2021. Adoption of ASU2019-12 did not have a material effect on the Company’s consolidated financial statements or disclosures.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (ASU 2016-13 or Topic 326): Measurement of Credit Losses on Financial Instruments, which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost. ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss methodology, which will result in more timely recognition of credit losses. The ASU will be effective for the Company's fiscal year beginning January 1, 2023. The Company is currently evaluating the impact of the adoption of ASU 2016-13 and does not expect adoption to have a material effect on the Company’s consolidated financial statements or disclosures.

Other accounting standards that have been issued or proposed by the FASB or other standards-setting bodies that do not require adoption until a future date are not expected to have a material impact on the Company’s financial statements upon adoption.

Fair Value of Financial Assets

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Fair Value of Financial Assets

3. Fair Value of Financial Assets

The following tables present information about the Company’s assets that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values:


	Fair Value Measurements as of December 31, 2021 using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	2,438	$	—	$	—	$	2,438
Investments:
Commercial paper		—		33,969		—		33,969
Corporate notes		—		6,366		—		6,366
Treasury bills		—		1,998		—		1,998
	$	2,438	$	42,333	$	—	$	44,771


	Fair Value Measurements as of December 31, 2020 using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Commercial paper	$	—	$	1,001	$	—	$	1,001
Money market funds		4,190		—		—		4,190
Investments:
Agency bonds		—		3,511		—		3,511
Commercial paper		—		1,999		—		1,999
Treasury bills		—		1,249		—		1,249
	$	4,190	$	7,760	$	—	$	11,950

As of December 31, 2021 and 2020, the Company’s cash equivalents and investments were invested in money market funds, corporate notes and commercial paper and were valued based on Level 1 and Level 2 inputs. In determining the fair value of its corporate notes and commercial paper at each date presented above, the Company relied on quoted prices for similar securities in active markets or using other inputs that are observable or can be corroborated by observable market data. The Company’s cash equivalents have original maturities of less than 90 days from the date of purchase. All available-for-sale investments have contractual maturities of less than one year. During the years ended December 31, 2021 and 2020, there were no transfers in or out of Level 3.

Investments Debt And Equity Securities [Abstract]

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

Investments

12 Months Ended

Dec. 31, 2021

Investments

4. Investments

As of December 31, 2021 and 2020, the fair value of available-for-sale investments by type of security was as follows:


	December 31, 2021
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Investments:
Commercial paper	$	33,976	$	—	$	(7	)	$	33,969
Corporate notes		6,368		—		(2	)		6,366
Treasury bills		2,002		—		(4	)		1,998
	$	42,346	$	—	$	(13	)	$	42,333


	December 31, 2020
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Investments:
Agency Bonds	$	3,511	$	—	$	—	$	3,511
Commercial paper		1,999		—		—		1,999
Treasury bills		1,249		—		—		1,249
	$	6,759	$	—	$	—	$	6,759

Property and Equipment, Net

12 Months Ended

Dec. 31, 2021

Property Plant And Equipment [Abstract]

Property and Equipment, Net

5. Property and Equipment, Net

Property and equipment, net consisted of the following:


	December 31,
	2021			2020
Computer equipment and software	$	340		$	181
		340			181
Less: Accumulated depreciation and amortization		(212	)		(166	)
	$	128		$	15

Depreciation and amortization expense for the years ended December 31, 2021 and 2020 was $121 and $163, respectively. During the year ended December 31, 2021, the Company received payment for disposed, fully depreciated assets, resulting in a gain on sale of $66. During the year ended December 31, 2020, assets with a cost of $640 were disposed of for $208 in proceeds, resulting in a gain on sale of $86.

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2021

Payables And Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

6. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	December 31, 2021		December 31, 2020
External research and development services	$	1,575	$	896
Payroll and payroll-related costs		1,182		922
Professional fees		388		135
Other		60		243
	$	3,205	$	2,196

Paycheck Protection Loan

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

Paycheck Protection Loan

7. Paycheck Protection Loan

On April 30, 2020, the Company received loan proceeds in the amount of approximately $384 under the Paycheck Protection Program (“PPP”). The PPP, established as part of the Coronavirus Aid, Relief and Economic Security Act (“CARES Act”), provides for loans to qualifying businesses for amounts up to 2.5 times of the average monthly payroll expenses of the qualifying business. The loan and accrued interest are forgivable after eight weeks if the borrower uses the loan proceeds for eligible purposes, including payroll, benefits, rent and utilities. The amount of loan forgiveness may be reduced if the borrower terminates employees or reduces salaries during the eight-week period. The unforgiven portion of the PPP loan is payable over two years at an interest rate of 1%, with a deferral of payments for the first six months. The Company used the proceeds for purposes consistent with the PPP.

The Company determined to account for the PPP loan as debt under Accounting Standards Update (“ASC 470”), “Debt”, and allocated and recorded the loan proceeds between current and non-current liabilities.

On May 20, 2021 the Small Business Administration notified the Company that the PPP loan had been forgiven in full. During the year ended December 31, 2021 the Company recognized income for debt extinguishment pursuant to ASC 470-50-15-4 as other income.

Preferred Stock

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Preferred Stock

8. Preferred Stock

On July 5, 2017, in connection with the closing of the Company’s IPO, the Company filed its restated certificate of incorporation, which authorizes the Company to issue up to 5,000,000 shares of preferred stock, $0.001 par value per share. As of December 31, 2021 and 2020, the Company had no shares of preferred stock issued or outstanding.

Common Stock

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Common Stock

9. Common Stock

On June 16, 2021, the Company filed a certificate of amendment to its restated certificate of incorporation which increased the authorized number of shares of common stock from 150,000,000 shares of $0.001 par value common stock to 300,000,000 shares of common stock.

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are entitled to receive dividends, as may be declared by the Company’s board of directors, if any, subject to the preferential dividend rights of the preferred stock. As of December 31, 2021 and 2020, no dividends had been declared.

On January 6, 2021, the Company entered into a securities purchase agreement with certain institutional investors, pursuant to which the Company issued and sold, in a registered direct offering (the “Offering”), an aggregate of 32,630,983 shares of common stock, $0.001 par value per share, at a purchase price per share of $1.10 (the “Shares”). The aggregate gross proceeds of the Offering were $35,894, before deducting $2,887 of fees payable to the placement agent and other offering expenses payable by the Company. The Offering closed on January 8, 2021.

Between January 1, 2021 and January 28, 2021, the Company issued and sold an aggregate 7,174,993 shares of its common stock pursuant to its sales agreement with JonesTrading Institutional Services LLC (“JonesTrading”), resulting in gross proceeds of $9,658, before deducting expenses of $290. The Company terminated its sales agreement with Jones Trading in January 2021.

On January 29, 2021, the Company entered into a Capital on Demand™ Sales Agreement (the “ATM Sales Agreement”) with JonesTrading and William Blair & Company, L.L.C. (“William Blair” and, collectively with JonesTrading, the “Agents”), pursuant to which the Company may offer and sell shares of its common stock having an aggregate offering price of up to $30,000 from time to time through or to the Agents (the “ATM Offering”). During the year ended December 31, 2021, the Company issued and sold an aggregate of 5,225,406 shares of its common stock pursuant to the ATM Sales Agreement, resulting in gross proceeds of $10,922 before deducting expenses of $329.

During the year ended December 31, 2021, the Company issued and sold an aggregate of 1,375,000 shares of its common stock to Lincoln Park Capital, LLC pursuant to a purchase agreement entered into between Lincoln Park Capital, LLC and the Company in September 2020, resulting in gross proceeds of $2,614. During the year ended December 31, 2020, the Company issued and sold 588,235 shares to LPC under the purchase agreement for proceeds of $500.

In June 2020, the Company issued and sold in an underwritten public offering an aggregate of 10,162,059 shares of common stock, including an additional 1,071,149 shares of common stock upon the partial exercise of an option of the underwriter to purchase additional shares, for a purchase price to the public of $1.10 per share. The Company received aggregate gross proceeds from the public offering of approximately $11,178, before deducting underwriting discounts and commissions and offering expenses of $932.

On April 2, 2019, the Company issued and sold in a private placement an aggregate of (i) 11,838,582 units, consisting of 11,838,582 shares of its common stock and associated warrants, or the common warrants, to purchase an aggregate of 11,838,582 shares of common stock, for a combined price of $2.01 per unit and (ii) 1,096,741 units, consisting of (a) pre-funded warrants to purchase 1,096,741 shares of our common stock and (b) associated common warrants to purchase 1,096,741 shares of common stock, for a combined price of $2.01 per unit. The pre-funded warrants had an exercise price of $0.01 per share and had no expiration. In July 2019, all outstanding pre-funded warrants were exercised for 1,096,741 shares of common stock. At December 31, 2021 there were 12,935,323 common warrants outstanding with an exercise price of $2.00 per share.

The Company has assessed the warrants for appropriate equity or liability classification and determined the warrants are freestanding instruments that do not meet the definition of a liability pursuant to ASC 480 and do not meet the definition of a derivative pursuant to ASC 815. The warrants are indexed to the Company’s common stock and meet all other conditions for equity classification under ASC 480 and ASC 815. Accordingly, the warrants are classified as equity and accounted for as a component of additional paid-in capital at the time of issuance.

As of December 31, 2021, the Company had reserved 11,029,308 shares for the exercise of outstanding stock options and grant of future awards under the Company’s stock incentive plans (see Note 10).

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

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Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Awards

12 Months Ended

Dec. 31, 2021

Stock-Based Awards

10. Stock-Based Awards

2021 Stock Incentive Plan

The Company’s 2021 Stock Incentive Plan (the “2021 Plan”) was approved by the Company’s stockholders on June 15, 2021 and became effective on June 16, 2021. Under the 2021 Plan, the Company may grant incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, awards of restricted stock units and other stock-based awards. The Company’s employees, officers, directors, consultants and advisors are eligible to receive awards under the 2021 Plan; however, incentive stock options may only be granted to employees. The 2021 Plan is administered by the board of directors or, at the discretion of the board of directors, by a committee of the board. The number of shares of common stock covered by options and the date those options become exercisable, type of options to be granted, exercise prices, vesting and other restrictions are determined at the discretion of the board of directors, or its committee if so delegated.

Stock options granted under the 2021 Plan with service-based vesting conditions generally vest over four years and may not have a duration in excess of ten years, although options have been granted with vesting terms of less than four years.

The total number of shares of common stock that may be issued under the 2021 Plan was 12,784,186 as of December 31, 2021, of which 7,934,686 shares remained available for grant. The Company initially reserved 12,500,000 shares of common stock, plus the number of shares of common stock subject to outstanding awards under the Company’s 2017 Stock Incentive Plan (the “2017 Plan”), and the Company’s 2016 Stock Incentive Plan (“the 2016 Plan”) and the Company’s 2006 Stock Incentive Plan, as amended (the “2006 Plan”) that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by the Company at their original issuance price pursuant to a contractual repurchase right up to 6,280,135 shares.

Shares that are expired, terminated, surrendered or canceled without having been fully exercised will be available for future awards. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards.

The exercise price for stock options granted may not be less than the fair market value of the common stock as of the date of grant.

2017 Stock Incentive Plan

The 2017 Plan was approved by the Company’s stockholders on June 16, 2017, and became effective on June 28, 2017. Under the 2017 Plan, the Company could grant incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, awards of restricted stock units and other stock-based awards. The Company’s employees, officers, directors, consultants and advisors were eligible to receive awards under the 2017 Plan; however, incentive stock options could only be granted to employees. The 2017 Plan is administered by the board of directors or, at the discretion of the board of directors, by a committee of the board. The number of shares of common stock covered by options and the date those options become exercisable, type of options granted, exercise prices, vesting and other restrictions were determined at the discretion of the board of directors, or its committee if so delegated.

Stock options granted under the 2017 Plan with service-based vesting conditions generally vest over four years and may not have a duration in excess of ten years, although options have been granted with vesting terms of less than four years. The exercise price for stock options granted may not be less than the fair market value of the common stock as of the date of grant.

As of the effective date of the 2021 Plan, the board of directors determined to grant no further awards under the 2017 Plan.

Shares that are expired, terminated, surrendered or canceled without having been fully exercised will be available for future awards under the 2021 Plan. In addition, shares of common stock that are tendered to the Company by a participant to exercise an award are added to the number of shares of common stock available for the grant of awards under the 2021 Plan.

2017 Employee Stock Purchase Plan

On June 16, 2017, the Company’s stockholders approved the 2017 Employee Stock Purchase Plan (the “2017 ESPP”), which became effective on June 28, 2017. A total of 150,000 shares of common stock were initially reserved for issuance under this plan. Under the 2017 ESPP, the number of shares of common stock that may be issued under the 2017 ESPP will automatically increase on each January 1, beginning with the fiscal year ending December 31, 2018 and continuing for each fiscal year until, and including, the fiscal year ending December 31, 2027, equal to the least of (i) 622,408 shares, (ii) 1% of the outstanding shares of common stock on such date and (iii) an amount determined by the Company’s board of directors. The compensation committee of the board of directors determined that the number of shares of common stock that may be issued under the 2017 ESPP would not be increased on January 1, 2020 or January 1, 2021. The Company has not issued any shares under the 2017 ESPP.

Stock Option Valuation

The assumptions that the Company used to determine the grant-date fair value of the stock options granted to employees and directors during the year ended December 31, 2021 and 2020 were as follows, presented on a weighted average basis:


	Year Ended December 31,
	2021			2020
Risk-free interest rate		0.96	%		1.17	%
Expected term (in years)		6.2			6.2
Expected volatility		91.0	%		76.0	%
Expected dividend yield		0	%		0	%

Stock Options

The following table summarizes the Company’s stock option activity since January 1, 2021:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding at December 31, 2020		4,665,586		$	2.39		8.1	$	622
Granted		5,371,900			1.30
Exercised		(113,040	)		0.62
Canceled		—			0.00
Forfeited		(358,557	)		1.23
Expired		(190,392	)		4.36
Outstanding at December 31, 2021		9,375,497		$	1.79		8.5	$	4

Options exercisable at December 31, 2021		2,944,622		$	2.89		6.9	$	4
Options vested and expected to vest at December 31, 2021		9,164,726		$	1.80		8.4	$	4
Options exercisable at December 31, 2020		2,377,533		$	3.28		7.6	$	197
Options vested and expected to vest at December 31, 2020		4,592,729		$	2.41		8.1	$	606

The weighted average grant-date fair value of stock options granted during the year ended December 31, 2021 and 2020 was $0.97 and $0.51, respectively.

The aggregate fair value of stock options that vested during the year ended December 31, 2021 and 2020 was $1,106 and $2,099, respectively.

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock. The aggregate intrinsic value of stock options exercised during the year ended December 31, 2021 and 2020 was $68 and $0, respectively.

Restricted Stock Units

The following table summarizes the Company’s restricted stock unit activity since December 31, 2020:


				Weighted-Average
				Grant Date
	Units			per Unit
Outstanding, non-vested at December 31, 2020		—		$	—
Issued		250,000			1.23
Vested		(250,000	)		—
Canceled/forfeited		—			—
Outstanding, non-vested at December 31, 2021		—			—

Stock-Based Compensation

The Company recorded stock-based compensation expense related to stock options and restricted stock units in the following expense categories of its statements of operations and comprehensive loss:


	Year Ended December 31,
	2021		2020
Research and development expenses	$	531	$	572
General and administrative expenses		1,729		1,321
	$	2,260	$	1,893

The Company used an estimated forfeiture rate of 2.43% to calculate its stock compensation expense for each of the years ended December 31, 2021 and 2020.

As of December 31, 2021, the Company had an aggregate of $5,120 of unrecognized stock-based compensation expense, which it expects to recognize over a weighted average period of 2.94 years.

Net Loss per Share

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Net Loss per Share

11. Net Loss per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Year Ended December 31,
	2021			2020
Numerator:
Net loss	$	(26,164	)	$	(21,157	)

Denominator:
Weighted average common shares outstanding—basic and diluted		88,806,763			34,866,690

Net loss per share attributable to common stockholders—basic and diluted	$	(0.29	)	$	(0.61	)

The Company’s potential dilutive securities, which include stock options as of December 31, 2021 and 2020, have been excluded from the computation of diluted net loss per share attributable to common stockholders whenever the effect of including them would be to reduce the net loss per share. In periods where there is a net loss, the weighted average number of shares of common stock outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The following potential shares of common stock, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2021		2020
Warrants to purchase common stock		12,935,323		12,935,323
Stock options to purchase common stock		9,375,497		4,665,586
Total		22,310,820		17,600,909

Commitments and Contingencies

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

12. Commitments and Contingencies

Operating Leases

285 Summer Street

On March 26, 2021, the Company entered into a lease agreement for office space located at 285 Summer Street, Boston, Massachusetts (the “285 Summer Street Lease”). Under the terms of the 285 Summer Street Lease, starting on April 1, 2021, the Company leases approximately 3,365 square feet of office space at $42.00 per square foot per year, or $141 per year in base rent, which is subject to scheduled annual rent increases plus certain operating expenses and taxes.

The Company accounted for this lease under ASC 842 using its initial two-year term through March 31, 2023. The Company classified this lease as an operating lease and recorded a right-of-use asset of $228 and lease liability of $228 on the effective date. The Company recognizes rent expense on a straight-line basis throughout the remaining term of the lease.

490 Arsenal Way

On April 4, 2018, the Company entered into a lease agreement for office and laboratory space located in a building (the “Building”) at 490 Arsenal Way, Watertown, Massachusetts (the “490 Arsenal Way Lease”). Under the terms of the 490 Arsenal Way Lease, starting on August 21, 2018, the Company leased approximately 18,768 square feet of office and laboratory space at $52.55 per square foot per year, or $986 per year in base rent, which is subject to scheduled annual rent increases plus certain operating expenses and taxes. The Company maintained $568 security deposit related to the 490 Arsenal Way Lease. Pursuant to the 490 Arsenal Way Lease, the landlord contributed an aggregate of $2,419 toward the cost of construction and tenant improvements for the Building.

The Company occupied the Building from August 21, 2018 through November 11, 2020 when the 490 Arsenal Way Lease was terminated. The Company accounted for this lease under ASC 842 using its initial eight-year term through August 31, 2026.

As part of its adoption of ASC 842, the Company de-recognized the building asset and corresponding financing obligation recorded on the Company’s consolidated balance sheets as of January 1, 2019, in accordance with the ASC 842 transition guidance. In applying the ASC 842 transition guidance, the Company classified this lease as an operating lease and recorded a right-of-use asset of $6,697 and lease liability of $5,401 on the effective date. The Company recognizes rent expense on a straight-line basis throughout the remaining term of the lease.

On November 11, 2020, the Company entered into a lease termination agreement with respect to its former corporate headquarters at 490 Arsenal Way, Watertown, Massachusetts. In connection with the lease termination the right of use assets and operating lease liabilities associated with the lease were derecognized. The derecognition of these assets and liabilities resulted in a charge of $823 in other income.

Summary of all lease costs recognized under ASC 842

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating leases for the year ended December 31, 2021 and 2020:


	Twelve Months Ended December 31, 2021			Twelve Months Ended December 31, 2020
Lease cost (1)
Operating lease cost	$	93		$	1,095
Total lease cost	$	93		$	1,095

Other Information
Cash paid for amounts included in the measurement of lease liabilities	$	82		$	884
Weighted average remaining lease term (in years)		1.3			—
Weighted average discount rate		12	%		—

(1)

Short-term lease costs and variable lease costs incurred by the Company for the twelve months ended December 31, 2021 and 2020 were not material.

As of December 31, 2021, future minimum commitments under ASC 842 under the Company’s operating leases were as follows:


	As of December 31, 2021
2022		141
2023 and thereafter		35
Total lease payments		176
Less: imputed interest		(14	)
Total operating lease liabilities	$	162

Intellectual Property Licenses

Harvard and Dana-Farber Agreement

In August 2006, the Company entered into an exclusive license agreement with President and Fellows of Harvard College (“Harvard”) and Dana-Farber Cancer Institute (“DFCI”). The agreement granted the Company an exclusive worldwide license, with the right to sublicense, under specified patents and patent applications to develop, obtain regulatory approval for and commercialize specified product candidates based on cell-permeating peptides. Under the agreement, the Company is obligated to use commercially reasonable efforts to develop and commercialize one or more licensed products and to achieve specified milestone events by specified dates. In connection with entering into the agreement, the Company paid an upfront license fee and issued to Harvard and DFCI shares of its common stock.

In February 2010, the agreement was amended and restated (the “Harvard/DFCI agreement”) under which additional patent rights were added to the scope of the license agreement and the annual license maintenance fees were increased. Under the Harvard/DFCI agreement, the Company is obligated to make aggregate milestones payments of up to $7,700 per licensed therapeutic product upon the Company’s achievement of specified clinical, regulatory and sales milestones with respect to such product and up to $700 per licensed diagnostic product upon the Company’s achievement of specified regulatory and sales milestones with respect to such product. In addition, the Company is obligated to pay royalties of low single-digit percentages on annual net sales of licensed products sold by the Company, its affiliates or its sublicensees. The royalties are payable on a product-by-product and country-by-country basis and may be reduced in specified circumstances. In addition, the agreement obligates the Company to pay a percentage, up to the mid-twenties, of fees received by the Company in connection with its sublicense of the licensed products. In accordance with the terms of the agreement, the Company’s sublicense payment obligations may be subject to specified reductions.

The Harvard/DFCI agreement requires the Company to pay annual license maintenance fees of $145 each year. Any payments made in connection with the annual license maintenance fees will be credited against any royalties due.

The Company incurred license fees of $145 during each of the years ended December 31, 2021 and 2020. In addition, the Company did not make any milestone payments during the years ended December 31, 2021 and 2020. During the years ended December 31, 2021 and 2020, no milestones were achieved and no liabilities for milestone payments were recorded in the Company’s financial statements. From 2010 through December 31, 2021 and December 31, 2020, the Company had made non-refundable cash payments, consisting of license and maintenance fees, milestone payments and sublicense fees, totaling $5,008 and $4,863, respectively.

As of December 31, 2021, the Company had not developed a commercial product using the licensed technologies and no royalties under the agreement had been paid or were due.

Under the Harvard/DFCI agreement, the Company is responsible for all patent expenses related to the prosecution and maintenance of the licensed patents and applications in-licensed under the agreement as well as cost reimbursement of amounts incurred for all documented patent-related expenses. The agreement will expire on a product-by-product and country-by-country basis upon the last to expire of any valid patent claim pertaining to licensed products covered under the agreement.

Umicore Agreement

In December 2006, the Company entered into a license agreement with Materia, Inc. (“Materia”), under which it was granted a non-exclusive worldwide license, with the right to sublicense, under specified patent and patent applications to utilize Materia’s catalysts to develop, obtain regulatory approval for and commercialize specified peptides owned or controlled by Materia and the right to manufacture specified compositions owned or controlled by Materia. In February 2017, Materia assigned the license agreement (the “Umicore agreement”) to Umicore Precious Metals Chemistry USA, LLC (“Umicore”), and Umicore agreed to continue to supply the Company under the agreement.

Under the Umicore agreement, the Company is obligated to make aggregate milestone payments to Umicore of up to $6,400 upon the Company’s achievement of specified clinical, regulatory and sales milestones with respect to each licensed product. In addition, the Company is obligated to pay tiered royalties ranging in the low single-digit percentages on annual net sales of licensed products sold by the Company or its sublicensees. The royalties are payable on a product-by-product and country-by-country basis, and may be reduced in specified circumstances.

The Umicore agreement requires the Company to pay annual license fees of $50. The Company incurred license fees of $50 during each of the years ended December 31, 2021 and 2020. The Company did not make any milestone payments during the years ended December 31, 2021 and 2020. During the year ended December 31, 2021, no milestones were achieved and no liabilities for additional milestone payments were recorded in the Company’s financial statements.

The agreement expires upon the expiration of the Company’s obligation to pay royalties in each territory covered under the agreement.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors and officers that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it had not accrued any liabilities related to such obligations in its financial statements as of December 31, 2021 or December 31, 2020.

Income Taxes

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Income Taxes

13. Income Taxes

There is no provision for income taxes because the Company has historically incurred operating losses and maintains a full valuation allowance against its net deferred tax assets. The reported amount of income tax expense for the years differs from the amount that would result from applying domestic federal statutory tax rates to pretax losses primarily because of changes in valuation allowance.

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended
	December 31,
	2021			2020
Federal statutory income tax rate		(21.0	)%		(21.0	)%
State taxes, net of federal benefit		(6.4	)		(5.9	)
Research and development tax credits		(2.7	)		(2.6	)
Other permanent items		0.5			0.6
Change in deferred tax asset valuation allowance		29.6			28.9
Effective income tax rate		—	%		—	%

Net deferred tax assets as of December 31, 2021 and 2020 consisted of the following:


	December 31,
	2021			2020
Deferred tax assets:
Net operating loss carryforwards	$	61,934		$	55,229
Research and development tax credit carryforwards		5,725			4,979
Capitalized research and development expenses		52			57
Accrued expenses and reserves		290			265
Depreciation and amortization		445			462
Lease Liability		44			—
Stock compensation		1,231			940
Total deferred tax assets		69,721			61,932
Valuation allowance		(69,680	)		(61,932	)
Net deferred tax assets	$	41		$	—
Deferred Tax Liabilities:
Right of Use Asset	$	(41	)		—
Total Deferred Tax Liabilities	$	(41	)	$	—
Net Deferred Tax Asset (Liability)	$	—		$	—

Since inception in 2001, the Company has not recorded any U.S. federal or state income tax benefits for the net losses the Company has incurred in any year or for its earned research and development tax credits, due to its uncertainty of realizing a benefit from those items. As of December 31, 2021, the Company had net operating loss carryforwards for federal and state purposes of $228,215 and $221,656, respectively. $129,596 of the U.S. federal tax operating loss carryforwards will begin to expire in 2029. Approximately $98,619 of the U.S. federal tax operating losses can be carried forward indefinitely. The state tax operating loss carryforwards expire beginning in 2030. As of December 31, 2021, the Company also had available research and development tax credit carryforwards for federal and state income tax purposes of $2,655 and $1,823, respectively, which begin to expire in 2025. As of December 31, 2021, the Company also had available orphan drug credit carryforwards of $1,631 for federal income tax purposes, which begin to expire in 2039.

Utilization of the net operating loss carryforwards and research and development tax credit carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership changes that have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain shareholders or public groups in the stock of a corporation by more than 50% over a three-year period. The Company has not conducted a study to assess whether a change of control has occurred or whether there have been multiple changes of control since inception due to the significant complexity and cost associated with such a study. If the Company has experienced a change of control, as defined by Section 382, at any time since inception, utilization of the net operating loss carryforwards or research and development tax credit carryforwards would be subject to an annual limitation under Section 382, which is determined by first multiplying the value of the Company’s stock at the time of the ownership change by the applicable long-term tax-exempt rate, and then could be subject to additional adjustments, as required. Any limitation may result in expiration of a portion of the net operating loss carryforwards or research and development tax credit carryforwards before utilization. Further, until a study is completed and any limitation is known, no amounts are being presented as an uncertain tax position.

The Company has evaluated the positive and negative evidence bearing upon its ability to realize the deferred tax assets. Management has considered the Company’s cumulative net losses and its lack of commercialization of any products or generation of any revenue from product sales since inception and has concluded that it is more likely than not that the Company will not realize the benefits of the deferred tax assets. Accordingly, a full valuation allowance has been established against the net deferred tax assets as of December 31, 2021 and 2020. Management reevaluates the positive and negative evidence at each reporting period. The increase in the valuation allowance for deferred tax assets during the years ended December 31, 2021 and 2020 related primarily to the increase in net operating loss carryforwards. Changes in the valuation allowance were as follows:


	Year Ended
	December 31,
	2021			2020
Valuation allowance at beginning of year	$	(61,932	)	$	(55,825	)
Increases recorded to income tax provision		(7,748	)		(6,107	)
Valuation allowance at end of year	$	(69,680	)	$	(61,932	)

The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2021 or 2020.

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations. The Company’s tax years are still open under statute from 2017 to the present. Earlier years may be examined to the extent that tax credit or net operating loss carryforwards are used in future periods. The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. As of December 31, 2021 and 2020, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statements of operations and comprehensive loss

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

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Compensation And Retirement Disclosure [Abstract]

401(k) Plan

12 Months Ended

Dec. 31, 2021

401(k) Plan

14. 401(k) Plan

The Company has a 401(k) plan available for participating employees who meet certain eligibility requirements. Eligible employees may defer a portion of their salary as defined by the plan. The Company provides a safe harbor match with a maximum amount of 4.0% of the participant’s compensation, and vests 100% at time of match. The Company accrued approximately $94.3 for the estimated safe harbor matching contribution for the year ended December 31, 2021.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2021

Concentration of Credit Risk and of Significant Suppliers

The Company classifies its available-for-sale debt security investments as current assets on the balance sheet if they mature within one year from the balance sheet date.

Fair Value Measurements

•

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

•

Property and Equipment

Laboratory equipment

5 years

Computer equipment and software

Furniture and fixtures

3 to 5 years

7 years

Leases

Impairment of Long-Lived Assets

Research and Development Costs

Research Contract Costs and Accruals

Patent Costs

Accounting for Stock-Based Compensation

Income Taxes

Segment Data

Comprehensive Loss

Net Income (Loss) per Share

Risks and Uncertainties

Recently Issued Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2021

Schedule of Property and Equipment Estimated Useful Lives

Depreciation and amortization expense is recognized using the straight-line method over the following estimated useful lives:

Laboratory equipment

5 years

Computer equipment and software

Furniture and fixtures

3 to 5 years

7 years

Fair Value of Financial Assets (Tables)

12 Months Ended

Dec. 31, 2021

Fair Value Disclosures [Abstract]

Summary of Assets Measured at Fair Value on Recurring Basis


	Fair Value Measurements as of December 31, 2021 using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Money market funds	$	2,438	$	—	$	—	$	2,438
Investments:
Commercial paper		—		33,969		—		33,969
Corporate notes		—		6,366		—		6,366
Treasury bills		—		1,998		—		1,998
	$	2,438	$	42,333	$	—	$	44,771


	Fair Value Measurements as of December 31, 2020 using:
	Level 1		Level 2		Level 3		Total
Cash equivalents:
Commercial paper	$	—	$	1,001	$	—	$	1,001
Money market funds		4,190		—		—		4,190
Investments:
Agency bonds		—		3,511		—		3,511
Commercial paper		—		1,999		—		1,999
Treasury bills		—		1,249		—		1,249
	$	4,190	$	7,760	$	—	$	11,950

Investments (Tables)

12 Months Ended

Dec. 31, 2021

Investments Debt And Equity Securities [Abstract]

Summary of Fair Value of Available for Sale Investments

As of December 31, 2021 and 2020, the fair value of available-for-sale investments by type of security was as follows:


	December 31, 2021
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Investments:
Commercial paper	$	33,976	$	—	$	(7	)	$	33,969
Corporate notes		6,368		—		(2	)		6,366
Treasury bills		2,002		—		(4	)		1,998
	$	42,346	$	—	$	(13	)	$	42,333


	December 31, 2020
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Investments:
Agency Bonds	$	3,511	$	—	$	—	$	3,511
Commercial paper		1,999		—		—		1,999
Treasury bills		1,249		—		—		1,249
	$	6,759	$	—	$	—	$	6,759

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2021

Property Plant And Equipment [Abstract]

Summary of Property and Equipment, Net

Property and equipment, net consisted of the following:


	December 31,
	2021			2020
Computer equipment and software	$	340		$	181
		340			181
Less: Accumulated depreciation and amortization		(212	)		(166	)
	$	128		$	15

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2021

Payables And Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	December 31, 2021		December 31, 2020
External research and development services	$	1,575	$	896
Payroll and payroll-related costs		1,182		922
Professional fees		388		135
Other		60		243
	$	3,205	$	2,196

Stock-Based Awards (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Valuation Assumptions of Stock Options Granted


	Year Ended December 31,
	2021			2020
Risk-free interest rate		0.96	%		1.17	%
Expected term (in years)		6.2			6.2
Expected volatility		91.0	%		76.0	%
Expected dividend yield		0	%		0	%

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity since January 1, 2021:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(in years)
Outstanding at December 31, 2020		4,665,586		$	2.39		8.1	$	622
Granted		5,371,900			1.30
Exercised		(113,040	)		0.62
Canceled		—			0.00
Forfeited		(358,557	)		1.23
Expired		(190,392	)		4.36
Outstanding at December 31, 2021		9,375,497		$	1.79		8.5	$	4

Options exercisable at December 31, 2021		2,944,622		$	2.89		6.9	$	4
Options vested and expected to vest at December 31, 2021		9,164,726		$	1.80		8.4	$	4
Options exercisable at December 31, 2020		2,377,533		$	3.28		7.6	$	197
Options vested and expected to vest at December 31, 2020		4,592,729		$	2.41		8.1	$	606

Summary of Restricted Stock Unit Activity

The following table summarizes the Company’s restricted stock unit activity since December 31, 2020:


				Weighted-Average
				Grant Date
	Units			per Unit
Outstanding, non-vested at December 31, 2020		—		$	—
Issued		250,000			1.23
Vested		(250,000	)		—
Canceled/forfeited		—			—
Outstanding, non-vested at December 31, 2021		—			—

Summary of Stock Based Compensation Expense

The Company recorded stock-based compensation expense related to stock options and restricted stock units in the following expense categories of its statements of operations and comprehensive loss:


	Year Ended December 31,
	2021		2020
Research and development expenses	$	531	$	572
General and administrative expenses		1,729		1,321
	$	2,260	$	1,893

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2021

Earnings Per Share [Abstract]

Basic and Diluted Net Loss per Share Attributable to Common Stockholders

Basic and diluted net loss per share attributable to common stockholders was calculated as follows:


	Year Ended December 31,
	2021			2020
Numerator:
Net loss	$	(26,164	)	$	(21,157	)

Denominator:
Weighted average common shares outstanding—basic and diluted		88,806,763			34,866,690

Net loss per share attributable to common stockholders—basic and diluted	$	(0.29	)	$	(0.61	)

Summary of Potential Common Shares Excluded from Calculation of Diluted Net Loss per Share

The following potential shares of common stock, presented based on amounts outstanding at each period end, were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Year Ended December 31,
	2021		2020
Warrants to purchase common stock		12,935,323		12,935,323
Stock options to purchase common stock		9,375,497		4,665,586
Total		22,310,820		17,600,909

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2021

Commitments And Contingencies Disclosure [Abstract]

Summary of Lease Costs Recognized Under ASC 842 and Other Information Pertaining to Operating Leases

The following table contains a summary of the lease costs recognized under ASC 842 and other information pertaining to the Company’s operating leases for the year ended December 31, 2021 and 2020:


	Twelve Months Ended December 31, 2021			Twelve Months Ended December 31, 2020
Lease cost (1)
Operating lease cost	$	93		$	1,095
Total lease cost	$	93		$	1,095

Other Information
Cash paid for amounts included in the measurement of lease liabilities	$	82		$	884
Weighted average remaining lease term (in years)		1.3			—
Weighted average discount rate		12	%		—

(1)

Short-term lease costs and variable lease costs incurred by the Company for the twelve months ended December 31, 2021 and 2020 were not material.

Schedule of Future Minimum Commitments under ASC 842

As of December 31, 2021, future minimum commitments under ASC 842 under the Company’s operating leases were as follows:


	As of December 31, 2021
2022		141
2023 and thereafter		35
Total lease payments		176
Less: imputed interest		(14	)
Total operating lease liabilities	$	162

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of U.S. Federal Statutory Income Tax Rate to Effective Income Tax Rate

A reconciliation of the U.S. federal statutory income tax rate to the Company’s effective income tax rate is as follows:


	Year Ended
	December 31,
	2021			2020
Federal statutory income tax rate		(21.0	)%		(21.0	)%
State taxes, net of federal benefit		(6.4	)		(5.9	)
Research and development tax credits		(2.7	)		(2.6	)
Other permanent items		0.5			0.6
Change in deferred tax asset valuation allowance		29.6			28.9
Effective income tax rate		—	%		—	%

Schedule of Net Deferred Tax Assets

Net deferred tax assets as of December 31, 2021 and 2020 consisted of the following:


	December 31,
	2021			2020
Deferred tax assets:
Net operating loss carryforwards	$	61,934		$	55,229
Research and development tax credit carryforwards		5,725			4,979
Capitalized research and development expenses		52			57
Accrued expenses and reserves		290			265
Depreciation and amortization		445			462
Lease Liability		44			—
Stock compensation		1,231			940
Total deferred tax assets		69,721			61,932
Valuation allowance		(69,680	)		(61,932	)
Net deferred tax assets	$	41		$	—
Deferred Tax Liabilities:
Right of Use Asset	$	(41	)		—
Total Deferred Tax Liabilities	$	(41	)	$	—
Net Deferred Tax Asset (Liability)	$	—		$	—

Schedule of Changes in Valuation Allowance

Changes in the valuation allowance were as follows:


	Year Ended
	December 31,
	2021			2020
Valuation allowance at beginning of year	$	(61,932	)	$	(55,825	)
Increases recorded to income tax provision		(7,748	)		(6,107	)
Valuation allowance at end of year	$	(69,680	)	$	(61,932	)

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Proceeds from collaboration agreement	$ 34,910
Cash, cash equivalents and investments	45,933
Accumulated deficit	(245,456)	$ (219,292)
Common Stock [Member]
Class of Stock [Line Items]
Proceeds from sales of stock	145,467
Preferred Stock [Member]
Class of Stock [Line Items]
Proceeds from sales of stock	$ 131,211

The cumulative amount of the reporting entity's undistributed earnings or deficit.

+ References + Details

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 25	$ 593
Change in accounting principle, ASU, Adopted [true false]	true
Change in accounting principle, ASU, Adoption Date	Jan. 01, 2019
Accounting Standards Update [Extensible Enumeration]	us-gaap:AccountingStandardsUpdate201602RetrospectiveMember
Lease, Practical Expedients, Package [true false]	true
Security Deposit Related to Credit Card Accounts [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 25	25
Security Deposit Related to Lease Facility [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		$ 568

Indicates amendment to accounting standards.

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Summary of Significant Accounting Policies - Schedule of Property and Equipment Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2021
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, estimated useful lives	5 years
Computer Equipment and Software [Member] \| Minimum [Member]
Property Plant And Equipment [Line Items]
Property and equipment, estimated useful lives	3 years
Computer Equipment and Software [Member] \| Maximum [Member]
Property Plant And Equipment [Line Items]
Property and equipment, estimated useful lives	5 years
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property and equipment, estimated useful lives	7 years

Fair Value of Financial Assets - Summary of Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	$ 42,333	$ 6,759
Agency Bonds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments		3,511
Commercial Paper [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	33,969	1,999
Corporate Notes [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	6,366
Treasury Bills [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	1,998	1,249
Recurring [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	44,771	11,950
Recurring [Member] \| Agency Bonds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments		3,511
Recurring [Member] \| Commercial Paper [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	33,969	1,999
Recurring [Member] \| Corporate Notes [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	6,366
Recurring [Member] \| Treasury Bills [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	1,998	1,249
Recurring [Member] \| Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	2,438	4,190
Recurring [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	42,333	7,760
Recurring [Member] \| Level 2 [Member] \| Agency Bonds [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments		3,511
Recurring [Member] \| Level 2 [Member] \| Commercial Paper [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	33,969	1,999
Recurring [Member] \| Level 2 [Member] \| Corporate Notes [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	6,366
Recurring [Member] \| Level 2 [Member] \| Treasury Bills [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Investments	1,998	1,249
Commercial Paper [Member] \| Recurring [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents		1,001
Commercial Paper [Member] \| Recurring [Member] \| Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents		1,001
Money Market Funds [Member] \| Recurring [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	2,438	4,190
Money Market Funds [Member] \| Recurring [Member] \| Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents	$ 2,438	$ 4,190

Fair Value of Financial Assets - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Available-for-sale investments, maximum contractual maturity period	1 year
Fair value, assets transfers from Level 1 to Level 2	$ 0	$ 0
Fair value, assets transfers from Level 2 to Level 1	0	0
Fair Value, assets transfers into (out of) Level 3	$ 0	$ 0

Investments - Summary of Fair Value of Available for Sale Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	$ 42,346	$ 6,759
Investments, Gross Unrealized Loss	(13)
Investments, Fair Value	42,333	6,759
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost		3,511
Investments, Fair Value		3,511
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	33,976	1,999
Investments, Gross Unrealized Loss	(7)
Investments, Fair Value	33,969	1,999
Corporate Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	6,368
Investments, Gross Unrealized Loss	(2)
Investments, Fair Value	6,366
Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Investments, Amortized Cost	2,002	1,249
Investments, Gross Unrealized Loss	(4)
Investments, Fair Value	$ 1,998	$ 1,249

Property and Equipment, Net - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 340	$ 181
Less: Accumulated depreciation and amortization	(212)	(166)
Property, plant and equipment, net	128	15
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Property, plant and equipment, gross	$ 340	$ 181

Property and Equipment, Net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Depreciation and amortization expense	$ 121	$ 163
Proceeds from property and equipment	66	208
Gain on sale of property and equipment	66	86
Fully Depreciated Assets [Member]
Property Plant And Equipment [Line Items]
Disposal of property and equipment		640
Proceeds from property and equipment		208
Gain on sale of property and equipment	$ 66	$ 86

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
External research and development services	$ 1,575	$ 896
Payroll and payroll-related costs	1,182	922
Professional fees	388	135
Other	60	243
Total accrued expenses and other current liabilities	$ 3,205	$ 2,196

Paycheck Protection Loan - Additional Information (Detail) - Paycheck Protection Program CARES Act [Member] $ in Thousands		12 Months Ended
	Apr. 30, 2020 USD ($)	Dec. 31, 2021
Debt Instrument [Line Items]
Proceeds from loan	$ 384
Number of times for loans to qualifying businesses average monthly payroll costs	2.5
Term of unforgiven portion of loan	2 years
Interest rate	1.00%
Term of deferral payments	6 months
Debt instrument, description		The PPP, established as part of the Coronavirus Aid, Relief and Economic Security Act (“CARES Act”), provides for loans to qualifying businesses for amounts up to 2.5 times of the average monthly payroll expenses of the qualifying business. The loan and accrued interest are forgivable after eight weeks if the borrower uses the loan proceeds for eligible purposes, including payroll, benefits, rent and utilities. The amount of loan forgiveness may be reduced if the borrower terminates employees or reduces salaries during the eight-week period. The unforgiven portion of the PPP loan is payable over two years at an interest rate of 1%, with a deferral of payments for the first six months. The Company used the proceeds for purposes consistent with the PPP
Minimum [Member]
Debt Instrument [Line Items]
Term of loan and accrued interest forgivable	56 days

Preferred Stock - Additional Information (Detail) - $ / shares	Dec. 31, 2021	Dec. 31, 2020	Jul. 05, 2017
Equity [Abstract]
Preferred stock, shares authorized	5,000,000	5,000,000	5,000,000
Preferred stock, par value	$ 0.001	$ 0.001	$ 0.001
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Common Stock - Additional Information (Detail) - USD ($)				1 Months Ended			12 Months Ended
	Jan. 29, 2021	Jan. 06, 2021	Apr. 02, 2019	Jan. 28, 2021	Jun. 30, 2020	Jul. 31, 2019	Dec. 31, 2021	Dec. 31, 2020
Class of Stock [Line Items]
Common stock, shares authorized							300,000,000	150,000,000
Common stock, par value							$ 0.001	$ 0.001
Common stock, dividends declared							$ 0	$ 0
Stock reserved for future issuance							11,029,308
Stock issued during period, value							$ 59,088,000	$ 16,897,000
Common and Pre-funded Warrants [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold			1,096,741
Pre-funded Warrants [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold			1,096,741
Warrants outstanding exercised						1,096,741
Warrants exercise price			$ 0.01
Common Stock [Member]
Class of Stock [Line Items]
Gross proceeds from common stock shares issued and sold							145,467,000
Stock issued during period, value							$ 46,000	$ 16,000
Stock issued during period, shares							46,406,382	15,961,193
Common Warrants [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold			1,096,741
Warrants outstanding							12,935,323
Warrants exercise price							$ 2.00
Common Warrants [Member] \| Common and Pre-funded Warrants [Member]
Class of Stock [Line Items]
Purchase price per share			$ 2.01
Underwritten Public Offering [Member]
Class of Stock [Line Items]
Purchase price per share					$ 1.10
Stock issued during period, shares					10,162,059
Additional shares of common stock issued upon partial exercise of option					1,071,149
Gross proceeds from issuance of common stock					$ 11,178,000
Discounts, commissions and offering expenses					$ 932,000
Private Placement [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold			11,838,582
Private Placement [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold			11,838,582
Private Placement [Member] \| Common Warrants [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold			11,838,582
Purchase price per share			$ 2.01
Securities Purchase Agreement [Member] \| Direct Public Offering [Member]
Class of Stock [Line Items]
Common stock, par value		$ 0.001
Aggregate number of common stock shares issued and sold		32,630,983
Gross proceeds from common stock shares issued and sold		$ 35,894,000
Expenses fees payable		$ 2,887,000
Securities Purchase Agreement [Member] \| Direct Public Offering [Member] \| Common Stock [Member]
Class of Stock [Line Items]
Purchase price per share		$ 1.10
Offering closed date		Jan. 08, 2021
ATM Sales Agreement [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold							5,225,406
Expenses fees payable							$ 329,000
Gross proceeds from common stock shares issued and sold							$ 10,922,000
ATM Sales Agreement [Member] \| Jones Trading Institutional Services LLC and William Blair & Company, LLC [Member] \| Maximum [Member]
Class of Stock [Line Items]
Stock issued during period, value	$ 30,000,000
Sales Agreement [Member] \| Jones Trading Institutional Services LLC [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold				7,174,993
Expenses fees payable				$ 290,000
Gross proceeds from common stock shares issued and sold				$ 9,658,000
Purchase Agreement [Member] \| Lincoln Park Capital, LLC [Member]
Class of Stock [Line Items]
Aggregate number of common stock shares issued and sold							1,375,000	588,235
Gross proceeds from common stock shares issued and sold							$ 2,614,000	$ 500,000

Stock-Based Awards - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
	Jan. 01, 2021	Jan. 01, 2020	Jun. 16, 2017	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock reserved for future issuance				11,029,308
Options granted				5,371,900
Options granted, weighted average exercise price per share				$ 1.30
Weighted average grant-date fair value of stock options				$ 0.97	$ 0.51
Aggregate fair value of stock options vested				$ 1,106	$ 2,099
Aggregate intrinsic value of stock options exercised				$ 68	$ 0
Share based compensation expense estimated forfeiture rate				2.43%	2.43%
Aggregate unrecognized stock-based compensation expense				$ 5,120
Unrecognized stock-based compensation expense, weighted average period expects for recognition				2 years 11 months 8 days
2021 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock option granted vesting period				4 years
Number of shares, available for grant				12,784,186
Number of shares remained available for grant				7,934,686
2017 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock option granted vesting period				4 years
Stock reserved for future issuance				12,500,000
2017 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Number of shares, available for grant				0
Stock reserved for future issuance			150,000
Maximum annual increase in common stock reserved for future issuance			622,408
Percentage of common stock shares outstanding			1.00%
Increase to shares authorized for issuance	0	0
Stock incentive plan description				On June 16, 2017, the Company’s stockholders approved the 2017 Employee Stock Purchase Plan (the “2017 ESPP”), which became effective on June 28, 2017. A total of 150,000 shares of common stock were initially reserved for issuance under this plan. Under the 2017 ESPP, the number of shares of common stock that may be issued under the 2017 ESPP will automatically increase on each January 1, beginning with the fiscal year ending December 31, 2018 and continuing for each fiscal year until, and including, the fiscal year ending December 31, 2027, equal to the least of (i) 622,408 shares, (ii) 1% of the outstanding shares of common stock on such date and (iii) an amount determined by the Company’s board of directors. The compensation committee of the board of directors determined that the number of shares of common stock that may be issued under the 2017 ESPP would not be increased on January 1, 2020 or January 1, 2021. The Company has not issued any shares under the 2017 ESPP.
2006 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Contractual repurchase right, shares				6,280,135
Maximum [Member] \| 2021 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock option granted vesting period				4 years
Stock option expiration period				10 years
Maximum [Member] \| 2017 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock option granted vesting period				4 years
Stock option expiration period				10 years

Stock-Based Awards - Valuation Assumptions of Stock Options Granted (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Risk-free interest rate	0.96%	1.17%
Expected term (in years)	6 years 2 months 12 days	6 years 2 months 12 days
Expected volatility	91.00%	76.00%
Expected dividend yield	0.00%	0.00%

Stock-Based Awards - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance	4,665,586
Number of Shares, Granted	5,371,900
Number of Shares, Exercised	(113,040)
Number of Shares, Forfeited	(358,557)
Number of Shares, Expired	(190,392)
Number of Shares, Ending balance	9,375,497	4,665,586
Number of Shares, Options exercisable	2,944,622	2,377,533
Number of Shares, Options vested and expected to vest	9,164,726	4,592,729
Weighted Average Exercise Price, Beginning balance	$ 2.39
Weighted Average Exercise Price, Granted	1.30
Weighted Average Exercise Price, Exercised	0.62
Weighted Average Exercise Price,Canceled	0.00
Weighted Average Exercise Price, Forfeited	1.23
Weighted Average Exercise Price, Expired	4.36
Weighted Average Exercise Price, Ending balance	1.79	$ 2.39
Weighted Average Exercise Price, Options exercisable	2.89	3.28
Weighted Average Exercise Price, Options vested and expected to vest	$ 1.80	$ 2.41
Weighted-Average Remaining Contractual Term, Outstanding	8 years 6 months	8 years 1 month 6 days
Weighted Average Remaining Contractual Term, Options exercisable	6 years 10 months 24 days	7 years 7 months 6 days
Weighted Average Remaining Contractual Term, Options vested and expected to vest	8 years 4 months 24 days	8 years 1 month 6 days
Aggregate Intrinsic Value	$ 4	$ 622
Aggregate Intrinsic Value, Options exercisable	4	197
Aggregate Intrinsic Value, Options vested and expected to vest	$ 4	$ 606

Stock-Based Awards - Summary of Restricted Stock Unit Activity (Detail) - 2017 Stock Incentive Plan [Member] - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2020 $ / shares shares
Units
Issued	250,000
Vested	(250,000)
Weighted-Average Grant Date per Unit
Issued \| $ / shares	$ 1.23

Stock-Based Awards - Summary of Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock-based compensation expense	$ 2,260	$ 1,893
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock-based compensation expense	531	572
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items
Stock-based compensation expense	$ 1,729	$ 1,321

Net Loss per Share - Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net loss	$ (26,164)	$ (21,157)
Denominator:
Weighted average common shares outstanding—basic and diluted	88,806,763	34,866,690
Net loss per share attributable to common stockholders—basic and diluted	$ (0.29)	$ (0.61)

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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