0000950170-22-023269 | 10-Q | XBRL Viewer

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Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2022	Nov. 01, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q3
Trading Symbol	AVRO
Entity Registrant Name	AVROBIO, INC.
Entity Central Index Key	0001681087
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		43,774,088
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Small Business	true
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-38537
Entity Tax Identification Number	81-0710585
Entity Address, Address Line One	100 Technology Square
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02139
City Area Code	617
Local Phone Number	914-8420
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Security Exchange Name	NASDAQ

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 115,968	$ 189,567
Restricted cash	492
Prepaid expenses and other current assets	9,773	9,578
Total current assets	126,233	199,145
Property and equipment, net	3,223	4,126
Restricted Cash		492
Other assets	41	74
Total assets	129,497	203,837
Current liabilities:
Accounts payable	1,814	3,486
Accrued expenses and other current liabilities	14,327	15,638
Deferred rent	51	262
Total current liabilities	16,192	19,386
Note payable, net of discount	15,205	14,945
Deferred rent, net of current portion	10	30
Total liabilities	31,407	34,361
Commitments and contingencies (Note 6)
Stockholders’ equity:
Common stock, $0.0001 par value; 150,000 shares authorized; 43,773 and 43,652 shares issued and outstanding as of September 30, 2022 and December 31, 2021, respectively	4	4
Additional paid-in capital	562,484	553,014
Accumulated deficit	(464,398)	(383,542)
Total stockholders’ equity	98,090	169,476
Total liabilities and stockholders’ equity	$ 129,497	$ 203,837

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, authorized	150,000,000	150,000,000
Common stock, issued	43,773,000	43,652,000
Common stock, outstanding	43,773,000	43,652,000

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Operating expenses:
Research and development	$ 15,919	$ 23,043	$ 54,049	$ 64,114
General and administrative	7,066	9,577	26,128	26,765
Total operating expenses	22,985	32,620	80,177	90,879
Loss from operations	(22,985)	(32,620)	(80,177)	(90,879)
Other (expense) income:
Interest income (expense), net	111	2	(544)	21
Other (expense) income, net	(95)	5	(135)	(41)
Total other income (expense), net	16	7	(679)	(20)
Net loss and comprehensive loss	$ (22,969)	$ (32,613)	$ (80,856)	$ (90,899)
Net loss per share - basic	$ (0.52)	$ (0.75)	$ (1.85)	$ (2.13)
Net loss per share - diluted	$ (0.52)	$ (0.75)	$ (1.85)	$ (2.13)
Weighted-average number of common shares outstanding - basic	43,773	43,623	43,722	42,588
Weighted-average number of common shares outstanding - diluted	43,773	43,623	43,722	42,588

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At The Market Facility Member	Common Stock [Member]	Common Stock [Member] At The Market Facility Member	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] At The Market Facility Member	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2020	$ 254,344		$ 4		$ 518,756		$ (264,416)
Beginning balance, shares at Dec. 31, 2020			41,569,000
Stock-based compensation expense	14,494				14,494
Exercise of stock options, shares			206,000
Exercise of stock options	872				872
Issuance of common stock under ATM facility, net of offering costs of $67, shares				1,829,000
Issuance of common stock under ATM facility, net of offering costs of $67		$ 14,550				$ 14,550
Issuance of common stock under 2018 employee stock purchase plan	208				208
Issuance of common stock under 2018 employee stock purchase plan, shares			28,000
Net loss	(90,899)						(90,899)
Ending balance at Sep. 30, 2021	193,569		$ 4		548,880		(355,315)
Ending balance, shares at Sep. 30, 2021			43,632,000
Beginning balance at Jun. 30, 2021	220,992		$ 4		543,690		(322,702)
Beginning balance, shares at Jun. 30, 2021			43,623,000
Stock-based compensation expense	5,168				5,168
Exercise of stock options, shares			9,000
Exercise of stock options	22				22
Net loss	(32,613)						(32,613)
Ending balance at Sep. 30, 2021	193,569		$ 4		548,880		(355,315)
Ending balance, shares at Sep. 30, 2021			43,632,000
Beginning balance at Dec. 31, 2021	169,476		$ 4		553,014		(383,542)
Beginning balance, shares at Dec. 31, 2021			43,652,000
Stock-based compensation expense	$ 9,267				9,267
Exercise of stock options, shares	0
Issuance of common stock under 2018 employee stock purchase plan	$ 203				203
Issuance of common stock under 2018 employee stock purchase plan, shares			121,000
Net loss	(80,856)						(80,856)
Ending balance at Sep. 30, 2022	98,090		$ 4		562,484		(464,398)
Ending balance, shares at Sep. 30, 2022			43,773,000
Beginning balance at Jun. 30, 2022	118,343		$ 4		559,768		(441,429)
Beginning balance, shares at Jun. 30, 2022			43,696,000
Stock-based compensation expense	2,656				2,656
Issuance of common stock under 2018 employee stock purchase plan	60				60
Issuance of common stock under 2018 employee stock purchase plan, shares			77,000
Net loss	(22,969)						(22,969)
Ending balance at Sep. 30, 2022	$ 98,090		$ 4		$ 562,484		$ (464,398)
Ending balance, shares at Sep. 30, 2022			43,773,000

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Statement of Stockholders' Equity [Abstract]
Issuance of common stock upon public offering, offering costs	$ 67

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Cash flows from operating activities:
Net loss	$ (80,856)	$ (90,899)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	9,267	14,494
Depreciation and amortization expense	1,105	963
Non-cash interest expense	260	0
Loss on disposal of property and equipment	59	0
Deferred rent expense	(231)	(159)
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(195)	(2,729)
Other assets	33	352
Accounts payable	(1,672)	284
Accrued expenses and other current liabilities	(1,305)	5,566
Net cash used in operating activities	(73,535)	(72,128)
Cash flows from investing activities:
Purchases of property and equipment	(267)	(1,611)
Net cash used in investing activities	(267)	(1,611)
Cash flows from financing activities:
Proceeds from exercise of stock options	0	872
Proceeds from issuance of common stock, net of offering costs	0	(204)
Net cash provided by financing activities	203	15,426
Net decrease in cash, cash equivalents and restricted cash	(73,599)	(58,313)
Cash, cash equivalents and restricted cash at beginning of period	190,059	260,174
Restricted cash	492
Cash, cash equivalents and restricted cash at end of period	116,460	201,861
Supplemental disclosure of non-cash investing and financing activities:
Purchases of property and equipment included in accounts payable and accrued expenses	0	507
Interest paid	1,002	0
Reconciliation of cash, cash equivalents and restricted cash reported within the condensed consolidated balance sheets:
Cash and cash equivalents, end of period	115,968	201,369
Restricted cash	492	492
Cash, cash equivalents and restricted cash at end of period	116,460	201,861
At The Market Facility [Member]
Cash flows from financing activities:
Proceeds from issuance of common stock, net of offering costs	0	14,550
ESPP [Member]
Cash flows from financing activities:
Proceeds from issuance of common stock, net of offering costs	$ 203	$ 208

Nature of the Business

9 Months Ended

Sep. 30, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Nature of the Business

1. Nature of the Business

AVROBIO, Inc. (the “Company” or “AVROBIO”) is a clinical-stage gene therapy company focused on developing potentially curative hematopoietic stem cell (“HSC”) gene therapies to treat rare diseases following a single dose treatment regimen.

The Company is subject to risks and uncertainties common to clinical-stage companies in the biotechnology industry, including but not limited to, risks associated with completing preclinical studies and clinical trials, developing and scaling a clinical and commercial supply chain, receiving regulatory approvals for product candidates, development by competitors of new biopharmaceutical products, dependence on key personnel, protection of proprietary technology, compliance with government regulations and the ability to secure additional capital to fund operations. Product candidates currently under development 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 and infrastructure and extensive compliance-reporting capabilities. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will realize revenue from product sales.

The Company has incurred recurring losses since its inception, including net losses of $80,856 and $90,899 for the nine months ended September 30, 2022 and 2021, respectively. In addition, as of September 30, 2022, the Company had an accumulated deficit of $464,398. The Company has primarily funded these losses through the proceeds from sales of common and preferred stock. In addition, in November 2021 the Company entered into the Loan Agreement (as defined below). Although the Company has incurred recurring losses and expects to continue to incur losses for the foreseeable future, the Company expects that its existing cash and cash equivalents on hand as of September 30, 2022 of $115,968 will be sufficient to fund current planned operations and capital expenditure requirements for at least the next twelve months from the filing date of this Quarterly Report on Form 10-Q with the Securities and Exchange Commission (“SEC”). However, the future viability of the Company is dependent on its ability to raise additional capital to finance its operations. The Company’s inability to raise capital as and when needed could have a negative impact on its financial condition and ability to pursue its business strategies. There can be no assurance that the current operating plan will be achieved or that additional funding will be available on terms acceptable to the Company, or at all.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2022

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying condensed consolidated financial statements (the “unaudited condensed consolidated financial statements”) have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”).

The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements as of and for the year ended December 31, 2021, and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2022, and the results of its operations for the three and nine months ended September 30, 2022 and 2021, its statements of stockholders’ equity for the three and nine months ended September 30, 2022 and 2021 and its statement of cash flows for the nine months ended September 30, 2022 and 2021.

The results for the three and nine months ended September 30, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022, any other interim periods, or any future year or period. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2021, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 17, 2022.

The unaudited condensed consolidated financial statements reflect the application of certain significant accounting policies as described below and elsewhere in these notes to the unaudited condensed consolidated financial statements. As of September 30, 2022, there have been no changes to the Company’s significant accounting policies as described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021.

Segment Information

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the chief executive officer (“CEO”). The Company and the CEO view the Company’s operations and manage its business as one operating segment. All material long-lived assets of the Company reside in the United States.

Use of Estimates

The preparation of the unaudited condensed consolidated financial statements in conformity with GAAP requires that the Company make estimates and judgments that may affect the reported amounts of assets, liabilities and expenses and the related disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ from these estimates. Changes in estimates are reflected in reported results in the period in which they become known.

Significant estimates relied upon in preparing the unaudited condensed consolidated financial statements include the determination of the fair value of share-based awards issued and the estimation of accrued research and development expenses.

Stock-based Compensation

For stock-based awards issued to employees and members of the Company’s board of directors (the “Board”) for their services on the Board, the Company measures the estimated fair value of the stock-based award on the date of grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. The Company issues stock-based awards with only service-based vesting conditions and records the expense for these awards using the straight-line method. The Company has not issued any stock-based awards with performance- or market-based vesting conditions. The Company accounts for forfeitures as they occur.

Prior to the adoption of Accounting Standards Update (“ASU”) No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, the measurement date for non-employee awards was generally the date the services are completed, resulting in financial reporting period adjustments to stock-based compensation during the vesting terms for changes in the fair value of the awards. After adoption of ASU 2018-07, the measurement date for non-employee awards is the later of the adoption date of ASU 2018-07, or the date of grant, without change in the fair value of the award. For stock-based awards granted to nonemployees subject to graded vesting that only contain service conditions, the Company has elected to recognize stock-based compensation expense using the straight-line recognition method.

The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s cash compensation costs are classified.

The fair value of each stock option award is estimated on the date of grant using the Black-Scholes option pricing model. As there was no public market for its common stock prior to June 21, 2018, which was the first day of trading, and as the trading history of the Company’s common stock was limited through December 31, 2021, the Company determined the volatility for awards granted up through December 31, 2021 based on an analysis of reported data for a group of guideline companies that issued options with substantially similar terms. Beginning with options granted in 2022, the Company estimates its expected stock volatility using a weighted-average calculation based on the historical volatility of the Company and publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. 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. The Company has not paid, and does not anticipate paying, cash dividends on its common stock; therefore, the expected dividend yield is assumed to be zero.

Emerging Growth Company Status

The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act, or JOBS Act, and may take advantage of certain exemptions from various reporting requirements applicable to other public companies, which are not emerging growth companies. The Company may take advantage of these exemptions until the Company is no longer an “emerging growth company.” Section 107 of the JOBS Act provides that an “emerging growth company” can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards and as a result of this election, its consolidated financial statements may not be comparable to companies that comply with public company effective dates. The Company may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of its IPO or such earlier time that it is no longer an “emerging growth company.”

Subsequent Event Considerations

The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the consolidated financial statements to provide additional evidence for certain estimates or to identify matters that require additional disclosure. Subsequent events have been evaluated as required.

Recently Issued Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, (Topic 842) Leases, or ASU 2016-02. ASU 2016-02 requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases. The ASU will also require new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. For public entities, ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2016-02 is effective for the Company for the year ended December 31, 2022, and all interim periods thereafter. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-02 will have on its consolidated financial statements. Based on this evaluation the Company currently expects that its operating lease commitments will be subject to the new standard and recognized as right-of-use assets and operating lease liabilities upon adoption of this standard, which will increase the Company’s total assets and total liabilities.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, or ASU 2016-13. ASU 2016-13 requires that credit losses be reported as an allowance using an expected losses model, representing the entity's current estimate of credit losses expected to be incurred. The accounting guidance currently in effect is based on an incurred loss model. For available-for-sale debt securities with unrealized losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. ASU 2016-13 is effective for non-EGCs for fiscal years beginning December 15, 2019 and interim periods within those fiscal years, and will be effective for the Company for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years, assuming the Company remains an EGC. Early adoption is permitted. The Company expects an immaterial impact to its financial statements.

In November 2019, the FASB issued ASU 2019-11, “Codification Improvements to Topic 326, Financial Instruments – Credit Losses,” or ASU 2019-11. ASU 2019-11 is an accounting pronouncement that amends ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” The amendments update guidance on reporting credit losses for financial assets. These amendments affect loans, debt securities, trade receivables, net investments in leases, off balance sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. The amendments in both ASU 2016-13 and ASU 2019-11 are effective for annual reporting periods beginning after December 15, 2019, including interim periods within those fiscal years. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, 2016-13 and ASU 2019-11 are effective for the Company for fiscal years beginning after December 15, 2022, and interim periods within those fiscal years. The Company is currently evaluating ASU 2016-13 and ASU 2019-11 and their impact on its consolidated financial statements and financial statement disclosures.

In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes, or ASU 2019-12. ASU 2019-12 eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. It also clarifies and simplifies other aspects of the accounting for income taxes. ASU 2019-12 is effective for non-EGCs for fiscal years beginning after December

15, 2020 and interim periods within those fiscal years and will be effective for the Company for fiscal years beginning after December 15, 2021 and interim periods beginning after December 15, 2022, assuming the Company remains an EGC. Early adoption is permitted. The Company is currently evaluating the effects the adoption of ASU 2019-12 may have on its financial statements.

License Agreements

9 Months Ended

Sep. 30, 2022

License Agreements [Abstract]

License Agreements

3. License Agreements

Agreement with The University of Manchester

On September 30, 2020, the Company entered into an agreement (“MPSII License Agreement”) with The University of Manchester, England (“UoM”), whereby UoM granted to the Company an exclusive worldwide license under certain patent and other intellectual property rights, subject to certain retained rights, to develop, commercialize and sell an ex vivo lentiviral gene therapy for use in the treatment of Hunter syndrome, or mucopolysaccharidosis type II. As consideration for the MPSII License Agreement, the Company agreed to pay UoM an upfront, one-time fee of $8,000, which was recognized as research and development expense during the year ended December 31, 2020.

As part of the agreement, the Company is obligated to make milestone payments of up to an aggregate of $80,000 upon the achievement of specified development and regulatory milestones, to pay royalties, on a product-by-product and country-by-country basis, of a mid-single digit percentage based on net sales of products licensed under the agreement and to pay a low double-digit percentage of any sublicense fees received by the Company. During the third quarter of 2022, a $2,000 milestone payment under the MPSII License Agreement became due following regulatory approval of the clinical trial application for the investigator-sponsored Phase 1/2 clinical trial sponsored by UoM, and the next anticipated payment milestone under the agreement is $4,000, upon the dosing of the first patient in the investigator-sponsored Phase 1/2 clinical trial sponsored by UoM.

Unless terminated earlier, the agreement expires upon the later of 15 years from the effective date or the expiration of the last valid claim of the licensed patents, subject to certain surviving rights and obligations. UoM and the Company can each terminate the agreement in the event of the bankruptcy or insolvency of the other party, or a material breach by the other party and failure to cure such breach within a certain period of time. UoM has the right to terminate the agreement in the event of certain actions relating to challenge or opposition to the licensed intellectual property brought by the Company or its affiliates or sublicensees.

Concurrently with the MPSII License Agreement, the Company entered into a collaborative research funding agreement with UoM (“CRFA”). Under the CRFA, the Company has agreed to fund the budgeted costs of an investigator-sponsored Phase 1/2 clinical trial to be sponsored by UoM in connection with the development activities under the MPSII License Agreement, which are currently expected to equal approximately £10,013 in the aggregate.

For the three months ended September 30, 2022 and 2021 the Company incurred $590 and $1,031, respectively, related to the CRFA. For the nine months ended September 30, 2022 and 2021 the Company incurred $1,970 and $1,832, respectively, related to the CRFA.

Agreements with University Health Network (“UHN”)

Fabry License Agreement—

On January 27, 2016, the Company entered into an agreement with UHN, pursuant to which UHN granted the Company an option to enter into an exclusive license under the UHN intellectual property related to Fabry disease in accordance with the pre-negotiated licensing terms. On November 4, 2016, the Company exercised its option and entered into a license agreement with UHN, pursuant to which UHN granted the Company an exclusive worldwide license under certain intellectual property rights and a non-exclusive worldwide license under certain know-how, in each case subject to certain retained rights, to develop, commercialize and sell products for use in the treatment of Fabry disease. In addition, for three years following the execution of the agreement, UHN granted the Company an exclusive option to obtain a license under certain improvements to the licensed intellectual property rights as well as an option to negotiate a license under certain other improvements.

Under this agreement, the Company paid an option fee of CAD $20, an upfront license fee of CAD $75, plus the annual license maintenance fee for the first year. Thereafter, the Company is also required to pay UHN future annual license maintenance fees until the first sale of a licensed product in certain markets. The Company is also obligated to make future milestone payments in an aggregate amount of up to CAD $2,450 upon the achievement of specified milestones as well as royalties on a country-by-country

basis of a low to mid-single-digit percentage of annual net sales of licensed products and a lower single-digit royalty percentage in certain circumstances. Additionally, the Company has agreed to pay a low double-digit royalty percentage of all sublicensing revenue.

The agreement requires the Company to meet certain performance milestones within specified timeframes. UHN may terminate the agreement if the Company fails to meet these performance milestones despite using commercially reasonable efforts and the Company is unable to reach agreement with UHN on revised timeframes. The Company’s royalty obligation expires on a licensed product-by-licensed product and country-by-country basis upon the latest to occur of the expiration or termination of the last valid claim under the licensed intellectual property rights in such country, the tenth anniversary of the first commercial sale of such licensed product in such country and the expiration of any applicable regulatory exclusivity in such country.

Unless terminated earlier, the agreement expires upon the expiration of the Company’s royalty obligation for all licensed products. UHN can terminate the agreement if the Company fails to make any payments within a specified period after receiving written notice of such failure, or in the event that the Company fails to obtain or maintain insurance. Either the Company or UHN may terminate the license agreement in the event of a material breach by the other party and failure to cure such breach within a certain period of time. The Company can voluntarily terminate the agreement with prior notice to UHN.

For the three months ended September 30, 2022 and 2021, the Company recorded research and development expense related to this agreement with UHN of $82 and $102, respectively, which consists of reimbursable funded study trial costs. For the nine months ended September 30, 2022 and 2021 the Company recorded research and development expense related to this agreement with UHN of $106 and $175, respectively, which consists of reimbursable funded study trial costs. No milestone or maintenance fees were incurred related to this agreement in the three and nine months ended September 30, 2022 and 2021.

Interleukin 12 License Agreement—

On January 27, 2016, the Company entered into an exclusive license agreement with UHN, pursuant to which UHN granted the Company a license to certain patent rights for the commercial development, manufacture, distribution and use of any products or processes resulting from development of those patent rights related to Interleukin 12. Upon execution of this agreement, the Company paid an upfront license fee of CAD $264. In addition, as part of the initial consideration for the license, the Company issued to UHN 1,161,665 shares of the Company’s common stock and agreed to pay UHN up to $2,000 upon the closing of an IPO if certain criteria are met. The fair value of the shares issued to UHN of $480 and the upfront fee was expensed upon the execution of the agreement. Upon the closing of the IPO in 2018, as the criteria were met, the Company paid UHN $2,000. The Company is also required to pay UHN future annual license maintenance fees of CAD $50 on each anniversary of the effective date of the license agreement prior to expiration or termination and potential future milestone payments of up to CAD $19,275 upon the achievement of specified clinical and regulatory milestones. The Company also agreed to pay UHN royalties of a low single-digit percentage of net sales of licensed products sold by the Company. If the Company grants any sublicense rights under the license agreement, the Company has agreed to pay UHN a low double-digit royalty percentage of any sublicense income received by the Company.

The agreement requires the Company to meet certain diligence requirements based upon specified milestones. The agreement expires on the later of the date the last patent rights expire in the last country or ten years from the date of first sale. UHN can terminate the agreement if the Company fails to make any payments within a specified period after receiving written notice of such failure, or in the event that the Company fails to obtain or maintain insurance. The Company can voluntarily terminate the agreement with prior notice to UHN. Either the Company or UHN may terminate the license agreement in the event of a material breach by the other party and failure to cure such breach within a certain period of time.

For the three months ended September 30, 2022 and 2021 the Company recorded no research and development expense related to this agreement with UHN. For the nine months ended September 30, 2022 and 2021 the Company recorded $39 for both periods, which consists of license maintenance fees. No milestone fees were incurred related to this agreement in the three and nine months ended September 30, 2022 and 2021.

Agreement with BioMarin Pharmaceutical Inc. (“BioMarin”)

On August 31, 2017, the Company entered into a license agreement with BioMarin, pursuant to which BioMarin granted the Company an exclusive worldwide license under certain intellectual property rights owned or controlled by BioMarin to develop, commercialize and sell products for use in the treatment of Pompe disease. The license agreement was amended in February 2018 and again in January 2020 to, among things, provide that BioMarin would supply the Company with certain technology materials. As consideration for this agreement, the Company paid an upfront license fee of $500 in cash and issued 233,765 shares of Series B Preferred Stock to BioMarin at the time of the Company’s Series B Preferred Stock financing in January 2018. The Company has a license agreement with BioMarin, pursuant to which BioMarin granted the Company an exclusive worldwide license under certain intellectual property rights owned or controlled by BioMarin to develop, commercialize and sell products for use in the treatment of Pompe disease. The Company is also obligated to make future milestone payments of up to $13,000 upon the achievement of certain specified milestones and agreed to pay BioMarin royalties of a low single-digit percentage of net sales of licensed products sold by the Company or its affiliates covered by patent rights in a relevant country.

The Company has recognized no expenses related to the license for the three and nine months ended September 30, 2022 and 2021.

Unless terminated earlier, the agreement expires upon the expiration of the Company’s royalty obligation for all licensed products throughout the world. BioMarin and the Company can terminate the agreement in the event of a material breach by the other party and failure to cure such breach within a certain period of time. The Company may terminate the agreement at will upon written notice to BioMarin. BioMarin has the right to terminate the agreement upon the Company’s bankruptcy or insolvency, or in the event of any challenge or opposition to the licensed patent rights or related actions brought by the Company or its affiliates or sublicensees, or if the Company, its affiliates or sublicensees knowingly assist a third-party in challenging or otherwise opposing the licensed patent rights, except as required under a court order or subpoena.

Agreement with Papillon Therapeutics, Inc. (previously GenStem Therapeutics, Inc.)

On October 2, 2017, the Company entered into a license agreement with GenStem Therapeutics, Inc. (“GenStem”), pursuant to which GenStem granted the Company an exclusive worldwide license, subject to certain retained rights, under certain intellectual property rights owned or controlled by GenStem to develop, commercialize and sell products for use in the treatment of cystinosis. Under this agreement, the Company paid an upfront license fee of $1,000 and is required to make payments upon completion of certain milestones up to an aggregate of $16,000. The Company also agreed to pay GenStem a tiered mid to high single-digit royalty percentage on annual net sales of licensed products as well as a low double-digit percentage of sublicense income received from certain third-party licensees. The Company’s royalty obligation expires on a licensed product-by-licensed product and country-by-country basis on the eleventh anniversary of the first commercial sale of such licensed product in such country or the expiration of the last valid claim under the licensed patent rights covering such licensed product in such country, whichever is later. Unless terminated earlier, the agreement expires upon the expiration of the Company’s royalty obligation for all licensed products throughout the world. GenStem and the Company can terminate the agreement in the event of a material breach by the other party and failure to cure such breach within a certain period of time. The Company may terminate the agreement at will upon the specified prior written notice to GenStem. In October 2021, the Company received notice that the license agreement with GenStem had been assigned to Papillon Therapeutics, Inc. (“Papillon”).

The Company has recognized no expenses related to this agreement for the three and nine months ended September 30, 2022 and 2021.

Agreement with Lund University Rights Holders

On November 17, 2016, the Company entered into a license agreement with affiliates of Lund University, along with certain other relevant rights holders that may be added from time to time, pursuant to which such rights holders granted to the Company an exclusive worldwide license, subject to certain retained rights, under certain intellectual property rights to develop, commercialize and sell products in any and all uses relevant to Gaucher disease. As consideration for the license, the Company is required to make payments in connection with the achievement of certain milestones up to an aggregate of $550. The agreement expires on the latest of (i) the twentieth anniversary of the end of a certain research project the Company is funding pursuant to an agreement with Lund University, (ii) the expiration of the term of any patent filed on the licensed rights that covers a licensed product, (iii) the expiration of any applicable marketing exclusivity right and (iv) such time that neither the Company nor any sublicensees, partners or contractors are commercializing a licensed product. Either the Company or the rights holders acting together may terminate the license agreement if the other such party commits a material breach and fails to cure such breach within a certain period of time, or if the other party enters into liquidation, becomes insolvent, or enters into composition or statutory reorganization proceedings.

The Company has recognized no expenses related to this agreement for the three and nine months ended September 30, 2022 and 2021.

Fair Value Measurement

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Fair Value Measurement

4. Fair Value Measurement

The following table presents information about the Company’s financial assets measured at fair value on a recurring basis and indicates the level of the fair value hierarchy utilized to determine such fair values as of September 30, 2022 and December 31, 2021:


	Fair Value Measurements as of September 30, 2022
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents — money market funds	$	114,674	$	—	$	—	$	114,674
	$	114,674	$	—	$	—	$	114,674


	Fair Value Measurements as of December 31, 2021
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents — money market funds	$	189,332	$	—	$	—	$	189,332
	$	189,332	$	—	$	—	$	189,332

The fair value of cash equivalents was determined through quoted prices by third-party pricing services.

During the nine months ended September 30, 2022, there were no transfers between levels.

- Definition

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

+ References + Details

Supplemental Balance Sheet Information

9 Months Ended

Sep. 30, 2022

Balance Sheet Related Disclosures [Abstract]

Supplemental Balance Sheet Information

5. Supplemental Balance Sheet Information

Prepaid expenses and other current assets

Prepaid expenses and other current assets consisted of the following:


	September 30, 2022		December 31, 2021
Prepaid research and development expenses	$	4,112	$	4,496
Tax incentive refund		2,984		2,697
Prepaid insurance		1,484		112
Other current assets		765		1,698
Prepaid compensation benefits		428		575
Prepaid expenses and other current assets	$	9,773	$	9,578

Property and equipment, net

Property and equipment, net consisted of the following:


	September 30, 2022			December 31, 2021
Laboratory and office equipment	$	5,947		$	6,162
Leasehold improvements		629			1,635
Computer equipment		102			149
		6,678			7,946
Less: Accumulated depreciation and amortization		(3,455	)		(3,820	)
Property and equipment, net	$	3,223		$	4,126

Depreciation and amortization expense was $336 and $374, respectively, for the three months ended September 30, 2022 and 2021. Depreciation and amortization expense was $1,105 and $963, respectively, for the nine months ended September 30, 2022 and 2021.

Restricted cash

As of September 30, 2022 and December 31, 2021, the Company had restricted cash of $492. $283 consists of cash used to secure a letter of credit for the benefit of the landlord in connection with the Company’s lease agreements. The cash will be restricted until the termination or modification of the lease arrangement. $209 consists of cash to be released within 60 days following the termination of a lease arrangement that was terminated on September 23, 2022.

Accrued expenses and other current liabilities

Accrued expenses and other current liabilities consisted of the following:


	September 30, 2022		December 31, 2021
Research and development expenses	$	7,645	$	8,882
Compensation and benefit costs		5,402		5,579
Consulting and professional fees		871		999
Other liabilities		409		178
Accrued expenses and other current liabilities	$	14,327	$	15,638

Commitments and Contingencies

9 Months Ended

Sep. 30, 2022

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

6. Commitments and Contingencies

Legal Proceedings

The Company, from time to time, may be party to litigation arising in the ordinary course of business. The Company was not subject to any material legal proceedings during the nine months ended September 30, 2022 and 2021 and to the best of the Company’s knowledge, no material legal proceedings are currently pending or threatened.

Other

The Company is also party to various agreements, principally relating to licensed technology, that require future payments relating to milestones not met at September 30, 2022 and December 31, 2021, or royalties on future sales. No milestone or royalty payments under these agreements are expected to be payable in the immediate future, except as disclosed in Note 3 “License Agreements.”

The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to the agreements, the Company agrees to indemnify, hold harmless, and to reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company’s business partners, in connection with any U.S. patent or any copyright or other intellectual property infringement claim by any third-party with respect to the Company’s products. Further, the Company indemnifies its directors and officers who are, or were, serving at the Company’s request in such capacities. The Company’s maximum exposure under these arrangements is unknown as of September 30, 2022. The Company does not anticipate recognizing any significant losses

relating to these arrangements. The term of these indemnification agreements is generally perpetual any time after execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements.

Note Payable

9 Months Ended

Sep. 30, 2022

Debt Disclosure [Abstract]

Note Payable

7. Note Payable

On November 2, 2021 (the “Closing Date”), the Company entered into a Loan and Security Agreement (the “Loan Agreement”) with the lenders party thereto from time to time and Silicon Valley Bank pursuant to which a term loan in an aggregate principal amount of up to $50,000 (the “Term Loan Facility”) is available to the Company in three tranches, subject to certain terms and conditions. The first tranche of $15,000 was advanced to the Company on the Closing Date. Subject to the terms and conditions of the Loan Agreement, the first tranche allows the Company to borrow an additional $15,000 through October 31, 2023. The second and third tranches under the Term Loan Facility, which, upon satisfaction of certain milestones, allow the Company to borrow an additional amount up to $10,000 in each tranche through October 31, 2023, can no longer be drawn due to the deprioritization of our Fabry program. Additionally, the Company may seek to borrow up to an additional $15,000 at the sole discretion of the lender through the term of the Loan Agreement. The Loan Agreement matures on October 1, 2026 (the “Maturity Date”). The Company is required to pay an end of term fee (“End of Term Charge”) equal to 9.00% of the aggregate principal amount of the Term Loan Facility advances upon repayment.

Advances under the Term Loan Facility will bear interest at a rate equal to the greater of either (i) the Prime Rate (as reported in The Wall Street Journal) plus 4.85%, and (ii) 8.10%. The Company will make interest only payments through November 1, 2024. Following the interest only period, the Company will repay the principal balance and interest of the advances in equal monthly installments through October 1, 2026.

The Company may prepay advances under the Loan Agreement, in whole or in part, at any time subject to a prepayment charge (the “Prepayment Premium”) equal to: (a) 1.50% of amounts so prepaid, if such prepayment occurs during the first year following the Closing Date; (b) 1.00% of the amount so prepaid, if such prepayment occurs during the second year following the Closing Date, and (c) 0.00% of the amount so prepaid, if such prepayment occurs after the second year following the Closing Date.

Upon prepayment or repayment of all or any of the term loans under the Term Loan Facility, the Company will pay (in addition to any Prepayment Premium) an end of term charge of 9.0% of the aggregate funded amount under the Term Loan Facility.

The Term Loan Facility is secured by substantially all of the Company’s assets, other than the Company’s intellectual property. The Company has agreed to not pledge or secure its intellectual property to others.

The End of Term Charge is recorded as a debt discount with an initial carrying balance of $1,350. During the year ended December 31, 2021 the Company recognized $103 of debt issuance costs related to legal expenses that has been included in the debt discount balance. The debt discount costs are being accreted to the principal amount of debt and being amortized from the date of issuance through the Maturity Date to interest expense using the effective-interest rate method. The effective interest rate of the outstanding debt under the Loan Agreement is approximately 14.19%.

As of September 30, 2022 the carrying value of the note payable consists of the following:


	September 30, 2022
	(in thousands)
Note payable, including End of Term Charge	$	16,350
Debt discount, net of accretion		(1,145	)
Note payable, net of discount, long-term	$	15,205

As of September 30, 2022, the future principal payments due under the arrangement, excluding interest and the end of term charge, are as follows:


Year Ending December 31,	Principal
2022	$	—
2023		—
2024		1,875
2025		7,500
2026		5,625
Total	$	15,000

During the three and nine months ended September 30, 2022, the Company recognized $482 and $1,280, respectively, of interest expense related to the Loan Agreement which is reflected in interest (expense) income, net on the consolidated statements of operations and comprehensive loss. During the three and nine months ended September 30, 2021, the Company recognized no interest expense related to the Loan Agreement.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

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+ Details

Stockholders' Equity

9 Months Ended

Sep. 30, 2022

Equity [Abstract]

Stockholders' Equity

8. Stockholders’ Equity

Common Stock

As of September 30, 2022 and December 31, 2021, the authorized capital stock of the Company included 150,000,000 shares of common stock, $0.0001 par value and 10,000,000 shares of undesignated preferred stock. As of September 30, 2022 and December 31, 2021, no undesignated preferred stock was outstanding.

As of September 30, 2022, no cash dividends have been declared or paid.

Common Stock Reserved for Future Issuance

As of September 30, 2022 and December 31, 2021, the Company has reserved the following shares of common stock for future issuance:


	September 30, 2022		December 31, 2021
Shares reserved for exercise of outstanding stock options		8,083,363		7,423,777
Shares reserved for vesting of restricted stock units		870,536		599,850
Shares reserved for issuance under the 2018 Stock Option and Grant Plan		6,661,524		2,583,736
Shares reserved for issuance under the 2018 Employee Stock Purchase Plan		1,467,026		1,151,010
Shares reserved for issuance under the 2019 Inducement Plan		752,048		412,686
Shares reserved for issuance under the 2020 Inducement Plan		1,637,000		1,637,000
Total shares of authorized common stock reserved for future issuance		19,471,497		13,808,059

- Definition

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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+ Details

Stock-Based Compensation

9 Months Ended

Sep. 30, 2022

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

9. Stock-based Compensation

Stock Option Valuation

The assumptions that the Company used to determine the grant-date fair value of stock options granted to employees and members of the board of directors were as follows, presented on a weighted-average basis:


	Nine Months Ended September 30,
	2022			2021
Expected option life (years)		5.96			6.07
Risk-free interest rate		1.80	%		0.76	%
Expected volatility		80.22	%		81.25	%
Expected dividend yield		—	%		—	%

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2022:


	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2021		7,423,777		$	13.54		6.79	$	1,469
Granted		3,455,157		$	1.79
Exercised		—		$	—
Cancelled or forfeited		(2,795,571	)	$	11.99
Outstanding as of September 30, 2022		8,083,363		$	9.05		7.69	$	50
Exercisable as of September 30, 2022		3,266,645		$	12.69		5.87	$	50

The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company’s common stock for those stock options that had exercise prices lower than the estimated fair value of the Company’s common stock.

The aggregate intrinsic value of options exercised during the nine months ended September 30, 2021 was $1,760. No options were exercised during the nine months ended September 30, 2022.

The weighted-average grant-date fair value of the Company’s stock options granted during the nine months ended September 30, 2022 and 2021 was $1.23 and $9.12, respectively.

Restricted Stock Units

The following table summarizes the Company’s restricted common stock units for the nine months ended September 30, 2022:


	Number of Shares			Weighted- Average Grant Date Fair Value
Issued and unvested as of December 31, 2021		599,850		$	9.64
Granted		850,168		$	1.62
Vested		(431	)	$	15.65
Forfeited, cancelled or expired		(579,051	)	$	6.56
Issued and unvested as of September 30, 2022		870,536		$	3.85

The total fair value of restricted stock units vested during the nine months ended September 30, 2022 and 2021 was $7 and $7, respectively.

Stock-Based Compensation

Stock-based compensation expense was allocated as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development	$	448	$	1,965	$	2,169	$	5,989
General and administrative		2,208		3,204		7,098		8,505
Total stock-based compensation expense	$	2,656	$	5,169	$	9,267	$	14,494

As of September 30, 2022, total unrecognized compensation cost related to the unvested stock-based awards was $21,345, which is expected to be recognized over a weighted-average period of 2.39 years.

Net Loss Per Share

9 Months Ended

Sep. 30, 2022

Earnings Per Share [Abstract]

Net Loss Per Share

10. Net Loss Per Share

For purposes of the diluted net loss per share calculation, stock options and unvested restricted stock are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive for all periods presented. Therefore, the weighted-average number of common shares outstanding used to calculate both basic and diluted net loss per share is the same.

The following potentially dilutive common stock equivalents, presented based on amounts outstanding at each period end, were excluded from the computation of diluted net loss per share for the periods indicated as they were anti-dilutive:


	Nine Months Ended September 30,
	2022		2021
Options to purchase common stock		8,083,363		7,999,382
Restricted stock units		870,536		709,025

Related Party Transactions

9 Months Ended

Sep. 30, 2022

Related Party Transactions

11. Related Party Transactions

UHN

For the three months ended September 30, 2022 and 2021, the Company recognized $82 and $102, respectively, of research and development expense related to the license agreements with UHN. For the nine months ended September 30, 2022 and 2021, the Company recognized $145 and $215, respectively, of research and development expense related to the license agreements with UHN. Refer to Note 3 “License Agreements” for additional information regarding the UHN license agreements.

Others

For the three months ended September 30, 2022 and 2021, the Company recorded expenses of $795 and $228, respectively, related to a sublease to rent lab space, provided by an entity affiliated with a member of the Company’s board of directors. For the nine months ended September 30, 2022 and 2021, the Company recorded expenses of $2,381 and $1,278, respectively, related to a sublease to rent lab space, provided by an entity affiliated with a member of the Company’s board of directors.

Restructuring Activities

9 Months Ended

Sep. 30, 2022

Restructuring and Related Activities [Abstract]

Restructuring Activities

12. Restructuring Activities

In January 2022, the Company announced the deprioritization of AVR-RD-01, its investigational gene therapy program for Fabry disease. This decision was made due to several factors, including new clinical data showing variable engraftment patterns from the five most recently dosed patients in the Company’s Phase 2 clinical trial of AVR-RD-01 for the treatment of Fabry disease, which the Company refers to as the FAB-GT clinical trial. The emergence of such new data would have significantly extended the program’s development timeline. That development, coupled with an increasingly challenging market and regulatory environment for Fabry disease, were among the primary factors leading to the Company’s deprioritization of its Fabry program. As a result of the deprioritization, the Company has stopped enrollment of its Phase 2 FAB-GT clinical trial and has shifted focus to its other pipeline programs.

In connection with the deprioritization of AVR-RD-01 noted above, in January 2022, the Company approved changes to the Company’s organization as well as a broader operational cost reduction plan. As part of this plan, the Company approved a reduction in the Company’s workforce by approximately 23% across different areas and functions in the Company (the “Workforce Reduction”).

Under the Workforce Reduction, the Company recognized total restructuring expenses for the three and nine months ended September 30, 2022 of $0 and $1,369, respectively. No restructuring expenses were incurred for the three and nine months ended September 30, 2021. These one-time employee termination benefits are related to affected employees, who were offered separation benefits, including severance payments. During the three and nine months ended September 30, 2022 approximately $0 and $1,369 of these payments were made. There are no accrued remaining payments at September 30, 2022.

The outstanding restructuring liabilities are included in accrued expenses and other current liabilities on the consolidated balance sheets. The following table summarizes the charges related to the restructuring activities as of September 30, 2022:


	Employee Severance and Other Benefits
Liability included in accrued expenses and other current liabilities at January 1, 2022	$	—
Restructuring expenses		1,369
Cash payments		(1,369	)
Liability included in accrued expenses and other current liabilities at September 30, 2022	$	—

Summary of Significant Accounting Policies (Policies)	9 Months Ended
Summary of Significant Accounting Policies (Policies)	Sep. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements (the “unaudited condensed consolidated financial statements”) have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative United States generally accepted accounting principles as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). The unaudited condensed consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements as of and for the year ended December 31, 2021, and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, necessary for the fair presentation of the Company’s financial position as of September 30, 2022, and the results of its operations for the three and nine months ended September 30, 2022 and 2021, its statements of stockholders’ equity for the three and nine months ended September 30, 2022 and 2021 and its statement of cash flows for the nine months ended September 30, 2022 and 2021. The results for the three and nine months ended September 30, 2022 are not necessarily indicative of the results to be expected for the year ending December 31, 2022, any other interim periods, or any future year or period. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2021, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 17, 2022. The unaudited condensed consolidated financial statements reflect the application of certain significant accounting policies as described below and elsewhere in these notes to the unaudited condensed consolidated financial statements. As of September 30, 2022, there have been no changes to the Company’s significant accounting policies as described in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2021.
Segment Information	Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker, or decision-making group, in making decisions on how to allocate resources and assess performance. The Company’s chief operating decision maker is the chief executive officer (“CEO”). The Company and the CEO view the Company’s operations and manage its business as one operating segment. All material long-lived assets of the Company reside in the United States.
Use of Estimates	Use of Estimates The preparation of the unaudited condensed consolidated financial statements in conformity with GAAP requires that the Company make estimates and judgments that may affect the reported amounts of assets, liabilities and expenses and the related disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting periods. On an ongoing basis, the Company evaluates its estimates, judgments and methodologies. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable, the results of which form the basis for making judgments about the carrying values of assets and liabilities. Actual results may differ from these estimates. Changes in estimates are reflected in reported results in the period in which they become known. Significant estimates relied upon in preparing the unaudited condensed consolidated financial statements include the determination of the fair value of share-based awards issued and the estimation of accrued research and development expenses.
Stock-Based Compensation	Stock-based Compensation For stock-based awards issued to employees and members of the Company’s board of directors (the “Board”) for their services on the Board, the Company measures the estimated fair value of the stock-based award on the date of grant and recognizes compensation expense for those awards over the requisite service period, which is generally the vesting period of the respective award. The Company issues stock-based awards with only service-based vesting conditions and records the expense for these awards using the straight-line method. The Company has not issued any stock-based awards with performance- or market-based vesting conditions. The Company accounts for forfeitures as they occur. Prior to the adoption of Accounting Standards Update (“ASU”) No. 2018-07, Compensation-Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting, the measurement date for non-employee awards was generally the date the services are completed, resulting in financial reporting period adjustments to stock-based compensation during the vesting terms for changes in the fair value of the awards. After adoption of ASU 2018-07, the measurement date for non-employee awards is the later of the adoption date of ASU 2018-07, or the date of grant, without change in the fair value of the award. For stock-based awards granted to nonemployees subject to graded vesting that only contain service conditions, the Company has elected to recognize stock-based compensation expense using the straight-line recognition method. The Company classifies stock-based compensation expense in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipient’s cash compensation costs are classified. The fair value of each stock option award is estimated on the date of grant using the Black-Scholes option pricing model. As there was no public market for its common stock prior to June 21, 2018, which was the first day of trading, and as the trading history of the Company’s common stock was limited through December 31, 2021, the Company determined the volatility for awards granted up through December 31, 2021 based on an analysis of reported data for a group of guideline companies that issued options with substantially similar terms. Beginning with options granted in 2022, the Company estimates its expected stock volatility using a weighted-average calculation based on the historical volatility of the Company and publicly traded peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. The expected term of the Company’s stock options has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. 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. The Company has not paid, and does not anticipate paying, cash dividends on its common stock; therefore, the expected dividend yield is assumed to be zero.
Emerging Growth Company Status	Emerging Growth Company Status The Company is an “emerging growth company,” as defined in the Jumpstart Our Business Startups Act, or JOBS Act, and may take advantage of certain exemptions from various reporting requirements applicable to other public companies, which are not emerging growth companies. The Company may take advantage of these exemptions until the Company is no longer an “emerging growth company.” Section 107 of the JOBS Act provides that an “emerging growth company” can take advantage of the extended transition period afforded by the JOBS Act for the implementation of new or revised accounting standards. The Company has elected to use the extended transition period for complying with new or revised accounting standards and as a result of this election, its consolidated financial statements may not be comparable to companies that comply with public company effective dates. The Company may take advantage of these exemptions up until the last day of the fiscal year following the fifth anniversary of its IPO or such earlier time that it is no longer an “emerging growth company.”
Subsequent Event Considerations	Subsequent Event Considerations The Company considers events or transactions that occur after the balance sheet date but prior to the issuance of the consolidated financial statements to provide additional evidence for certain estimates or to identify matters that require additional disclosure. Subsequent events have been evaluated as required.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, (Topic 842) Leases, or ASU 2016-02. ASU 2016-02 requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases. The ASU will also require new qualitative and quantitative disclosures to help investors and other financial statement users better understand the amount, timing, and uncertainty of cash flows arising from leases. For public entities, ASU 2016-02 is effective for fiscal years beginning after December 15, 2018. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, ASU 2016-02 is effective for the Company for the year ended December 31, 2022, and all interim periods thereafter. Early adoption is permitted. The Company is currently evaluating the impact that the adoption of ASU 2016-02 will have on its consolidated financial statements. Based on this evaluation the Company currently expects that its operating lease commitments will be subject to the new standard and recognized as right-of-use assets and operating lease liabilities upon adoption of this standard, which will increase the Company’s total assets and total liabilities. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, or ASU 2016-13. ASU 2016-13 requires that credit losses be reported as an allowance using an expected losses model, representing the entity's current estimate of credit losses expected to be incurred. The accounting guidance currently in effect is based on an incurred loss model. For available-for-sale debt securities with unrealized losses, this standard now requires allowances to be recorded instead of reducing the amortized cost of the investment. ASU 2016-13 is effective for non-EGCs for fiscal years beginning December 15, 2019 and interim periods within those fiscal years, and will be effective for the Company for fiscal years beginning after December 15, 2022 and interim periods within those fiscal years, assuming the Company remains an EGC. Early adoption is permitted. The Company expects an immaterial impact to its financial statements. In November 2019, the FASB issued ASU 2019-11, “Codification Improvements to Topic 326, Financial Instruments – Credit Losses,” or ASU 2019-11. ASU 2019-11 is an accounting pronouncement that amends ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments.” The amendments update guidance on reporting credit losses for financial assets. These amendments affect loans, debt securities, trade receivables, net investments in leases, off balance sheet credit exposures, reinsurance receivables, and any other financial assets not excluded from the scope that have the contractual right to receive cash. The amendments in both ASU 2016-13 and ASU 2019-11 are effective for annual reporting periods beginning after December 15, 2019, including interim periods within those fiscal years. As a result of the Company having elected the extended transition period for complying with new or revised accounting standards pursuant to Section 107(b) of the JOBS Act, 2016-13 and ASU 2019-11 are effective for the Company for fiscal years beginning after December 15, 2022, and interim periods within those fiscal years. The Company is currently evaluating ASU 2016-13 and ASU 2019-11 and their impact on its consolidated financial statements and financial statement disclosures. In December 2019, the FASB issued ASU No. 2019-12, Simplifying the Accounting for Income Taxes, or ASU 2019-12. ASU 2019-12 eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences. It also clarifies and simplifies other aspects of the accounting for income taxes. ASU 2019-12 is effective for non-EGCs for fiscal years beginning after December 15, 2020 and interim periods within those fiscal years and will be effective for the Company for fiscal years beginning after December 15, 2021 and interim periods beginning after December 15, 2022, assuming the Company remains an EGC. Early adoption is permitted. The Company is currently evaluating the effects the adoption of ASU 2019-12 may have on its financial statements.

Fair Value Measurement (Tables)

9 Months Ended

Sep. 30, 2022

Fair Value Disclosures [Abstract]

Summary of Financial Assets Measured at Fair Value on Recurring Basis


	Fair Value Measurements as of September 30, 2022
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents — money market funds	$	114,674	$	—	$	—	$	114,674
	$	114,674	$	—	$	—	$	114,674


	Fair Value Measurements as of December 31, 2021
	Level 1		Level 2		Level 3		Total
Assets:
Cash equivalents — money market funds	$	189,332	$	—	$	—	$	189,332
	$	189,332	$	—	$	—	$	189,332

- Definition

Tabular disclosure of financial instruments measured at fair value, including those classified in shareholders' equity measured on a recurring or nonrecurring basis. Disclosures include, but are not limited to, fair value measurements recorded and the reasons for the measurements, level within the fair value hierarchy in which the fair value measurements are categorized and transfers between levels 1 and 2. Nonrecurring fair value measurements are those that are required or permitted in the statement of financial position in particular circumstances.

+ References + Details

Supplemental Balance Sheet Information (Tables)

9 Months Ended

Sep. 30, 2022

Balance Sheet Related Disclosures [Abstract]

Summary of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following:


	September 30, 2022		December 31, 2021
Prepaid research and development expenses	$	4,112	$	4,496
Tax incentive refund		2,984		2,697
Prepaid insurance		1,484		112
Other current assets		765		1,698
Prepaid compensation benefits		428		575
Prepaid expenses and other current assets	$	9,773	$	9,578

Summary of Property and Equipment, Net

Property and equipment, net consisted of the following:


	September 30, 2022			December 31, 2021
Laboratory and office equipment	$	5,947		$	6,162
Leasehold improvements		629			1,635
Computer equipment		102			149
		6,678			7,946
Less: Accumulated depreciation and amortization		(3,455	)		(3,820	)
Property and equipment, net	$	3,223		$	4,126

Summary of Accrued Expenses

Accrued expenses and other current liabilities consisted of the following:


	September 30, 2022		December 31, 2021
Research and development expenses	$	7,645	$	8,882
Compensation and benefit costs		5,402		5,579
Consulting and professional fees		871		999
Other liabilities		409		178
Accrued expenses and other current liabilities	$	14,327	$	15,638

Note Payable (Tables)

9 Months Ended

Sep. 30, 2022

Debt Disclosure [Abstract]

Carrying Value of Note Payable

As of September 30, 2022 the carrying value of the note payable consists of the following:


	September 30, 2022
	(in thousands)
Note payable, including End of Term Charge	$	16,350
Debt discount, net of accretion		(1,145	)
Note payable, net of discount, long-term	$	15,205

Future Principal Payments

As of September 30, 2022, the future principal payments due under the arrangement, excluding interest and the end of term charge, are as follows:


Year Ending December 31,	Principal
2022	$	—
2023		—
2024		1,875
2025		7,500
2026		5,625
Total	$	15,000

Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2022

Equity [Abstract]

Summary of Common Stock Reserved for Future Issuance

As of September 30, 2022 and December 31, 2021, the Company has reserved the following shares of common stock for future issuance:


	September 30, 2022		December 31, 2021
Shares reserved for exercise of outstanding stock options		8,083,363		7,423,777
Shares reserved for vesting of restricted stock units		870,536		599,850
Shares reserved for issuance under the 2018 Stock Option and Grant Plan		6,661,524		2,583,736
Shares reserved for issuance under the 2018 Employee Stock Purchase Plan		1,467,026		1,151,010
Shares reserved for issuance under the 2019 Inducement Plan		752,048		412,686
Shares reserved for issuance under the 2020 Inducement Plan		1,637,000		1,637,000
Total shares of authorized common stock reserved for future issuance		19,471,497		13,808,059

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

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+ Details

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2022

Share-Based Payment Arrangement [Abstract]

Summary of Assumptions that Used to Determine Grant-Date Fair Value of Stock Options Granted to Employees and Members of Board of Directors


	Nine Months Ended September 30,
	2022			2021
Expected option life (years)		5.96			6.07
Risk-free interest rate		1.80	%		0.76	%
Expected volatility		80.22	%		81.25	%
Expected dividend yield		—	%		—	%

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity for the nine months ended September 30, 2022:


	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2021		7,423,777		$	13.54		6.79	$	1,469
Granted		3,455,157		$	1.79
Exercised		—		$	—
Cancelled or forfeited		(2,795,571	)	$	11.99
Outstanding as of September 30, 2022		8,083,363		$	9.05		7.69	$	50
Exercisable as of September 30, 2022		3,266,645		$	12.69		5.87	$	50

Summary of Restricted Common Stock Units

The following table summarizes the Company’s restricted common stock units for the nine months ended September 30, 2022:


	Number of Shares			Weighted- Average Grant Date Fair Value
Issued and unvested as of December 31, 2021		599,850		$	9.64
Granted		850,168		$	1.62
Vested		(431	)	$	15.65
Forfeited, cancelled or expired		(579,051	)	$	6.56
Issued and unvested as of September 30, 2022		870,536		$	3.85

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was allocated as follows:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development	$	448	$	1,965	$	2,169	$	5,989
General and administrative		2,208		3,204		7,098		8,505
Total stock-based compensation expense	$	2,656	$	5,169	$	9,267	$	14,494

Net Loss Per Share (Tables)

9 Months Ended

Sep. 30, 2022

Earnings Per Share [Abstract]

Schedule of Dilutive Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share


	Nine Months Ended September 30,
	2022		2021
Options to purchase common stock		8,083,363		7,999,382
Restricted stock units		870,536		709,025

Restructuring Activities (Tables)

9 Months Ended

Sep. 30, 2022

Restructuring and Related Activities [Abstract]

Summary of Charges Related to Restructuring Activities


	Employee Severance and Other Benefits
Liability included in accrued expenses and other current liabilities at January 1, 2022	$	—
Restructuring expenses		1,369
Cash payments		(1,369	)
Liability included in accrued expenses and other current liabilities at September 30, 2022	$	—

Nature of the Business - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ (22,969)	$ (32,613)	$ (80,856)	$ (90,899)
Accumulated deficit	(464,398)		(464,398)		$ (383,542)
Cash and cash equivalents	$ 115,968	$ 201,369	$ 115,968	$ 201,369	$ 189,567

- Definition

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

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+ Details

Summary of Significant Accounting Policies - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2022 Segment
Significant Accounting Policies [Abstract]
Number of operating segment	1

License Agreements - Additional Information (Detail) £ in Thousands, shares in Thousands, $ in Thousands				1 Months Ended	3 Months Ended				9 Months Ended		12 Months Ended
	Oct. 02, 2017 USD ($)	Jan. 27, 2016 CAD ($) shares	Jan. 27, 2016 USD ($)	Aug. 31, 2017 USD ($) shares	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($)	Sep. 30, 2020 GBP (£)	Sep. 30, 2020 USD ($)	Sep. 30, 2022 USD ($) shares	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2021 shares	Nov. 17, 2016 USD ($)
License Agreement [Line Items]
Collaborative agreement expenses					$ 590,000	$ 1,031,000			$ 1,970,000	$ 1,832,000
Common stock, issued \| shares					43,773				43,773				43,652
Research and development					$ 15,919,000	23,043,000			$ 54,049,000	64,114,000
University of Manchester Agreement [Member] \| MPSII License Agreement [Member]
License Agreement [Line Items]
Upfront license fee											$ 8,000,000
Milestone payments payable								$ 80,000,000
Milestone payment paid								2,000,000
Milestone payment due								$ 4,000,000
Agreement Expiration Period									15 years
Agreement Expiration Description									upon the later of 15 years from the effective date or the expiration of the last valid claim of the licensed patent
Research and development expense \| £							£ 10,013
UHN Agreement [Member]
License Agreement [Line Items]
Research and development expense					82,000	102,000			$ 106,000	175,000
Milestone fees					0	0			0	0
UHN Agreement [Member] \| Fabry License Agreement [Member]
License Agreement [Line Items]
Upfront license fee		$ 75
Milestone payments payable		2,450
Option fee		20
UHN Agreement [Member] \| Interleukin 12 License Agreement [Member]
License Agreement [Line Items]
Upfront license fee		264
Milestone payments payable		19,275
Milestone fees					0	0			0	0
Annual maintenance fees		$ 50
Common stock, issued \| shares		1,161,665
Fair value of shares issued			$ 480,000
Payments upon closing of an initial public offering			$ 2,000,000									$ 2,000,000
Research and development					0	0			39,000	39,000
BioMarin Pharmaceutical Inc [Member]
License Agreement [Line Items]
Upfront license fee				$ 500,000
Preferred stock issued \| shares				233,765
Milestone payments					13,000,000
Expenses related to license					0	0			0	0
GenStem Therapeutics Inc [Member]
License Agreement [Line Items]
Upfront license fee	$ 1,000,000
Milestone payments payable	$ 16,000,000
Expenses related to license					0	0			0	0
Lund University Rights Holders Agreement [Member]
License Agreement [Line Items]
Milestone payments payable														$ 550,000
Expenses related to license					$ 0	$ 0			$ 0	$ 0

Fair Value Measurement - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value on Recurring Basis [Member] - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Assets Fair Value Disclosure
Assets Fair Value Disclosure	$ 114,674	$ 189,332
Money Market Funds [Member] \| Cash Equivalents [Member]
Assets Fair Value Disclosure
Assets Fair Value Disclosure	114,674	189,332
Level 1 [Member]
Assets Fair Value Disclosure
Assets Fair Value Disclosure	114,674	189,332
Level 1 [Member] \| Money Market Funds [Member] \| Cash Equivalents [Member]
Assets Fair Value Disclosure
Assets Fair Value Disclosure	$ 114,674	$ 189,332

Fair Value Measurement - Additional Information (Detail)	Sep. 30, 2022 USD ($)
Fair Value Disclosures [Abstract]
Fair value input transfer between levels	$ 0

Supplemental Balance Sheet Information - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Supplemental Balance Sheet Information Disclosures [Abstract]
Prepaid research and development expenses	$ 4,112	$ 4,496
Tax incentive refund	2,984	2,697
Prepaid insurance	1,484	112
Other current assets	765	1,698
Prepaid compensation benefits	428	575
Prepaid expenses and other current assets	$ 9,773	$ 9,578

Supplemental Balance Sheet Information - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 6,678	$ 7,946
Less: Accumulated depreciation and amortization	(3,455)	(3,820)
Property and equipment, net	3,223	4,126
Laboratory and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	5,947	6,162
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	629	1,635
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$ 102	$ 149

Supplemental Balance Sheet Information - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Supplemental Balance Sheet Information Disclosures [Abstract]
Depreciation and amortization expense	$ 336	$ 374	$ 1,105	$ 963
Restricted Cash	492	$ 492	492	$ 492	$ 492
Cash used to secure a letter of credit	$ 283		283		$ 283
Cash to be released from termination of lease arrangement			$ 209
Termination date of lease arrangement			Sep. 23, 2022

Supplemental Balance Sheet Information - Summary of Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Accrued Liabilities, Current [Abstract]
Research and development expenses	$ 7,645	$ 8,882
Compensation and benefit costs	5,402	5,579
Consulting and professional fees	871	999
Other liabilities	409	178
Accrued expenses and other current liabilities	$ 14,327	$ 15,638

Note Payable - Additional Information (Details) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Nov. 02, 2021 USD ($) Tranche	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt Disclosure [Line Items]
Debt Issuance Costs, Net		$ 1,145		$ 1,145
Loan Agreement [Member] \| Silicon Valley Bank [Member]
Debt Disclosure [Line Items]
Loan, interest rate						14.19%
Debt discount	$ 1,350
Interest expense recognized		$ 482	$ 0	$ 1,280	$ 0
Loan Agreement [Member] \| Silicon Valley Bank [Member] \| Legal Expenses [Member]
Debt Disclosure [Line Items]
Debt Issuance Costs, Net						$ 103
Term Loan Facility [Member] \| Silicon Valley Bank [Member]
Debt Disclosure [Line Items]
Loan maturity date	Oct. 01, 2026
End of term charge as percentage on principal amount	9.00%
Loan, interest rate	8.10%
Term Loan Facility [Member] \| Silicon Valley Bank [Member] \| Prime Rate [Member]
Debt Disclosure [Line Items]
Loan, interest rate	4.85%
Term Loan Facility [Member] \| Loan Agreement [Member] \| Silicon Valley Bank [Member]
Debt Disclosure [Line Items]
Borrowing amount	$ 50,000
Debt instrument number of tranches \| Tranche	3
Proceeds from loan agreement	$ 15,000
Additional borrowing amount	15,000
Line of credit facility additional discretionary	$ 15,000
Loan maturity date	Oct. 01, 2026
End of term charge as percentage on principal amount	9.00%
Term Loan Facility [Member] \| Loan Agreement [Member] \| Silicon Valley Bank [Member] \| Regulatory Milestone [Member]
Debt Disclosure [Line Items]
Additional borrowing amount	$ 10,000
Term Loan Prepayment During First Year [Member] \| Silicon Valley Bank [Member]
Debt Disclosure [Line Items]
Line of credit facility prepayment of premium percentage	1.50%
Term Loan Prepayment During Second Year [Member] \| Silicon Valley Bank [Member]
Debt Disclosure [Line Items]
Line of credit facility prepayment of premium percentage	1.00%
Term Loan Prepayment After Second Year [Member] \| Silicon Valley Bank [Member]
Debt Disclosure [Line Items]
Line of credit facility prepayment of premium percentage	0.00%

Note Payable - Carrying Value of Note Payable (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Disclosure [Abstract]
Note payable, including End of Term Charge	$ 16,350
Debt discount, net of accretion	(1,145)
Note payable, net of discount, long-term	$ 15,205	$ 14,945

Note Payable - Future Principal Payments (Details) $ in Thousands	Sep. 30, 2022 USD ($)
Debt Disclosure [Abstract]
2024	$ 1,875
2025	7,500
2026	5,625
Total	$ 15,000

- Definition

Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References + Details

Stockholders' Equity - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Equity [Abstract]
Common stock, authorized	150,000,000	150,000,000
Common stock, par value	$ 0.0001	$ 0.0001
Undesignated preferred stock	10,000,000	10,000,000
Undesignated shares of preferred stock outstanding	0	0
Cash dividends	$ 0

Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2022	Dec. 31, 2021
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	19,471,497	13,808,059
Employee Stock Option [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	8,083,363	7,423,777
Restricted Stock Units [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	870,536	599,850
2018 Stock Option and Incentive Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	6,661,524	2,583,736
2018 Employee Stock Purchase Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	1,467,026	1,151,010
2019 Inducement Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	752,048	412,686
2020 Inducement Plan [Member]
Class Of Stock [Line Items]
Total shares of authorized common stock reserved for future issuance	1,637,000	1,637,000

Stock-Based Compensation - Summary of Assumptions that Used to Determine Grant-Date Fair Value of Stock Options Granted to Employees and Members of Board of Directors (Detail)	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected option life (years)	5 years 11 months 15 days	6 years 25 days
Risk-free interest rate	1.80%	0.76%
Expected volatility	80.22%	81.25%

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2022	Dec. 31, 2021
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Number of options, Outstanding beginning balance	7,423,777
Number of options, Granted	3,455,157
Number of options, Exercised	0
Number of options, Cancelled or forfeited	(2,795,571)
Number of options, Outstanding ending balance	8,083,363	7,423,777
Number of options, Exercisable	3,266,645
Weighted average exercise price, Outstanding beginning balance	$ 13.54
Weighted average exercise price, Granted	1.79
Weighted average exercise price, Cancelled or forfeited	11.99
Weighted average exercise price, Outstanding ending balance	9.05	$ 13.54
Weighted average exercise price, Exercisable	$ 12.69
Weighted average remaining contractual term, Outstanding balance	7 years 8 months 8 days	6 years 9 months 14 days
Weighted average remaining contractual term, Exercisable	5 years 10 months 13 days
Aggregate intrinsic value, Outstanding balance	$ 50	$ 1,469
Aggregate intrinsic value, Exercisable	$ 50

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Share-Based Payment Arrangement [Abstract]
Aggregate intrinsic value of options exercised		$ 1,760
Exercise of stock options, shares	0
Options Granted, Weighted-average grant-date fair value	$ 1.23	$ 9.12
Total fair value of restricted stock units vested		$ 7
Unrecognized stock-based compensation expenses	$ 21,345
Unrecognized stock-based compensation expense, period for recognition	2 years 4 months 20 days

Stock-Based Compensation - Summary of Restricted Common Stock Units (Detail) - Restricted Stock Units [Member]	9 Months Ended
	Sep. 30, 2022 $ / shares shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares, Issued and unvested beginning balance \| shares	599,850
Number of shares, Granted \| shares	850,168
Number of shares, Vested \| shares	(431)
Number of shares, Forfeited, cancelled or expired \| shares	(579,051)
Number of shares, Issued and unvested ending balance \| shares	870,536
Weighted average grant date fair value, Issued and unvested, beginning balance \| $ / shares	$ 9.64
Weighted average grant date fair value, Granted \| $ / shares	1.62
Weighted average grant date fair value, Vested \| $ / shares	15.65
Weighted average grant date fair value, Forfeited, canceled or expired \| $ / shares	6.56
Weighted average grant date fair value, Issued and unvested, ending balance \| $ / shares	$ 3.85

Stock-Based Compensation - Schedule of Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,656	$ 5,169	$ 9,267	$ 14,494
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	448	1,965	2,169	5,989
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,208	$ 3,204	$ 7,098	$ 8,505

Net Loss Per Share - Schedule of Dilutive Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share (Detail) - shares	9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	8,083,363	7,999,382
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	870,536	709,025

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Related Party Transaction [Line Items]
Research and development expense	$ 15,919	$ 23,043	$ 54,049	$ 64,114
License Agreement [Member]
Related Party Transaction [Line Items]
Research and development expense	82	102	145	215
Sub-lease Agreement [Member] \| Officers and Board Members [Member]
Related Party Transaction [Line Items]
Expense related to related party	$ 795	$ 228	$ 2,381	$ 1,278

Restructuring Activities - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Restructuring Cost And Reserve [Line Items]
Expected workforce reduction percentage			23.00%
Employee Severance and Other Benefits [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring expenses	$ 0	$ 0	$ 1,369	$ 0
Payments for restructuring	0		1,369
Accrued remaining payments	$ 0		$ 0		$ 0

Restructuring Activities - Summary of Charges Related to Restructuring Activities (Detail) - Employee Severance and Other Benefits [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Restructuring Cost And Reserve [Line Items]
Liability included in accrued expenses and other current liabilities at January 1, 2022			$ 0
Restructuring expenses	$ 0	$ 0	1,369	$ 0
Cash payments	0		(1,369)
Liability included in accrued expenses and other current liabilities at June 30, 2022	$ 0		$ 0