Tectonic Therapeutic (TECX) 10-Q 12 Nov 24 2024 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2024	Nov. 01, 2024
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Entity Registrant Name	TECTONIC THERAPEUTIC, INC.
Entity Central Index Key	0001681087
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-38537
Entity Tax Identification Number	81-0710585
Entity Address, Address Line One	490 Arsenal Way
Entity Address, Address Line Two	Suite 210
Entity Address, City or Town	Watertown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02472
City Area Code	339
Local Phone Number	666-3320
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	TECX
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		14,752,689

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 159,095	$ 28,769
Prepaid expenses and other current assets	3,503	2,115
Total current assets	162,598	30,884
Property, equipment and improvements, net	2,550	3,122
Finance right-of-use assets, net	1,025	1,437
Operating right-of-use assets	1,767	2,669
Deferred offering costs	0	669
Restricted cash	587	587
Other assets	190	31
Total assets	168,717	39,399
Current liabilities:
Accounts payable	2,635	409
Accrued expenses and other current liabilities	12,737	8,141
SAFE liabilities	0	30,515
Operating lease liability - current portion	1,470	1,348
Finance lease liability - current portion	478	475
Total current liabilities	17,320	40,888
Operating lease liability - net of current portion	523	1,644
Finance lease liability - net of current portion	513	876
Total liabilities	18,356	43,408
Commitments and contingencies (Note 7)
Convertible preferred stock (Series A-1, A-2, A-3 and A-4), $0.0001 par value; 6,825,483 shares authorized as of December 31, 2023; 6,825,483 shares issued and outstanding as of December 31, 2023; aggregate liquidation preference of $87,459 as of December 31, 2023	0	80,627
Stockholders' Equity (Deficit):
Preferred stock, 10,000,000 shares authorized and 0 shares issued and outstanding as of September 30, 2024 and December 31, 2023, respectively	0	0
Common stock, $0.0001 par value; 150,000,000 shares authorized as of September 30, 2024 and December 31, 2023; 14,744,477 and 2,634,246 shares issued and outstanding as of September 30, 2024 and December 31, 2023	2	0
Additional paid-in capital	286,649	5,979
Accumulated other comprehensive loss	(77)	(11)
Accumulated deficit	(136,213)	(90,604)
Total stockholders' equity (deficit)	150,361	(84,636)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	$ 168,717	$ 39,399

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Preferred Stock, Shares Authorized	10,000,000	0
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, authorized	150,000,000	150,000,000
Common stock, issued	14,744,477	2,634,246
Common stock, outstanding	14,744,477	2,634,246
Convertible Preferred Stock [Member]
Convertible Preferred stock, par value	$ 0.0001	$ 0.0001
Convertible Preferred stock, authorized	0	6,825,483
Convertible Preferred stock, issued	0	6,825,483
Convertible Preferred stock, outstanding	0	6,825,483
Temporary Equity, Liquidation Preference		$ 87,459

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating expenses:
Research and development	$ 14,317	$ 8,134	$ 32,208	$ 29,774
General and administrative	5,320	1,980	11,816	5,500
Total operating expenses	19,637	10,114	44,024	35,274
Loss from operations	(19,637)	(10,114)	(44,024)	(35,274)
Other income (expense), net:
Change in fair value of SAFE liabilities	0	0	(3,610)	0
Interest income	1,952	97	2,526	448
Interest expense	(25)	(36)	(85)	(118)
Other expense	(7)	(1)	(416)	(10)
Total other income (expense), net	1,920	60	(1,585)	320
Net loss	$ (17,717)	$ (10,054)	$ (45,609)	$ (34,954)
Net loss per share attributable to common stockholders, basic	$ (1.2)	$ (7.62)	$ (7.16)	$ (28.06)
Net loss per share attributable to common stockholders, diluted	$ (1.2)	$ (7.62)	$ (7.16)	$ (28.06)
Weighted-average common shares outstanding, basic	14,729,018	1,319,147	6,373,717	1,245,745
Weighted-average common shares outstanding, diluted	14,729,018	1,319,147	6,373,717	1,245,745
Other comprehensive loss:
Foreign currency translation adjustment	$ (16)	$ 0	$ (66)	$ 0
Comprehensive loss	$ (17,733)	$ (10,054)	$ (45,675)	$ (34,954)

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Convertible Preferred Stock [Member] Preferred Stock [Member]
Beginning balance at Dec. 31, 2022	$ (45,654)	$ 0	$ 2,127	$ 0	$ (47,781)	$ 80,627
Beginning balance (in shares) at Dec. 31, 2022		2,525,771				6,825,483
Retroactive application of reverse recapitalization		(1,175,948)				(3,177,808)
Adjusted balance, beginning of period	(45,654)		2,127		(47,781)	$ 80,627
Adjusted balance, beginning of period (in shares)		1,349,823				3,647,675
Exercise of stock options	1		1
Exercise of stock options (in shares)		686
Stock-based compensation expense	275		275
Net Income (Loss)	(14,445)				(14,445)
Ending balance at Mar. 31, 2023	(59,823)		2,403		(62,226)	$ 80,627
Ending balance (in shares) at Mar. 31, 2023		1,350,509				3,647,675
Beginning balance at Dec. 31, 2022	(45,654)	$ 0	2,127	0	(47,781)	$ 80,627
Beginning balance (in shares) at Dec. 31, 2022		2,525,771				6,825,483
Net Income (Loss)	(34,954)
Ending balance at Sep. 30, 2023	(79,780)	$ 0	2,955	0	(82,735)	$ 80,627
Ending balance (in shares) at Sep. 30, 2023		1,350,509				3,647,675
Beginning balance at Mar. 31, 2023	(59,823)		2,403		(62,226)	$ 80,627
Beginning balance (in shares) at Mar. 31, 2023		1,350,509				3,647,675
Stock-based compensation expense	277		277
Net Income (Loss)	(10,455)				(10,455)
Ending balance at Jun. 30, 2023	(70,001)		2,680		(72,681)	$ 80,627
Ending balance (in shares) at Jun. 30, 2023		1,350,509				3,647,675
Stock-based compensation expense	275		275
Net Income (Loss)	(10,054)				(10,054)
Ending balance at Sep. 30, 2023	(79,780)	$ 0	2,955	0	(82,735)	$ 80,627
Ending balance (in shares) at Sep. 30, 2023		1,350,509				3,647,675
Beginning balance at Dec. 31, 2023	(84,636)	$ 0	5,979	(11)	(90,604)	$ 80,627
Beginning balance (in shares) at Dec. 31, 2023		2,634,246				6,825,483
Retroactive application of reverse recapitalization		(1,226,452)				(3,177,808)
Adjusted balance, beginning of period	(84,636)		5,979	(11)	(90,604)	$ 80,627
Adjusted balance, beginning of period (in shares)		1,407,794				3,647,675
Exercise of stock options	4		4
Exercise of stock options (in shares)		1,535
Stock-based compensation expense	321		321
Foreign currency translation adjustment	(42)			(42)
Net Income (Loss)	(15,221)				(15,221)
Ending balance at Mar. 31, 2024	(99,574)	$ 0	6,304	(53)	(105,825)	$ 80,627
Ending balance (in shares) at Mar. 31, 2024		1,409,329				3,647,675
Beginning balance at Dec. 31, 2023	$ (84,636)	$ 0	5,979	(11)	(90,604)	$ 80,627
Beginning balance (in shares) at Dec. 31, 2023		2,634,246				6,825,483
Exercise of stock options (in shares)	276,854
Net Income (Loss)	$ (45,609)
Ending balance at Sep. 30, 2024	150,361	$ 2	286,649	(77)	(136,213)	$ 0
Ending balance (in shares) at Sep. 30, 2024		14,744,477				0
Beginning balance at Mar. 31, 2024	(99,574)	$ 0	6,304	(53)	(105,825)	$ 80,627
Beginning balance (in shares) at Mar. 31, 2024		1,409,329				3,647,675
Exercise of stock options	644		644
Exercise of stock options (in shares)		265,165
Stock-based compensation expense	403		403
Conversion of convertible preferred stock into common stock in connection with the Merger	80,627		80,627			$ (80,627)
Conversion of convertible preferred stock into common stock in connection with the Merger (in shares)		3,647,675				(3,647,675)
Issuance of common stock to related party investors upon redemption of the SAFEs	34,125		34,125
Issuance of common stock to related party investors upon redemption of the SAFEs (in shares)		1,470,839
Issuance of common stock under subscription agreement	94,601	$ 1	94,600
Issuance of common stock under subscription agreement (in shares)		4,163,606
Issuance of common stock upon the Merger	78,157	$ 1	78,156
Issuance of common stock upon the Merger (in shares)		3,777,709
Transaction cost in connection with the Merger	(9,937)		(9,937)
Foreign currency translation adjustment	(8)			(8)
Net Income (Loss)	(12,671)				(12,671)
Ending balance at Jun. 30, 2024	166,367	$ 2	284,922	(61)	(118,496)	$ 0
Ending balance (in shares) at Jun. 30, 2024		14,734,323				0
Exercise of stock options	77		77
Exercise of stock options (in shares)		10,154
Stock-based compensation expense	1,650		1,650
Foreign currency translation adjustment	(16)			(16)
Net Income (Loss)	(17,717)				(17,717)
Ending balance at Sep. 30, 2024	$ 150,361	$ 2	$ 286,649	$ (77)	$ (136,213)	$ 0
Ending balance (in shares) at Sep. 30, 2024		14,744,477				0

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Jun. 30, 2024 USD ($)
At the Market Facility [Member]
Net of offering costs	$ 2,000

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net loss	$ (45,609)	$ (34,954)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense	1,137	1,105
Stock-based compensation expense	2,374	827
Non-cash lease expense	903	830
Change in fair value of SAFE liabilities	3,610	0
Change in operating assets and liabilities:
Prepaid expenses and other current assets	(1,080)	91
Other non-current assets	(160)	(7)
Accounts payable	16	4,019
Accrued expenses and other current liabilities	(2,451)	(239)
Operating lease liabilities	(999)	(640)
Other non-current liabilities	0	(56)
Net cash used in operating activities	(42,259)	(29,024)
Cash flows from investing activities:
Purchase of property, equipment and improvements	(153)	(229)
Net cash used in investing activities	(153)	(229)
Cash flows from financing activities:
Proceeds from the Subscription Agreement, net of offering costs of $2,000	94,600	0
Cash acquired in connection with the Merger	85,230	0
Payment for Merger transaction costs	(7,412)	0
Proceeds from exercise of common stock options	725	1
Repayment of finance lease obligations	(360)	(384)
Net cash provided by (used in) financing activities	172,783	(383)
Effect of exchange rate changes on cash and cash equivalents	(45)	0
Net increase (decrease) in cash and cash equivalents and restricted cash	130,326	(29,636)
Cash and cash equivalents and restricted cash as of beginning of period	29,356	36,553
Cash and cash equivalents and restricted cash as of end of period	159,682	6,917
Components of cash, cash equivalents and restricted cash:
Cash and cash equivalents	159,095	6,330
Restricted cash	587	587
Total cash, cash equivalents and restricted cash	159,682	6,917
Supplemental disclosure of non-cash financing activities:
Merger transaction costs included in accounts payable and accrued expenses	2,524	0
Conversion of SAFEs to Common Stock	34,125	0
Conversion of Convertible Preferred Stock to Common Stock	80,627	0
Purchase of equipment through the end of the finance leases		234
Supplemental disclosure of cash flow information:
Cash paid for interest	$ 59	$ 118

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (unaudited) (Parenthetical) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Statement of Cash Flows [Abstract]
Offering Cost	$ 2,000

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (17,717)	$ (12,671)	$ (15,221)	$ (10,054)	$ (10,455)	$ (14,445)	$ (45,609)	$ (34,954)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	1. DESCRIPTION OF BUSINESS Business Tectonic Therapeutic, Inc. (formerly AVROBIO, Inc.) (the “Company” or “Tectonic”) is a clinical-stage biotechnology company focused on the discovery and development of therapeutic proteins and antibodies that modulate the activity of Reverse Merger and Pre-Merger Financing Transaction On June 20, 2024, the Company completed its previously announced merger transaction in accordance with the terms of the Agreement and Plan of Merger and Reorganization, dated as of January 30, 2024 (the “Merger Agreement”) with AVROBIO, Inc. (“AVROBIO”), pursuant to which Alpine Merger Subsidiary, Inc., a wholly owned subsidiary of AVROBIO, merged with and into the entity formerly known as Tectonic Therapeutic, Inc., now known as Tectonic Operating Company, Inc. (“Legacy Tectonic”), with Legacy Tectonic continuing as a wholly owned subsidiary of the surviving corporation of AVROBIO (the “Merger”). The Merger is being accounted for as a reverse recapitalization in accordance with generally accepted accounting principles in the United States of America (“GAAP”), with AVROBIO treated as the acquired company for financial reporting purposes, and Legacy Tectonic treated as the accounting acquirer. Upon the closing of the Merger, each outstanding share of Legacy Tectonic’s common stock, including outstanding and unvested restricted stock, was converted into the right to receive a number of shares of AVROBIO’s common stock based on an exchange ratio of 0.53 (the “Exchange Ratio”), as defined in the Merger Agreement, after giving effect to the 1-for-12 reverse stock split of AVROBIO common stock that was effected on June 20, 2024. The exchange ratio was retroactively applied to all outstanding common shares, convertible preferred shares, stock options and restricted stock. Each outstanding and unexercised option to purchase shares of Legacy Tectonic’s common stock immediately prior to closing was assumed by AVROBIO and was converted into an option to purchase shares of AVROBIO common stock, with necessary adjustments to the number of shares and exercise price to reflect the Exchange Ratio. All of Legacy Tectonic’s restricted common stock outstanding and unvested immediately prior to the closing that was assumed by AVROBIO in the Merger remains unvested to the same extent and is subject to the same repurchase option, risk of forfeiture or other condition under any applicable restricted stock purchase agreement. Legacy Tectonic stockholders received 10,956,614 shares of AVROBIO common stock in connection with the Merger, including 11,447 shares of AVROBIO restricted common stock subject to vesting terms, of which 4,588 have since vested subsequent to the closing of the Merger, based on the number of shares of Legacy Tectonic common stock outstanding immediately prior to the Merger, including restricted stock, the number of shares of common stock issued to investors participating in the Subscription Agreements (as defined below) and SAFEs, and Legacy Tectonic convertible preferred stock outstanding immediately prior to the Merger, which was converted into shares of Legacy Tectonic common stock on a one-for-one basis immediately prior to the closing of the Merger. In connection with the Merger, the Company and its designated rights agent entered into a contingent value rights agreement (the “CVR Agreement”). Pursuant to the CVR Agreement, each holder of AVROBIO common stock immediately prior to the closing received a contractual contingent value right (“CVR”) subject to and in accordance with the terms and conditions of the CVR Agreement, representing the contractual right to receive a pro rata portion of any net proceeds, if any, as a resulting from a disposition of certain AVROBIO intellectual property (including a license of AVROBIO’s pre-closing assets as defined in the CVR Agreement) after the closing and prior to the 18 -month anniversary of the closing, received within a 10 -year period following the closing; provided that no contingent payment will be payable to any holder of the CVRs until such time as the then-outstanding and undistributed proceeds exceeds $ 0.4 million in the aggregate. As of September 30, 2024 , no proceeds have been received under the CVR Agreement. As of September 30, 2024 there is no liability recorded in connection with the CVR Agreement. Concurrently with the closing of the Merger, certain investors of Legacy Tectonic completed the purchase of 7,790,889 shares of Legacy Tectonic common stock pursuant to that certain Subscription Agreement dated January 30, 2024 (the “Subscription Agreement”) at a purchase price of $ 12.40 per share for an aggregate purchase price of $ 96.6 million. Shares of Legacy Tectonic common stock issued pursuant to the Subscription Agreements were converted into 4,163,606 shares of AVROBIO common stock at the closing of the Merger based on the Exchange Ratio, pursuant to the Merger Agreement. Risks and Uncertainties The Company is subject to risks common to companies in the biotechnology industry including, but not limited to, new technological innovations, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing. Product candidates currently under development will require significant additional research and development efforts, including extensive pre-clinical and clinical testing and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure, and extensive compliance reporting capabilities. The Company’s proprietary GEODe ™ platform is currently in development. There can be no assurance that current and future research and development activities will be successfully completed, that adequate protection for owned intellectual property will be obtained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. Liquidity and Going Concern As of September 30, 2024, the Company had an accumulated deficit of $ 136.2 million and has incurred losses and negative cash flows from operations since inception, including a net loss of $ 17.7 million and $ 45.6 million for the three and nine months ended September 30, 2024, respectively. To date, the Company has financed its operations primarily through the issuance of common stock, convertible preferred stock, convertible promissory notes and Simple Agreements for Future Equity (“SAFEs”). The Company has devoted substantially all of its financial resources and efforts to business planning, conducting research and development, recruiting management and technical staff, and raising capital. Management expects that the Company’s operating losses and negative cash flows will continue for the foreseeable future as it continues to develop its product candidates. As the Company continues to develop its proprietary platform and potential product candidates, it will require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. It may never achieve profitability, and unless and until it does, it will continue to need to raise additional capital to fund its operations. Management believes that its current cash on hand, which includes the proceeds related to the Merger and Subscription Agreements, is sufficient to fund the Company’s planned operations for at least one year from the date of issuance of these unaudited condensed consolidated financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES During the nine months ended September 30, 2024, there were no significant changes to the Company’s significant accounting policies as described in the Company’s audited consolidated financial statements as of and for the years ended December 31, 2023 and 2022. Basis of Presentation The accompanying unaudited interim condensed consolidated financial statements have been prepared in conformity with GAAP and the rules and regulations of the Securities and Exchange Commission (“SEC”). Any reference in these notes to applicable guidance is meant to refer to GAAP, as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). In the opinion of the Company, the accompanying unaudited condensed consolidated financial statements contain all adjustments, consisting of only normal recurring adjustments, necessary for a fair presentation of its financial position and its results of operations, changes in convertible preferred stock and stockholders’ equity (deficit) and cash flows. The information as of December 31, 2023 included in the unaudited interim condensed consolidated balance sheets was derived from audited annual consolidated financial statements but does not contain all of the footnote disclosures from the audited annual consolidated financial statements. These unaudited interim condensed consolidated financial statements should be read in conjunction with the audited annual consolidated financial statements as of and for the years ended December 31, 2023 and 2022 . Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include the contract research accruals, stock-based compensation expense, the fair value of the Company’s common stock, the income tax valuation allowance, and the fair value determination of the SAFEs. Management’s estimates are based on historical experience and various other assumptions that it believes are reasonable under the circumstances. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates. Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB, or other standard setting bodies and are adopted by the Company as of the specified effective dates. Unless otherwise discussed, the impact of recently issued standards that are not yet effective are not anticipated to have a material impact on the Company’s condensed consolidated financial statements upon adoption. Recently Issued Accounting Pronouncements Not Yet Adopted In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280) (“ASU 2023-07”), which enhances the segment disclosure requirements for public entities on an annual and interim basis. Under ASU 2023-07, public entities will be required to disclose significant segment expenses that are regularly provided to the chief operating decision maker (“CODM”) and included within each reported measure of segment profit or loss. Additionally, current annual disclosures about a reportable segment’s profit or loss and assets will be required on an interim basis. Entities will also be required to disclose information about the CODM’s title and position at the Company along with an explanation of how the CODM uses the reported measures of segment profit or loss in their assessment of segment performance and deciding whether how to allocate resources. Finally, ASU 2023-07 requires all segment disclosures for public entities that have only a single reportable segment. The amendments in ASU 2023-07 are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2023-07 on its financial statements. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740) (“ASU 2023-09”), which enhances the income tax disclosure requirements for public entities on an annual basis. Under ASU 2023-09, public entities will be required to disclose in their rate reconciliation, on an annual basis, both percentages and amounts in their reporting currency for certain categories in a tabular format, with accompanying qualitative disclosures. The amendments in ASU 2023-09 are effective for fiscal years beginning after December 15, 2024, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2023-09 on its financial statements.

Merger

Merger	9 Months Ended
	Sep. 30, 2024
Merger [Abstract]
Merger	3. Merger As described in Note 1 “Description of Business,” the Company completed its previously announced Merger with AVROBIO on June 20, 2024. The Merger was accounted for as a reverse recapitalization in accordance with GAAP with Legacy Tectonic as the accounting acquirer of AVROBIO. At the effective time of the Merger, substantially all the assets of AVROBIO consisted of cash and cash equivalents, as well as other nominal non-operating assets. Under such reverse recapitalization accounting, the assets and liabilities of AVROBIO were recorded at their fair value in AVROBIO’s financial statements at the effective time of the Merger, which approximated book value due to their short-term nature. No goodwill or intangible assets were recognized. Consequently, the condensed consolidated financial statements of the Company reflect the historical operations of Legacy Tectonic for accounting purposes together with the issuance of shares to the former shareholders of AVROBIO, the legal acquirer, and a recapitalization of the equity of Legacy Tectonic, the accounting acquirer. The exchange ratio was retroactively applied to all outstanding common shares, convertible preferred shares, stock options and restricted stock of Legacy Tectonic. As part of the recapitalization, Legacy Tectonic obtained the assets and liabilities listed below: Cash and cash equivalents $ 85,230 Prepaid expenses and other current assets 319 Accounts payable ( 1,988 ) Accrued expenses and other current liabilities ( 5,405 ) Net assets acquired $ 78,156 The Company incurred transaction costs of $ 9.9 million, of which $ 2.3 million was recorded within accrued expenses and other current liabilities and $ 0.2 million was recorded within accounts payable on the condensed consolidated balance sheet as of September 30, 2024. $ 9.9 million was recorded as a reduction to additional paid-in capital in the condensed consolidated balance sheet. With respect to the CVRs issued in connection with the Merger, the Company believes that any receipt of payments resulting from an AVROBIO disposition of AVROBIO’s pre-closing assets described in the CVR Agreement are highly susceptible to factors outside the Company’s influence that are not expected to be resolved within the timeline outlined in the CVR Agreement, if at all. In particular, these amounts are primarily influenced by the actions and judgments of third parties and the buyers of such assets and are based on the buyers of such assets progressing the specific platform and intellectual property and early stage of research and development programs. If the Company were to record a receivable for such contingent payments, it would also record a corresponding liability. As of September 30, 2024 , no receivables or liabilities were recorded on the condensed consolidated balance sheet relating to such contingent payments.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. FAIR VALUE MEASUREMENTS The following tables present information about financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): September 30, 2024 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 160,769 $ — $ — $ 160,769 $ 160,769 $ — $ — $ 160,769 le December 31, 2023 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 27,278 $ — $ — $ 27,278 Total assets $ 27,278 $ — $ — $ 27,278 Liabilities: SAFE liabilities $ — $ — $ 30,515 $ 30,515 Total liabilities $ — $ — $ 30,515 $ 30,515 Money market funds are included in cash and cash equivalents on the condensed consolidated balance sheets and are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices. There were no transfers between the Level 1, Level 2 or Level 3 categories during the nine months ended September 30, 2024 and 2023. SAFE Liabilities From October through December 2023, Legacy Tectonic entered into multiple SAFE agreements with certain existing investors and received $ 34.1 million. Prior to redemption, the SAFE liabilities were valued using a probability weighted scenario analysis and discount rates derived by application of the build-up method to reflect the cost of equity. The valuation model required a variety of inputs, including the probability of occurrence of events that would trigger conversion or redemption of the SAFEs, the expected timing of such events, and a discount rate. All investors were considered related parties of the Company. Upon the closing of the Merger, the principal balance of the SAFEs was automatically redeemed for 2,752,216 shares of Legacy Tectonic common stock at the conversion price of $ 12.40 per share immediately prior to the Merger closing. As such the valuation inputs utilized to adjust the SAFE liability to fair value upon the closing of the Merger was $ 12.40 . At closing, shares of Legacy Tectonic common stock issued pursuant to the redemption of Legacy Tectonic SAFEs were converted into 1,470,839 shares of AVROBIO common stock based on the Exchange Ratio, pursuant to the Merger Agreement. The following table presents activity for the SAFE liabilities that were measured at fair value using significant unobservable Level 3 inputs during the nine months ended September 30, 2024 and the year ended December 31, 2023 (in thousands): SAFE Liabilities Balance as of January 1, 2023 $ — Initial fair value recognition 31,515 Loss on issuance 255 Fair value adjustments ( 1,255 ) Balance as of December 31, 2023 30,515 Fair value adjustments 3,610 Conversion ( 34,125 ) Balance as of September 30, 2024 $ —

Property, Equipment and Improve

Property, Equipment and Improvements, Net	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Property, Equipment and Improvements, Net	5. PROPERTY, EQUIPMENT AND IMPROVEMENTS, NET Property, equipment and improvements, net is comprised of the following (in thousands): September 30, December 31, Laboratory equipment $ 4,721 $ 4,510 Furniture and office equipment 244 244 Computer equipment 212 161 Construction in progress — 38 Leasehold improvements 25 25 5,202 4,978 Less: accumulated depreciation ( 2,652 ) ( 1,856 ) Property and equipment, net $ 2,550 $ 3,122 Depreciation expense during the three and nine months ended September 30, 2024 and 2023 was recorded as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 General and administrative $ 16 $ 4 $ 25 $ 13 Research and development 265 251 783 719 $ 281 $ 255 $ 808 $ 732

Accrued Expenses and Other Curr

Accrued Expenses and Other Current Liabilities	9 Months Ended
	Sep. 30, 2024
Payables and Accruals [Abstract]
Accrued Expenses and Other Current Liabilities	6. ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES Accrued expenses and other current liabilities is comprised of the following (in thousands): September 30, December 31, Accrued Tectonic transaction costs $ 2,303 $ — Accrued AVROBIO transaction costs 1,369 — Employee compensation related costs 3,106 2,840 Accrued professional fees 1,934 1,798 Accrued contract research organization fees 2,196 2,298 Accrued contract development and manufacturing organization fees 985 660 Accrued office and laboratory costs 100 211 Other current liabilities 744 334 $ 12,737 $ 8,141

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. COMMITMENTS AND CONTINGENCIES Harvard Agreement In July 2020, Legacy Tectonic entered into an agreement with the President and Fellows of Harvard College (“Harvard”), for an option fee in the low five digits, whereby Harvard granted Legacy Tectonic an exclusive option to negotiate a worldwide, exclusive, royalty-bearing license under Harvard’s interest in the patent rights covering certain technology that was developed by Harvard. In October 2021, Legacy Tectonic exercised the option and on February 10, 2022, entered into a license agreement (“License Agreement”) with Harvard to conduct research and development activities using certain materials, technology and patent rights owned by Harvard, with the intent to develop, obtain regulatory approval for, and commercialize products. The License Agreement will remain in effect until the expiration of the last valid claim within the patent rights covering a product developed under the License Agreement or the termination of the License Agreement. Management concluded that the acquisition of patents and materials received under the License Agreement represents an asset acquisition of an in-progress research and development asset without future alternative use; therefore, any consideration paid was expensed. As consideration for the License Agreement, Legacy Tectonic agreed to pay Harvard a non-refundable license fee, consisting of a cash payment due in three equal annual installments, in total amounting to $ 170,000 . The first two installments were paid in July 2022 and 2023 and the third installment was made in July 2024. As partial consideration for the Harvard License Agreement, the Company entered into a subscription agreement with Harvard in July 2022, pursuant to which Harvard was granted 227,486 shares of common stock with a fair market value in the mid six digits. The Company also will be responsible for payment of (1) annual maintenance fees ranging from the low five digits to the low six digits during the term of the License Agreement (through the first commercial sale of a royalty-bearing product); (2) royalty payments as a percentage in the low single digits of the annual net sales that the Company generates from products that utilize the license technology (“Licensed Products”) and royalty payments as a percentage in the low single digits of the annual net sales that the Company generates from know-how enabled product licenses (“Know-How Enabled Products”) and (3) a percentage between 10 - 20 % of all non-royalty income received by the Company under sublicenses, strategic partnerships and know-how enabled product licenses that utilize the license technology. Subsequent to the first commercial sale of a royalty-bearing product, annual maintenance fees will increase to a low six digits for the remainder of the term of the License Agreement. The royalty term from sales of Licensed Products will terminate on a country-by-country and product-by-product basis on the earlier of (i) the expiration of the patent rights covering the product, expected to be no earlier than May 2041, and (ii) the termination of the License Agreement. The Company is also required to pay a one-time milestone payment of $ 100,000 for each discovered product granted FDA marketing authorization as well as for the first licensed product or know-how enabled product to reach certain clinical developmental milestones, up to $ 8.5 million and for the first licensed product or know-how enabled product to reach certain commercial milestones, up to $ 2.0 million. The royalty term from sales of Know-How Enabled Products will terminate on the earlier of (i) ten years after the first commercial sale of the first Know-How Enabled Product and (ii) twelve years after the first commercial sale of the first Licensed Product. There was $ 0.1 million due to Harvard as of September 30, 2024. During the three months ended September 30, 2024 and 2023, the Company paid $ 0.1 million and less than $ 0.1 million , respectively, and during each of the nine months ended September 30, 2024 and 2023, the Company paid $ 0.2 million to Harvard. The Harvard License Agreement meets the criteria to be considered a related party transaction due to the Company’s co-founders’ employment as professors in the Harvard Department of Molecular Pharmacology. Additionally, both co-founders served on the board for a portion of the nine months ended September 30, 2024, with one stepping down in June. One co-founder is a shareholder in the Company. Alloy Therapeutics License Agreement On November 29, 2021, Legacy Tectonic executed a license agreement with Alloy Therapeutics, LLC (“ATX”), whereby the Company will use ATX technology for the purpose of preclinical development, clinical development and commercialization of potential product candidates, for an initial period of three years, with an option to extend the term for an additional two years. The Company will pay ATX a non-refundable and non-creditable annual fee of $ 0.1 million on each anniversary of the agreement. On November 7, 2022, Legacy Tectonic and ATX amended the agreement and extended the period of payment for the first fee due, which was paid in May 2023. Additionally, the Company will be responsible for annual partnering fees if the Company decides to pursue clinical development of a product candidate using the ATX technology. The partnering fees may be creditable against future milestone development fees paid by the Company. The Company will also be responsible to pay ATX development milestone payments for the movement of certain product candidates through clinical trials, which range from the low six digits to the low seven digits upon completion of each milestone and amount to $ 4.8 million in total milestone payments under the license agreement. Provided the Company is able to commercialize a product using ATX technology, the Company will be responsible to pay ATX commercial payments in the low seven digits per year during the first six years of commercial sales, amounting to an amount in the high eight digits in total commercial payments under the license agreement. Pursuant to the terms of the agreement, the Company had no expense for the three and nine months ended September 30, 2024, and less than $ 0.1 million during the three and nine months ended September 30, 2023. The Company intends to terminate the agreement with Alloy effective November 14, 2024. Adimab Agreement On May 1, 2023, Legacy Tectonic entered into a discovery agreement with Adimab, LLC (“Adimab”), an antibody discovery company, whereby Legacy Tectonic and Adimab are collaborating on human antibody discovery in accordance with an agreed upon research program. Legacy Tectonic paid an upfront technology access fee totaling $ 20,000 upon execution of the agreement. This agreement is considered to be a related party agreement. The Company terminated the agreement with Adimab in July 2024. Pursuant to the terms of the agreement, the Company recorded no expense and $ 0.2 million for the three and nine months ended September 30, 2024, and $ 0.1 million for the three and nine months ended September 30, 2023. As a result of the termination of the agreement, there are no further amounts due to Adimab and there is no accrual related to the agreement as of September 30, 2024. Indemnification Agreements In accordance with the Company’s amended and restated certificate of incorporation (“ARCOI”) and certain indemnification agreements, the Company indemnifies certain officers and directors for specified events or occurrences, subject to certain limits, in which the officer or director is or was serving at the Company’s request in such capacity. The Company enters into certain types of contracts that contingently requires it to indemnify various parties against claims from third parties. These contracts primarily relate to (i) the Company’s bylaws, under which it must indemnify directors and executive officers, and may indemnify other officers and employees, for liabilities arising out of their relationship with the Company, (ii) contracts under which it must indemnify directors and certain officers and consultants for liabilities arising out of their relationship, and (iii) procurement, service or license agreements under which the Company may be required to indemnify vendors, service providers or licensees for certain claims, including claims that may be brought against them arising from the Company’s acts or omissions with respect to the its products, technology, intellectual property or services. From time to time, the Company may receive indemnification claims under these contracts in the normal course of business. In the event that one or more of these matters were to result in a claim against the Company, an adverse outcome, including a judgment or settlement, may cause a material adverse effect on future business, operating results or financial condition. It is not possible to estimate the maximum amount potentially payable under these contracts since there is no history of prior indemnification claims and the unique facts and circumstances involved in each particular claim will be determinative. As of September 30, 2024 and December 31, 2023 , no amounts were accrued related to indemnification claims. Litigation In the normal course of operations, the Company may become involved in various legal proceedings. As of September 30, 2024 and December 31, 2023 , the Company has not recorded accruals for probable losses related to any existing or pending litigation as the Company’s management has determined that there are no matters where a potential loss is probable and reasonably estimable. The Company does not believe that any existing or pending claims would have a material impact on the Company’s condensed consolidated financial statements.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Stockholders' Equity	8. STOCKHOLDERS’ EQUITY Convertible Preferred Stock Prior to the conversion upon the closing of the Merger, Legacy Tectonic issued Series A-1, A-2, A-3 and A-4 convertible preferred stock (the “Preferred Stock”). Prior to the completion of the Merger, Legacy Tectonic classified the Preferred Stock outside of permanent equity as the shares had redemption features that were not entirely within the control of Legacy Tectonic. Upon the closing of the Merger, all outstanding shares of the Preferred Stock were converted into 3,647,675 shares of common stock. No shares of the Preferred Stock were outstanding as of September 30, 2024. Preferred Stock Subsequent to consummation of the Merger, the Company authorized the issuance of 10,000,000 shares of new undesignated preferred stock, however no such shares were issued or outstanding as of September 30, 2024. Common Stock In connection with the Merger, the Company authorized the issuance of 150,000,000 shares of common stock at a par value of $ 0.0001 . Holders of voting common stock are entitled to one vote per share . In addition, holders of voting common stock are entitled to receive dividends, if and when declared by the Company’s Board of Directors. As of September 30, 2024 , no dividends had been declared.

Equity Incentive Plans

Equity Incentive Plans	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Equity Incentive Plans	9. EQUITY INCENTIVE PLANS 2019 Equity Incentive Plan The Legacy Tectonic 2019 Equity Incentive Plan (the “2019 Plan”) provides employees, consultants and advisors and non-employee members of the Board of Directors and its affiliates with the opportunity to receive grants of stock options, stock awards and equity awards. Since inception, Legacy Tectonic has only issued stock options. 2024 Equity Incentive Plan On June 20, 2024, the Company adopted the 2024 Equity Incentive Plan (the “2024 Plan”) which became effective upon completion of the Merger. The 2024 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance awards and other forms of awards to employees, consultants, and non-employee directors of the Company. The terms of stock award agreements, including vesting requirements, are determined by the Company’s Board of Directors and are subject to the provisions of the 2024 Plan. The term of each stock option shall be no more than ten years from the date of grant. Following the effectiveness of the 2024 Plan, no further grants will be made under the 2019 Plan; however, any outstanding equity awards granted under the 2019 Plan will continue to be governed by the terms of the 2019 Plan. The 2024 Plan initially provided for the issuance of up to 1,938,799 shares of common stock (the “Initial Share Reserve”). Subject to any other adjustments as defined in the 2024 Plan, such aggregate number of shares of common stock will automatically increase on January 1st of each year for a period of ten years commencing on January 1, 2025 and ending on (and including) January 1, 2034, in an amount equal to 5% of the total number of shares of common stock issued and outstanding determined as of the day prior to such increase; provided , however that the board of directors may act prior to January 1st of a given year to provide that the increase for such year will be a lesser number of shares of common stock. The maximum number of shares of common stock that may be issued under the 2024 Plan pursuant to the exercise of incentive stock options shall not exceed three times the Initial Share Reserve. As of September 30, 2024, there were 1,004,299 shares available for issuance under the 2024 Plan. 2024 Employee Stock Purchase Plan On June 20, 2024, the Company adopted the 2024 Employee Stock Purchase Plan (the “2024 ESPP”), which became effective upon completion of the Merger. The maximum number of shares of common stock that may be issued under the 2024 ESPP will not exceed 147,343 shares (the “Initial ESPP Share Reserve”), plus the number of shares of common stock that are automatically added on January 1st of each year for a period of up to ten years commencing on January 1, 2025 and ending on (and including) January 1, 2034, in an amount equal to the lesser of (x) 1% of the total number of shares of common stock issued and outstanding determined as of the day prior to such increase and (y) a number of shares equal to three times the Initial ESPP Share Reserve . Notwithstanding the foregoing, the Board of Directors may act prior to the first day of any calendar year to provide that there will be no January 1st increase in the share reserve for such calendar year or that the increase in the share reserve for such calendar year will be a lesser number of shares of common stock than would otherwise occur pursuant to the preceding sentence. No offering periods under the 2024 ESPP had been initiated as of September 30, 2024. Stock Options The following table summarizes the stock option activity under the 2019 Plan and 2024 Plan for the nine months ended September 30, 2024 is as follows (in thousands except share, contractual term and per share amounts): Number of Weighted- Weighted-Average Aggregate Balance as of January 1, 2024 1,002,485 $ 3.11 8.2 $ 2,276 Options Granted 934,500 16.80 Options Exercised ( 276,854 ) 2.62 $ 2,767 Options Forfeited and Expired ( 224,963 ) 110.43 Options assumed from AVROBIO upon Merger 365,428 89.92 Balance as of September 30, 2024 1,800,596 $ 14.50 8.1 $ 33,499 Options vested and exercisable as of September 30, 2024 543,994 $ 16.72 5.2 $ 12,429 Options vested and expected to vest 1,800,596 $ 14.50 8.1 $ 33,499 The weighted-average grant-date fair value of options granted during the nine months ended September 30, 2024 and 2023 was $ 13.94 and $ 2.51 per share, respectively. As of September 30, 2024, total compensation cost not yet recognized related to unvested stock options was $ 13.4 million , which is expected to be recognized over a weighted-average period of 3.4 years. The fair values of the options granted in the nine months ended September 30, 2023 were estimated based on the Black-Scholes-Merton option pricing model, using the following assumptions: Nine Months Ended September 30, 2024 2023 Fair value per share of underlying common stock $ 16.09 - $ 16.80 $ 2.51 Expected term (in years) 6.00 - 6.25 5.93 Expected volatility 104 % 111 % Risk-free interest rate 4.23 % - 4.26 % 3.65 % Expected dividend yield — % — % Restricted Common Stock Since 2019, Legacy Tectonic has granted restricted common stock to founders, employees and consultants. The purchase price of the restricted common stock is the estimated fair value on the grant date and the restricted stock is subject to various vesting schedules. Unvested restricted common stock is subject to repurchase rights held by the Company at the original issuance price in the event the restricted common stockholders’ service to the Company is terminated either voluntarily or involuntarily. The 6,859 unvested restricted common shares are included in the total shares of common stock outstanding as of September 30, 2024 and a repurchase liability of $ 0.1 million is recorded in accrued expenses and other current liabilities in the accompanying condensed consolidated balance sheet. The following table summarizes restricted stock activity for the nine months ended September 30, 2024: Number of Shares Unvested restricted common stock as of January 1, 2024 18,968 Granted — Early exercise of options 6,859 Vested ( 18,968 ) Forfeited — Unvested restricted common stock as of September 30, 2024 6,859 The weighted-average grant date fair value of unvested restricted common stock and restricted common stock vested and forfeited for the nine months ended September 30, 2024 and 2023 was immaterial. Stock-Based Compensation Expense The Company recorded stock-based compensation expense relating to its employees and nonemployees is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 General and administrative $ 1,227 $ 174 $ 1,648 $ 522 Research and development 423 101 726 305 $ 1,650 $ 275 $ 2,374 $ 827 The Company records compensation expense for options with service based vesting conditions on a straight-line basis over the vesting period. Modification of Certain Stock Options In July 2024, the Company entered into a separation agreement with the Company’s Chief Operating Officer (the “Former Executive”). As part of the termination of employment, the Former Executive will serve as an advisor to the Company through March 31, 2025 (“Consulting Period”) on an as needed basis and certain modifications to the Former Executive’s vested and non-vested stock option awards were executed including continued vesting of options during the Consulting Period and the extension of the post-termination exercise period of certain stock option awards. The services performed during the Consulting Period do not qualify as substantive services under ASC 718, Compensation—Stock Compensation; therefore, the continued vesting of these awards represents a modification to the original award. During the three months ended September 30, 2024, the Company recorded stock compensation expense of $ 0.4 million for the modification of the stock options of the Former Executive. This amount is included in general and administrative expenses on the condensed consolidated statement of operations and comprehensive loss.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	10. INCOME TAXES During the three and nine months ended September 30, 2024 and 2023 , the Company recorded no income tax provision or benefit. The Company has evaluated the positive and negative evidence bearing upon its ability to realize its deferred tax assets, which primarily consist of net operating loss carryforwards. The Company has considered its history of cumulative net losses, estimated future taxable income and prudent and feasible tax planning strategies and has concluded that it is more likely than not that the Company will not realize the benefits of its deferred tax assets. As a result, as of September 30, 2024 , the Company has maintained a full valuation allowance against its net deferred tax assets.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Net Loss Per Share	11. Net loss per share Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Numerator: Net loss $ ( 17,717 ) $ ( 10,054 ) $ ( 45,609 ) $ ( 34,954 ) Denominator: Weighted-average common shares outstanding, basic 14,729,018 1,319,147 6,373,717 1,245,745 Net loss per share attributable to common stockholders, $ ( 1.20 ) $ ( 7.62 ) $ ( 7.16 ) $ ( 28.06 ) T he following shares of potentially diluted securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: As of September 30, 2024 2023 Convertible preferred stock — 3,647,675 Options to purchase common stock 1,800,596 849,959 Unvested restricted common stock 6,859 27,280 1,807,455 4,524,914

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2024
Related Party Transactions [Abstract]
Related Party Transactions	12. RELATED PARTY TRANSACTIONS Other than the items discussed below, see Note 4 “Fair Value Measurements” and Note 7 “Commitments and Contingencies” for further discussion of related party transactions. Scientific Advisory Board Member One of the Company’s co-founders and former director is a member of the Company’s Scientific Advisory Board (“SAB”) and meets the criteria of a related party. The Company paid the SAB member fees in the amount of less than $ 0.1 million during three months ended September 30, 2024 and 2023 , and $ 0.1 million and less than $ 0.1 million for the nine months ended September 30, 2024 and 2023 , respectively, for advisory services provided. There was less than $ 0.1 million and $ 0 included in accounts payable for this related party as of September 30, 2024 and December 31, 2023, respectively .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited interim condensed consolidated financial statements have been prepared in conformity with GAAP and the rules and regulations of the Securities and Exchange Commission (“SEC”). Any reference in these notes to applicable guidance is meant to refer to GAAP, as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) of the Financial Accounting Standards Board (“FASB”). In the opinion of the Company, the accompanying unaudited condensed consolidated financial statements contain all adjustments, consisting of only normal recurring adjustments, necessary for a fair presentation of its financial position and its results of operations, changes in convertible preferred stock and stockholders’ equity (deficit) and cash flows. The information as of December 31, 2023 included in the unaudited interim condensed consolidated balance sheets was derived from audited annual consolidated financial statements but does not contain all of the footnote disclosures from the audited annual consolidated financial statements. These unaudited interim condensed consolidated financial statements should be read in conjunction with the audited annual consolidated financial statements as of and for the years ended December 31, 2023 and 2022 .
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the condensed consolidated financial statements, and the reported amounts of expenses during the reporting periods. Significant items subject to such estimates and assumptions include the contract research accruals, stock-based compensation expense, the fair value of the Company’s common stock, the income tax valuation allowance, and the fair value determination of the SAFEs. Management’s estimates are based on historical experience and various other assumptions that it believes are reasonable under the circumstances. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of the Company and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the FASB, or other standard setting bodies and are adopted by the Company as of the specified effective dates. Unless otherwise discussed, the impact of recently issued standards that are not yet effective are not anticipated to have a material impact on the Company’s condensed consolidated financial statements upon adoption.
Recently issued accounting pronouncements not yet adopted	Recently Issued Accounting Pronouncements Not Yet Adopted In November 2023, the FASB issued ASU No. 2023-07, Segment Reporting (Topic 280) (“ASU 2023-07”), which enhances the segment disclosure requirements for public entities on an annual and interim basis. Under ASU 2023-07, public entities will be required to disclose significant segment expenses that are regularly provided to the chief operating decision maker (“CODM”) and included within each reported measure of segment profit or loss. Additionally, current annual disclosures about a reportable segment’s profit or loss and assets will be required on an interim basis. Entities will also be required to disclose information about the CODM’s title and position at the Company along with an explanation of how the CODM uses the reported measures of segment profit or loss in their assessment of segment performance and deciding whether how to allocate resources. Finally, ASU 2023-07 requires all segment disclosures for public entities that have only a single reportable segment. The amendments in ASU 2023-07 are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2023-07 on its financial statements. In December 2023, the FASB issued ASU No. 2023-09, Income Taxes (Topic 740) (“ASU 2023-09”), which enhances the income tax disclosure requirements for public entities on an annual basis. Under ASU 2023-09, public entities will be required to disclose in their rate reconciliation, on an annual basis, both percentages and amounts in their reporting currency for certain categories in a tabular format, with accompanying qualitative disclosures. The amendments in ASU 2023-09 are effective for fiscal years beginning after December 15, 2024, and early adoption is permitted. The Company is currently evaluating the impact of ASU 2023-09 on its financial statements.

Merger (Tables)

Merger (Tables)	9 Months Ended
	Sep. 30, 2024
Business Combinations [Abstract]
Summary Of The Company Obtain The Assets And Liabilities	As part of the recapitalization, Legacy Tectonic obtained the assets and liabilities listed below: Cash and cash equivalents $ 85,230 Prepaid expenses and other current assets 319 Accounts payable ( 1,988 ) Accrued expenses and other current liabilities ( 5,405 ) Net assets acquired $ 78,156

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2024
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following tables present information about financial assets and liabilities measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): September 30, 2024 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 160,769 $ — $ — $ 160,769 $ 160,769 $ — $ — $ 160,769 le December 31, 2023 Level 1 Level 2 Level 3 Total Assets: Cash equivalents: Money market funds $ 27,278 $ — $ — $ 27,278 Total assets $ 27,278 $ — $ — $ 27,278 Liabilities: SAFE liabilities $ — $ — $ 30,515 $ 30,515 Total liabilities $ — $ — $ 30,515 $ 30,515
Summary of Activity for the Safe Liabilities that were Measured at Fair Value	The following table presents activity for the SAFE liabilities that were measured at fair value using significant unobservable Level 3 inputs during the nine months ended September 30, 2024 and the year ended December 31, 2023 (in thousands): SAFE Liabilities Balance as of January 1, 2023 $ — Initial fair value recognition 31,515 Loss on issuance 255 Fair value adjustments ( 1,255 ) Balance as of December 31, 2023 30,515 Fair value adjustments 3,610 Conversion ( 34,125 ) Balance as of September 30, 2024 $ —

Property, Equipment and Impro_2

Property, Equipment and Improvements, Net (Tables)	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Summary of Property Equipment and Improvements Net	Property, equipment and improvements, net is comprised of the following (in thousands): September 30, December 31, Laboratory equipment $ 4,721 $ 4,510 Furniture and office equipment 244 244 Computer equipment 212 161 Construction in progress — 38 Leasehold improvements 25 25 5,202 4,978 Less: accumulated depreciation ( 2,652 ) ( 1,856 ) Property and equipment, net $ 2,550 $ 3,122
Summary of Depreciation Expenses	Depreciation expense during the three and nine months ended September 30, 2024 and 2023 was recorded as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 General and administrative $ 16 $ 4 $ 25 $ 13 Research and development 265 251 783 719 $ 281 $ 255 $ 808 $ 732

Accrued Expenses and Other Cu_2

Accrued Expenses and Other Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2024
Payables and Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities is comprised of the following (in thousands): September 30, December 31, Accrued Tectonic transaction costs $ 2,303 $ — Accrued AVROBIO transaction costs 1,369 — Employee compensation related costs 3,106 2,840 Accrued professional fees 1,934 1,798 Accrued contract research organization fees 2,196 2,298 Accrued contract development and manufacturing organization fees 985 660 Accrued office and laboratory costs 100 211 Other current liabilities 744 334 $ 12,737 $ 8,141

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Summary of The Stock Option Activity	the stock option activity under the 2019 Plan and 2024 Plan for the nine months ended September 30, 2024 is as follows (in thousands except share, contractual term and per share amounts): Number of Weighted- Weighted-Average Aggregate Balance as of January 1, 2024 1,002,485 $ 3.11 8.2 $ 2,276 Options Granted 934,500 16.80 Options Exercised ( 276,854 ) 2.62 $ 2,767 Options Forfeited and Expired ( 224,963 ) 110.43 Options assumed from AVROBIO upon Merger 365,428 89.92 Balance as of September 30, 2024 1,800,596 $ 14.50 8.1 $ 33,499 Options vested and exercisable as of September 30, 2024 543,994 $ 16.72 5.2 $ 12,429 Options vested and expected to vest 1,800,596 $ 14.50 8.1 $ 33,499
Summary of Fair Values of the Options Granted	The fair values of the options granted in the nine months ended September 30, 2023 were estimated based on the Black-Scholes-Merton option pricing model, using the following assumptions: Nine Months Ended September 30, 2024 2023 Fair value per share of underlying common stock $ 16.09 - $ 16.80 $ 2.51 Expected term (in years) 6.00 - 6.25 5.93 Expected volatility 104 % 111 % Risk-free interest rate 4.23 % - 4.26 % 3.65 % Expected dividend yield — % — %
Summary of Restricted Stock Activity	The following table summarizes restricted stock activity for the nine months ended September 30, 2024: Number of Shares Unvested restricted common stock as of January 1, 2024 18,968 Granted — Early exercise of options 6,859 Vested ( 18,968 ) Forfeited — Unvested restricted common stock as of September 30, 2024 6,859
Summary of Stock Based Compensation Expense Regarding its Employees and Nonemployees	The Company recorded stock-based compensation expense relating to its employees and nonemployees is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 General and administrative $ 1,227 $ 174 $ 1,648 $ 522 Research and development 423 101 726 305 $ 1,650 $ 275 $ 2,374 $ 827

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Summary of Basic and Diluted Earnings Per Share	Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2024 2023 2024 2023 Numerator: Net loss $ ( 17,717 ) $ ( 10,054 ) $ ( 45,609 ) $ ( 34,954 ) Denominator: Weighted-average common shares outstanding, basic 14,729,018 1,319,147 6,373,717 1,245,745 Net loss per share attributable to common stockholders, $ ( 1.20 ) $ ( 7.62 ) $ ( 7.16 ) $ ( 28.06 )
Summary of Diluted Net Loss Per Share Attributable to Common Stockholders	he following shares of potentially diluted securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because including them would have been anti-dilutive: As of September 30, 2024 2023 Convertible preferred stock — 3,647,675 Options to purchase common stock 1,800,596 849,959 Unvested restricted common stock 6,859 27,280 1,807,455 4,524,914

Description of Business - Addit

Description of Business - Additional Information (Detail) - USD ($)		3 Months Ended						9 Months Ended
	Jan. 30, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Nature Of Operations [Line Items]
Retained earnings (accumulated deficit)		$ 136,213,000						$ 136,213,000		$ 90,604,000
Net loss		(17,717,000)	$ (12,671,000)	$ (15,221,000)	$ (10,054,000)	$ (10,455,000)	$ (14,445,000)	(45,609,000)	$ (34,954,000)
Proceeds received pursuant to agreement								$ 0
Avorbio Common Stock [Member]
Nature Of Operations [Line Items]
Stock issued during the period shares new issues converted pursuant to reverse recapitalization								4,163,606
AVROBIO [Member]
Nature Of Operations [Line Items]
Business combination, contingent consideration, liability, current		$ 0						$ 0
AVRO Avrobio Common Stock [Member]
Nature Of Operations [Line Items]
Conversion of stock shares percentage								0.53%
Stock issued during the period shares reverse recapitalization								10,956,614
Stock shares issued during the period subject to reverse recapitalization								11,447
Restricted stock shares vested after merger		4,588						4,588
Subscription Agreement [Member]
Nature Of Operations [Line Items]
Stock issued during the period shares new issues	7,790,889
Sale of stock issue price per share	$ 12.4
Proceeds from the issuance of common stock	$ 96,600,000
CVR Agreement [Member]
Nature Of Operations [Line Items]
Business combination, acquired receivables, gross contractual amount		$ 400,000						$ 400,000
Liability recorded		$ 0						$ 0
AVROBIO, Inc [Member]
Nature Of Operations [Line Items]
Period after closing with which assets may be disposed to pay the amount as per agreement								18 months
Threshold period of receipt of consideration on disposal of assets based on which amount as per agreement shall be paid								10 years

Merger - Additional Information

Merger - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($)
Merger [Line Items]
Selling, General and administrative expense	$ 9.9
Other receivables	0
Reduction to additional paid-in capital	9.9
Other Current Liabilities [Member]
Merger [Line Items]
Business combination transaction costs payable current	2.3
Accounts Payable [Member]
Merger [Line Items]
Business combination transaction costs payable current	$ 0.2

Merger - Summary Of The Company

Merger - Summary Of The Company Obtain The Assets And Liabilities (Detail) $ in Thousands	Sep. 30, 2024 USD ($)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Cash and cash equivalents	$ 85,230
Prepaid expenses and other current assets	319
Accounts payable	(1,988)
Accrued expenses and other current liabilities	(5,405)
Net assets acquired	$ 78,156

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Dec. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Proceeds from simple agreement for future equity	$ 34,100
Common stock, shares, issued	2,634,246	14,744,477
Common stock, par or stated value per share	$ 0.0001	$ 0.0001
Fair value input amount transfer in between levels		$ 0	$ 0
Simple Agreements for Future Equity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock, shares, issued		2,752,216
Common stock, par or stated value per share		$ 12.4
Simple Agreements for Future Equity [Member] | AVROBIO [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Common stock, shares, issued		1,470,839
Common stock, par or stated value per share		$ 12.4

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) - Fair Value, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Assets:
Assets	$ 160,769	$ 27,278
Liabilities:
Liabilities		30,515
SAFE Liabilities [Member]
Liabilities:
Liabilities		30,515
Money Market Funds [Member] | Cash Equivalents [Member]
Assets:
Assets	160,769	27,278
Fair Value, Inputs, Level 1 [Member]
Assets:
Assets	160,769	27,278
Liabilities:
Liabilities		0
Fair Value, Inputs, Level 1 [Member] | SAFE Liabilities [Member]
Liabilities:
Liabilities		0
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member] | Cash Equivalents [Member]
Assets:
Assets	160,769	27,278
Fair Value, Inputs, Level 2 [Member]
Assets:
Assets	0	0
Liabilities:
Liabilities		0
Fair Value, Inputs, Level 2 [Member] | SAFE Liabilities [Member]
Liabilities:
Liabilities		0
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member] | Cash Equivalents [Member]
Assets:
Assets	0	0
Fair Value, Inputs, Level 3 [Member]
Assets:
Assets	0	0
Liabilities:
Liabilities		30,515
Fair Value, Inputs, Level 3 [Member] | SAFE Liabilities [Member]
Liabilities:
Liabilities		30,515
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member] | Cash Equivalents [Member]
Assets:
Assets	$ 0	$ 0

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Activity for the Safe Liabilities that were Measured at Fair Value (Detail) - SAFE Liabilities [Member] - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening Balance	$ 30,515	$ 0
Initial fair value recognition		31,515
Loss on issuance		255
Fair value adjustments	3,610	(1,255)
Conversion	(34,125)
Ending Balance	$ 0	$ 30,515

Property, Equipment and Impro_3

Property, Equipment and Improvements, Net - Summary of Property Equipment and Improvements Net (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	$ 5,202	$ 4,978
Less: accumulated depreciation	(2,652)	(1,856)
Property and equipment, net	2,550	3,122
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	4,721	4,510
Furniture and office equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	244	244
Computer equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	212	161
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	0	38
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment gross	$ 25	$ 25

Property, Equipment and Impro_4

Property, Equipment and Improvements, Net - Summary of Depreciation Expenses (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Line Items]
Depreciation	$ 281	$ 255	$ 808	$ 732
General and administrative [Member]
Property, Plant and Equipment [Line Items]
Depreciation	16	4	25	13
Research and development [Member]
Property, Plant and Equipment [Line Items]
Depreciation	$ 265	$ 251	$ 783	$ 719

Accrued Expenses and Other Cu_3

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Payables and Accruals [Abstract]
Accrued Tectonic transaction costs	$ 2,303	$ 0
Accrued AVROBIO transaction costs	1,369	0
Employee compensation related costs	3,106	2,840
Accrued professional fees	1,934	1,798
Accrued contract research organization fees	2,196	2,298
Accrued contract development and manufacturing organization fees	985	660
Accrued office and laboratory costs	100	211
Other current liabilities	744	334
Total	$ 12,737	$ 8,141

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
	May 01, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	May 31, 2023	Dec. 31, 2023	Feb. 10, 2022	Nov. 29, 2021
Other Commitments [Line Items]
Accounts payable and accrued liabilities, current		$ 12,737,000		$ 12,737,000			$ 8,141,000
Indemnification Agreement [Member]
Other Commitments [Line Items]
Other commitment		0		0			$ 0
License Agreement [Member] | Maximum [Member]
Other Commitments [Line Items]
Developmental milestones				8,500,000
Commercial milestones				2,000,000
License Agreement [Member] | Harvard [Member]
Other Commitments [Line Items]
Non refundable license fee amount								$ 170,000
Due to related party		100,000		100,000
Milestone payment				100,000,000,000
Target range of initial and completion fees payable		200,000		$ 200,000
Cash paid to Harvard		$ 100,000			$ 200,000
License Agreement [Member] | Harvard [Member] | Maximum [Member]
Other Commitments [Line Items]
Cash paid to Harvard			$ 100,000
License Agreement [Member] | Harvard [Member] | License [Member] | Maximum [Member]
Other Commitments [Line Items]
Percentage of non royalty income received		20%		20%
License Agreement [Member] | Harvard [Member] | License [Member] | Minimum [Member]
Other Commitments [Line Items]
Percentage of non royalty income received		10%		10%
License Agreement [Member] | Harvard [Member] | Common Stock [Member]
Other Commitments [Line Items]
Non refundable license fee shares								227,486
License Agreement [Member] | Alloy Therapeutics, LLC [Member]
Other Commitments [Line Items]
Non refundable and non creditable annul fee									$ 100,000
Milestone payment						$ 4,800,000
Milestone fees		$ 0		$ 0
License Agreement [Member] | Alloy Therapeutics, LLC [Member] | Maximum [Member]
Other Commitments [Line Items]
Milestone fees			100,000		100,000
Discovery Agreement [Member] | Adimab, LLC [Member]
Other Commitments [Line Items]
Payment of upfront technology access fee	$ 20,000
Payment towards quarterly funding		$ 0	$ 100,000	$ 200,000	$ 100,000

Leases - Schedule of Informatio

Leases - Schedule of Information About the Company's Leases (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash Paid for Amounts included in the Measurement of Lease Liabilities [Abstract]
Finance leases - financing cash flows	$ 360	$ 384

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Common stock, authorized	150,000,000	150,000,000
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, issued	14,744,477	2,634,246
Common stock, outstanding	14,744,477	2,634,246
Common stock, voting rights	Holders of voting common stock are entitled to one vote per share
Common stock, dividends, per share, declared	$ 0
Preferred Stock [Member]
Class of Stock [Line Items]
Common stock issuable upon conversion	3,647,675
Convertible Preferred stock, outstanding	0
Undesignated Preferred Stock [Member]
Class of Stock [Line Items]
Convertible Preferred stock, outstanding	0
Convertible Preferred stock, issued	0
Unrestricted Common Stock [Member]
Class of Stock [Line Items]
Convertible Preferred stock, authorized	10,000,000

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award equity instruments other than options unvested and outstanding unrecognized compensation	$ 13,400	$ 13,400
Share-based payment arrangement, nonvested award, cost not yet recognized, period for recognition		3 years 4 months 24 days
Proceeds from the exercise of stock options		$ 725	$ 1
Stock Compensation Expense	$ 400
Restricted Stock Units (RSUs) [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award equity instruments other than options non vested	6,859	6,859		18,968
Repurchase Liability For Restricted Common Stock	$ 100	$ 100
Restricted Stock Units (RSUs) [Member] | Maximum [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share based compensation by share based award equity instruments other than options non vested	6,859	6,859
2019 Equity Incentive Plan [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Options Granted, Weighted-average grant-date fair value		$ 13.94	$ 2.51
2024 Equity Incentive Plan [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock, capital shares reserved for future issuance	1,938,799	1,938,799
Common stock capital shares reserved for future issuance term description		such aggregate number of shares of common stock will automatically increase on January 1st of each year for a period of ten years commencing on January 1, 2025 and ending on (and including) January 1, 2034, in an amount equal to 5% of the total number of shares of common stock issued and outstanding determined as of the day prior to such increase; provided
Common stock, other shares, outstanding	1,004,299	1,004,299
2024 Employee Stock Purchase Plan [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Common stock, capital shares reserved for future issuance	147,343	147,343
Common stock capital shares reserved for future issuance term description		the number of shares of common stock that are automatically added on January 1st of each year for a period of up to ten years commencing on January 1, 2025 and ending on (and including) January 1, 2034, in an amount equal to the lesser of (x) 1% of the total number of shares of common stock issued and outstanding determined as of the day prior to such increase and (y) a number of shares equal to three times the Initial ESPP Share Reserve

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of the Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Issued and outstanding at January 1, 2024 | shares	1,002,485
Options Granted, Number of Shares | shares	934,500
Options Exercised, Number of Shares | shares	(276,854)
Options Forfeited and expired, Number of Shares | shares	(224,963)
Options assumed from AVROBIO upon Merger closing | shares	365,428
Closing Balance, Number of shares | shares	1,800,596	1,002,485
Options vested and exercisable, Number of Shares | shares	543,994
Options vested and expected to vest, Number of Shares | shares	1,800,596
Opening Balance, Weighted- Average Exercise Price | $ / shares	$ 3.11
Options Granted, Weighted- Average Exercise Price | $ / shares	16.8
Options Exercised, Weighted- Average Exercise Price | $ / shares	2.62
Options Forfeited and expired, Weighted- Average Exercise Price | $ / shares	110.43
Options assumed from AVROBIO upon Merger closing | $ / shares	89.92
Closing Balance, Weighted- Average Exercise Price | $ / shares	14.5	$ 3.11
Options vested and exercisable, Weighted- Average Exercise Price | $ / shares	16.72
Options vested and expected to vest, Weighted- Average Exercise Price | $ / shares	$ 14.5
Weighted-Average Remaining Contractual Term (Years)	8 years 1 month 6 days	8 years 2 months 12 days
Options vested and exercisable, Weighted-Average Remaining Contractual Term (Years)	5 years 2 months 12 days
Options vested and expected to vest, Weighted-Average Remaining Contractual Term (Years)	8 years 1 month 6 days
Opening Balance, Aggregate Intrinsic Value | $	$ 2,276
Options Exercised, Aggregate Intrinsic Value | $	2,767
Ending Balance, Aggregate Intrinsic Value | $	33,499	$ 2,276
Options vested and exercisable, Aggregate Intrinsic Value | $	12,429
Options vested and expected to vest, Aggregate Intrinsic Value | $	$ 33,499

Equity Incentive Plans - Summ_2

Equity Incentive Plans - Summary of Fair Values of the Options Granted (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Fair value per share of underlying common stock		$ 2.51
Expected term (in years)		5 years 11 months 4 days
Expected volatility ,Maximum	104%	111%
Risk-free interest rate		3.65%
Expected dividend yield	0%	0%
Maximum [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Fair value per share of underlying common stock	$ 16.8
Expected term (in years)	6 years 3 months
Risk-free interest rate	4.26%
Minimum [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Fair value per share of underlying common stock	$ 16.09
Expected term (in years)	6 years
Risk-free interest rate	4.23%

Equity Incentive Plans - Summ_3

Equity Incentive Plans - Summary of Restricted Stock Activity (Detail) - Restricted Common Stock [Member]	9 Months Ended
	Sep. 30, 2024 shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Unvested restricted common stock as of January 1, 2024	18,968
Granted	0
Early exercise of options	6,859
Vested	(18,968)
Forfeited	0
Unvested restricted common stock as of September 30, 2024	6,859

Equity Incentive Plans - Summ_4

Equity Incentive Plans - Summary of Stock Based Compensation Expense Regarding its Employees and Nonemployees (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expense	$ 1,650	$ 275	$ 2,374	$ 827
General and administrative [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expense	1,227	174	1,648	522
Research and development [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-Based Payment Arrangement, Expense	$ 423	$ 101	$ 726	$ 305

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Taxes [Line Items]
Income tax expense benefit	$ 0	$ 0	$ 0	$ 0

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net Income (Loss) Attributable to Parent [Abstract]
Net loss, basic	$ (17,717)	$ (10,054)	$ (45,609)	$ (34,954)
Net loss, diluted	$ (17,717)	$ (10,054)	$ (45,609)	$ (34,954)
Weighted-average common shares outstanding, basic	14,729,018	1,319,147	6,373,717	1,245,745
Weighted-average common shares outstanding, diluted	14,729,018	1,319,147	6,373,717	1,245,745
Net loss per share attributable to common stockholders, basic	$ (1.2)	$ (7.62)	$ (7.16)	$ (28.06)
Net loss per share attributable to common stockholders, diluted	$ (1.2)	$ (7.62)	$ (7.16)	$ (28.06)

Net Loss Per Share - Summary _2

Net Loss Per Share - Summary of Diluted Net Loss Per Share Attributable to Common Stockholders (Detail) - shares	3 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	1,807,455	4,524,914
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	0	3,647,675
Employee Stock Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	1,800,596	849,959
Unvested Restricted Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share amount	6,859	27,280

Related Party Transactions - A

Related Party Transactions - Additional Information (Detail) - Member of the Scientific Advisory Board [Member] - Advisory Services Agreement [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Related Party Transaction [Line Items]
Other payables current	$ 0.1		$ 0.1		$ 0
Maximum [Member]
Related Party Transaction [Line Items]
Professional fees	$ 0.1	$ 0.1	$ 0.1	$ 0.1