OrbiMed updates Q32 Bio (QTTB) ownership at 13.3% of common stock

Rhea-AI Filing Summary

Q32 Bio Inc. received an updated Schedule 13D/A from OrbiMed Advisors LLC and OrbiMed Capital GP VII LLC reporting their current stake in the company. Through OrbiMed Private Investments VII, LP, they beneficially own 2,252,987 shares of common stock, representing about 13.3% of Q32 Bio’s 16,956,415 shares outstanding as referenced in a recent quarterly report. The filing notes this percentage fell by more than 1% because the total shares outstanding increased, not because OrbiMed sold shares. OrbiMed states it may buy more or sell shares over time depending on Q32 Bio’s performance and market conditions. An OrbiMed employee, Diyong Xu, sits on Q32 Bio’s board, and any equity awards he receives as a director are assigned back to OrbiMed’s fund. The filing also highlights a registration rights agreement requiring Q32 Bio to file a shelf registration to allow resale of certain shares issued in connection with a prior financing and merger.

Key Figures

Beneficial ownership: 2,252,987 shares Ownership percentage: 13.3% Shares outstanding: 16,956,415 shares +3 more

6 metrics

Beneficial ownership 2,252,987 shares Shares of Q32 Bio common stock held by OrbiMed Private Investments VII, LP

Ownership percentage 13.3% Portion of Q32 Bio common stock represented by OrbiMed’s 2,252,987 shares

Shares outstanding 16,956,415 shares Q32 Bio shares outstanding referenced from Form 10-Q filed May 5, 2026

Pre-Closing Financing shares 8,852,000 shares Shares purchased by OrbiMed Private Investments VII, LP under the March 25, 2024 Subscription Agreement

Shelf registration deadline 45 calendar days Time after merger closing for Q32 Bio to file shelf registration for resale

Shared voting power 2,252,987 shares Shares with shared voting and dispositive power reported by each OrbiMed reporting person

Key Terms

beneficial ownership, Registration Rights Agreement, shelf registration statement, Pre-Closing Financing, +2 more

6 terms

beneficial ownership financial

"may be deemed directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by OPI VII"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

Registration Rights Agreement regulatory

"Legacy Q32 and the investors ... entered into a registration rights agreement (the "Registration Rights Agreement")"

A registration rights agreement is a contract that gives investors the option to have their ownership stakes officially registered with the government, making it easier to sell their shares later. This agreement matters because it provides investors with a clearer path to cash out their investments if they choose, offering more liquidity and confidence in their ability to sell their holdings when desired.

shelf registration statement regulatory

"the Issuer is obligated to prepare and file a shelf registration statement covering the resale of covered Shares"

A shelf registration statement is a document a company files with regulators that allows it to sell shares or bonds quickly when it’s a good time to raise money. It’s like having a pre-approved plan ready so the company can act fast without going through lengthy paperwork each time they want to sell, making fundraising more flexible.

Pre-Closing Financing financial

"the transaction resulting in OVI VII's purchase of 8,852,000 Shares ... (the "Pre-Closing Financing")"

shared voting power financial

"Number of Shares Beneficially Owned by Each Reporting Person With: 7 Sole Voting Power 0.00 8 Shared Voting Power 2,252,987.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

Schedule 13D/A regulatory

"This Amendment No. 2 ("Amendment No. 2") to supplements and amends the Statement on of OrbiMed Advisors LLC"

A Schedule 13D/A is an amended disclosure filed with regulators by an investor who already reported owning more than 5% of a company’s shares and needs to update their original filing. Think of it as a public status update that tells markets whether the investor’s ownership, plans, or source of funds have changed; such updates matter because they can signal a push for control, major strategic moves, or increased pressure on management, which can affect stock prices.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)

Q32 Bio Inc.

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

746964105

(CUSIP Number)

OrbiMed Advisors LLC
601 Lexington Avenue, 54th Floor,
New York, NY, 10022
(212) 739-6400

OrbiMed Capital GP VII LLC
601 Lexington Avenue, 54th Floor,
New York, NY, 10022
(212) 739-6400

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

05/05/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 746964105

1

Name of reporting person

ORBIMED ADVISORS LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 2,252,987.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,252,987.00

11

Aggregate amount beneficially owned by each reporting person

2,252,987.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

13.3 %

14

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13D

CUSIP Number(s): 746964105

1

Name of reporting person

ORBIMED CAPITAL GP VII LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 2,252,987.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 2,252,987.00

11

Aggregate amount beneficially owned by each reporting person

2,252,987.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

13.3 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: COMMON STOCK
(b)	Name of Issuer: Q32 Bio Inc.
(c)	Address of Issuer's Principal Executive Offices: 830 Winter Street, Waltham, MASSACHUSETTS , 02451.
Item 1 Comment: This Amendment No. 2 ("Amendment No. 2") to Schedule 13D supplements and amends the Statement on Schedule 13D of OrbiMed Advisors LLC ("OrbiMed Advisors") and OrbiMed Capital GP VII LLC, ("OrbiMed GP") (collectively, the "Reporting Persons") originally filed with the Securities and Exchange Commission (the "SEC") on March 28, 2024, as amended by Amendment No. 1 filed with the SEC on March 12, 2026. This Amendment No. 2 is being filed to report that the beneficial ownership of the outstanding Shares held by the Reporting Persons decreased by more than 1% as a result of an increase in the number of Shares outstanding.
Item 2.	Identity and Background
(a)	OrbiMed Advisors is a limited liability company organized under the laws of Delaware and a registered investment adviser under the Investment Advisers Act of 1940, as amended. OrbiMed GP is a limited liability company organized under the laws of Delaware. Carl L. Gordon is a United States citizen. Sven H. Borho is a German and Swedish citizen. W. Carter Neild is a United States citizen. Geoffrey C. Hsu is a United States citizen. C. Scotland Stevens is a United States citizen. David P. Bonita is a United States citizen. Peter A. Thompson is a United States citizen. Matthew S. Rizzo is a United States citizen. Mona Ashiya is a United States citizen. Trey Block is a United States citizen.
(b)	601 Lexington Avenue, 54th Floor, New York, New York 10022.
(c)	OrbiMed Advisors is the managing member or general partner of certain entities as more particularly described in Item 6 below. OrbiMed GP is the general partner of a limited partnership as more particularly described in Item 6 below. Carl L. Gordon is a member of OrbiMed Advisors. Sven H. Borho is a member of OrbiMed Advisors. W. Carter Neild is a member of OrbiMed Advisors. Geoffrey C. Hsu is a member of OrbiMed Advisors. C. Scotland Stevens is a member of OrbiMed Advisors. David P. Bonita is a member of OrbiMed Advisors. Peter A. Thompson is a member of OrbiMed Advisors. Matthew S. Rizzo is a member of OrbiMed Advisors. Mona Ashiya is a member of OrbiMed Advisors. Trey Block is the Chief Financial Officer of OrbiMed Advisors.
(d)	Not applicable.
(e)	Not applicable.
(f)	Item 2(a) is incorporated herein by reference.
Item 3.	Source and Amount of Funds or Other Consideration
	Not applicable.
Item 4.	Purpose of Transaction
	The Reporting Persons from time to time intend to review their investment in the Issuer on the basis of various factors, including the Issuer's business, financial condition, results of operations and prospects, general economic and industry conditions, the securities markets in general and those for the Issuer's Shares in particular, as well as other developments and other investment opportunities. Based upon such review, the Reporting Persons will take such actions in the future as the Reporting Persons may deem appropriate in light of the circumstances existing from time to time. If the Reporting Persons believe that further investment in the Issuer is attractive, whether because of the market price of Shares or otherwise, they may acquire Shares or other securities of the Issuer either in the open market or in privately negotiated transactions. Similarly, depending on market and other factors, the Reporting Persons may determine to dispose of some or all of the Shares currently owned by the Reporting Persons or otherwise acquired by the Reporting Persons either in the open market or in privately negotiated transactions. Except as set forth in this Schedule 13D, the Reporting Persons have not formulated any plans or proposals which relate to or would result in: (a) the acquisition by any person of additional securities of the Issuer or the disposition of securities of the Issuer, (b) an extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries, (c) a sale or transfer of a material amount of the assets of the Issuer or any of its subsidiaries, (d) any change in the present Board of Directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board, (e) any material change in the Issuer's capitalization or dividend policy of the Issuer, (f) any other material change in the Issuer's business or corporate structure, (g) any change in the Issuer's charter or bylaws or other instrument corresponding thereto or other action which may impede the acquisition of control of the Issuer by any person, (h) causing a class of the Issuer's securities to be deregistered or delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association, (i) a class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Act or (j) any action similar to any of those enumerated above.
Item 5.	Interest in Securities of the Issuer
(a)	The following disclosure is based upon 16,956,415 outstanding Shares, as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on May 5, 2026. As of the date of this filing, OrbiMed Private Investments VII, LP ("OPI VII"), a limited partnership organized under the laws of Delaware, holds 2,252,987 Shares constituting approximately 13.3% of the issued and outstanding Shares. OrbiMed GP is the general partner of OPI VII pursuant to the terms of the limited partnership agreement of OPI VII, and OrbiMed Advisors is the managing member of OrbiMed GP pursuant to the terms of the limited liability company agreement of OrbiMed GP. As a result, OrbiMed Advisors and OrbiMed GP share power to direct the vote and disposition of the Shares held by OPI VII and may be deemed directly or indirectly, including by reason of their mutual affiliation, to be the beneficial owners of the Shares held by OPI VII. OrbiMed Advisors exercises this investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the Shares held by OPI VII. In addition, OrbiMed Advisors and OrbiMed GP, pursuant to their authority under the limited partnership agreements of OPI VII, caused OPI VII to enter into the agreements referred to in Item 6 below.
(b)	Item 5(a) is incorporated by reference herein.
(c)	Not applicable.
(d)	Not applicable.
(e)	Not applicable.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	In addition to the relationships between the Reporting Persons described in Items 2 and 5 above, OrbiMed GP is the general partner of OPI VII pursuant to the terms of the limited partnership agreement of OPI VII. Pursuant to this agreement and relationship, OrbiMed GP has discretionary investment management authority with respect to the assets of OPI VII. Such authority includes the power to vote and otherwise dispose of securities held by OPI VII. The number of outstanding Shares of the Issuer attributable to OPI VII is 2,252,987. OrbiMed GP, pursuant to its authority under the limited partnership agreement of OPI VII, may be considered to hold indirectly 2,252,987 Shares. OrbiMed Advisors is the managing member of OrbiMed GP pursuant to the terms of the limited liability company agreement of OrbiMed GP. Pursuant to this agreement and relationship, OrbiMed Advisors and OrbiMed GP have discretionary investment management authority with respect to the assets of OPI VII. Such authority includes the power of OrbiMed GP to vote and otherwise dispose of securities held by OPI VII. The number of outstanding Shares attributable to OPI VII is 2,252,987 Shares. OrbiMed Advisors, pursuant to its authority under the terms of the limited liability company agreement of OrbiMed GP, may also be considered to hold indirectly 2,252,987 Shares. Diyong Xu ("Xu"), an employee of OrbiMed Advisors, is a member of the Board of Directors of the Issuer and, accordingly, OrbiMed Advisors and OrbiMed GP may have the ability to affect and influence control of the Issuer. From time to time, Xu may receive stock options or other awards of equity-based compensation pursuant to the Issuer's compensation arrangements for non-employee directors. Pursuant to an agreement with OrbiMed Advisors and OrbiMed GP, Xu is obligated to transfer any securities issued under any such stock options or other awards, or the economic benefit thereof, to OrbiMed Advisors and OrbiMed GP, which will in turn ensure that such securities or economic benefits are provided to OPI VII. Registration Rights Agreement Pursuant to the Subscription Agreement OPI VII entered into with Admirx, Inc. ("Legacy Q32" and such Subscription Agreement, the "Subscription Agreement"), on March 25, 2024, Legacy Q32 and the investors in the transaction resulting in OVI VII's purchase of 8,852,000 Shares immediately prior to the consummation of the Merger pursuant to the Subscription Agreement (the "Pre-Closing Financing"), including OPI VII entered into a registration rights agreement (the "Registration Rights Agreement"). Pursuant to the Registration Rights Agreement, among other things, Legacy Q32 agreed to register for resale certain shares of its common stock held by such investors from time to time, including Shares issued in the Issuer's merger with Homology Medicines, Inc. (the "Merger") in exchange for the shares of Legacy Q32 common stock issued in the Pre-Closing Financing. Pursuant to the Registration Rights Agreement, the Issuer is obligated to prepare and file a shelf registration statement covering the resale of covered Shares within 45 calendar days following the closing of the Merger, subject to certain exceptions, pursuant to Rule 415 of the Securities Act of 1933, as amended (the "Securities Act"). The Issuer also agreed to use its reasonable best efforts to keep such registration statement continuously effective under the Securities Act until the earlier of the date that all registrable securities covered by such registration statement (i) have been sold, thereunder or pursuant to Rule 144 of the Securities Act or (ii) may be sold without volume or manner-of-sale restrictions pursuant to Rule 144 of the Securities Act and without the requirement for the Issuer to be in compliance with the current public information requirement under Rule 144 of the Securities Act. The Registration Rights Agreement also provides that the Issuer will pay certain expenses of the securityholders and indemnify the applicable securityholders against certain liabilities.
Item 7.	Material to be Filed as Exhibits.
	Exhibit Description 1. Joint Filing Agreement among OrbiMed Advisors LLC and OrbiMed Capital GP VII LLC 2. Registration Rights Agreement, dated March 25, 2024, by and among Q32 Bio Operations Inc. (formerly Q32 Bio Inc.) and certain parties thereto (incorporated by reference to Exhibit 10.2 to the Issuer's Form 8-K filed with the SEC on March 27, 2024 (File No. 001-38433)).

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

ORBIMED ADVISORS LLC

Signature:	/s/ Carl L. Gordon
Name/Title:	Carl L. Gordon/Member
Date:	05/06/2026

ORBIMED CAPITAL GP VII LLC

Signature:	/s/ Carl L. Gordon
Name/Title:	Carl L. Gordon/Member of OrbiMed Advisors LLC
Date:	05/06/2026

FAQ

What percentage of Q32 Bio (QTTB) does OrbiMed currently own?

OrbiMed, through OrbiMed Private Investments VII, LP, beneficially owns about 13.3% of Q32 Bio’s common stock, representing 2,252,987 shares out of 16,956,415 shares outstanding as referenced in the company’s Form 10-Q filed on May 5, 2026.

Did OrbiMed sell Q32 Bio (QTTB) shares in this Schedule 13D/A amendment?

The amendment states OrbiMed’s ownership percentage decreased by more than 1% due to an increase in Q32 Bio’s shares outstanding, not because OrbiMed sold shares. Their beneficial ownership remains 2,252,987 shares according to the filing’s disclosure.

How many Q32 Bio (QTTB) shares does OrbiMed Private Investments VII, LP hold?

OrbiMed Private Investments VII, LP directly holds 2,252,987 shares of Q32 Bio common stock. OrbiMed Capital GP VII LLC is its general partner, and OrbiMed Advisors LLC is the managing member, giving them shared voting and dispositive power over these shares.

What board representation does OrbiMed have at Q32 Bio (QTTB)?

The filing notes that Diyong Xu, an employee of OrbiMed Advisors, serves on Q32 Bio’s board of directors. Under an agreement, any equity compensation he receives as a non-employee director is transferred, or its economic benefit assigned, to OrbiMed entities and ultimately to OrbiMed Private Investments VII, LP.

What is the registration rights agreement mentioned for Q32 Bio (QTTB)?

Q32 Bio and investors, including OrbiMed Private Investments VII, LP, entered a registration rights agreement tied to a Pre-Closing Financing of 8,852,000 shares. Q32 Bio must file a shelf registration statement to permit resale of covered shares and cover specified expenses and indemnification obligations.

How does OrbiMed describe its future plans for Q32 Bio (QTTB) shares?

OrbiMed says it will review its investment based on Q32 Bio’s business, financial condition, results, prospects, and market conditions. Depending on those factors, it may buy additional shares or sell some or all of its existing holdings in open-market or private transactions.