[Form 4] Turnstone Biologics Corp. Insider Trading Activity

Rhea-AI Filing Summary

Turnstone Biologics Corp. (TSBX) Form 4 shows that reporting persons affiliated with OrbiMed disposed of shares pursuant to an Agreement and Plan of Merger dated June 26, 2025. The transaction date reported is 08/08/2025. The purchaser is XOMA Royalty Corporation, which completed a cash tender offer paying $0.34 per share plus one non-transferable contractual contingent value right (CVR) per share.

The filing identifies 3,099,265 common shares in the ownership table and explains those shares are held of record by OrbiMed Private Investments VI, LP, with OrbiMed Capital GP VI LLC as general partner and OrbiMed Advisors LLC as managing member. The report is jointly filed by OrbiMed Advisors and GP VI and includes standard disclaimers about beneficial ownership and the designation of a board representative.

Positive

• Transaction completed under a formal merger agreement, providing shareholders with $0.34 cash per share plus a contingent value right (CVR) as consideration

Negative

• Disposition of securities by OrbiMed-affiliated reporting persons, which materially alters the public record of significant beneficial ownership

Insights

Financial Analyst

TL;DR: OrbiMed-affiliated entities disposed of Turnstone shares via a merger tender offer for $0.34 plus a CVR; transaction is material to ownership structure.

This Form 4 documents a disposition of Turnstone common stock by entities controlled by OrbiMed, executed under a merger agreement dated June 26, 2025, with the purchaser identified as XOMA Royalty Corporation. The economic terms reported are $0.34 per share in cash plus one non-transferable contractual contingent value right per share. The filing clarifies record ownership and the chain of control through OrbiMed Private Investments VI, LP, GP VI, and OrbiMed Advisors, and notes a board representative was designated. For investors, the filing changes the public record of significant holders but does not provide operational or forward-looking company details.

Corporate Governance Expert

TL;DR: Joint Form 4 filing clarifies ownership relationships and records an arm's-length disposition under a completed tender offer; governance disclosures are appropriately noted.

The disclosure includes footnotes describing the record holder (OPI VI), the general partner (GP VI), and the managing member (OrbiMed Advisors), and explicitly states that each reporting person disclaims beneficial ownership except to the extent of pecuniary interest. It also notes OrbiMed designated a representative to the issuer's board. The filing follows Section 16 reporting conventions and documents the transfer method and consideration; it supplies no allegations of misconduct or governance breaches but does materially update public ownership records.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

ORBIMED ADVISORS LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE

54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Turnstone Biologics Corp. [ TSBX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
08/08/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	08/08/2025		U(1)		3,099,265	D	(1)	0	I	See Footnote(2)(3)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person^*

ORBIMED ADVISORS LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE

54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

OrbiMed Capital GP VI LLC

(Last) (First) (Middle)

601 LEXINGTON AVENUE, 54TH FLOOR

(Street)

NEW YORK NY 10022

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. Disposed of pursuant to the terms of the Agreement and Plan of Merger, dated June 26, 2025, by and among the Issuer, XOMA Royalty Corporation ("Purchaser") and XRA 3 Corp., a wholly-owned subsidiary of Purchaser, pursuant to which Purchaser completed a cash tender offer for all outstanding shares of common stock of the Issuer for (i) $0.34 per share in cash, payable subject to any applicable tax withholding and without interest, plus (ii) one non-transferable contractual contingent value right per share, payable subject to any applicable tax withholding and without interest.

2. These securities are held of record by OrbiMed Private Investments VI, LP ("OPI VI"). OrbiMed Capital GP VI LLC ("GP VI") is the general partner of OPI VI, and OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP VI. By virtue of such relationships, GP VI and OrbiMed Advisors may be deemed to have voting power and investment power over the securities held by OPI VI and, as a result, may be deemed to have beneficial ownership over such securities. OrbiMed Advisors exercises voting and investment 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 securities held by OPI VI.

3. This report on Form 4 is jointly filed by OrbiMed Advisors and GP VI. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of his or its pecuniary interest therein, if any. OrbiMed Advisors has designated a representative, Rishi Gupta ("Gupta"), an employee of OrbiMed Advisors, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any of the Reporting Persons or Gupta is a beneficial owner of such securities for the purpose of Section 16 of the Exchange Act, or for any other purpose.

	/s/ Carl L. Gordon, Member of OrbiMed Advisors LLC	08/12/2025
	/s/ Carl L. Gordon, Member of OrbiMed Capital GP VI LLC	08/12/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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FAQ

What did the Form 4 filed for TSBX report?

The Form 4 reports a disposition of Turnstone common stock by OrbiMed-affiliated reporting persons pursuant to a merger agreement, with the transaction dated 08/08/2025.

Who purchased the shares and what was the per-share consideration?

The purchaser is XOMA Royalty Corporation. Consideration was $0.34 per share in cash plus one non-transferable contractual contingent value right (CVR) per share.

How many shares are indicated in the filing?

The ownership table shows 3,099,265 common shares in the reported holdings following the reported transaction(s).

Which OrbiMed entities filed the Form 4 and what are their roles?

The Form 4 is jointly filed by OrbiMed Advisors LLC and OrbiMed Capital GP VI LLC. OrbiMed Private Investments VI, LP holds the securities of record, with GP VI as general partner and OrbiMed Advisors as managing member.

Was there any designation to the issuer's board noted?

Yes. OrbiMed Advisors designated Rishi Gupta to serve on the issuer's board of directors, as noted in the filing.