[SCHEDULE 13D/A] Turnstone Biologics Corp. SEC Filing

Rhea-AI Filing Summary

Turnstone Biologics Corp. agreed to be acquired by XOMA Royalty Corporation through a tender-offer merger structure culminating in a merger that made Turnstone a wholly owned subsidiary of XOMA. Versant-related stockholders (the "Versant Stockholders") participated in the Offer and aggregately tendered 3,381,692 shares of Turnstone common stock in exchange for $0.34 per share in cash and one non-transferable contractual contingent value right (CVR) representing potential milestone payments.

The Purchaser accepted for payment all validly tendered shares and, following satisfaction of the merger conditions, completed the merger so Turnstone survived as XOMA's wholly owned subsidiary. As a result, the reporting persons disclosed in this Amendment ceased to beneficially own more than 5.0% of Turnstone common stock.

Positive

• 3,381,692 shares aggregately tendered by Versant Stockholders, demonstrating full participation by those holders
• Purchaser accepted for payment all validly tendered shares and completed the merger, making Turnstone a wholly owned subsidiary

Negative

• The reporting persons ceased to beneficially own more than 5% of Turnstone common stock as of August 11, 2025
• Cover page data show the reporting persons with 0.00 shares and 0.0% beneficial ownership following the transaction

Insights

Financial Analyst

TL;DR: Deal closed via tender offer; Versant realized holdings for cash plus CVRs, and reporting persons dropped below 5% ownership.

This Amendment documents the closing mechanics: the Offer satisfied its minimum tender condition, Purchaser accepted all valid tenders, and the merger closed with Turnstone as a XOMA subsidiary. Key quantified outcomes are 3,381,692 shares tendered and a $0.34 per-share cash payment plus CVRs. For holders disclosed here, the transaction converted equity stakes into cash and contingent rights and eliminated their >5% beneficial ownership status.

M&A Specialist

TL;DR: Tender offer and merger executed as planned; contractual Offer Agreement and Merger Agreement governed the sale and were filed as exhibits.

The filing references the operative agreements (the Merger Agreement and the Amended and Restated Offer to Purchase) and confirms delivery of consideration and the statutory merger closing. The use of a tender offer followed by a short-form merger indicates a standard two-step deal execution. The inclusion of non-transferable CVRs preserves potential milestone upside for former holders while transferring control to the Purchaser.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

Turnstone Biologics Corp.

(Name of Issuer)

Common Stock, $0.001 par value per share

(Title of Class of Securities)

90042W100

(CUSIP Number)

Max Eisenberg
One Sansome Street, Suite 1650
San Francisco, CA, 94104
415-801-8100

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

08/08/2025

(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).

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Venture Capital V, L.P.

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)

WC

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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Affiliates Fund V, L.P.

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)

WC

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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Ophthalmic Affiliates Fund I, L.P.

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)

WC

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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Ventures V, 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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Venture Capital V (Canada) LP

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)

WC

5

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

6

Citizenship or place of organization

ONTARIO, CANADA

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Ventures V GP-GP (Canada), Inc.

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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Ventures V (Canada), L.P.

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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Vantage II, L.P.

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)

WC

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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Vantage II GP, L.P.

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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 90042W100

1

Name of reporting person

Versant Vantage II GP-GP, 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 0.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

0.00

12

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

13

Percent of class represented by amount in Row (11)

0.0 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, $0.001 par value per share
(b)	Name of Issuer: Turnstone Biologics Corp.
(c)	Address of Issuer's Principal Executive Offices: 9310 Athena Circle, Suite 300, La Jolla, CALIFORNIA , 92037.
Item 1 Comment: This Amendment No. 1 (this "Amendment") amends and supplements the Schedule 13D originally filed by certain of the Reporting Persons with the Securities and Exchange Commission on August 3, 2023 (the "Original Schedule 13D"). Only those items that are hereby reported are amended; all other items reported in the Original Schedule 13D remain unchanged; provided, however, that all references in the Original Schedule 13D to the number of shares of the Issuer's Common Stock outstanding as of the closing of the IPO are hereby deleted in their entirety. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable. Capitalized terms not defined in this Amendment have the meanings ascribed to them in the Original Schedule 13D.
Item 4.	Purpose of Transaction
	On June 26, 2025, the Issuer entered into an Agreement and Plan of Merger (the "Merger Agreement") with XOMA Royalty Corporation ("XOMA") and XOMA's wholly owned subsidiary XRA 3 Corp., a Delaware corporation ("Purchaser"), relating to, among other things, the merger of Purchaser with the Issuer in an all cash transaction, pursuant to a tender offer (the "Offer), with the Issuer surviving as a wholly owned subsidiary of XOMA. In connection with the Merger Agreement, VVC V, VAF V, VOA, VVC CAN and Vantage LP (collectively, the "Versant Stockholders") and certain other stock holders (each a "Stockholder" and together, the "Stockholders") entered into an Amended and Restated Offer to Purchase (the "Offer Agreement") with XOMA and Purchaser pursuant to which each Stockholder agreed, among other things, and subject to the terms and conditions of the Offer Agreement, to tender all of the shares of Common Stock held by such Stockholder in the Offer. The foregoing descriptions of the Merger Agreement and the Offer Agreement are qualified in their entirety by reference to the full text of such agreements. The Offer Agreement is included as Exhibit (a)(1)(E) of the Issuer's Schedule TO filed with the Commission on July 24, 2025. The Merger Agreement is included as Exhibit 2.1 of the Issuer's Current Report on Form 8-K, filed with the Commission on June 27, 2025. Both the Offer Agreement and the Merger Agreement are incorporated herein by reference. The Offer and related withdrawal rights expired on August 7, 2025, and as a result of the satisfaction of the Minimum Tender Condition (as defined in the Offer Agreement) and each of the other conditions to the Offer, on August 11, 2025, Purchaser accepted for payment all Common Stock that was validly tendered (and not properly withdrawn) pursuant to the Offer. The Versant Stockholders aggregately tendered 3,381,692 shares of Common Stock, which constituted all of each of their respective shares of Common Stock of the Issuer in the Offer for the right to receive (a) a cash payment of $0.34 per share (the "Cash Amount") and (b) one non-transferable contractual contingent value right representing the right to receive any applicable milestone payment if specified milestones are achieved. Following the consummation of the Offer, the remaining conditions to the merger set forth in the Merger Agreement were satisfied, and on August 11, 2025, Purchaser was merged with and into the Issuer, with the Issuer surviving the merger as a wholly owned subsidiary of XOMA. The terms of the Offer are described more fully in the Issuer's Current Report on Form 8-K (the "Form 8-K") (File No. 001-41747) filed with the Commission on August 11, 2025, and the above summary is qualified by reference to such description and the full text of the Form 8-K, which is filed as Exhibit 9 to this Amendment and is incorporated herein by reference.
Item 5.	Interest in Securities of the Issuer
(a)	See Items 7-11 and 13 of the cover pages of this Amendment for each Reporting Person and the corresponding comments.
(b)	See Items 7-11 and 13 of the cover pages of this Amendment for each Reporting Person and the corresponding comments.
(c)	Except as reported in this Statement, none of the Reporting Persons has effected any transactions in the Issuer's securities within the past 60 days.
(e)	As of August 11, 2025, the Reporting Persons ceased to beneficially own more than 5% of the Issuer's outstanding Common Stock.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	The information set forth in Item 4 of this Amendment is incorporated herein by reference.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 7: Agreement and Plan of Merger dated as of June 26, 2025 (filed as Exhibit 2.1 to the Issuer's Current Report on Form 8-K as filed with the Commission on June 27, 2025 (SEC File No. 001-41747) and incorporated herein by reference). Exhibit 8: Amended and Restated Offer to Purchase dated as of July 23, 2025 (filed as Exhibit (a)(1)(E) to the Issuer's Tender Offer Statement on Schedule TO as filed with the Commission on July 24, 2025 (SEC File No. 005-94123) and incorporated herein by reference). Exhibit 9: The Issuer's Current Report on Form 8-K (filed with the Commission on August 11, 2025 (SEC File No. 001-41747) and incorporated herein by reference).

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.

Versant Venture Capital V, L.P.

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer of Versant Ventures V, LLC, the general partner of Versant Venture Capital V, L.P.
Date:	08/12/2025

Versant Affiliates Fund V, L.P.

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer of Versant Ventures V, LLC, the general partner of Versant Affiliates Fund V, L.P.
Date:	08/12/2025

Versant Ophthalmic Affiliates Fund I, L.P.

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer of Versant Ventures V, LLC, the general partner of Versant Ophthalmic Affiliates Fund I, L.P.
Date:	08/12/2025

Versant Ventures V, LLC

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer
Date:	08/12/2025

Versant Venture Capital V (Canada) LP

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, COO of Versant Ventures V GP-GP (Canada), Inc., GP of Versant Ventures V (Canada), L.P., GP of Versant Venture Capital V (Canada) LP
Date:	08/12/2025

Versant Ventures V GP-GP (Canada), Inc.

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer
Date:	08/12/2025

Versant Ventures V (Canada), L.P.

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer of Versant Ventures V GP-GP (Canada), Inc., the general partner of Versant Ventures V (Canada), L.P.
Date:	08/12/2025

Versant Vantage II, L.P.

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer of Versant Vantage II GP-GP, LLC, the GP of Versant Vantage II GP, L.P., the GP of Versant Vantage II, L.P.
Date:	08/12/2025

Versant Vantage II GP, L.P.

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer of Versant Vantage II GP-GP, LLC, the general partner of Versant Vantage II GP, L.P.
Date:	08/12/2025

Versant Vantage II GP-GP, LLC

Signature:	/s/ Max Eisenberg
Name/Title:	Max Eisenberg, Chief Operating Officer
Date:	08/12/2025

FAQ

What did Versant tender in the Turnstone (TSBX) offer?

The Versant Stockholders aggregately tendered 3,381,692 shares of Turnstone common stock pursuant to the Offer.

What consideration did Tendering stockholders receive for TSBX shares?

Each tendered share received a $0.34 cash payment and one non-transferable contractual contingent value right (CVR) for potential milestone payments.

Did the Purchaser accept the tendered shares and close the merger?

Yes. Purchaser accepted for payment all validly tendered shares and, after satisfaction of the merger conditions, merged with the Issuer so it survived as a wholly owned subsidiary of XOMA.

Do the reporting persons still own more than 5% of Turnstone after the transaction?

No. The Amendment states that as of August 11, 2025, the reporting persons ceased to beneficially own more than 5% of Turnstone common stock.

Which agreements are filed as exhibits to this Amendment?

The Merger Agreement and the Amended and Restated Offer to Purchase are incorporated by reference as exhibits, along with the Issuer's Current Report describing the Offer.