HLVX: Merger Completes, HilleVax Becomes Wholly Owned Subsidiary; Shares Cancelled

Rhea-AI Filing Summary

HilleVax, Inc. completed a merger on September 17, 2025 under which XOMA Royalty Corporation's subsidiary merged into HilleVax, making HilleVax a wholly owned subsidiary of Parent. Pursuant to the merger agreement, each issued and outstanding share of HilleVax common stock was cancelled. The filing amends a prior Schedule 13D to state that the listed Reporting Persons no longer beneficially own any HilleVax common stock and that they ceased to be beneficial owners of 5% or more of the class as of the closing date. No other transactions in the past 60 days are reported.

Positive

• Merger closed on September 17, 2025, completing the corporate transaction described.
• Issuer became a wholly owned subsidiary of XOMA Royalty Corporation pursuant to the Merger Agreement.
• Clear disclosure that Reporting Persons no longer beneficially own any common stock, updating prior filings.

Negative

• All issued and outstanding common shares were cancelled, eliminating the public float as described.
• Reporting Persons ceased to be beneficial owners of 5% or more of the class as of September 17, 2025.

Insights

M&A Specialist

TL;DR The merger closed, HilleVax became a wholly owned subsidiary and public common shares were cancelled.

The filing confirms the closing of the Merger Agreement dated through September 17, 2025, under which XRA 4 Corp. merged into HilleVax and HilleVax continued as a wholly owned subsidiary of XOMA Royalty Corporation. The explicit corporate effect—cancellation of all issued and outstanding common shares—terminates the public float. The amendment updates Items 4 and 5 of the prior Schedule 13D to reflect zero beneficial ownership by the Reporting Persons and cessation of >5% ownership status.

Securities Analyst

TL;DR Material corporate event: share cancellation and change in ownership structure are disclosed without additional transactions.

This Schedule 13D/A is narrowly focused: it amends prior disclosure to report the merger closing and the resulting cancellation of all HilleVax common stock. The Reporting Persons state they hold 0 shares and report no transactions in the past 60 days aside from the effects described. The amendment is procedural and factual, documenting the change in capital structure and ownership following the merger.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

HilleVax, Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

43157M102

(CUSIP Number)

Kevin Tang
4747 Executive Drive, Suite 210
San Diego, CA, 92121
858-200-3830

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

09/17/2025

(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. 43157M102

1

Name of reporting person

TANG CAPITAL MANAGEMENT, 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)

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 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 43157M102

1

Name of reporting person

KEVIN TANG

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

UNITED STATES

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 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 43157M102

1

Name of reporting person

TANG CAPITAL PARTNERS, 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

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 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 43157M102

1

Name of reporting person

TANG CAPITAL PARTNERS INTERNATIONAL, 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

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 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 43157M102

1

Name of reporting person

TANG CAPITAL PARTNERS III, 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)

WC

5

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

6

Citizenship or place of organization

NEVADA

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 %

14

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13D

CUSIP No. 43157M102

1

Name of reporting person

TANG CAPITAL PARTNERS IV, 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)

WC

5

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

6

Citizenship or place of organization

NEVADA

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 %

14

Type of Reporting Person (See Instructions)

CO

SCHEDULE 13D

CUSIP No. 43157M102

1

Name of reporting person

CONCENTRA BIOSCIENCES, 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)

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 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, par value $0.0001 per share
(b)	Name of Issuer: HilleVax, Inc.
(c)	Address of Issuer's Principal Executive Offices: 321 Harrison Avenue, Suite 500, Boston, MASSACHUSETTS , 02118.
Item 1 Comment: This Schedule 13D/A (this "Statement") amends the Schedule 13D (the "Original Schedule 13D") filed on May 2, 2025. Items 4 and 5 of the Statement are hereby amended and supplemented to the extent hereinafter expressly set forth. Except as amended hereby, the original disclosure set forth in the Statement shall remain unchanged. All capitalized terms used and not expressly defined herein have the respective meanings ascribed to such terms in the Original Schedule 13D.
Item 4.	Purpose of Transaction
	Item 4 of the Schedule 13D is amended by adding the following: Closing of the Merger: On September 17, 2025, the Issuer completed its merger with XOMA Royalty Corporation ("Parent") and Parent's wholly-owned subsidiary, XRA 4 Corp. ("Merger Sub") pursuant to the terms of the Merger Agreement, whereby Merger Sub merged with and into the Issuer, in accordance with the General Corporation Law of the State of Delaware, with the Issuer continuing as the surviving corporation and as a wholly owned subsidiary of Parent. Pursuant to the Merger Agreement, on September 17, 2025, each issued and outstanding share of the Issuer's Common Stock was cancelled.
Item 5.	Interest in Securities of the Issuer
(a)	The information previously provided in response to Item 5 is hereby amended and restated by replacing the text thereof in its entirety with the following: The information set forth in the cover pages of this Schedule 13D is hereby incorporated by reference into this Item 5. As of the date hereof the Reporting Persons do not own any shares of the Issuer's Common Stock.
(b)	See item 5(a) above.
(c)	Except as described in this Amendment No. 1, there have been no transactions in the Issuer's Common Stock during the past 60 days by the Reporting Persons.
(d)	No person other than a Reporting Person has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, Common Stock beneficially owned by the Reporting Persons.
(e)	The Reporting Persons ceased to be beneficial owners of 5% or more of the Issuer's Common Stock on September 17, 2025.

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.

TANG CAPITAL MANAGEMENT, LLC

Signature:	/s/ Kevin Tang
Name/Title:	Manager
Date:	09/19/2025

KEVIN TANG

Signature:	/s/ Kevin Tang
Name/Title:	Self
Date:	09/19/2025

TANG CAPITAL PARTNERS, LP

Signature:	/s/ Kevin Tang
Name/Title:	Manager, Tang Capital Management, LLC, General Partner
Date:	09/19/2025

TANG CAPITAL PARTNERS INTERNATIONAL, LP

Signature:	/s/ Kevin Tang
Name/Title:	Manager, Tang Capital Management, LLC, General Partner
Date:	09/19/2025

TANG CAPITAL PARTNERS III, INC

Signature:	/s/ Kevin Tang
Name/Title:	Chief Executive Officer
Date:	09/19/2025

TANG CAPITAL PARTNERS IV, INC

Signature:	/s/ Kevin Tang
Name/Title:	Chief Executive Officer
Date:	09/19/2025

CONCENTRA BIOSCIENCES, LLC

Signature:	/s/ Kevin Tang
Name/Title:	Chief Executive Officer
Date:	09/19/2025

FAQ

What happened to HilleVax (HLVX) common stock on September 17, 2025?

The Merger closed and, per the Merger Agreement, each issued and outstanding share of HilleVax common stock was cancelled on September 17, 2025.

Does the Schedule 13D/A show any shares still held by the reporting persons?

No. The cover pages and Item 5 state the Reporting Persons beneficially own 0 shares of HilleVax common stock as of the date of this filing.

Did the reporting persons transact in HilleVax shares in the past 60 days?

Except for the effects described in this amendment, the filing states there have been no transactions in the past 60 days by the Reporting Persons.

What corporate change resulted from the merger?

HilleVax continued as the surviving corporation and became a wholly owned subsidiary of XOMA Royalty Corporation following the merger.

When did the Reporting Persons cease to be 5% beneficial owners?

The Reporting Persons ceased to be beneficial owners of 5% or more of HilleVax common stock on September 17, 2025.