Gossamer Bio: Valence stake falls to 4.9%

Valence ceased to be a more-than-5% beneficial owner on September 24, 2026, while related reporting persons reported shared power over 5.1%.

Rhea-AI Filing Summary

Gossamer Bio, Inc. (GOSS) ownership amendment updates beneficial-ownership figures following the issuer’s 1-for-80 reverse stock split, effective September 10, 2026. Valence reported 296,858 common shares, approximately 4.9% of the class, and ceased to be a beneficial owner of more than 5% on September 24, 2026; Cogence reported 15,190 shares, approximately 0.2%.

D. E. Shaw & Co., L.P., the investment adviser, D. E. Shaw & Co., L.L.C., the manager, and David E. Shaw may be deemed to share voting and dispositive power over 312,048 shares, or 5.1%; each disclaims beneficial ownership as stated. Gossamer Bio had 6,116,391 common shares outstanding as of September 14, 2026. The amendment also says that, as a result of the split, Valence and Cogence maintained open short positions referencing 44,364 and 2,290 common shares, respectively.

Key Figures

Valence beneficially owned shares: 296,858 shares (approximately 4.9%) Cogence beneficially owned shares: 15,190 shares (approximately 0.2%) Shares under shared voting and dispositive power: 312,048 shares (5.1%) +3 more

6 metrics

Valence beneficially owned shares 296,858 shares (approximately 4.9%) Common shares

Cogence beneficially owned shares 15,190 shares (approximately 0.2%) Common shares

Shares under shared voting and dispositive power 312,048 shares (5.1%) May be deemed shared by D. E. Shaw & Co., L.P., D. E. Shaw & Co., L.L.C., and David E. Shaw

Common shares outstanding 6,116,391 shares As of September 14, 2026

Valence open short position 44,364 shares Common shares referenced

Cogence open short position 2,290 shares Common shares referenced

Key Terms

beneficial owner, Shared Voting Power, Shared Dispositive Power, open short positions, +1 more

5 terms

beneficial owner regulatory

"ceased to be the beneficial owner of more than 5 percent"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

Shared Voting Power regulatory

"Shared Voting Power 312,048.00"

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.

Shared Dispositive Power regulatory

"Shared Dispositive Power 312,048.00"

open short positions financial

"maintain open short positions referencing"

reverse stock split financial

"Issuer effected the Reverse Stock Split"

A reverse stock split reduces a company's number of outstanding shares while raising the price per share proportionally, so the total value of each investor's holding is unchanged; a 1-for-10 split turns 100 shares worth $1 each into 10 shares worth $10 each. Companies often do this to regain compliance with an exchange's minimum price rule or to attract investors who avoid very low-priced stocks.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many GOSS shares did D. E. Shaw-related reporting persons report?

D. E. Shaw & Co., L.P. and D. E. Shaw & Co., L.L.C. each reported shared voting and dispositive power over 312,048 shares, representing 5.1%. David E. Shaw may be deemed to share that power and disclaims beneficial ownership.

What GOSS short positions were reported?

Valence and Cogence maintained open short positions referencing 44,364 and 2,290 Gossamer Bio common shares, respectively, as a result of the reverse stock split.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/28/2026 - 07:49 PM Accepted by SEC EDGAR 09/28/2026 - 07:49 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)

Gossamer Bio, Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

38341P201

(CUSIP Number)

D. E. Shaw & Co., L.P.
Legal & Compliance, Two Manhattan West,, 375 Ninth Ave., 52nd Floor
New York, NY, 10001
212-478-0000

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

09/24/2026

(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): 38341P201

1

Name of reporting person

D. E. Shaw Valence Portfolios, L.L.C.

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 296,858.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 296,858.00

11

Aggregate amount beneficially owned by each reporting person

296,858.00

12

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

13

Percent of class represented by amount in Row (11)

4.9 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

i) As further described in Item 5, D. E. Shaw Valence Portfolios, L.L.C. ceased to be the beneficial owner of more than 5 percent of the class of securities on September 24, 2026. ii) The number of shares beneficially owned by each Reporting Person reported herein reflects the Issuer's 1-for-80 reverse stock split, which became effective at 11:59 p.m. Eastern Time on September 10, 2026 (the "Reverse Stock Split"), as disclosed in the Issuer's Form 8-K filed with the Securities and Exchange Commission (the "SEC") on September 9, 2026. See Item 5(a) for further detail.

SCHEDULE 13D

CUSIP Number(s): 38341P201

1

Name of reporting person

D. E. Shaw & Co., L.L.C.

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 312,048.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 312,048.00

11

Aggregate amount beneficially owned by each reporting person

312,048.00

12

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

13

Percent of class represented by amount in Row (11)

5.1 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

The number of shares beneficially owned by each Reporting Person reported herein reflects the Issuer's Reverse Stock Split, as disclosed in the Issuer's Form 8-K filed with the SEC on September 9, 2026. See Item 5(a) for further detail.

SCHEDULE 13D

CUSIP Number(s): 38341P201

1

Name of reporting person

D. E. Shaw & Co., 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 312,048.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 312,048.00

11

Aggregate amount beneficially owned by each reporting person

312,048.00

12

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

13

Percent of class represented by amount in Row (11)

5.1 %

14

Type of Reporting Person (See Instructions)

IA, PN

Comment for Type of Reporting Person:

The number of shares beneficially owned by each Reporting Person reported herein reflects the Issuer's Reverse Stock Split, as disclosed in the Issuer's Form 8-K filed with the SEC on September 9, 2026. See Item 5(a) for further detail.

SCHEDULE 13D

CUSIP Number(s): 38341P201

1

Name of reporting person

David E. Shaw

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

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 312,048.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 312,048.00

11

Aggregate amount beneficially owned by each reporting person

312,048.00

12

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

13

Percent of class represented by amount in Row (11)

5.1 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

The number of shares beneficially owned by each Reporting Person reported herein reflects the Issuer's Reverse Stock Split, as disclosed in the Issuer's Form 8-K filed with the SEC on September 9, 2026. See Item 5(a) for further detail.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, $0.0001 par value per share
(b)	Name of Issuer: Gossamer Bio, Inc.
(c)	Address of Issuer's Principal Executive Offices: 3115 Merryfield Row, Suite 120, San Diego, CALIFORNIA , 92121.
Item 1 Comment: Introductory Note: This Amendment No. 4 to Schedule 13D ("Amendment No. 4") is filed by and on behalf of each of the Reporting Persons to amend and supplement the Schedule 13D related to the Common Shares of the Issuer previously filed by the Reporting Persons with the SEC on June 11, 2026, as amended and supplemented by Amendment No. 1 to Schedule 13D filed on July 1, 2026, by Amendment No. 2 to Schedule 13D filed on July 24, 2026, and by Amendment No. 3 to Schedule 13D filed on August 24, 2026 (as amended, the "Schedule 13D"). Each capitalized term used and not defined herein shall have the meaning assigned to such term in the Schedule 13D. Except as provided herein, each Item of the Schedule 13D remains unchanged.
Item 4.	Purpose of Transaction
	Item 4 of the Schedule 13D is hereby amended and supplemented by adding the following at the end of the section entitled "Voting Agreements": On July 14, 2026, shareholders approved the Shareholder Proposals (i) through (iv). Subsequently, as disclosed in the Issuer's Form 8-K filed with the SEC on September 9, 2026, the Issuer effected the Reverse Stock Split.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5(a) of the Schedule 13D is hereby amended and restated as follows: (a) - (b) In connection with the Reverse Stock Split, on September 11, 2026, the Reporting Persons received 1 Common Share in exchange for every 80 Common Shares directly held by them as of the close of business on September 10, 2026. Based upon the Issuer's definitive proxy statement, filed with the SEC on September 16, 2026, there were 6,116,391 Common Shares issued and outstanding as of September 14, 2026. Common Shares are beneficially owned by Valence and Cogence. Each of Valence and Cogence is a Delaware limited liability company and has its business address and principal office at Two Manhattan West, 375 Ninth Avenue, 52nd Floor, New York, NY 10001. The 296,858 Common Shares beneficially owned by Valence (the "Valence Shares") represent approximately 4.9% of the outstanding Common Shares. The 15,190 Common Shares beneficially owned by Cogence (the "Cogence Shares") represent approximately 0.2% of the outstanding Common Shares. Valence has the power to vote or direct the vote of (and the power to dispose or direct the disposition of) the Valence Shares. Cogence has the power to vote or direct the vote of (and the power to dispose or direct the disposition of) the Cogence Shares. DESCO LP, as the investment adviser of Valence and Cogence, may be deemed to have the shared power to vote or direct the vote of, and the shared power to dispose or direct the disposition of, 312,048 Common Shares. DESCO LLC, as the manager of Valence and Cogence, may be deemed to have the shared power to vote or direct the vote of, and the shared power to dispose or direct the disposition of, 312,048 Common Shares. As general partner of DESCO LP, DESCO Inc. may be deemed to have the shared power to vote or direct the vote of, and the shared power to dispose or direct the disposition of, 312,048 Common Shares. As managing member of DESCO LLC, DESCO II, Inc. may be deemed to have the shared power to vote or direct the vote of, and the shared power to dispose or direct the disposition of, 312,048 Common Shares. None of DESCO LP, DESCO LLC, DESCO Inc., or DESCO II, Inc. owns any Common Shares directly, and each such entity disclaims beneficial ownership of any Common Shares. Dr. Shaw does not own any Common Shares directly. By virtue of Dr. Shaw's position as President and sole shareholder of DESCO Inc., which is the general partner of DESCO LP, which in turn is the investment adviser of Valence and Cogence, and by virtue of Dr. Shaw's position as President and sole shareholder of DESCO II, Inc., which is the managing member of DESCO LLC, which in turn is the manager of Valence and Cogence, Dr. Shaw may be deemed to have the shared power to vote or direct the vote of, and the shared power to dispose or direct the disposition of, the 312,048 Common Shares as described above constituting 5.1% of the outstanding Common Shares, and, therefore, Dr. Shaw may be deemed to be the beneficial owner of such Common Shares. Dr. Shaw disclaims beneficial ownership of any Common Shares.
(b)	Item 5(b) of the Schedule 13D is hereby amended and supplemented as follows: See Item 5(a) of Amendment No. 4 to the Schedule 13D.
(c)	Item 5(c) of the Schedule 13D is hereby amended and supplemented as follows: Schedule I to Amendment No. 4, which is incorporated by reference into this Item 5(c) as if restated in full herein, describes all of the transactions in Common Shares by the Reporting Persons and/or any affiliates of the Reporting Persons since Amendment No. 3.
(d)	Item 5(d) of the Schedule 13D is hereby amended and supplemented as follows: To the best of the Reporting Persons' knowledge, no person other than the Reporting Persons or their affiliates has the right to receive or power to direct the receipt of dividends from, or proceeds from the sale of, the 312,048 Common Shares, except for such rights and powers as the corresponding investors in Valence and Cogence.
(e)	On September 24, 2026, Valence ceased to be the beneficial owner of more than 5 percent of the class of securities.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Item 6 of the Schedule 13D is hereby amended and supplemented by adding the following at the end of the second paragraph: As a result of the Reverse Stock Split, Valence and Cogence maintain open short positions referencing 44,364 and 2,290 Common Shares, respectively.
Item 7.	Material to be Filed as Exhibits.
	Item 7 of the Schedule 13D is hereby amended and supplemented as follows: Exhibit 99.1 - Schedule I (Transactions in the Securities of the Issuer Since Amendment No. 3) Exhibit 99.2 - Power of Attorney, granted by David E. Shaw relating to D. E. Shaw & Co., Inc., in favor of the signatories hereto, among others, dated August 1, 2024. Exhibit 99.3 - Power of Attorney, granted by David E. Shaw relating to D. E. Shaw & Co. II, Inc., in favor of the signatories hereto, among others, dated August 1, 2024. Exhibit 99.4 - Joint Filing Agreement, by and among the Reporting Persons, dated September 28, 2026. Exhibit 99.5 - Transaction Support Agreement with the Issuer, dated May 18, 2026, incorporated by reference to Exhibit 10.1 to the Form 8-K filed by the Issuer on May 18, 2026. (https://www.sec.gov/Archives/edgar/data/1728117/000172811726000036/goss-20260518xexx101xtsa.htm) Exhibit 99.6 - Form of Voting Agreement, dated May 18, 2026, incorporated by reference herein to Exhibit 10.2 to the Form 8-K filed by the issuer on May 18, 2026. (https://www.sec.gov/Archives/edgar/data/1728117/000172811726000036/goss-20260518xexx102xformo.htm) Exhibit 99.7 - Indenture governing Senior Secured First Lien Convertible Notes due 2030, incorporated by reference to Exhibit 10.1 to the Form 8-K filed by the Issuer on June 5, 2026. (https://www.sec.gov/Archives/edgar/data/1728117/000172811726000045/goss-20260604xexx101inde.htm) Exhibit 99.8 - Purchase Warrant Agreement, dated June 4, 2026, incorporated by reference herein to Exhibit 10.3 to the Form 8-K filed by the issuer on June 5, 2026. (https://www.sec.gov/Archives/edgar/data/1728117/000172811726000045/goss-20260604xexx103warr.htm)

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.

D. E. Shaw Valence Portfolios, L.L.C.

Signature:	/s/ Daniel R. Marcus
Name/Title:	Daniel R. Marcus / Authorized Signatory
Date:	09/28/2026

D. E. Shaw & Co., L.L.C.

Signature:	/s/ Daniel R. Marcus
Name/Title:	Daniel R. Marcus / Authorized Signatory
Date:	09/28/2026

D. E. Shaw & Co., L.P.

Signature:	/s/ Daniel R. Marcus
Name/Title:	Daniel R. Marcus / Chief Compliance Officer
Date:	09/28/2026

David E. Shaw

Signature:	/s/ Daniel R. Marcus
Name/Title:	Daniel R. Marcus / Attorney-in-Fact for David E. Shaw
Date:	09/28/2026