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)

(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).

SCHEDULE 13D

CUSIP No.

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 No.

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 No.

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 No.

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

SCHEDULE I

Transactions in the Securities of the Issuer Since Amendment No. 3

¹Price per Common Share does not include any brokerage commissions or service charges. Where weighted average price is used for the reported transactions, the Reporting Persons undertake to provide upon request by the SEC, full information regarding the number of Common Shares purchased or sold at each separate price.

²A weighted average price based on prices ranging from $0.1693 to $0.2115.

³A weighted average price based on prices ranging from $0.1693 to $0.2115.

⁴A weighted average price based on prices ranging from $0.1800 to $0.1999.

⁵A weighted average price based on prices ranging from $0.1800 to $0.2015.

⁶A weighted average price based on prices ranging from $0.1651 to $0.1765.

⁷A weighted average price based on prices ranging from $0.1641 to $0.1773.

⁸A weighted average price based on prices ranging from $0.1662 to $0.1726.

⁹A weighted average price based on prices ranging from $0.1656 to $0.1728.

¹⁰A weighted average price based on prices ranging from $0.1680 to $0.1790.

¹¹A weighted average price based on prices ranging from $0.1680 to $0.1796.

¹²A weighted average price based on prices ranging from $0.1603 to $0.1705.

¹³A weighted average price based on prices ranging from $0.1602 to $0.1705.

¹⁴A weighted average price based on prices ranging from $0.1620 to $0.1711.

¹⁵A weighted average price based on prices ranging from $0.1616 to $0.1727.

¹⁶A weighted average price based on prices ranging from $0.1644 to $0.1742.

¹⁷A weighted average price based on prices ranging from $0.1640 to $0.1748.

¹⁸A weighted average price based on prices ranging from $0.1693 to $0.1779.

¹⁹A weighted average price based on prices ranging from $0.1690 to $0.1804.

²⁰A weighted average price based on prices ranging from $0.1693 to $0.1835.

²¹A weighted average price based on prices ranging from $0.1693 to $0.1844.

²²A weighted average price based on prices ranging from $0.1500 to $0.1689.

²³A weighted average price based on prices ranging from $0.1499 to $0.1717.

²⁴A weighted average price based on prices ranging from $0.1405 to $0.1463.

²⁵A weighted average price based on prices ranging from $0.1403 to $0.1463.

²⁶A weighted average price based on prices ranging from $10.53 to $11.17.

²⁷A weighted average price based on prices ranging from $10.50 to $11.45.

²⁸A weighted average price based on prices ranging from $10.36 to $10.90.

²⁹A weighted average price based on prices ranging from $10.14 to $11.00.

³⁰A weighted average price based on prices ranging from $10.38 to $10.51.

³¹A weighted average price based on prices ranging from $10.17 to $10.89.

³²A weighted average price based on prices ranging from $10.71 to $10.87.

³³A weighted average price based on prices ranging from $10.01 to $11.00.

³⁴A weighted average price based on prices ranging from $11.02 to $11.07.

³⁵A weighted average price based on prices ranging from $11.29 to $11.76.

³⁶A weighted average price based on prices ranging from $11.29 to $12.20.

³⁷A weighted average price based on prices ranging from $11.09 to $11.10.

³⁸A weighted average price based on prices ranging from $10.96 to $11.67.

³⁹A weighted average price based on prices ranging from $11.57 to $11.67.

⁴⁰A weighted average price based on prices ranging from $11.37 to $12.25.

⁴¹A weighted average price based on prices ranging from $10.03 to $10.99.

⁴²A weighted average price based on prices ranging from $10.03 to $10.99.

⁴³A weighted average price based on prices ranging from $11.12 to $11.90.

⁴⁴A weighted average price based on prices ranging from $10.92 to $10.99.

⁴⁵A weighted average price based on prices ranging from $10.80 to $11.60.

⁴⁶A weighted average price based on prices ranging from $10.34 to $10.90.

⁴⁷A weighted average price based on prices ranging from $10.26 to $11.01.

⁴⁸A weighted average price based on prices ranging from $11.27 to $11.74.

⁴⁹A weighted average price based on prices ranging from $10.43 to $11.36.

⁵⁰A weighted average price based on prices ranging from $11.46 to $11.74.

Exhibit 2

POWER OF ATTORNEY

FOR CERTAIN REGULATORY FILINGS

INCLUDING CERTAIN FILINGS

UNDER THE SECURITIES EXCHANGE ACT OF 1934

AND THE INVESTMENT ADVISERS ACT OF 1940

I, David E. Shaw, hereby make, constitute, and appoint each of

Adam Deaton,

Anne Dinning,

Edward Fishman,

Alexis Halaby,

Edwin Jager,

Martin Lebwohl,

Daniel Marcus,

Anoop Prasad,

Maximilian Stone, and

David Sweet,

acting individually in such person’s capacity as an employee of D. E. Shaw & Co., L.P. or one of its subsidiaries, as my agent and attorney-in-fact, with full power of substitution, for the purpose of, from time to time, (i) executing in my name, in my capacity as President of D. E. Shaw & Co., Inc. (acting for itself or as the general partner of D. E. Shaw & Co., L.P. and general partner, managing member, or manager of other entities, any of which in turn may be acting for itself or other entities), all documents, certificates, instruments, statements, other filings, and amendments to the foregoing (collectively, “documents”) determined by such person to be necessary or appropriate to comply with any registration or regulatory disclosure requirements and/or ownership or control-person reporting requirements imposed by any U.S. or non-U.S. governmental or regulatory authority, including without limitation Form ADV, Forms 3, 4, 5, and 13F, and Schedules 13D and 13G required to be filed with the U.S. Securities and Exchange Commission, and/or (ii) delivering, furnishing, or filing, in each case whether themself or through their designee, any such documents to or with the appropriate governmental or regulatory authority.  Any such determination shall be conclusively evidenced by such person’s execution of, and/or their (or their designee’s) delivery, furnishing, and/or filing of, the applicable document.

This power of attorney shall be valid as of the date set forth below and replaces the power granted on March 1, 2017, which is hereby cancelled.  Furthermore, this power of attorney shall be valid with respect to any particular individual set forth above only for so long as such person remains employed by D. E. Shaw & Co., L.P. or one of its subsidiaries.

IN WITNESS HEREOF, I have executed this instrument as of the date set forth below.

Date:   August 1, 2024

/s/ David E. Shaw

David E. Shaw,

as President of D. E. Shaw & Co., Inc.

Exhibit 3

POWER OF ATTORNEY

FOR CERTAIN REGULATORY FILINGS

INCLUDING CERTAIN FILINGS

UNDER THE SECURITIES EXCHANGE ACT OF 1934

AND THE INVESTMENT ADVISERS ACT OF 1940

I, David E. Shaw, hereby make, constitute, and appoint each of

Adam Deaton,

Anne Dinning,

Edward Fishman,

Alexis Halaby,

Edwin Jager,

Martin Lebwohl,

Daniel Marcus,

Anoop Prasad,

Maximilian Stone, and

David Sweet,

acting individually in such person’s capacity as an employee of D. E. Shaw & Co., L.P. or one of its subsidiaries, as my agent and attorney-in-fact, with full power of substitution, for the purpose of, from time to time, (i) executing in my name, in my capacity as President of D. E. Shaw & Co. II, Inc. (acting for itself or as the managing member of D. E. Shaw & Co., L.L.C. and general partner, managing member, or manager of other entities, any of which in turn may be acting for itself or other entities), all documents, certificates, instruments, statements, other filings, and amendments to the foregoing (collectively, “documents”) determined by such person to be necessary or appropriate to comply with any registration or regulatory disclosure requirements and/or ownership or control-person reporting requirements imposed by any U.S. or non-U.S. governmental or regulatory authority, including without limitation Form ADV, Forms 3, 4, 5, and 13F, and Schedules 13D and 13G required to be filed with the U.S. Securities and Exchange Commission, and/or (ii) delivering, furnishing, or filing, in each case whether themself or through their designee, any such documents to or with the appropriate governmental or regulatory authority.  Any such determination shall be conclusively evidenced by such person’s execution of, and/or their (or their designee’s) delivery, furnishing, and/or filing of, the applicable document.

This power of attorney shall be valid as of the date set forth below and replaces the power granted on March 1, 2017, which is hereby cancelled.  Furthermore, this power of attorney shall be valid with respect to any particular individual set forth above only for so long as such person remains employed by D. E. Shaw & Co., L.P. or one of its subsidiaries.

IN WITNESS HEREOF, I have executed this instrument as of the date set forth below.

Date:   August 1, 2024

/s/ David E. Shaw

David E. Shaw,

as President of D. E. Shaw & Co. II, Inc.

Exhibit 4

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k)(1) under the Securities Exchange Act of 1934, as amended, each of the undersigned Reporting Persons hereby agrees to the joint filing, along with all other such Reporting Persons, on behalf of each of them of a statement on Schedule 13D (including amendments thereto) with respect to the Common Stock, $0.0001 par value per share, of Gossamer Bio, Inc., and that this Agreement be included as an Exhibit to such joint filing. This Agreement may be executed in any number of counterparts, all of which taken together shall constitute one and the same instrument.

IN WITNESS WHEREOF, each of the undersigned hereby executes this Agreement as of this 28th day of September, 2026.