5AM Ventures revises Rallybio (RLYB) ownership and discloses stock sales

Rhea-AI Filing Summary

Rallybio Corp’s major venture backer 5AM Ventures and related entities have updated their ownership positions in the company’s common stock. The amendment shows 5AM Ventures V, L.P. holding 135,319 shares, or 2.6% of Rallybio’s outstanding common stock, and 5AM Opportunities I, L.P. holding 156,469 shares, or 3.0%.

Managing members Andrew J. Schwab and Dr. Kush Parmar each report beneficial ownership of 291,788 shares, representing 5.5% of the common stock, while Dr. Scott M. Rocklage reports 135,319 shares, or 2.6%. These percentages are based on 5,280,471 shares outstanding as of December 30, 2025, after an 8‑for‑1 reverse stock split effective February 2, 2026.

The filing also notes recent open‑market sales by 5AM Ventures V. On February 25, 2025, it sold 87,052 shares at prices between $6.00 and $6.15 per share, with a weighted average of $6.07. On February 26, 2025, it sold 75,000 shares at prices between $6.00 and $6.14, with a weighted average of $6.06.

Insights

Equity ownership and governance analyst

5AM Ventures updates Rallybio ownership and discloses recent share sales.

The amendment details how 5AM Ventures and its affiliates currently hold Rallybio common stock and clarifies control relationships. Key individuals, including Andrew J. Schwab and Dr. Kush Parmar, each report beneficial ownership of 5.5% of the company’s outstanding shares.

The document ties these percentages to 5,280,471 shares outstanding as of December 30, 2025, adjusted for an 8‑for‑1 reverse stock split effective February 2, 2026. It also lists recent open‑market sales by 5AM Ventures V at prices around $6.06–$6.07 per share, indicating trading activity but not specifying any strategic shift.

This type of ownership update mainly informs investors about current concentration and control of Rallybio’s equity rather than signaling a defined operational or financial change. Subsequent company filings may offer additional context on how ownership dynamics evolve after these reported transactions.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)

Rallybio Corp

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

75120L209

(CUSIP Number)

Lauren A. Daniel
c/o 5AM Venture Management, LLC, 4 Embarcadero Center, Suite 3110
San Francisco, CA, 94111
(415) 993-8570

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

02/25/2026

(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. 75120L209

1

Name of reporting person

5AM Ventures 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 135,319.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 135,319.00

11

Aggregate amount beneficially owned by each reporting person

135,319.00

12

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

13

Percent of class represented by amount in Row (11)

2.6 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 75120L209

1

Name of reporting person

5AM Partners 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 135,319.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 135,319.00

11

Aggregate amount beneficially owned by each reporting person

135,319.00

12

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

13

Percent of class represented by amount in Row (11)

2.6 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 75120L209

1

Name of reporting person

5AM Opportunities 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 156,469.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 156,469.00

11

Aggregate amount beneficially owned by each reporting person

156,469.00

12

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

13

Percent of class represented by amount in Row (11)

3.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP No. 75120L209

1

Name of reporting person

5AM Opportunities I (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 156,469.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 156,469.00

11

Aggregate amount beneficially owned by each reporting person

156,469.00

12

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

13

Percent of class represented by amount in Row (11)

3.0 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP No. 75120L209

1

Name of reporting person

Andrew J. Schwab

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 291,788.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 291,788.00

11

Aggregate amount beneficially owned by each reporting person

291,788.00

12

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

13

Percent of class represented by amount in Row (11)

5.5 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 75120L209

1

Name of reporting person

Kush Parmar

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 291,788.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 291,788.00

11

Aggregate amount beneficially owned by each reporting person

291,788.00

12

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

13

Percent of class represented by amount in Row (11)

5.5 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP No. 75120L209

1

Name of reporting person

Scott M. Rocklage

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 135,319.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 135,319.00

11

Aggregate amount beneficially owned by each reporting person

135,319.00

12

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

13

Percent of class represented by amount in Row (11)

2.6 %

14

Type of Reporting Person (See Instructions)

IN

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: Rallybio Corp
(c)	Address of Issuer's Principal Executive Offices: 234 CHURCH STREET, SUITE 1020, NEW HAVEN, CONNECTICUT , 06510.
Item 1 Comment: This Amendment No. 2 (this "Amendment No. 2" or this "Schedule 13D/A") amends and supplements the statement on Schedule 13D originally filed with the Securities and Exchange Commission (the "SEC") on August 12, 2021 and amended on June 7, 2022 (as amended, the "Statement") by the Reporting Persons. Unless otherwise defined herein, capitalized terms used in this Amendment No. 2 shall have the meanings ascribed to them in the Statement. Unless amended or supplemented below, the information in the Statement remains unchanged.
Item 2.	Identity and Background
(a)	This Schedule 13D/A is being filed on behalf of 5AM Ventures V, L.P. ("5AM V"), 5AM Partners V, LLC ("5AM Partners V"), 5AM Opportunities I, L.P. ("5AM Opportunities"), 5AM Opportunities I (GP), LLC ("5AM Opportunities GP"), Andrew J. Schwab ("Schwab"), Dr. Kush Parmar ("Dr. Parmar") and Dr. Scott M. Rocklage ("Dr. Rocklage"). 5AM V, 5AM Partners V, 5AM Opportunities, 5AM Opportunities GP, Schwab, Dr. Parmar and Dr. Rocklage are collectively referred to herein as the "Reporting Persons." The agreement among the Reporting Persons to file this Schedule 13D/A jointly in accordance with Rule 13d-1(k) of the Securities Exchange Act of 1934, as amended, (the "Act") is attached hereto as Exhibit 99.1.
(b)	The principal business and principal business office of the Reporting Persons is 4 Embarcadero Center, Suite 3110, San Francisco, CA 94111.
(c)	The principal business of the Reporting Persons is venture capital investments. Each of the individuals serves as a Managing Member of 5AM Partners V, which is the general partner of 5AM V. Schwab and Dr. Parmar serve as Managing Members of 5AM Opportunities GP, which is the general partner of 5AM Opportunities.
(d)	During the last five years, none of the Reporting Persons has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).
(e)	During the last five years, none of the Reporting Persons was a party to a civil proceeding of a judicial of administrative body of competent jurisdiction or were subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(f)	Each of 5AM V, 5AM Partners V, 5AM Opportunities and 5AM Opportunities GP was organized in the state of Delaware and each of the individuals is a citizen of the United States.
Item 5.	Interest in Securities of the Issuer
(a)	Rows 11 and 13 of each Reporting Person's cover page to this Schedule 13D/A set forth the aggregate number of shares of common stock and percentages of the shares of common stock beneficially owned by such Reporting Person and are incorporated by reference. The percentage set forth in each row 13 is based upon 5,280,471 shares of common stock outstanding as of December 30, 2025 as reported in the Issuer's definitive proxy statement filed with the SEC on January 2, 2026 and giving effect to an 8-for-1 reverse split of the Issuer's common stock, which was effected on February 2, 2026. The Reporting Persons' beneficial ownership of the Issuer's common stock consists of (i) 135,319 shares of common stock directly held by 5AM V; and (ii) 156,469 shares of common stock directly held by 5AM Opportunities. 5AM Partners V is the sole general partner of 5AM V and shares voting and dispositive power over the securities held by 5AM Partners V. 5AM Opportunities GP is the sole general partner of 5AM Opportunities and shares voting and dispositive power over the securities held by 5AM Opportunities. Schwab and Drs. Parmar and Rocklage are the managing members of 5AM Partners V and share voting and dispositive power over the securities held by 5AM V. Schwab and Dr. Parmar are the managing members of 5AM Opportunities GP and share voting and dispositive power over the securities held by 5AM Opportunities.
(b)	Rows 7 through 10 of each Reporting Person's cover page to this Schedule 13D/A set forth the number of shares of common stock as to which such Reporting Person has the sole or shared power to vote or direct the vote and sole or shared power to dispose or to direct the disposition and are incorporated by reference.
(c)	Except as set forth below, none of the Reporting Persons has effected any transactions with respect to the securities of the Issuer during the past sixty days. On February 25, 2025, 5AM V sold an aggregate of 87,052 shares in open market transactions at prices ranging from $6.00 to $6.15 (weighted average sales price of $6.07 per share). On February 26, 2025, 5AM V sold an aggregate of 75,000 shares in open market transactions at prices ranging from $6.00 to $6.14 (weighted average sales price of $6.06 per share).
(d)	No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, the securities beneficially owned by any of the Reporting Persons.
(e)	Not Applicable.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 99.1 Joint Filing Agreement (incorporated by reference to Exhibit A to the Reporting Persons' Schedule 13D, filed with the SEC on August 12, 2021).

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.

5AM Ventures V, L.P.

Signature:	/s/ Scott M. Rocklage
Name/Title:	By 5AM Partners V, LLC, its General Partner, By Scott M. Rocklage, Managing Member
Date:	02/27/2026

5AM Partners V, LLC

Signature:	/s/ Scott M. Rocklage
Name/Title:	By Scott M. Rocklage, Managing Member
Date:	02/27/2026

5AM Opportunities I, L.P.

Signature:	/s/ Kush Parmar
Name/Title:	By 5AM Opportunities I (GP), LLC, its General Partner, By Kush Parmar, Managing Member
Date:	02/27/2026

5AM Opportunities I (GP), LLC

Signature:	/s/ Kush Parmar
Name/Title:	By Kush Parmar, Managing Member
Date:	02/27/2026

Andrew J. Schwab

Signature:	/s/ Andrew J. Schwab
Name/Title:	Andrew J. Schwab
Date:	02/27/2026

Kush Parmar

Signature:	/s/ Kush Parmar
Name/Title:	Kush Parmar
Date:	02/27/2026

Scott M. Rocklage

Signature:	/s/ Scott M. Rocklage
Name/Title:	Scott M. Rocklage
Date:	02/27/2026

FAQ

What ownership stake does 5AM Ventures report in Rallybio (RLYB)?

5AM Ventures V, L.P. reports beneficial ownership of 135,319 Rallybio common shares, representing 2.6% of shares outstanding. 5AM Opportunities I, L.P. reports 156,469 shares, or 3.0%, giving 5AM-affiliated funds a significant but non‑controlling equity position in the company.

How many Rallybio (RLYB) shares are outstanding in this Schedule 13D/A?

The filing bases ownership percentages on 5,280,471 Rallybio common shares outstanding as of December 30, 2025. This figure reflects the company’s 8‑for‑1 reverse stock split of its common stock, which became effective on February 2, 2026, according to the disclosure.

What recent Rallybio (RLYB) share sales did 5AM Ventures disclose?

5AM Ventures V disclosed two recent open‑market sale days. On February 25, 2025, it sold 87,052 shares at $6.00–$6.15, with a $6.07 weighted average. On February 26, 2025, it sold 75,000 shares at $6.00–$6.14, with a $6.06 weighted average sale price.

Which individuals associated with 5AM report more than 5% of Rallybio (RLYB)?

Andrew J. Schwab and Dr. Kush Parmar each report beneficial ownership of 291,788 Rallybio common shares. For each individual, this represents 5.5% of the outstanding common stock, based on 5,280,471 shares outstanding after the company’s reverse stock split adjustment.

How did Rallybio’s reverse stock split affect the ownership figures in this filing?

Ownership percentages are calculated after an 8‑for‑1 reverse split of Rallybio’s common stock, effective February 2, 2026. The filing states that 5,280,471 shares were outstanding as of December 30, 2025, and all reported percentage interests, such as 2.6% and 3.0%, use this adjusted share count.

Who are the reporting persons in the Rallybio (RLYB) Schedule 13D/A Amendment No. 2?

The reporting persons are 5AM Ventures V, L.P., 5AM Partners V, LLC, 5AM Opportunities I, L.P., 5AM Opportunities I (GP), LLC, Andrew J. Schwab, Dr. Kush Parmar, and Dr. Scott M. Rocklage. They jointly report their beneficial ownership and control relationships over Rallybio shares.