Climb Bio (CLYM) director reports 20.44M-share exchange into pre-funded warrant

Rhea-AI Filing Summary

Climb Bio director and 10% owner entities affiliated with RA Capital reported a major restructuring of their holdings and additional open-market share purchases. On December 11, 2025, RA Capital Healthcare Fund, L.P. exchanged 20,440,000 shares of Climb Bio common stock for a pre-funded warrant exercisable for up to 20,440,000 shares at an exercise price of $0.0001 per share, for no additional consideration.

The filing also reports open-market purchases of Climb Bio common stock: 213,099 shares on December 11, 2025 at a weighted average price of $2.18 per share and 101,462 shares on December 12, 2025 at a weighted average price of $2.86. The warrant has no expiration date, is exercisable immediately, and includes a 33.0% beneficial ownership cap, limiting how many shares can be exercised based on total outstanding stock. Climb Bio shares are held across multiple RA Capital funds and a separately managed account, with beneficial ownership relationships detailed among the affiliated entities.

Insights

Insider transactions analyst

RA Capital restructured a large Climb Bio stake into a pre-funded warrant and added shares in open-market buys.

Affiliates of RA Capital, identified as a director and 10% owner of Climb Bio, exchanged 20,440,000 common shares for a pre-funded warrant exercisable for the same number of shares at an exercise price of $0.0001 per share. This shifts part of the position from common stock into a derivative security while keeping the underlying share exposure available via exercise.

The filing also discloses purchases of 213,099 shares at a weighted average price of $2.18 on December 11, 2025 and 101,462 shares at a weighted average price of $2.86 on December 12, 2025, with detailed price ranges provided. The pre-funded warrant has no expiration date, is exercisable immediately, and contains a 33.0% beneficial ownership limitation, which constrains exercises that would push aggregate ownership above that threshold. Overall, the filing documents a sizable position restructuring and incremental share accumulation, without stating any change in strategy or guidance.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

RA CAPITAL MANAGEMENT, L.P.

(Last) (First) (Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Climb Bio, Inc. [ CLYM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
12/11/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	12/11/2025		D(1)		20,440,000	D	$0	3,081,757	I	See footnotes(2)(3)
Common Stock	12/11/2025		P		213,099	A	$2.18(4)	3,294,856	I	See footnotes(2)(3)
Common Stock	12/12/2025		P		101,462	A	$2.86(5)	3,396,318	I	See footnotes(2)(3)
Common Stock								2,479,872	I	See footnotes(3)(6)
Common Stock								1,226,497	I	See footnotes(3)(7)
Common Stock								483,679	I	See footnotes(3)(8)
Common Stock								2,866,375	I	See footnotes(3)(9)
Common Stock								841,087	I	See footnotes(3)(10)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Pre-Funded Warrants (Right to Buy)	$0.0001	12/11/2025		A(1)		20,440,000		(11)	(11)	Common Stock	20,440,000	(1)	20,440,000	I	See footnotes(2)(3)

1. Name and Address of Reporting Person^*

RA CAPITAL MANAGEMENT, L.P.

(Last) (First) (Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

RA Capital Healthcare Fund LP

(Last) (First) (Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

RA Capital Nexus Fund, L.P.

(Last) (First) (Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

RA Capital Nexus Fund II, L.P.

(Last) (First) (Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

RA Capital Nexus Fund III, L.P.

(Last) (First) (Middle)

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Kolchinsky Peter

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

1. Name and Address of Reporting Person^*

Shah Rajeev M.

(Last) (First) (Middle)

C/O RA CAPITAL MANAGEMENT, L.P.

200 BERKELEY STREET, 18TH FLOOR

(Street)

BOSTON MA 02116

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. On December 11, 2025, RA Capital Healthcare Fund, L.P. (the "Fund") entered into an Exchange Agreement with the Issuer pursuant to which the Fund exchanged, for no additional consideration, 20,440,000 shares of the Issuer's Common Stock for a pre-funded warrant exercisable for up to 20,440,000 shares of the Issuer's Common Stock at an exercise price of $0.0001 per share.

2. These securities are held directly by RA Capital Healthcare Fund, L.P. (the "Fund").

3. RA Capital Management, L.P. (the "Adviser") is the investment manager for the Fund, RA Capital Nexus Fund, L.P. (the "Nexus Fund"), RA Capital Nexus II Fund, L.P. (the "Nexus Fund II"), RA Capital Nexus III Fund, L.P. (the "Nexus Fund III") and a separately managed account (the "Account"). The general partner of the Adviser is RA Capital Management GP, LLC (the "Adviser GP"), of which Dr. Peter Kolchinsky and Mr. Rajeev Shah are the managing members. The Fund and the Nexus Fund III collectively own approximately 75% of the outstanding equity interests of Sera Medicines, LLC ("Sera"). Accordingly, each of the Fund, the Nexus Fund III and the Adviser may be deemed to beneficially own the securities held by Sera. The Adviser, the Adviser GP, the Fund, the Nexus Fund, the Nexus Fund II, the Nexus Fund III, Dr. Kolchinsky and Mr. Shah disclaim beneficial ownership of the reported securities, except to the extent of their respective pecuniary interest therein.

4. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $2.11 to $2.20 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote.

5. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $2.32 to $3.00 inclusive. The Reporting Persons undertake to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares purchased at each separate price within the range set forth in this footnote.

6. These securities are held directly by Sera.

7. These securities are held directly by the Nexus Fund.

8. These securities are held directly by the Nexus Fund II.

9. These securities are held directly by Nexus Fund III.

10. These securities are held directly by the Account.

11. The Pre-Funded Warrants have no expiration date and are exercisable immediately. Notwithstanding the foregoing, the Reporting Persons shall not be entitled to exercise the Pre-Funded Warrant if it would cause the aggregate number of shares of Common Stock beneficially owned by the Reporting Persons, their affiliates and any persons who are members of a Section 13(d) group with the Reporting Persons or their affiliates to exceed 33.0% of the total number of issued and outstanding shares of Common Stock of the Issuer following such exercise.

Remarks:

Dr. Andrew Levin, a Partner and Managing Director of the Adviser, serves on the Issuer's board of directors.

	/s/ Peter Kolchinsky, Manager of RA Capital Management, L.P.	12/15/2025
	/s/ Peter Kolchinsky, Manager of RA Capital Healthcare Fund GP, LLC the General Partner of RA Capital Healthcare Fund, L.P.	12/15/2025
	/s/ Peter Kolchinsky, Manager of RA Capital Nexus Fund GP, LLC, the General Partner of RA Capital Nexus Fund, L.P.	12/15/2025
	/s/ Peter Kolchinsky, Manager of RA Capital Nexus Fund II GP, LLC, the General Partner of RA Capital Nexus Fund II, L.P.	12/15/2025
	/s/ Peter Kolchinsky, Manager of RA Capital Nexus Fund III GP, LLC, the General Partner of RA Capital Nexus Fund III, L.P.	12/15/2025
	/s/ Peter Kolchinsky, individually	12/15/2025
	/s/ Rajeev Shah, individually	12/15/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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FAQ

What insider transactions did RA Capital report for Climb Bio (CLYM)?

The reporting persons disclosed that on December 11, 2025 RA Capital Healthcare Fund, L.P. exchanged 20,440,000 Climb Bio common shares for a pre-funded warrant exercisable for up to 20,440,000 shares at $0.0001 per share, for no additional consideration. They also reported open-market purchases of 213,099 shares on December 11, 2025 and 101,462 shares on December 12, 2025.

What are the key terms of the Climb Bio pre-funded warrant held by RA Capital?

The pre-funded warrant reported by RA Capital Healthcare Fund, L.P. is exercisable for up to 20,440,000 shares of Climb Bio common stock at an exercise price of $0.0001 per share. It has no expiration date, is exercisable immediately, and includes a 33.0% beneficial ownership cap that prevents exercises which would raise the reporting persons' aggregate beneficial ownership above 33.0% of Climb Bio’s outstanding common stock after exercise.

At what prices did RA Capital entities buy Climb Bio (CLYM) shares?

The filing shows two weighted average purchase prices. On December 11, 2025, 213,099 shares were bought at a weighted average price of $2.18 per share, with individual trades between $2.11 and $2.20. On December 12, 2025, 101,462 shares were bought at a weighted average price of $2.86, with trade prices ranging from $2.32 to $3.00.

How do RA Capital and its affiliates hold their Climb Bio shares?

The reported Climb Bio securities are held through several RA Capital-affiliated vehicles, including RA Capital Healthcare Fund, L.P., RA Capital Nexus Fund, L.P., RA Capital Nexus II Fund, L.P., RA Capital Nexus III Fund, L.P., Sera Medicines, LLC, and a separately managed account. RA Capital Management, L.P. serves as investment manager, and various entities and individuals, including Dr. Peter Kolchinsky and Mr. Rajeev Shah, may be deemed to share beneficial ownership as described, while disclaiming ownership beyond their pecuniary interests.

What beneficial ownership limitation applies to RA Capital’s Climb Bio pre-funded warrant?

The pre-funded warrant includes a 33.0% beneficial ownership limitation. The reporting persons are not entitled to exercise the warrant if doing so would cause the aggregate number of Climb Bio common shares beneficially owned by them, their affiliates, and any Section 13(d) group members with them to exceed 33.0% of Climb Bio’s issued and outstanding common stock after that exercise.

What is the relationship between RA Capital and Climb Bio’s board of directors?

The filing notes that Dr. Andrew Levin, a Partner and Managing Director of RA Capital Management, L.P., serves on Climb Bio’s board of directors. The reporting persons are identified as a director and 10% owner of Climb Bio.