Common Stock, par value $0.0001 per share

Climb Bio, Inc.

20 William Street, Wellesley Hills, MA, 02481

The disclosure in Items 5(a), (b), (c) and (d) is hereby amended and restated as follows: (a) (b) The responses of each of the Reporting Persons with respect to Rows 11, 12, and 13 of the cover pages of this Schedule 13D that relate to the aggregate number and percentage of common stock (including but not limited to footnotes to such information) are incorporated herein by reference.

The responses of each of the Reporting Persons with respect to Rows 7, 8, 9, and 10 of the cover pages of this Schedule 13D that relate to the number of common stock as to which each of the persons or entities referenced in Item 2 above has sole or shared power to vote or to direct the vote of and sole or shared power to dispose of or to direct the disposition of (including but not limited to footnotes to such information) are incorporated herein by reference.

On September 25, 2025, AI ETI sold 37,371 shares of Common Stock at a weighted average price of $2.1148 per share in open market transactions.(1) On September 26, 2025, AI ETI sold 32,629 shares of Common Stock at a weighted average price of $2.1135 per share in open market transactions.(2) On September 29, 2025, AI ETI sold 2,383 shares of Common Stock at a weighted average price of $2.1175 per share in open market transactions.(3) On October 3, 2025, AI ETI sold 1,900 shares of Common Stock at a price of $2.1000 per share in open market transactions. On October 3, 2025, AI ETI sold 1,100,000 shares of Common Stock at a price of $1.9501 per share in a block trade. (1) These shares were sold in multiple transactions at prices ranging from $2.1000 to $2.1500, inclusive. The Reporting Persons undertake to provide to the staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within such range. (2) These shares were sold in multiple transactions at prices ranging from $2.1000 to $2.1550, inclusive. The Reporting Persons undertake to provide to the staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within such range. (3) These shares were sold in multiple transactions at prices ranging from $2.1000 to $2.1650, inclusive. The Reporting Persons undertake to provide to the staff of the SEC, upon request, full information regarding the number of shares purchased at each separate price within such range.

3,835,117 shares of Common Stock are owned directly by AI ETI and may be deemed to be beneficially owned by AIH, AIM and Mr. Blavatnik because (i) AIH indirectly controls all of the outstanding voting interests in AI ETI, (ii) AIM controls AIH and (iii) Mr. Blavatnik controls AIM and holds a majority of the outstanding voting interests in AIH. Each of the Reporting Persons (other than AI ETI), and each of their affiliated entities and the officers, partners, members and managers thereof, disclaims beneficial ownership of these securities.