Amendment: SEC Form SCHEDULE 13D/A filed by Vor Biopharma Inc.

This Schedule 13D/A is being filed on behalf of RA Capital Management, L.P. ("RA Capital"), Peter Kolchinsky, Rajeev Shah, and RA Capital Healthcare Fund, L.P. (the "Fund"). RA Capital, Dr. Kolchinsky, Mr. Shah and the Fund 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. The Reporting Persons' beneficial ownership of the Issuer's common stock consists of (i) 1,891,035 shares of common stock directly held by the Fund; (ii) 91,266 shares of common stock directly held by the RA Capital Nexus Fund, L.P. (the "Nexus Fund"); (iii) Common Stock Warrants exercisable for up to 1,056,072 shares of common stock held directly by the Fund; (iv) pre-funded warrants (the "Pre-Funded Warrants" and, together with the Common Stock Warrants, the "Warrants") exercisable for up to 10,000,000 shares of common stock directly held by the Fund; (v) a total of 6,190 shares of common stock underlying vested stock options (right to buy) held by Joshua Resnick for the benefit of RA Capital; and (vi) a total of 166 shares of common stock underlying stock options (right to buy) scheduled to vest within 60 days of this filing held by Sarah Reed for the benefit of RA Capital. Each of the Common Stock Warrants and the Pre-Funded Warrants contains a provision (the "Beneficial Ownership Blockers") which precludes exercise of the Warrants to the extent that, following exercise, the Fund, together with its affiliates and other attribution parties, would own more than 9.99% of the common stock outstanding. The ownership percentages reported in this Amendment No, 6 reflect an increase in the number of outstanding shares of the Issuer, as reported by the Issuer in its Current Report on Form 8-K, filed with the SEC on September 17, 2025. The Fund is currently prohibited from exercising the Pre-Funded Warrants and/or the Common Stock Warrants by virtue of the Beneficial Ownership Blockers. RA Capital Healthcare Fund GP, LLC is the general partner of the Fund and RA Capital Nexus Fund GP, LLC is the general partner of the Nexus Fund. The general partner of RA Capital is RA Capital Management GP, LLC, of which Dr. Kolchinsky and Mr. Shah are the controlling persons. RA Capital serves as investment adviser for each of the Fund and the Nexus Fund and may be deemed a beneficial owner, for purposes of Section 13(d) of the Act, of any securities of the Issuer held by the Fund or the Nexus Fund. Each of the Fund and the Nexus Fund has delegated to RA Capital the sole power to vote and the sole power to dispose of all securities held in its portfolio, including the shares of the Issuer's common stock reported herein. Because each of the Fund and the Nexus Fund has divested itself of voting and investment power over the reported securities it holds and may not revoke that delegation on less than 61 days' notice, each of the Fund and the Nexus Fund disclaims beneficial ownership of the securities it holds for purposes of Section 13(d) of the Act and therefore disclaims any obligation to report ownership of the reported securities under Section 13(d) of the Act. As managers of RA Capital, Dr. Kolchinsky and Mr. Shah may be deemed beneficial owners, for purposes of Section 13(d) of the Act, of any securities of the Issuer beneficially owned by RA Capital. RA Capital, Dr. Kolchinsky, and Mr. Shah disclaim beneficial ownership of the securities reported in this Schedule 13D/A other than for the purpose of determining their obligations under Section 13(d) of the Act, and the filing of this Schedule 13D/A shall not be deemed an admission that either RA Capital, Dr. Kolchinsky, or Mr. Shah is the beneficial owner of such securities for any other purpose.