X0609 4 2026-05-19 0 0001374690 Larimar Therapeutics, Inc. LRMR 0001352546 Flynn James E false 345 PARK AVENUE SOUTH, 12TH FLOOR NEW YORK NY 10010 1 0 1 1 * Director by Deputization 0001009258 DEERFIELD MANAGEMENT COMPANY, L.P. false 345 PARK AVENUE SOUTH, 12TH FLOOR NEW YORK NY 10010 1 0 1 1 * Director by Deputization 0 Stock Option (Right to Buy) 3.33 2026-05-19 4 A 0 55150 0 A 2036-05-19 Common Stock 55150 55150 I Through Deerfield Management Company, L.P. Jonathan S. Leff, a partner in Deerfield Management Company, L.P., serves as a director of the Issuer. The option granted to Jonathan S. Leff and reported herein is held for the benefit, and at the direction, of Deerfield Management Company, L.P. ("Deerfield Management"). The option was granted on May 19, 2026 and is scheduled to vest on the earlier of May 19, 2027 and the date of the Issuer's next annual meeting of stockholders, in each case, subject to Jonathan S. Leff 's continued service on the board of directors of the Issuer. This Form 4 is being filed by the undersigned as well as the entity listed on the Joint Filer Information Statement attached as an exhibit hereto (the "Reporting Persons"). James E. Flynn is the sole member of the general partner of Deerfield Management Company, L.P. For purposes of Section 16 of the Securities Exchange Act of 1934, as amended, each Reporting Person disclaims beneficial ownership of any such securities, except to the extent of his/its indirect pecuniary interest therein, if any, and this report shall not be deemed an admission that such Reporting Person is the beneficial owner of such securities for purposes of Section 16 or otherwise. Jonathan S. Leff, a partner in Deerfield Management, serves as a director of the Issuer. Jonathan Isler, Attorney-in-Fact: Power of Attorney, which is hereby incorporated by reference to Exhibit 24 to a Form 3 with regard to BiomX Inc. filed with the Securities and Exchange Commission on March 19, 2024 by Deerfield Private Design Fund V, L.P., Deerfield Healthcare Innovations Fund II, L.P., Deerfield Mgmt V, L.P., Deerfield Mgmt HIF II, L.P., Deerfield Management Company, L.P. and James E. Flynn. /s/ Jonathan Isler, Attorney-in-Fact 2026-05-20