X0609 4 2026-04-20 0002093101 Atrium Therapeutics, Inc. RNA 0002048409 Gallagher Kathleen P. false C/O ATRIUM THERAPEUTICS, INC. 10578 SCIENCE CENTER DRIVE, SUITE 125 SAN DIEGO CA 92121 true true false false See Remarks false Common Stock 2026-04-20 4 A false 102500 0 A 131361 D Stock Option (Right to Buy) 14.30 2026-04-20 4 A false 205000 0 A 2036-04-20 Common Stock 205000 205000 D Represents an award of restricted stock units ("RSUs"). Each RSU represents a contingent right to receive one share of the Issuer's common stock. Twenty-five percent (25%) of the RSUs shall vest on March 20, 2027, with the remaining RSUs vesting in three (3) substantially equal yearly installments each year thereafter, subject to the Reporting Person's continuous service to the Issuer on each such vesting date. Twenty-five percent (25%) of the shares underlying this option shall vest and become exercisable on March 20, 2027, with the remaining shares vesting in thirty-six (36) substantially equal monthly installments each month thereafter, subject to the Reporting Person's continuous service to the Issuer on each such vesting date. Chief Executive Officer and President /s/ Brendan Winslow, Attorney-in-Fact 2026-04-22