X0508 4 2026-02-06 0001984086 Septerna, Inc. SEPN 0002040350 Klein Uwe C/O SEPTERNA, INC. 250 EAST GRAND AVENUE SOUTH SAN FRANCISCO CA 94080 false true false false SVP, Biological Sciences false Stock Option (Right to Buy) 25.41 2026-02-06 4 A false 80000 0 A 2036-02-05 Common Stock 80000 80000 D 2/48th of the shares subject to such option shall vest and become exercisable on March 1, 2026 and the remaining shares subject to the option shall vest in 46 substantially equal monthly installments on each monthly anniversary thereafter, subject to the Reporting Person's continuous service to the Issuer on each such date. Exhibit 24.2 - Substitute Power of Attorney /s/ Mark A. Wilson, Attorney-in-Fact 2026-02-10