X0609 4 2026-09-17 0 0002036042 Sionna Therapeutics, Inc. SION 0001772518 Ridloff Elena false C/O SIONNA THERAPEUTICS, INC. 21 HICKORY DRIVE, SUITE 500 WALTHAM MA 02451 0 1 0 0 CFO and CBO 0 Common Stock 2026-09-17 4 A 0 47269 0.0 A 85801 D Common Stock 2026-09-17 4 A 0 47268 0.0 A 133069 D Non-Qualified Stock Option (right to buy) 7.18 2026-09-17 4 A 0 165440 0.0 A 2036-01-01 Common Stock 165440 165440 D Non-Qualified Stock Option (right to buy) 39.21 2026-09-17 4 D 0 165440 0.0 D 2036-01-01 Common Stock 165440 0 D Represents a grant of restricted stock units ("RSUs"). Each RSU represents a contingent right to receive one share of Common Stock of the Issuer. The RSUs will vest on June 17, 2027, subject to the Reporting Person's continued service with the Issuer as of the vesting date. Represents a grant of RSUs. Each RSU represents a contingent right to receive one share of Common Stock of the Issuer. The RSUs will vest upon the achievement of a designated performance milestone, subject to the Reporting Person's continued service with the Issuer as of the vesting date. The exercise price of the option is $7.18 per share, representing the fair market value per share of the Issuer's Common Stock on September 17, 2026 (the "Repricing Date"). Unless otherwise provided by the Issuer's board of directors or its compensation committee, if the option is exercised before the applicable retention period ends, the exercise price will revert to its original exercise price. The retention period begins on the Repricing Date and ends on the earliest of (i) the 18-month anniversary of the Repricing Date (March 17, 2028), (ii) a Sale Event (as defined in the Sionna Therapeutics, Inc. 2025 Stock Option and Incentive Plan (the "2025 Plan")) or (iii) certain qualifying terminations of service. Effective on the Repricing Date, the Issuer's board of directors approved an option repricing. All of the other terms of the options remain unchanged. Such transactions were exempt pursuant to Rule 16b-6(d) and Rule 16b-3 of the Exchange Act, as applicable. This stock option award was issued pursuant to the 2025 Plan, and becomes exercisable in accordance with the vesting schedule specified in the award agreement and as previously reported on the applicable Form 4, subject to the Reporting Person's continued service with the Issuer as of the applicable vesting date. Jennifer Fitzpatrick, Attorney-in-Fact 2026-09-18