Elena Ridloff - 17 Sep 2026 Form 4 Insider Report for Sionna Therapeutics, Inc. (SION)

Reporting relationship: CFO and CBO
Issuer ticker: SION
Reported as of: 17 Sep 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 18 Sep 2026, 16:59:23 UTC
Prior SEC filing: 10 Aug 2026
Source filing: View source filing
Reporting owner signature: Jennifer Fitzpatrick, Attorney-in-Fact

Key filing fact

Elena Ridloff filed Form 4 for Sionna Therapeutics, Inc. (SION) on 18 Sep 2026.

Key facts

This page summarizes Elena Ridloff's Form 4 filing for Sionna Therapeutics, Inc. (SION).
4 reported transactions and 2 derivative rows are listed below.
Accepted by SEC: 18 Sep 2026, 16:59.

Change

Previous filing in this sequence was filed on 10 Aug 2026.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001772518 Primary reporting owner

Ridloff Elena

Relationship: CFO and CBO
Address: C/O SIONNA THERAPEUTICS, INC., 21 HICKORY DRIVE, SUITE 500, WALTHAM
Signature: Jennifer Fitzpatrick, Attorney-in-Fact
Signature date: 18 Sep 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

SION transaction

Common Stock

Award

Transaction value
Shares: +47,269
Change %: +123%
Price: $0.000000^*
Shares after: 85,801
Date: 17 Sep 2026
Ownership: Direct
Footnotes: F1

SION transaction

Common Stock

Award

Transaction value
Shares: +47,268
Change %: +55%
Price: $0.000000^*
Shares after: 133,069
Date: 17 Sep 2026
Ownership: Direct
Footnotes: F2

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

SION transaction Derivative

Non-Qualified Stock Option (right to buy)

Award

Transaction value
Shares: +165,440
Change %
Price: $0.000000^*
Shares after: 165,440
Date: 17 Sep 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 165,440
Exercise price: $7.18
Footnotes: F3, F4, F5

SION transaction Derivative

Non-Qualified Stock Option (right to buy)

Disposed to Issuer

Transaction value
Shares: -165,440
Change %: -100%
Price: $0.000000^*
Shares after: 0
Date: 17 Sep 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 165,440
Exercise price: $39.21
Footnotes: F4, F5

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 5 footnotes

Footnote F1

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.

Footnote F2

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.

Footnote F3

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.

Footnote F4

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.

Footnote F5

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.