Thompson Peter A. 4

4 · Sionna Therapeutics, Inc. · Filed May 29, 2026

AI-generated summary of this filing

Updated May 30, 2026

Sionna (SION) Director Peter A. Thompson Sells 101 Shares

What Happened

Peter A. Thompson, a director of Sionna Therapeutics, sold 101 shares in an open-market or private sale on May 27, 2026. The shares were disposed at $44.49 each for total proceeds of $4,493. The filing reports the sale was made pursuant to a 10b5-1 trading plan.

Key Details

Transaction date: 2026-05-27; Filing date: 2026-05-29 (filed two days after the transaction).
Transaction type: Sale (code S) — 101 shares at $44.49 per share; total $4,493.
Shares owned after transaction: Not specified in the Form 4 filing.
Footnotes of note:
- F1: Sale executed under a 10b5-1 plan (pre-arranged trading plan).
- F2/F3: The reported shares are held of record by OrbiMed Private Investments VIII, LP (OPI VIII). OrbiMed Capital GP VIII LLC is the general partner and OrbiMed Advisors LLC is the managing member; Thompson is a member of OrbiMed Advisors. These entities disclaim beneficial ownership except to the extent of any pecuniary interest.
Timeliness: Filing appears timely (reported within two business days of the transaction).

Context

This sale was executed under a 10b5-1 plan, which typically means trades were pre-scheduled and do not necessarily reflect current views on the company. The shares are held of record by an institutional investment vehicle (OPI VIII); the reporting person’s connection is through OrbiMed Advisors rather than direct personal holdings.

Form 4

Period: 2026-05-27

Director

Transactions

Sale
Common Stock
[F1][F2][F3]
2026-05-27$44.49/sh−101$4,493→ 2,671,721 total(indirect: See footnotes)

Footnotes (3)

[F1]These securities were sold pursuant to a 10b5-1 plan.
[F2]These securities are held of record by OrbiMed Private Investments VIII, LP ("OPI VIII"). OrbiMed Capital GP VIII LLC ("GP VIII") is the general partner of OPI VIII and OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP VIII. By virtue of such relationships, GP VIII and OrbiMed Advisors may be deemed to have voting and investment power with respect to the shares held by OPI VIII and as a result may be deemed to have beneficial ownership of such shares. OrbiMed Advisors exercises investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the shares held by OPI VIII. The Reporting Person is a member of OrbiMed Advisors.
[F3]Each of the Reporting Person, OrbiMed Advisors, and GP VIII disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein, if any. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for purposes of Section 16 of the Exchange Act, or for any other purpose.

Signature

/s/ Peter A. Thompson|2026-05-29

1 file