Thompson Peter A. 4

4 · Sionna Therapeutics, Inc. · Filed Jul 2, 2026

AI-generated summary of this filing

Updated Jul 2, 2026

Sionna (SION) Director Peter A. Thompson Sells 115,844 Shares

What Happened

Peter A. Thompson, reported as a director and a member of OrbiMed Advisors, disposed of 115,844 Sionna Therapeutics (SION) shares on June 30, 2026. The shares were sold at $45.50 each for a total proceeds of $5,270,902. The filing indicates the sale was made pursuant to a 10b5-1 plan (pre-arranged automatic sales).

Key Details

Transaction date and price: 2026-06-30 — 115,844 shares sold at $45.50/share.
Total value: $5,270,902.
Transaction type: Sale (open market or private sale; reported with code S).
Shares owned after transaction: Not specified in the Form 4 provided.
Notable footnotes:
- F1: Sale executed pursuant to a 10b5-1 plan (preplanned sale program).
- F2–F3: The securities are held of record by OrbiMed Private Investments VIII, LP (OPI VIII). OrbiMed Capital GP VIII LLC and OrbiMed Advisors have relationships that may give them voting/investment power; Thompson is a member of OrbiMed Advisors. The parties disclaim beneficial ownership except to the extent of any pecuniary interest.
Filing timeliness: Report filed July 2, 2026 for a June 30, 2026 transaction (appears to be timely under Form 4 rules).

Context

Sales made under a 10b5-1 plan are typically prearranged and do not necessarily reflect current sentiment. This report is associated with an institutional structure (OrbiMed entities) rather than a personal, discretionary trade by a company executive.

Form 4

Period: 2026-06-30

Director

Transactions

Sale
Common Stock
[F1][F2][F3]
2026-06-30$45.50/sh−115,844$5,270,902→ 2,555,877 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|2026-07-02

1 file