Thompson Peter A. 4

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.