Thompson Peter A. 4

What Happened

• Peter A. Thompson, a director of Sionna Therapeutics, sold 85,918 shares on July 7, 2026. The shares were sold at $44.86 per share for total proceeds of $3,854,281. This was a sale (not a purchase or award).

Key Details

• Transaction date and price: 2026-07-07 at $44.86 per share.
• Total value: $3,854,281 (85,918 shares × $44.86).
• Shares owned after transaction: Not specified in the Form 4. The reported shares were held of record by OrbiMed Private Investments VIII, LP; see footnotes.
• Notable footnotes:
  • F1: Sale executed pursuant to a prearranged 10b5-1 trading plan.
  • F2/F3: Shares are held of record by OrbiMed Private Investments VIII, with OrbiMed entities and the reporting person linked by management relationships; the reporting parties disclaim beneficial ownership except to the extent of any pecuniary interest.
• Filing timeliness: Form 4 was filed July 9, 2026 for a July 7 transaction, which appears to be timely (within the standard two business days required under Section 16).

Context

• 10b5-1 plan: The sale was made under a prearranged plan, which typically means the trade was scheduled in advance and not an ad hoc decision based on current company developments.
• Institutional/manager role: The transaction involves securities held by an institutional vehicle (OrbiMed Private Investments VIII) and related managerial relationships; this may reflect an institutional disposition rather than a direct personal sale by an individual executive.