Thompson Peter A. 4

What Happened

• Peter A. Thompson, a director of Sionna Therapeutics, sold a total of 30,953 shares in open-market/private-sale transactions. On 2026-02-02 he disposed of 1,890 shares at $44.57 each for $84,237; on 2026-02-03 he disposed of 29,063 shares at $44.58 each for $1,295,629. Total proceeds were $1,379,866 (approx. $1.38M). These were sales (S), not purchases.

Key Details

• Transaction dates and prices: 2026-02-02 — 1,890 sh @ $44.57; 2026-02-03 — 29,063 sh @ $44.58.
• Total shares sold: 30,953; total proceeds: $1,379,866 (~$1.38M).
• Shares owned after transaction: Not specified in the provided summary of the Form 4.
• Filing timeliness: Report filed 2026-02-04; covers transactions on Feb 2–3, 2026 and appears to be filed within the standard two-business-day Form 4 window.
• Footnotes of note:
  • The shares are held of record by OrbiMed Private Investments VIII, LP (OPI VIII). OrbiMed Advisors LLC and OrbiMed Capital GP VIII LLC are related entities; Thompson is a member of OrbiMed Advisors (F1).
  • The filing includes disclaimers that the Reporting Person, OrbiMed Advisors, and GP VIII disclaim beneficial ownership except to the extent of any pecuniary interest (F2).

Context

• These were straight sales of existing shares (S codes), not option exercises, awards, purchases, or gifts. Sales can be routine (portfolio rebalancing, fund-level liquidity, tax planning, etc.) and do not, by themselves, prove a change in insider sentiment.
• Because the securities are held of record by an OrbiMed investment vehicle and Thompson is linked through OrbiMed Advisors, this reflects transactions associated with an investment fund structure rather than necessarily a direct personal transfer of individually held shares.