ORBIMED ADVISORS LLC 4

What Happened

• OrbiMed Advisors LLC, listed as a director-level reporting person for Sionna Therapeutics (SION), sold 115,844 shares of Sionna common stock in an open‑market/private sale on June 30, 2026. The shares were sold at $45.50 per share for total proceeds of approximately $5,270,902. The filing indicates the trades were made pursuant to a pre-established 10b5‑1 plan.

Key Details

• Transaction date & price: 2026-06-30 — 115,844 shares sold at $45.50 each.
• Proceeds: ~$5,270,902.
• Filing date / report period: Form 4 filed July 2, 2026; Period of Report 2026-06-30. Filing appears timely (filed within the standard two-business-day window).
• Shares owned after transaction: Not specified in the provided filing.
• Notable footnotes:
  • F1: Sale executed pursuant to a 10b5‑1 trading plan.
  • F2: Shares are held of record by OrbiMed Private Investments VIII, LP; OrbiMed Advisors and related entities may be deemed to have voting/investment power but disclaim beneficial ownership except for any pecuniary interest.
  • F3: This Form 4 is jointly filed by OrbiMed Advisors and OrbiMed Capital GP VIII LLC; a representative (Peter A. Thompson) serves on Sionna’s board.
• Reporting type: Institutional/investor entity (OrbiMed), not an individual executive; treated differently from insider executive buying/selling.

Context

• Sales under 10b5‑1 plans are pre-arranged and often scheduled in advance, so they can be routine and do not necessarily signal a change in insider sentiment. Because this is an institutional holder/affiliate transaction (with record ownership through a fund entity), the filing’s disclaimers clarify the limited beneficial‑ownership assertion.