ORBIMED ADVISORS LLC 4

What Happened OrbiMed Advisors LLC, reported as a director-related reporting person for Sionna Therapeutics (SION), sold a total of 292,952 shares in three open-market transactions. The sales were: 48,546 shares on 2026-05-07 at $44.61 ($2,165,637); 59,767 shares on 2026-05-08 at $44.58 ($2,664,413); and 184,639 shares on 2026-05-11 at $46.22 ($8,534,015). Combined proceeds were about $13.36 million. These were disposals (sales), not purchases.

Key Details

• Transaction dates & prices:
  • 2026-05-07: 48,546 shares @ $44.61 — $2,165,637
  • 2026-05-08: 59,767 shares @ $44.58 — $2,664,413
  • 2026-05-11: 184,639 shares @ $46.22 — $8,534,015
• Total shares sold: 292,952; total proceeds: ~$13.36M.
• Filing: Form 4 filed 2026-05-11 (reporting transactions through 2026-05-11); the report shows no late-filing flag.
• Post-transaction shares owned: not specified in the provided filing details.
• Notable footnotes:
  • F1: The sales were made pursuant to a pre-arranged 10b5-1 trading plan.
  • F2–F3: The shares are held of record by OrbiMed Private Investments VIII, LP (OPI VIII); OrbiMed Advisors and its general-partner entities describe voting/investment relationships and disclaim beneficial ownership except for any pecuniary interest. The Form 4 was jointly filed by OrbiMed Advisors and the GP entity.

Context These sales were executed by an institutional investor and reported by its advisory/GP entities — not an individual executive. The use of a 10b5-1 plan indicates the trades were pre-arranged, which commonly reduces the indication that they were timed based on nonpublic information. For retail investors, purchases by insiders can be more informative than routine institutional sales; this filing documents sizable disposals by an OrbiMed-managed vehicle rather than a CEO/CFO buy.