ORBIMED ADVISORS LLC 4

What Happened
OrbiMed Advisors LLC, reported as a director of Sionna Therapeutics (SION), disposed of a total of 30,953 shares in two sale transactions on Feb 2–3, 2026. The first sale was 1,890 shares at $44.57 each ($84,237) on Feb 2; the second was 29,063 shares at $44.58 each ($1,295,629). Combined proceeds were approximately $1,379,866. These were sales (not purchases), so they represent liquidity-taking rather than a direct bullish signal.

Key Details

• Transaction dates and prices:
  • 2026-02-02: Sold 1,890 shares @ $44.57 = $84,237
  • 2026-02-03: Sold 29,063 shares @ $44.58 = $1,295,629
• Total shares sold: 30,953; total proceeds ≈ $1,379,866.
• Shares owned after transaction: Not specified in the information provided in this summary/filing excerpt.
• Footnotes of note:
  • F1: The shares are held of record by OrbiMed Private Investments VIII, LP (OPI VIII). OrbiMed Advisors is the managing member of the GP and may be deemed to have voting/investment power; individual committee members disclaim beneficial ownership.
  • F2: This Form 4 is jointly filed by OrbiMed Advisors and the related GP. They disclaim beneficial ownership except to the extent of any pecuniary interest; Peter A. Thompson (OrbiMed) serves as the fund’s designated director on Sionna’s board.
• Filing timeliness: Form 4 was filed on 2026-02-04 for transactions on 2026-02-02 and 02-03 — filed within the standard Section 16 reporting window (timely).

Context
These were institutional/director sales reported by a fund-affiliated reporting person (not an individual executive). Sales by insiders or affiliated funds can be routine (liquidity, portfolio rebalancing, fund-level decisions) and do not, by themselves, indicate company performance or management outlook.