Septerna (SEPN) 10% Owner Third Rock Ventures V Sells Shares

What Happened Third Rock Ventures V, L.P. (a reported >10% owner of Septerna, ticker SEPN) sold a total of 147,200 Septerna shares on August 12, 2026 for roughly $7.4 million. The filing shows 147,059 shares sold at a weighted-average price of $50.27 (≈ $7,392,656) and 141 shares sold at a weighted-average price of $51.08 (≈ $7,202). These were sales (not purchases), so they represent liquidity-taking rather than an explicit bullish insider buy.

Key Details

• Transaction date: August 12, 2026 (reported on Form 4 filed Aug 14, 2026; filing appears timely).
• Sales: 147,059 shares @ weighted avg $50.27 (prices ranged $50.05–$50.81); 141 shares @ weighted avg $51.08 (prices ranged $51.00–$51.10).
• Total proceeds: approximately $7,399,858 (~$7.4M).
• Plan: Transactions were made pursuant to a Rule 10b5-1 trading plan adopted March 26, 2026 (Footnote F1).
• Ownership/structure notes: Shares are directly held by Third Rock Ventures V, L.P.; related general partner entities disclaim beneficial ownership except to the extent of pecuniary interest (Footnote F3). The filing also includes customary disclaimers about grouping with other Third Rock funds (Footnote F5).
• Shares owned after transaction: not specified in the provided filing details.

Context

• These sales were executed under a pre-established 10b5-1 plan, which often schedules trades automatically and can indicate routine liquidity rather than a change in view on the company.
• As a >10% institutional owner (not an individual executive), this is institutional-level selling and should be read differently than an insider executive purchasing or selling.