Septerna (SEPN) 10% Owner RA Capital Sells 1.49M Shares

What Happened
RA Capital Management, L.P. (reported as a 10% owner) disposed of a total of 1,493,000 shares of Septerna, Inc. (SEPN) on August 12, 2026. The sales occurred in two identical transactions of 746,500 shares each at $42.50 per share, generating aggregate proceeds of $63,452,500. These entries are reported as sales (dispositions), not purchases.

Key Details

• Transaction date: 2026-08-12. Price: $42.50 per share.
• Quantity: Two sales of 746,500 shares = 1,493,000 shares total.
• Total proceeds: $31,726,250 per transaction; $63,452,500 total.
• Shares held after transaction: Not specified in the provided filing details.
• Footnotes: The Adviser (RA Capital Management, L.P.) is investment manager for RA Capital Healthcare Fund, L.P. (F2) and RA Capital Nexus Fund III, L.P. (F3); the Adviser and managing members disclaim beneficial ownership except for pecuniary interest. The two reported sales appear to be held directly by the Fund (F2) and Nexus Fund III (F3).
• Board connection: Jake Simson, a Partner of the Adviser, serves on Septerna’s board of directors.
• Filing timeliness: No late-filing flag indicated in the provided information.

Context
This is institutional selling by a 10% owner (an investment manager acting for funds), not an individual executive. Such disposals by funds can reflect portfolio rebalancing or liquidity needs and are not direct indicators of company fundamentals. For retail investors, note the distinction between institutional fund sales and insider executive sales when interpreting insider activity.