RA Capital Files to Sell $36M of Septerna Shares
SEPN has more than doubled off its 52-week low of $10.616 on elevated volume (2.9× avg).
Summary
RA Capital Nexus Fund III, L.P. filed a Form 144 to sell 746,500 shares of Septerna, Inc. common stock, valued at approximately $35.97 million. This is a significant proposed sale from a major institutional holder, representing about 1.6% of outstanding shares.
Key Events · Ownership and Investor Activity · SEPN
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RA Capital Files $36M Sale
RA Capital Nexus Fund III, L.P. filed a Form 144 to sell 746,500 shares of Septerna common stock, with an aggregate market value of $35,973,835.
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Significant Institutional Selling
The proposed sale represents approximately 1.6% of Septerna's 46,676,947 outstanding shares, a substantial position reduction by a major institutional holder.
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Cluster of Selling Activity
This filing follows a same-day Form 144 from Third Rock Ventures V, L.P. for $7.5 million, indicating coordinated institutional selling pressure.
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10b5-1 Plan Context
The sale is being executed under a pre-existing 10b5-1 trading plan, which may reduce the informational content of the sale but still creates supply overhang.
Analysis · SEPN · Life Sciences
A substantial proposed sale from a major institutional holder is on the table: RA Capital Nexus Fund III, L.P. has filed a Form 144 to sell 746,500 shares of Septerna, Inc. common stock, valued at approximately $35.97 million based on the filing's aggregate market value. This represents about 1.6% of the company's outstanding shares. The filing comes on the same day as another Form 144 from Third Rock Ventures V, L.P. for $7.5 million, indicating a cluster of institutional selling activity. While the sale is under a pre-existing 10b5-1 plan, the size and timing may pressure the stock price.
How filings like this one have moved
In the 30 days to Oct 16, 2026, 29.2% of the 1503 measured filings Wiseek scored 7 moved their stock by 5% or more by the next session's close. The median move was -0.39%. These are measured outcomes after filings of this importance, not a forecast for this one.
Measured one observation per ticker per day, after exclusions. Current figures: Filing Impact Tracker · open dataset
At the time of this filing, SEPN was trading at $48.19 on NASDAQ in the Life Sciences sector, with a market capitalization of approximately $2.2B. The 52-week trading range was $10.62 to $51.10. This filing was assessed with negative market sentiment and an importance score of 7 out of 10.