RA Capital Files to Sell $21.8M of Sionna Shares
SION sits 85% above its 52-week low of $4.01.
Summary
RA Capital Healthcare Fund, a director and 10% stockholder, filed a Form 144 to sell 3,448,811 shares of Sionna Therapeutics worth approximately $21.8 million.
Key Events · Ownership and Investor Activity · SION
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RA Capital Files $21.8M Sale
RA Capital Healthcare Fund, L.P., a director and 10% stockholder, filed a Form 144 to sell 3,448,811 shares of common stock with an approximate market value of $21,834,318.
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Sale Represents 7.6% of Outstanding Shares
The 3,448,811 shares to be sold represent approximately 7.6% of the 45,212,399 shares outstanding, a substantial distribution by a major insider.
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Follows Clinical Failure and Layoffs
The filing comes three days after Sionna announced a 46% workforce reduction and strategic pivot following the failure of its lead CF drug, SION-719, in a Phase 2a trial.
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Shares Acquired Across Three Tranches
The shares were acquired in private transactions on 02/02/2022 (606,502 shares) and 03/04/2024 (1,819,723 shares), and in the IPO on 02/07/2025 (1,022,586 shares).
Analysis · SION · Life Sciences
A director-affiliated 10% stockholder, RA Capital Healthcare Fund, has filed to sell 3,448,811 shares worth approximately $21.8 million. This is a significant distribution by a major insider, especially against the backdrop of Sionna's recent clinical failure and 46% workforce reduction. The sale represents roughly 7.6% of the company's outstanding shares and comes just three days after the company announced a strategic pivot following the SION-719 Phase 2a failure.
How filings like this one have moved
In the 30 days to Sep 23, 2026, 29.1% of the 1683 measured filings Wiseek scored 7 moved their stock by 5% or more by the next session's close. The median move was -0.32%. 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, SION was trading at $7.41 on NASDAQ in the Life Sciences sector, with a market capitalization of approximately $324.6M. The 52-week trading range was $4.01 to $54.97. This filing was assessed with negative market sentiment and an importance score of 7 out of 10.