$SION

RA CAPITAL MANAGEMENT, L.P. sold 3,448,811 indirectly-held shares of Sionna Therapeutics, Inc. (SION) at an average of $6.33 ($6.32–$7.46, $21.84M total) across 2 trades on 2026-09-17. Filed jointly with RA Capital Healthcare Fund LP (Director), RA Capital Nexus Fund, L.P. (Director), RA Capital Nexus Fund III, L.P. (Director), Kolchinsky Peter (Director) and Shah Rajeev M. (Director).

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Sionna Therapeutics (SION) announced a 46% workforce reduction to extend its cash runway to mid-2029. The company will focus on SION-451 and SION-2222 for cystic fibrosis, with a Phase 2a trial planned for Q1 2027. The restructuring aims to save $6.4M but carries risks related to trial outcomes and execution.

Sionna Therapeutics' stock fell 3% after-hours following a strategic reset, including a 46% workforce reduction and a shift in clinical trial focus. The company also confirmed it will not pursue SION-719. Raymond James downgraded the stock to Market Perform. The broader market showed minimal gains, with the S&P 500, Dow Jones, and Nasdaq each rising 0.1% or 0.2%.

Sionna Therapeutics (NASDAQ:SION) shares fell 3% after announcing a 46% workforce reduction and a pivot to a new cystic fibrosis drug combination, SION-451 + SION-2222, for a Phase 2a trial starting in Q1 2027. The company cited data from its PreciSION CF trial and expects $6.4M in restructuring charges, with cash runway extending into 2H 2029.

Sionna Therapeutics, Inc. (SION) filed an SEC Form 8-K — Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers: Compensatory Arrangements of Certain Officers. Exhibit 99.1 Sionna Therapeutics Announces Plans to Advance SION-451 + SION-2222 Dual Combination into Phase 2a Proof-of-Concept Trial Post hoc analyses of SION-719 PreciSION CF subset showed a mean placebo-adjusted sweat chloride reduction of up to -8.6 mmol/L consistent with NB

Vertex Pharmaceuticals (VRTX) maintains dominance in the cystic fibrosis (CF) drug market. Sionna Therapeutics (SION) reported a phase 2 trial failure for its CF drug candidate, SION-719, causing its stock to drop 90%. Vertex's CF drugs, including Trikafta and Alyftrek, now target 95% of CF patients. Vertex is also expanding into other therapeutic areas, such as gene-editing therapy Casgevy for sickle cell disease and beta-thalassemia, developed with CRISPR Therapeutics (CRSP).

Sionna Therapeutics (SION) shares fell about 92% after it said its Phase 2a trial of SION-719 in 15 cystic fibrosis adults failed to meet its main goal. The add-on drug did not significantly improve sweat chloride versus placebo, so Sionna will not advance it. SION had $268M cash. Analysts cited reduced overhang for Vertex (VRTX).

Sionna Therapeutics (NASDAQ:SION) shares fell over 90% after its Phase 2a PreciSION CF trial of SION-719 as an add-on to Vertex’s Trikafta failed its main activity endpoint, so Sionna said it will not proceed SION-719. Vertex (NASDAQ:VRTX) rose to new highs as the CF competitive overhang eased. Sionna will prioritize SION-451; Vertex cited prior strength and guidance.

Sionna Therapeutics (Nasdaq: SION) said its PreciSION CF Phase 2a study of SION-719, tested as an add-on to Trikafta, did not meet the key activity endpoint of sweat chloride reduction. The company discontinued SION-719 development in that role, according to the company. The article also references other SION updates and financial results.