San Diego, California--(Newsfile Corp. - August 10, 2026) - Johnson Fistel, PLLP, a leading stockholder rights law firm, is investigating potential violations of the federal securities laws involving Sionna Therapeutics, Inc. (NASDAQ: SION).

Click here to join the investigation.

On August 10, 2026, Sionna announced topline results from its PreciSION CF Phase 2a proof-of-concept trial evaluating SION-719 as an add-on to the standard of care for cystic fibrosis. The Company disclosed that the trial failed to demonstrate meaningful improvement in its key measure of CFTR activity and announced that it does not plan to advance SION-719 as an add-on to the standard of care.

The disappointing results came just days after Sionna reported its second-quarter results on August 6, 2026, when the Company stated that the SION-719 Phase 2a trial was "on track" and that management remained focused on "execution and delivering topline data."

Following the August 10 announcement, Sionna shares plummeted in premarket trading, causing substantial losses to investors.

Johnson Fistel's investigation seeks to determine whether Sionna investors suffered losses as a result of potentially misleading statements or omissions concerning SION-719, the therapeutic potential of the Company's NBD1 stabilizers, and the prospects for its cystic fibrosis development programs.

Click here to join the investigation.

For more information, contact Jim Baker at jimb@johnsonfistel.com or (619) 814-4471. There is no cost or obligation to you.

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Source: Johnson Fistel, PLLP