Sionna Therapeutics, a Waltham company developing cystic fibrosis treatments, announced plans Sept. 14 to eliminate about 46% of its workforce as it shifts resources to a different experimental treatment following a clinical trial setback.
The company expected the workforce reduction to be substantially complete by the end of September. Its securities filing did not specify how many employees would lose their jobs or how many affected positions were based in Waltham.
The restructuring follows disappointing results for SION-719, an experimental drug tested alongside the existing cystic fibrosis treatment Trikafta. Sionna reported Aug. 10 that the study missed a key goal for reducing chloride levels in patients’ sweat, a measure of the function of the protein affected by cystic fibrosis. It said it would not advance the drug as an add-on treatment.
Sionna is instead prioritizing a combination of two experimental drugs, SION-451 and SION-2222. It plans to begin a trial in the first quarter of 2027 in which participants would switch from Trikafta to the combination, rather than add another drug to their existing treatment.
The company estimated $6.4 million in restructuring-related charges, including $5.3 million for severance and other employee benefits.
Sionna reported approximately $268.3 million in cash, cash equivalents and marketable securities at the end of June. It said the workforce reduction and other cost-saving measures were expected to extend its funding into the second half of 2029.