Single-arm BLA for a CAR-T that erases myositis in small cohorts: does FDA accept the data without a randomized control?

Cabaletta Bio is a clinical-stage biopharmaceutical company seeking regulatory approval for a cell therapy that treats dermatomyositis and antisynthetase syndrome, diseases not yet approved for this treatment.

Rese-cel, Cabaletta's CD19-targeted CAR-T, achieved 80% primary endpoint response in dermatomyositis and antisynthetase syndrome with durability to 1.5 years and a clean safety profile enabling outpatient dosing. The thesis resolves on whether FDA accepts single-arm data from roughly 17 patients as sufficient for approval across multiple autoimmune indications simultaneously. The central risk is regulatory: single-arm filings in serious but non-life-threatening disease face heightened scrutiny, and a cash runway extending only to mid-2027 leaves little buffer if the BLA is delayed or receives a complete response letter.