Cereno Scientific has reported initial long-term safety findings from a 12-month Expanded Access Program (EAP) evaluating its lead candidate CS1 in pulmonary arterial hypertension (PAH), supporting earlier Phase 2a results.

The EAP enrolled 10 patients who had previously completed the company’s Phase 2a trial, allowing continued treatment with CS1 under physician supervision. The programme was conducted under a formal US Food and Drug Administration protocol.

Across the 12-month treatment period, CS1 was reported to be well tolerated, with no unexpected safety concerns and no treatment-related deaths or discontinuations. Six of the 10 patients completed the full 12 months of treatment.

Two patients discontinued treatment following atrial fibrillation events, which were assessed as not related to CS1. One patient withdrew consent, and one was lost to follow-up.

Rahul Agrawal, chief medical officer and head of research and development at Cereno Scientific, said: “These results provide important confirmation that the favorable safety and tolerability profile observed in the Phase 2a trial is maintained over longer-term use. In PAH, where existing therapies can be associated with safety and tolerability challenges, there remains a significant unmet need for safer, well-tolerated treatment options. These findings support the continued development of CS1 as a potential disease-modifying therapy.”

The company said the EAP extends earlier Phase 2a findings, which evaluated safety, pharmacokinetics and exploratory efficacy over a three-month period in 25 patients across 10 US clinical sites. That study met its primary endpoint of safety and tolerability, with no drug-related serious adverse events reported.

Early exploratory signals from the Phase 2a study included improvements in right heart function, functional class and patient-reported quality of life, alongside indications consistent with potential reverse vascular remodelling.

Cereno Scientific said combined data from the Phase 2a trial and EAP now provide up to 15 months of treatment experience with CS1 in patients with PAH, strengthening the overall clinical dataset as the programme advances towards a planned global Phase 2b study.

The company is preparing a larger placebo-controlled Phase 2b trial, with first patient enrolment expected in June 2026.

CS1 is being developed as an oral, once-daily therapy intended to offer disease-modifying potential in PAH, a condition characterised by progressive narrowing of pulmonary arteries and increasing strain on the right side of the heart.

Further analyses from the Expanded Access Program, including imaging data from a sub-study using Fluidda technology, are expected in the second quarter of 2026.

The findings add to a growing body of early clinical evidence supporting CS1’s safety profile, though efficacy remains to be confirmed in later-stage controlled studies.