The data confirm a favorable safety and tolerability profile over long-term treatment, consistent with previous Phase IIa results, further strengthening the value proposition of CS1 as an oral, once-daily potentially disease-modifying therapy, the company states.

The Expanded Access Program

The Expanded Access Program (EAP) enrolled ten patients who had completed the Phase IIa trial, enabling continued treatment with CS1 under physician supervision. Initial learnings from the completed 12-month treatment period show that CS1 was well tolerated, with no unexpected safety concerns observed. No deaths were reported, and no discontinuations were reported to be related to CS1. Six out of ten patients completed the full 12 months of continuous treatment with CS1. Of the remaining patients, two discontinued CS1 treatment following atrial fibrillation events, which was assessed as not related to CS1; one withdrew consent, and one was lost to follow-up.

“These results provide important confirmation that the favorable safety and tolerability profile observed in the Phase IIa 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,” says Rahul Agrawal, CMO and Head of R&D of Cereno Scientific.

The EAP was conducted under a formal FDA protocol and initiated following requests from patients and physicians. It enabled the generation of additional long-term data beyond the three-month Phase IIa trial, which had demonstrated that CS1 had favorable safety and tolerability and showed encouraging efficacy signals, including improvements in right heart function, functional class and patient quality of life, with signs consistent with reverse vascular remodeling. Together, the Phase IIa trial and the EAP provide up to 15 months of treatment experience in patients, further strengthening the overall clinical understanding of CS1 in PAH.

“The accumulated clinical Phase II data representing up to 15 months of treatment with CS1 in patients with PAH, provides us with further confidence in our goal to develop and deliver CS1 as a new treatment for patients with PAH. The results from the EAP study support the value proposition of CS1 as an oral, once-daily PAH therapy with a favorable safety and tolerability profile and potential disease-modifying effects,” said Sten R. Sörensen, CEO of Cereno Scientific.

The EAP was initiated following positive results of the Phase IIa trial, which evaluated the safety, tolerability, pharmacokinetics, and exploratory efficacy of CS1 on top of standard therapy in patients with PAH. The Phase IIa trial was conducted at 10 US clinics over 3 months with a total of 25 patients of which 21 were evaluated for efficacy parameters. The trial successfully met its primary endpoint of safety and tolerability, with no drug-related serious adverse events. Encouraging efficacy signals were observed in the trial, including improvements in right heart function, functional class and patient quality of life, with early signs consistent with reverse vascular remodeling. Preparations for a larger, placebo-controlled global Phase IIb study of CS1 in PAH are ongoing, with first patient enrollment anticipated in June 2026.