Cereno Scientific has completed the last patient’s last visit in its expanded access program for CS1 in pulmonary arterial hypertension, marking the end of the 12-month active treatment period and triggering the start of data handling and analysis activities.

The expanded access program was initiated following completion of a Phase 2a study to allow eligible patients with pulmonary arterial hypertension to continue receiving CS1 under physician supervision. The program enrolled 10 patients who had completed the earlier trial and was designed to generate longer-term information on safety and tolerability during extended use.

Cereno said initial learnings from the program are expected to be available in the first quarter of 2026, with further analyses planned during the second quarter of 2026. The findings are intended to contribute to the ongoing clinical development of CS1 and inform next-stage trial planning.

The earlier Phase 2a study, conducted over three months, showed that CS1 was well tolerated and demonstrated a favourable safety profile. According to the company, the trial also generated efficacy signals including improvements in right heart function, patient quality of life and indicators consistent with reverse vascular remodelling.

Rahul Agrawal, chief medical officer and head of R&D at Cereno Scientific, said the expanded access program enabled longer-term treatment in a progressive disease setting. Agrawal said: “From a clinical perspective, the Expanded Access Program has enabled longer-term treatment with CS1 beyond the Phase 2a study, which is particularly relevant in a progressive disease like PAH.” He added that while patient numbers were limited, the program was designed to support the collection of additional information on continued use of CS1 as the company moves into the data evaluation phase.

Insights generated from the expanded access program include data from an exploratory imaging sub-study examining vascular changes in the lung. Cereno said these findings are intended to complement the Phase 2a results and support further development of CS1 as a potential disease-modifying therapy.

Sten Sörensen, chief executive officer of Cereno Scientific, said completion of the last patient’s last visit represents continued progress for the programme. Sörensen said: “Reaching last patient last visit in the Expanded Access Program is an important milestone for CS1 and reflects continued progress as we advance the program toward the next stage of development.” He added that learnings from the program could help inform preparations for the planned Phase 2b study in pulmonary arterial hypertension.

The expanded access program is now entering standard processes including database lock, quality assurance and subsequent analysis and interpretation. Cereno said initial communications from the program are planned for early 2026, followed by additional analyses later in the year.

In parallel, preparations are under way for a global Phase 2b study of CS1 in pulmonary arterial hypertension. Start-up activities are progressing in the United States, alongside planned regulatory interactions in Europe and South America. First patient enrolment in the Phase 2b study is anticipated during the second quarter of 2026.

Pulmonary arterial hypertension is a rare, progressive condition characterised by elevated blood pressure in the pulmonary arteries, leading to right heart failure and premature death. Current treatments largely focus on symptom management, and Cereno has said there remains a need for therapies that address underlying disease mechanisms.

CS1 is an orally administered histone deacetylase inhibitor being developed as an add-on therapy to standard of care. The compound has received orphan drug designation in the US and EU and was granted Fast Track designation by the FDA in 2025.