A stem-cell therapy misses its endpoint in infant heart surgery

Longeveron reported topline results from ELPIS II on 16 September 2026. The Phase 2b trial did not meet its primary endpoint.

Infants born with hypoplastic left heart syndrome have a left ventricle too small to pump blood to the body, so surgeons rebuild the circulation in stages and leave the right ventricle doing the work of both. The question the trial asked is whether that overloaded right ventricle can be helped. Forty infants were randomised one to one, during Stage 2 surgery, to receive laromestrocel — an allogeneic medicinal signalling cell therapy — or standard care alone.

At twelve months the least-squares mean difference in right ventricular ejection fraction between the two groups was −0.7 percentage points, with a 95% confidence interval from −7.3 to 5.9 and a p-value of 0.8336. That is not a near miss; it is an interval sitting squarely across zero.

Safety was unremarkable and consistent with the company’s earlier trials, with no new signals. Longeveron says it will run further analyses, take the results to the FDA, and review its strategic options. Follow-up of the cohort is planned to continue for five years.