Longeveron trial misses primary endpoint, records about 31% fewer cardiac events
Key Facts
Longeveron’s ELPIS II trial failed to meet its primary endpoint of changing right ventricular ejection fraction after 12 months, while an exploratory result showed an approximately 31% reduction in adjudicated major adverse cardiovascular events among laromestrocel recipients. The company said the reduction was not statistically significant in a negative binomial regression analysis. The trial included 40 infants with hypoplastic left heart syndrome, randomly assigned 1:1 to treatment alongside surgery and usual care or to usual care alone. The results leave the program facing two divergent findings: a failed primary endpoint and a secondary signal that was not statistically established. The company said it is conducting additional analyses of the full dataset ahead of discussions with the U.S. Food and Drug Administration.
In the intention-to-treat analysis, the adjusted mean difference between the study groups in the change in right ventricular ejection fraction at month 12 was minus 0.7 percentage points. The 95% confidence interval ranged from minus 7.3 to 5.9 percentage points, with a p-value of 0.8336. The result did not meet the trial’s primary endpoint. In the exploratory analysis of cardiac events, the laromestrocel arm recorded 12 events versus 19 in the usual-care arm. The company estimated the difference at about 31%, but said the analysis was not statistically significant; therefore, these numbers do not establish the treatment’s efficacy in reducing those events.
The exploratory composite endpoint combining all-cause mortality and length of hospital stay also did not reach statistical significance in the intention-to-treat group. In the as-treated analysis, the company said no deaths were recorded over 12 months among patients who received laromestrocel, compared with one death in the control group. It also said researchers identified no treatment-related adverse events or serious adverse events linked to the drug, and no new safety signals emerged. These results remain part of a phase 2b trial involving a limited number of infants and do not represent regulatory approval or proof of the treatment’s efficacy. According to the company’s statement, the study was conducted in collaboration with the National Heart, Lung, and Blood Institute through grants from the National Institutes of Health; the statement added that the company is responsible for the content, which does not necessarily represent the official views of the institutes.
The Food and Drug Administration held a Type C meeting about the trial in late March 2026, according to an earlier company update. In May, Longeveron said the independent data monitoring committee had completed its prespecified review, found no safety concerns and authorized the study to continue as designed through completion. An Investing.com report said the agency no longer considered ELPIS II a pivotal trial after the March meeting, and quoted the company as saying the FDA viewed the right ventricular ejection fraction endpoint as unsuitable for establishing efficacy. This regulatory development adds significance to the review of the full dataset, as the program’s path is not limited to interpreting the exploratory signal. The company has not announced a specific date for its next discussion with the agency in the information available.
The study comes amid an unmet treatment need that surgeon Sunjay Kaushal said remains substantial among children with hypoplastic left heart syndrome. The company’s statement quoted him as saying that the survival rate to adolescence for children who undergo standard surgeries is 50–60%, and that about 20% require a heart transplant. Kaushal presented the trial as evidence of the safety of using stem cells to address this need, while the primary and exploratory efficacy results remain statistically inconclusive. Longeveron said it will complete analyses of the full dataset and discuss the results with the FDA to determine potential next steps for its HLHS program. Alongside the results announcement, the company said it had begun a cost-reduction process and was exploring options aimed at maximizing shareholder value.