Longeveron Inc.'s (Nasdaq: LGVN) laromestrocel failed to improve right ventricular function in infants with hypoplastic left heart syndrome (HLHS), according to topline results from the ELPIS II Phase IIb trial, prompting a review of strategic alternatives. Longeveron posted the results on September 16, 2026.
HLHS affects approximately 1,000 infants per year in the US. The underdeveloped left ventricle forces the right ventricle to sustain systemic circulation through a complex three-stage surgical palliation process. Even with surgery, only about 50%-60% of patients survive to adolescence, with roughly 20% requiring heart transplant.
Laromestrocel is an allogeneic mesenchymal stem cell (MSC) therapy derived from the bone marrow of healthy adult donors. The cells are hypothesized to secrete bioactive factors with anti-inflammatory and pro-vascular regenerative effects, potentially supporting right ventricular repair when delivered as a single intramyocardial injection during Stage 2 palliative surgery. The FDA had previously advised Longeveron that right ventricular ejection fraction (RVEF) alone would not be sufficient to demonstrate efficacy for regulatory approval.
In the intent-to-treat (ITT) population of the randomized, double-blind, multicenter trial enrolling 40 infants, the least-squares mean difference in RVEF change from baseline at 12 months was −0.7 percentage points (95% CI: −7.3 to 5.9; p=0.8336). A sponsor-defined exploratory hierarchical composite endpoint of all-cause mortality and inpatient hospitalization duration was also not statistically significant in the ITT population. Exploratory as-treated analyses showed zero deaths in the laromestrocel arm versus one in the control group over 12 months, and approximately 31% fewer adjudicated major adverse cardiovascular events (MACE) — 12 versus 19 events — though the negative binomial analysis for MACE did not reach statistical significance. Longeveron said no new safety signals were identified and no treatment-emergent adverse events were assessed as related to laromestrocel.
The trial was conducted in collaboration with the National Heart, Lung, and Blood Institute (NHLBI) through National Institutes of Health (NIH) grants. The independent Data Monitoring Committee had cleared the study to continue following its final prespecified safety review in May 2026. Earlier in the year, the FDA had advised Longeveron during a Type C meeting that right ventricular ejection fraction alone would not be considered an appropriate efficacy endpoint for approval, prompting the company to develop a statistical analysis plan incorporating a composite clinical endpoint ahead of the readout.