PHILADELPHIA, PA — iECURE said new data from its ongoing OTC-HOPE clinical trial showed sustained clinical benefit in the first infant treated with its experimental gene-editing therapy ECUR-506 and statistically significant reductions in disease-related medical crises across the study’s completed low-dose cohort, findings that could support further development of the treatment for a rare and often fatal genetic disorder.
The preliminary results, presented at the Society for Inherited Metabolic Disorders 2026 Annual Meeting, come as the Philadelphia-based biotechnology company continues evaluating ECUR-506 in neonatal-onset ornithine transcarbamylase deficiency, a severe inherited liver disorder that can cause toxic ammonia buildup, neurological injury, and death.
Among the three patients in the completed low-dose cohort, treatment was associated with a 57% reduction in the annualized rate of hyperammonemic events and a 65% reduction in hyperammonemic crises compared with pre-treatment rates, according to the company. Both reductions reached statistical significance.
The first infant treated in the trial remained free of reported hyperammonemic events through 18 months after receiving ECUR-506 and was able to discontinue standard ammonia-scavenging medications while gradually increasing dietary protein intake to age-appropriate levels.
“In infants with neonatal-onset OTC deficiency, HACs, which are spikes in plasma ammonia greater than 100 umol/L associated with neurological status change, are a primary driver of mortality and morbidity,” said Dr. Gabriel Cohn, iECURE’s chief medical officer. He said the findings provide additional evidence of clinical activity, including durability of response and reductions in disease-related events.
The company reported that two of the three low-dose participants experienced no hyperammonemic events or crises after treatment. The third participant showed lower event rates following dosing.
One patient was removed from a liver transplant waiting list after treatment, while another later underwent transplantation during long-term follow-up as part of ongoing clinical management.
Across all dose groups evaluated to date, seven patients have received ECUR-506. iECURE said the therapy was generally well tolerated, with no unexpected treatment-related safety findings reported.
The safety analysis included participants from the completed low-dose and intermediate-dose cohorts, along with the first patient treated in the high-dose group. The company reported no infusion-related reactions or cases of thrombotic microangiopathy.
Investigators observed asymptomatic liver enzyme elevations in some participants. According to the company, those cases were managed with immunosuppressive therapy and did not recur after treatment tapering.
One participant died from hypoxemic respiratory failure during the study. The company said investigators determined the death was unrelated to ECUR-506 and attributed it to progression of the underlying disease and associated complications.
Joe Truitt, chief executive officer of iECURE, said the emerging data suggest the therapy may help reduce disease burden for families managing neonatal-onset OTC deficiency.
“The emerging data, which now include statistically significant reductions in hyperammonemic events and evidence of durability in the first treated participant, are encouraging and highlight the potential to meaningfully reduce disease burden,” Truitt said.
ECUR-506 is designed as a variant-agnostic gene insertion therapy intended to address the underlying genetic cause of OTC deficiency. The trial remains ongoing, with evaluation of the intermediate- and high-dose cohorts continuing. Additional data are expected to help determine future dosing strategies and guide further clinical development.
OTC deficiency is a rare genetic disorder caused by the absence or dysfunction of an enzyme responsible for removing ammonia from the bloodstream. Current treatment typically relies on strict dietary management, ammonia-scavenging medications, and, in some cases, liver transplantation.
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