Shares of Arcturus Therapeutics Holdings Inc. (NASDAQ:ARCT) edged up 2% after the company shared encouraging interim results from two Phase 2 trials evaluating its investigational mRNA therapy, ARCT-810, for patients with ornithine transcarbamylase (OTC) deficiency.
The biotech firm reported that ARCT-810 produced significant biological responses across both clinical studies. Notably, the therapy led to consistent reductions in elevated glutamine levels—a key biomarker tied to urea cycle function—which were normalized in many cases. In its U.S.-based Phase 2 trial, patients receiving ARCT-810 for the first time showed meaningful gains in relative ureagenesis function, tracked using a new optimized assay developed by the company.
In a pooled analysis covering both trials, participants who remained on their standard treatment regimens while receiving ARCT-810 showed statistically significant drops in glutamine levels following repeated doses, with a p-value of 0.0055. All three participants in the U.S. open-label portion of the study experienced sustained reductions in glutamine levels, reaching a normal range after three doses.
Further results from the U.S. trial demonstrated a meaningful boost in relative ureagenesis function—from a baseline average of 29.0% to 43.7%—28 days after the fifth dose. Impressively, two of the three subjects surpassed the 50% threshold, which the company has identified as a marker of clinically significant improvement.
In terms of safety and metabolic control, both trials reported that patients maintained normal ammonia levels after at least two doses of ARCT-810, with stability lasting for around four weeks after the treatment period ended.
Thus far, the therapy has shown a favorable safety profile. Across all trials conducted to date, including 40 participants (20 of whom have OTC deficiency), ARCT-810 has been generally well-tolerated. Arcturus has also enhanced its infusion protocol—now delivered over three hours—without requiring corticosteroid pre-treatment. No serious infusion-related side effects have been reported under this updated regimen.