Mesoblast Partners With NIH Network On Phase 3 Study Testing Ryoncil As First-Line Therapy For Severe Steroid-Refractory aGvHD In Adults

Mesoblast Limited has announced a collaboration with the National Institutes of Health-funded Blood and Marrow Transplant Clinical Trials Network to conduct a pivotal Phase 3 study evaluating Ryoncil in adults with severe acute graft versus host disease who do not respond to corticosteroids. The initiative responds to the large population of patients who are unresponsive to current treatment options and face extremely high mortality rates.

Clinical experts leading the BMT CTN stated that the goal of the joint effort is to expand the use of Ryoncil, which is already approved in children and adolescents, to the adult patient population. Previous studies supporting the approval of ruxolitinib showed that nearly 44 to 58 percent of adults with Grade III or IV steroid-refractory aGvHD failed to respond within 28 days, and survival rates for those who do not respond may be as low as 20 to 30 percent by Day 100. In contrast, Mesoblast reported a 76 percent Day 100 survival rate among patients aged 12 and older treated under its Expanded Access Program.

Mesoblast recently met with the FDA to align on patient selection and timing of treatment for the pivotal study. To maximize clinical benefit, the trial will randomize patients as early as possible after corticosteroid refractoriness to receive either ruxolitinib alone or the combination of ruxolitinib with Ryoncil. The protocol will be submitted to the FDA so that trial enrollment can begin in the first quarter of 2026.

According to Mesoblast CEO Silviu Itescu, expanding Ryoncil access to adult patients addresses a major unmet medical need and represents a significant commercial opportunity, potentially three to four times larger than the pediatric market.