Mesoblast (ASX:MSB) has taken a step toward expanding the use of its flagship cell therapy Ryoncil, announcing a significant collaboration with the U.S. National Institutes of Health–funded Blood and Marrow Transplant Clinical Trials Network (BMT CTN) to conduct a pivotal trial in adults with severe steroid-refractory acute graft versus host disease (SR-aGvHD).
The new study marks a significant advance for a patient population with few effective treatment options and historically poor outcomes. While Ryoncil is already approved by the U.S. Food and Drug Administration (FDA) for children and adolescents with SR-aGvHD, Mesoblast is now moving to demonstrate its therapeutic benefit in adults.
Dr John Levine, Chair of the BMT CTN Steering Committee and Professor of Internal Medicine and Pediatrics at the Icahn School of Medicine at Mount Sinai, said the partnership reflects both urgency and promise. “We are delighted to be partnering with Mesoblast in this pivotal Phase 3 trial of Ryoncil®. We are aiming to extend the use of this potentially life-saving treatment, already approved by FDA in children and adolescents, to adults with severe SR-aGvHD.”
Across two key studies underpinning FDA approval of ruxolitinib, between 44 per cent and 58 per cent of adults with Grade III/IV SR-aGvHD failed to respond by day 28. For those who do not respond to ruxolitinib, survival can fall to just 20 to 30 per cent by Day 100. Against this backdrop, Mesoblast said its Expanded Access Program has shown far more encouraging signs. Among patients aged 12 and older who failed ruxolitinib or other second-line agents, Ryoncil was associated with a 76 per cent Day-100 survival rate.
Following recent discussions with the FDA on trial design and patient selection, the pivotal adult trial will randomise patients as early as possible after demonstrating steroid refractoriness, assigning them to ruxolitinib alone or ruxolitinib combined with Ryoncil. Mesoblast said it expects to submit the protocol to the FDA and begin enrolling participants in the first quarter of 2026.
Mesoblast Chief Executive Silviu Itescu said the collaboration underscores both the clinical need and the commercial potential. “We are pleased to be partnering with the BMT CTN to expand the availability of Ryoncil to adult patients with severe SR-aGvHD given the poor outcome with existing therapies. This clearly remains a major unmet need and a market opportunity 3–4 times larger than the pediatric market.”