Mesoblast Presents New Data Supporting Early Use of Ryoncil® And Pivotal Trial In Adult SR-aGvHD

Mesoblast Limited presented new clinical data at the February 2026 Tandem Meetings of ASTCT and CIBMTR in Salt Lake City, highlighting outcomes for Ryoncil® (remestemcel-L-rknd) in steroid-refractory acute graft-versus-host disease (SR-aGvHD). The findings showed consistently high survival rates regardless of whether the therapy was used in children or adults, as second- or third-line treatment, or in patients who were ruxolitinib-naïve or resistant.

Ryoncil® is the first FDA-approved mesenchymal stromal cell (MSC) therapy for any indication and remains the only approved treatment for children under 12 years with SR-aGvHD. Data from 53 patients treated under the Emergency Investigational New Drug (EIND) program demonstrated that among those receiving Ryoncil® as third-line or later therapy, most with severe Grade III/IV disease, 15% died before completing the full treatment course. In contrast, only 2% of patients treated in second-line settings in the Phase 3 MSB-GVHD001 study were unable to complete therapy due to early death.

“Treatment initiation as early as possible is essential in order to give Ryoncil® the best chance to save as many precious lives as possible,” said Mesoblast Chief Executive Dr. Silviu Itescu. "The Phase 3 trial in adults with SR-aGvHD will position Ryoncil® as the earliest treatment regimen for severe disease after steroid resistance." 

These findings underscore the potential benefit of initiating Ryoncil® earlier after steroid resistance is confirmed, allowing more patients to complete the recommended treatment course and potentially improve survival outcomes. Early intervention appears to play a critical role in maximising therapeutic benefit.

Additionally, survival at Day 100 among adult patients treated under the EIND program was at least comparable to outcomes seen in pediatric patients. This supports Mesoblast’s plan to initiate a pivotal trial evaluating Ryoncil® as part of second-line therapy in adults with severe SR-aGvHD. Enrollment is expected to begin this quarter following central IRB approval. A successful study could enable label expansion into the adult population, which is estimated to be approximately three times larger than the pediatric SR-aGvHD population.