Mesoblast (MESO.US) announced on July 24th that the US FDA has accepted the biological product license application (BLA) for its cell therapy Ryoncil (remestemcel-L) for re-submission, for the treatment of steroid-refractory acute graft versus host disease (SR-aGVHD) in children. The PDUFA date for this application is January 7th, 2025. The press release stated that, if approved, Ryoncil will become the first allogeneic 'off-the-shelf' cell therapy in the US, and the first cell therapy for SR-aGVHD pediatric patients under the age of 18 years old.

A previously disclosed Phase 3 trial showed that the objective response rate (ORR) at Day 28 after treatment was 69% for patients receiving Ryoncil, which is a statistical significant increase compared to the historical control rate of 45%. Among patients who received at least one infusion treatment and were followed up for 100 days, the mortality rate was 22%. However, the mortality rate was as high as 70% on Day 100 for patients who had initial steroid treatment failure.

Ryoncil is a mesenchymal stem cell that regulates T-cell mediated inflammatory response by inhibiting T-cell proliferation, and down-regulating pro-inflammatory cytokines and interferon production. Its biological product license application had previously been awarded priority review by the US FDA. Currently, Ryoncil is being developed for the treatment of other diseases, including a Phase 3 trial examining its efficacy in treating the acute respiratory distress syndrome of severe COVID-19 patients.