The Food and Drug Administration (FDA) has accepted for Priority Review the Biologics License Application (BLA) for remestemcel-L (RyoncilTM; Mesoblast Limited) for the treatment of children with steroid-refractory acute graft versus host disease (SR-aGVHD). 

Remestemcel-L consists of culture-expanded mesenchymal stem cells derived from the bone marrow of an unrelated donor. It is believed to work by down-regulating the production of proinflammatory cytokines, increasing production of anti-inflammatory cytokines, and enabling recruitment of naturally occurring anti-inflammatory cells to involved tissues.

The BLA is supported by data from 3 clinical trials that included 309 children with SR-aGVHD. Results across all trials showed consistent treatment responses and survival outcomes with 66% of patients (n=204) achieving an overall response at Day 28 after a 4-week course of remestemcel-L administered by intravenous infusion. Moreover, among International Bone Marrow Transplant Registry Severity Index grade C/D patients, which accounted for 82% of all treated patients, the Day 28 overall response was 65%. Day 28 responders also had greater survival rates vs nonresponders (84% vs 39% at Day 100, and 83% vs 38% at Day 180). Remestemcel-L was well tolerated with no infusion-related toxicity and no identified safety concerns.

Additionally, data from an open-label phase 3 trial evaluating remestemcel-L in 55 children with SR-aGVHD (89% of whom had grade C/D disease) support the application. Findings from the trial showed that 70% of patients treated with remestemcel-L achieved an overall response at Day 28 and 75% achieved Day 100 survival. These outcomes were superior to those from a cohort of 30 pediatric patients with SR-aGVHD from the Mount Sinai Acute GVHD International Consortium (Day 28 overall response was 43% and Day 100 survival was 57%).

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Remestemcel-L is also being investigated as a treatment for patients with acute respiratory distress syndrome caused by COVID-19, among other rare diseases.

A Prescription Drug User Fee Act (PDUFA) target date of September 30, 2020 has been set for this application. If approved, the Company expects to launch Ryoncil in 2020.

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