FDA Grants First-Ever Approval for MSC Therapy to Australian Company Mesoblast After Attempting for 4 Years

The FDA has approved Ryoncil (remestemcel-L-rknd), an allogeneic bone marrow-derived mesenchymal stromal cell (MSC) therapy, marking the Australian Company Mesoblast’s first drug approval after more than four years and two prior rejections. The agency authorized the therapy for treating steroid-refractory acute graft-versus-host disease (SR-aGVHD) in pediatric patients aged 2 months and older. Recognized as the first FDA-approved MSC therapy, Ryoncil uses MSCs derived from the bone marrow of healthy adult donors, which perform various roles and can differentiate into multiple cell types.

Ryoncil Demonstrated Successful 70% Response Rate in Pediatric SR-aGVHD Patients Leading to Approval

The FDA based its approval of Ryoncil on data from a Phase III single-arm, multicenter trial, which reported a 70% overall response rate at 28 days in pediatric patients with steroid-refractory acute GVHD, including a 30% complete response rate. The trial identified infections, hemorrhage, fever, and abdominal pain as the most common side effects. The FDA advises physicians to closely monitor Ryoncil infusions and to discontinue treatment if patients exhibit signs of dyspnea, hypotension, fever, tachypnea, cyanosis, or hypoxia.

Ryoncil’s approval process has been lengthy and challenging. The FDA initially rejected the therapy in October 2020, requesting at least one additional randomized controlled trial to demonstrate the efficacy of the therapy. Mesoblast resubmitted the application in early 2023, including long-term survival data spanning over four years and additional data from high-risk patients. However, in August 2023, the FDA rejected Ryoncil once more, requesting further data from adult patients due to lack of a suitable potency assay. 

5,000 Out of 10,000 Patients Likely to Develop GVHD and Fail to Respond to Steroid Treatment 

Each year in the United States, about 10,000 patients undergo an allogeneic bone marrow transplant, with 1,500 children included in this range. Around 50% of these patients develop acute graft-versus-host disease (aGVHD), and nearly half of them fail to respond to steroids, the standard first-line treatment. GVHD develops when the transplanted cells identify the recipient’s cells as foreign and attack them, resulting in hospital treatments or death.

Unlike steroids, Ryoncil uses mesenchymal stromal cells from the bone marrow of an unrelated donor and works by modulating the immune response to reduce inflammation in GVHD. The drug is then successfully able to suppress the immune system by specifically targeting the immune response involved in GVHD.

Dr. Silviu Itescu, Chief Executive of Mesoblast, expressed, “We are very pleased that the FDA has granted approval of Ryoncil and are proud of the company’s commitment to the GVHD community in bringing this important new treatment to children and families with no other acceptable options.”

Author

Denisse Sandoval