Ryoncil Becomes First FDA-Approved Mesenchymal Stromal Cell (MSC) Therapy

In a groundbreaking move for pediatric medicine, the US Food and Drug Administration (FDA) has approved Ryoncil (remestemcel-L), the first mesenchymal stromal cell (MSC) therapy ever approved in the US. Mesoblast’s Ryoncil is now available for children aged two months and older with steroid-refractory acute graft-versus-host disease (SR-aGVHD).

Acute graft versus host disease (aGVHD) occurs when donor immune cells attack the recipient’s tissues after an allogeneic (donor) bone marrow transplant. Steroids are the first-line treatment, but nearly half of the patients don’t respond — leaving many children with SR-aGVHD facing intense treatments that carry high risks of infections, cancer relapse and significantly worsened outcomes.

Ryoncil, administered via intravenous (IV) infusion twice a week for four weeks, provides an option for those who fail steroid therapy.

MSCs are unique for their ability to modulate immune responses and promote tissue repair, making them ideal for treating complex inflammatory diseases like SR-aGVHD.

Derived from healthy adult bone marrow, MSCs are immune privileged, meaning they can be administered without the need for donor-recipient matching or immune suppression. This makes MSC-based therapies scalable and available as off-the-shelf treatments for a range of diseases.

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Ryoncil’s mechanism of action involves MSCs, which help control immune responses by down-regulating pro-inflammatory cytokines, boosting anti-inflammatory cytokines and recruiting natural anti-inflammatory cells to affected tissues. This treatment not only addresses SR-aGVHD but may also be applicable to other inflammatory diseases.

The safety and efficacy of Ryoncil were evaluated in a multicenter, single-arm Phase III study of 54 pediatric patients with SR-aGVHD. Results showed that 30 percent achieved a complete response, and 41 percent showed partial improvement.

Most participants completed the treatment without interruption. The study’s primary endpoint was a 28-day evaluation of treatment response, showing Ryoncil’s significant impact on survival outcomes.

Related: Niktimvo (Axatilimab) Approved as First-in-Class Therapy for Chronic GVHD

Mesoblast is preparing for the early 2025 launch of Ryoncil, targeting transplant centers with high pediatric case volumes to ensure the therapy reaches those who need it most.

In addition to its pediatric use, Mesoblast is expanding Ryoncil’s indications to include adults with SR-aGVHD. In collaboration with the Blood and Marrow Transplant Clinical Trials Network (BMT CTN), Mesoblast plans to conduct a pivotal trial for adults. Expanded access use has shown survival rates exceeding 70 percent, a significant improvement over the historically poor prognosis.

Mesoblast is also advancing Revascor (rexlemestrocel-L) for two key conditions: chronic heart failure with reduced ejection fraction (HFrEF), especially in patients with ischemic HFrEF supported by a left ventricular assist device (LVAD) and chronic low back pain (CLBP) due to degenerative disc disease. The FDA has granted Regenerative Medicine Advanced Therapy (RMAT) designation for both conditions, with a Phase III confirmatory trial underway for CLBP.

For families affected by SR-aGVHD, the availability of Ryoncil offers new hope as the first FDA-approved MSC therapy for any indication and the first for pediatric SR-aGVHD, providing a much-needed treatment option for a life-threatening condition.