Mesoblast (ASX:MSB) received approval from the U.S. Food and Drug Administration (FDA) for Ryoncil (remestemcel-L), making it the first mesenchymal stromal cell (MSC) therapy to be approved in the United States for any indication whatever.
Ryoncil is the only FDA-approved therapy for the treatment of steroid-refractory acute graft-versus-host disease (SR-aGvHD) in children.
The disease
“Allogeneic stem cell transplantation” involves a patient receiving stem cells from a donor. The procedure is used to treat blood cancers (such as leukemia), inherited blood disorders (such as sickle cell disease), and immune system deficiencies.
However, such transplants carry a risk of graft-versus-host disease (GvHD), in which the donor’s immune cells attack the patient’s body. First-line treatment for GvHD is corticosteroids, which suppress the immune system.
Steroid-refractory (SR) GvHD occurs when a patient’s GvHD does not improve, or actually worsens, after three to seven days of high-dose corticosteroids.
Once GvHD becomes refractory to steroids, the disease becomes much more difficult to treat and patients are at higher risk of death.
Enter Ryoncil.
Ryoncil is a therapy using bone marrow cells (mesenchymal stromal cells). It is usually administered by intravenous infusion. MSCs modulate the immune system, inhibiting the activation of T cells, a type of white blood cell that attack infected and foreign cells. They also reduce the release of cytokines, small proteins that control inflammation.
This mechanism allows Ryoncil to target conditions linked to excessive immune responses, such as aGVHD.
Significant clinical results
The FDA approval follows a Phase 3 trial in pediatric patients with SR-aGvHD, 89% of whom had severe grade C or D disease. The trial showed that 70% of patients achieved an overall response on day 28 of Ryoncil treatment, a rate predictive of survival in GVHD.
More than 85% of patients completed the full course of Ryoncil without interruption, without interruption due to laboratory abnormalities.
Transplant physician Dr. Joanne Kurtzberg, Director of the Marcus Center for Cellular Cures at Duke University Medical Center, commented: “Acute steroid-refractory graft-versus-host disease is a devastating disease with an extremely poor prognosis. . Starting today, we are able to offer Ryoncil, the first FDA-approved treatment that will save the lives of many children and have a big impact on their families. »
Commercial importance
The global graft-versus-host disease market has been valued at approximately $3 billion in 2024 and is expected to reach approximately $10 billion by 2031.
Managing Director, Dr. Silviu Itescu, commented: “With the FDA approval of Ryoncil, Mesoblast has demonstrated its ability to commercialize the first MSC product. We will continue to work closely with the FDA to achieve approval of our other late-stage products, including REVASCOR for cardiovascular disease and rexlemestrocel-L for inflammatory pain indications.
Once approved, Ryoncil will be made available at U.S. transplant centers and other treatment hospitals.
Mesoblast also aims to expand the use of Ryoncil to address the adult GvHD market.
Shares of Mesoblast closed up 54.04% at $3.05 yesterday.
