NEW YORK, July  08, 2024  (GLOBE NEWSWIRE) -- Mesoblast Limited (Nasdaq:MESO; ASX:MSB), global leader in allogeneic cellular medicines for inflammatory diseases, announced today it has resubmitted its BLA for approval of Ryoncil (remestemcel-L) in the treatment of children with SR-aGVHD.

The filing comes after Mesoblast was informed by FDA at the end of March that, following additional consideration, the available clinical data from the Phase 3 study MSB-GVHD001 appears sufficient to support submission of the proposed BLA for remestemcel-L for treatment of pediatric patients with SR-aGVHD. As a result, the filing addresses remaining CMC (Chemistry, Manufacturing, and Control) items.

"We have worked closely with the agency and thank them for their ongoing guidance, facilitating the potential approval of RYONCIL and addressing the urgent need for a therapy that improves the dismal survival outcome in children with SR-aGVHD," said Mesoblast CEO Dr. Silviu Itescu.

FDA granted remestemcel-L Fast Track designation, a process to facilitate the development and expedited review of therapies for serious conditions that fill unmet medical needs, and Priority Review designation, which is given to drugs that treat a serious condition and provide a significant improvement in safety or effectiveness over existing treatments.

The BLA resubmission upon acceptance is expected to have a review period of between two and six months from receipt.

About Ryoncil (remestemcel-L)
Mesoblast's lead product candidate, Ryoncil (remestemcel-L), is an investigational therapy comprising culture expanded mesenchymal stromal cells derived from the bone marrow of an unrelated donor. It is administered to patients in a series of intravenous infusions. RYONCIL has immunomodulatory properties which counteract the inflammatory processes that are implicated in SR-aGVHD by inhibiting activation and proliferation of effector T cells, down-regulating the production of pro-inflammatory cytokines, and enabling recruitment of anti-inflammatory cells to involved tissues.

About the Phase 3 Trial of Ryoncil (remestemcel-L) in Children with Steroid-Refractory Acute Graft Versus Host Disease
The Phase 3 Study GVHD001/002 was conducted in 54 children (89% Grade C/D) across 20 centers in the US where RYONCIL was used as the first line of treatment for children who failed to respond to steroids for acute GVHD.1 The trial met its pre-specified primary endpoint, Day 28 Overall Response (OR), 70.4% versus 45%, p=0.0003. An overall response at day 28 was highly predictive of improved survival through day 100 (87% compared to 47% in patients that did not achieve day 28 OR p= 0.0001).

Compared with a matched control group of pediatric subjects from the contemporaneous database of the Mount Sinai Acute GVHD International Consortium (MAGIC) treated with best available therapy, treatment with Ryoncil achieved higher Day 28 OR (70% vs 43%) and higher Day 100 survival (74% vs 57%). A propensity-matched study of outcomes in 25 children from Mesoblast's Phase 3 trial and 27 control children who received best available treatment, including ruxolitinib, from the MAGIC database showed that 67% of high-risk children (MAP scores >0.29) who received Ryoncil achieved a Day 28 overall response and were alive after 180 days compared to just 10% in both categories in the MAGIC group.

In addition, results of a 4-year survival study performed by the Center for International Blood and Marrow Transplant Research (CIBMTR) on 51 evaluable patients with SR-aGVHD who were enrolled in the Phase 3 trial, demonstrated durability of the survival benefits, with 67% survival at 6 months, 63% survival at 1 year, 51% at 2 years, and 49% survival through 4 years in children with expected 2 year survival of just 25-38% using best available therapy.2-4

About Steroid-Refractory Acute Graft Versus Host Disease
Acute GVHD occurs in approximately 50% of patients who receive an allogeneic bone marrow transplant (BMT). Over 30,000 patients worldwide undergo an allogeneic BMT annually, primarily during treatment for blood cancers, including about 20% in pediatric patients.5,6 SR-aGVHD is associated with mortality as high as 90% and significant extended hospital stay costs.7,8 There are currently no FDA-approved treatments in the US for children under 12 with SR-aGVHD.

Survival outcomes have not improved over the past two decades for children or adults with the most severe forms of SR-aGVHD.2,9-10 The lack of any approved treatments for children under 12 means that there is an urgent need for a therapy that improves the dismal survival outcomes in children.

References / Footnotes

1. Kurtzberg J. et al. A Phase 3, Single-Arm, Prospective Study of Remestemcel-L, Ex Vivo Culture-Expanded Adult Human Mesenchymal Stromal Cells for the Treatment of Pediatric Patients Who Failed to Respond to Steroid Treatment for Acute Graft-versus-Host Disease. Biol Blood Marrow Transplant 26 (2020) 845-854

2. Rashidi A et al. Outcomes and predictors of response in steroid-refractory acute graft-versus-host disease: single-center results from a cohort of 203 patients. Biol Blood Bone Marrow Transplant 2019; 25(11):2297-2302

3. MacMillan ML et al. Pediatric acute GVHD: clinical phenotype and response to upfront steroids. Bone Marrow Transplant 2020; 55(1): 165-171

4. Zeiser R et al. Ruxolitinib for Glucocorticoid-Refractory Acute Graft-versus-Host Disease. N Engl J Med 2020;382:1800-10.

5. Niederwieser D, Baldomero H, Szer J. (2016) Hematopoietic stem cell transplantation activity worldwide in 2012 and a SWOT analysis of the Worldwide Network for Blood and Marrow Transplantation Group including the global survey.

6. HRSA Transplant Activity Report, CIBMTR, 2019

7. Westin, J., Saliba, RM., Lima, M. (2011) Steroid-refractory acute GVHD: predictors and outcomes. Advances in Hematology.

8. Axt L, Naumann A, Toennies J (2019) Retrospective single center analysis of outcome, risk factors and therapy in steroid refractory graft-versus-host disease after allogeneic hematopoietic cell transplantation. Bone Marrow Transplantation.

9. Berger M, Pessolano R, Carraro F, Saglio F, Vassallo E, Fagioli F. Steroid-refractory acute graft-versus-host disease graded III-IV in pediatric patients. A mono-institutional experience with a long-term follow-up. Pediatric Transplantation. 2020; 24(7):e13806

10. Biavasco F, Ihorst G, Wasch R, Wehr C, Bertz H, Finke J, Zeiser R. Therapy response of glucocorticoid-refractory acute GVHD of the lower intestinal tract. Bone Marrow Transplantation. 2022