Ann: Remestemcel-L Reduces Biomarkers for Mortality in SR-aGVHD, page-2

REMESTEMCEL-L REDUCES INFLAMMATORY BIOMARKERS PREDICTIVE OF HIGH MORTALITY IN ACUTE GRAFT VERSUS HOST DISEASE Biomarker Study Results Presented at the 62nd American Society of Hematology Annual Meeting

Melbourne, Australia; December 7 and New York, USA; December 6, 2020: Mesoblast Limited (ASX:MSB; Nasdaq:MESO), global leader in allogeneic cellular medicines for inflammatory diseases, today announced results presented at the 62nd annual meeting American Society of Hematology (ASH), which provide in vivo biomarker evidence linking remestemcel-L’s immunomodulatory activity to survival outcomes in children with steroid-refractory acute graft versus host disease (SR-aGVHD).

The results were presented on December 6, 2020 by the Phase 3 trial’s lead investigator and pediatric transplant physician, Dr Joanne Kurtzberg, the Jerome Harris Distinguished Professor of Pediatrics and Professor of Pathology, and Director, Pediatric Blood and Marrow Transplant Program at Duke University Medical Center.

Key conclusions were:

• Clinically meaningful overall responses and survival in children with SR-aGVHD treated with remestemcel-L were associated with significant reductions in certain biomarkers of inflammation which have been validated as predictors of mortality risk
• These biomarkers provide evidence of in vivo bioactivity of remestemcel-L in pediatric SRaGVHD, where children under 12 are at high-risk for mortality, with no approved therapies in the United States
• The durable reductions in blood levels of certain biomarkers associated with inflammatory diseases of the gut suggest that these could be more generally reflective of remestemcel-L activity in vivo in other inflammatory bowel diseases such as Crohn’s disease and ulcerative colitis.

Blood levels of soluble suppression of tumorigenicity 2 (ST2)1,2 and MAGIC Biomarker Score (MBS)3,4, validated biomarkers that predict high mortality in SR-aGVHD and active gut inflammation more broadly, were measured at baseline and sequentially over 180 days in 40 of the 54 children with SRaGVHD who received at least four weeks of remestemcel-L treatment in the single-arm Phase 3 trial. Both the elevated baseline levels of ST2 and MBS were significantly reduced after remestemcel-L treatment at Days 100, 160 and 180 (all timepoints p<0.001 for both markers). This was accompanied by significant reductions in activated circulating T cells. Day 100 survival was 74% in the 54 remestemcel-L children with SR-aGVHD (89% with Grade C/D disease), which compares very
favourably with a mortality approaching 70-90% in children of similar severity treated with other therapies.

Dr Kurtzberg said: “These results support the bioactivity of remestemcel-L in treating the severe inflammation in children with acute graft versus host disease refractory to steroids and provide
evidence linking the immunomodulatory properties of remestemcel-L with the excellent responses and survival we see when treating these desperately ill children.”