Bone marrow-derived mesenchymal stem cells (JR-031) for steroid-refractory grade III or IV acute graft-versus-host disease: a phase II/III study.

Following a phase I/II study using mesenchymal stem cells (MSCs; JR-031) for steroid-refractory grade II or III acute graft-versus-host disease (aGVHD), a phase II/III study using the cells focused on steroid-refractory grade III or IV aGVHD was conducted. The number of infused MSCs and the number of MSC infusions were the same as the phase I/II study. No additional immunosuppressant was given for steroid-refractory aGVHD during the course of MSC infusions. Twenty-five patients (grade III, 22 patients and grade IV, 3 patients) were enrolled in this study. At 4 weeks after the first MSC infusions, six (24 %) and nine patients (36 %) achieved a complete response (CR) and partial response (PR), respectively. Durable CR by 24 weeks, which was the primary end-point, was obtained in 12 of 25 patients (48 %). At 52 weeks, 12 patients (48 %) treated with MSCs only (six patients) and MSCs plus additional treatments (six patients) were alive in CR. The survival was significantly better in patients showing overall response (OR; CR+PR) than in those showing no OR at 4 weeks. Adverse effects commonly associated with MSC infusions were not observed. Taken together, our two clinical trials suggest JR-031 to be effective for steroid-refractory aGVHD.