Treatment of Steroid Resistant Grade II to IV Acute Gvhd by Infusion of Mesenchymal Stroma Cells Expanded with Platelet Lysate - a Phase I/II Study

Introduction: Despite improvements in the last decade in the field of HSCT, acute graft versus host disease (aGVHD) remains a life-threatening complication of HSCT. In particular, the outcome of patients with severe steroid-resistant aGVHD is very poor. Therefore, it remains important to search for new therapeutic strategies.

Objective: The feasibility of the generation of MSCs expanded with platelet lysate (PL) was tested as well as the feasibility and safety of the application in patients with steroid-refractory aGVHD. Immunological changes after infusion of MSC were characterized, in vitro. However, truly active mechanisms in human are poorly understood as well as whether infusion of MSC selectively impairs GVHD-inducing immune cells or also anti-virus and anti-leukemia reactive T-cells. Phenotypical and functional changes in immunological cell types and cytokine levels were investigated.

Method: In an open-label, non-randomized prospective phase I/II study MSCs from the bone marrow of healthy volunteers, expanded with PL. Patients with steroid-refractory aGVHD grade II -IV were treated with PL-MSC. 50 patients were included and received up to 4 infusions. Response rate, transplantation-related deaths, and other adverse events were assessed for up to 12 months after inclusion. In addition, a comprehensive phenotypical and functional analysis was performed with PBMCs and serum isolated from all patients before, during, and after infusion of MSC.

Results: Between 2009 -2012, 50 patients were included, 2 dropped out, 5 are so far incompletely documented. Thus 43 were available for analysis, 6 children and 37 adults. Median age was 51,5 yr (1.3-65.9). Organs involved in aGVHD were skin (56%), gi-tract (86%) and liver (33%). Overall grade was II 26%, III 65%, and IV 7%. Mean number of infusion were 3 (1-4). No severe side effects were observed. Median follow-up was 4 months (0.4-12). Complete overall response was observed in 56% patients after a median of 53 days (3-116). The overall survival was significantly better in responders when compared to non-responders (p <0.001). Immunological monitoring suggests that anti-viral and anti-leukemia reactive T-cells are well preserved in all patients who responded to MSC treatment. In addition, we identified biomarkers which associate even 2 weeks after MSC infusion with complete resolution of GVHD.

Conclusion: Generation and infusion of PL-MSCs in steroid-resistant aGVHD grade II- IV is feasible, safe and is effective. In addition, also patients who initially responded to PL-MSCs but develop later a relapse of aGVHD during tapering or cessation of immunosuppressive drugs become again sensitive to the treatment with steroids. Infusion of MSC did not impair anti-virus and anti-leukemia reactive T-cells. Identified biomarkers predict very early a usually late clinical resolution of GVHD, thus might be useful.