P021 Desensitization is beneficial in highly anti-hla antibody sensitized patients with platelet refractoriness undergoing hematopoietic cell transplantation

Abstract

Introduction Management of platelet (Plt) refractoriness can be very challenging, expensive and time consuming. Inability to find compatible Plts for hematopoietic cell transplantation (HCT) recipients may result in delay in transplantation and post-transplantation morbidity/mortality. While desensitization protocols are often utilized in DSA-sensitized organ transplant recipients, there is little information available about utility of desensitization in the setting of Plt refractoriness in highly-sensitized HCT recipients. We describe our successful experience with desensitization using a specified protocol. Methods Desensitization protocol: 3weeks, IVIg (daily), plasmapheresis (PP) 3 days/week, and rituximab and bortezomib (once/week after each PP). Anti-HLA antibody studies were performed using LABScreen® (One Lambda®) after each PP and compared with historical antibody results of each patient. Plt-XM studies were performed using Capture-P®, Immucor® assay. Mean MFI values were determined for each HLA antibody, and in aggregate, before and after desensitization. Statistical analyses were by Student t-test, p 0.05 was considered significant, for each and total anti-HLA antibodies. Results Slight reduction in mean MFI values were noted after desensitization (see table), however no statistical significance was noted. %cPRA did not change. None of the individual anti-HLA antibodies changed with statistical significance. All patients achieved adequate Plt incremental increases with transfusions after desensitization. All patients achieved adequate engraftment. Conclusions 1) “Desensitization” is beneficial in the management of Plt refractoriness and allows for successful HCT engraftment. 2) MFI and % cPRA do not appear to be reflective of successful desensitization. (In previous studies we have found that >12-16 weeks of treatment are generally required to see a demonstrable fall in MFI values.) 3) Additional studies are needed for understanding the mechanism(s) that result in the improvement in Plt refractoriness with desensitization, since it does not appear to be due to reduction in anti-HLA antibodies.