(P-IG-34) Red Blood Cell Alloimmunization Is Not Observed Following Administration of anti-CD38 Therapy for the Treatment of Non-plasma Cell Dyscrasia Conditions

Background/Case Studies: It has been established that minimal new red blood cell (RBC) alloimmunization occurs in patients who receive anti-CD38 therapy for multiple myeloma. However, the risk of RBC alloimmunization in those who receive anti-CD38 therapy for expanded indications and who do not exhibit pathologic plasma cell function, has not been described. In this study, we evaluated the incidence of RBC alloimmunization in patients who received daratumumab, a monoclonal anti-CD38 therapy, for the treatment of conditions other than plasma cell dyscrasias.

Study

Design/Methods: This single center retrospective study received an exemption from the University of Michigan IRB. Inclusion criteria were as follows: any age, receipt of at least one dose of daratumumab for any non-plasma cell dyscrasia indication and transfused with at least one cellular blood product within 90 days of infusion. Only subjects who received daratumumab after FDA approval in 2015 were included. Using an institutional free-text search tool, electronic records containing the term “daratumumab” and excluding terms describing plasma cell disorders were identified and screened for eligibility. Variables collected from each record included basic demographics and daratumumab-specific information: indication, dates and doses of administration, pre- and post-administration RBC alloimmunization status, blood product exposure, and concurrent immunosuppression. Basic descriptive statistics were performed in Microsoft Excel. Continuous variables were given as means with standard deviations. There were insufficient data available to perform statistical tests.

Results/Findings: Fifteen subjects met inclusion criteria. Most subjects were female (60%). The mean age of the cohort was 40 years (25). The most common daratumumab indications were non-plasma cell hematologic (33%) and solid tumor (27%) malignancies. The most commonly co-administered immunosuppressives were malignancy-targeted therapies (66%) and systemic corticosteroids (53%). Subjects received a mean of 9 (10) RBC units after daratumumab infusion. RBC units were matched for ABO, RhD, and Kell prophylactically and antigen negative, if the recipient was alloimmunized. No new RBC alloantibodies were detected up to 90 days after the daratumumab course and following cellular transfusions (Table 1). Notably, two subjects exhibited pre-daratumumab positive antibody screens, which subsequently became negative.

Conclusions: In this study, we observed no new RBC alloimmunization events in individuals who received daratumumab for non-plasma cell dyscrasia indications. These findings suggest that minimal prophylactic RBC matching strategies may be adequate to prevent RBC alloimmunization in patients receiving daratumumab for expanded indications.