Efficacy and safety of daratumumab in multiresistant immune‐mediated thrombotic thrombocytopenic purpura

Summary The immunosuppressive treatment of immune‐mediated thrombotic thrombocytopenic purpura (iTTP) in patients with intolerance or refractoriness to the B‐cell depleting monoclonal antibody rituximab remains debated. Daratumumab, a plasma cell‐directed monoclonal antibody targeting CD38, represents a therapeutic option, but data are scarce. The French Thrombotic Microangiopathies Reference Center conducted a nationwide survey on iTTP patients treated with daratumumab. Nine episodes from seven patients were identified. Treatment was administered for A Disintegrin And Metalloproteinase with ThromboSpondin‐1 motifs, 13th member (ADAMTS13) relapses while patients were otherwise in clinical response (N = 8), or during the acute phase of the disease following rituximab intolerance (N = 1). Patients have received a median of three previous therapeutic lines. ADAMTS13 activity improved in eight cases following daratumumab administration, including three cases where ADAMTS13 normalized. ADAMTS13 relapses occurred in three patients; in two cases, retreatment with daratumumab was successful. Median ADAMTS13 relapse‐free survival was not reached; 12‐month ADAMTS13 relapse‐free survival was 56%. Daratumumab‐related adverse events occurred in five cases and were non‐severe infusion‐related reactions in all cases. These results suggest that daratumumab may be an effective treatment option for iTTP patients with intolerance or refractoriness to rituximab. The immunosuppressive treatment of immune‐mediated thrombotic thrombocytopenic purpura (iTTP) in patients with intolerance or refractoriness to rituximab remains debated. Daratumumab, a plasma cell‐directed monoclonal antibody, represents a therapeutic option, but data are scarce. In our study, nine daratumumab‐treated iTTP episodes from seven patients were identified. A Disintegrin And Metalloproteinase with ThromboSpondin‐1 motifs, 13th member (ADAMTS13) activity improved in eight cases following daratumumab administration, including three cases where ADAMTS13 normalized. ADAMTS13 relapses occurred in three patients; in two cases, retreatment with daratumumab was successful. Based on our results, daratumumab may be an effective treatment option for iTTP patients with intolerance or refractoriness to rituximab.