A Novel Anti-CD38 Monoclonal Antibody for Treating Immune Thrombocytopenia

Abstract

Background: Immune thrombocytopenia (ITP) is an autoimmune disease characterized by autoantibody-mediated platelet destruction. Treatment with CM313, a novel anti-CD38 monoclonal antibody, can result in targeted clearance of CD38-positive cells, including plasma cells.

Methods: We conducted a phase 1-2, open-label study to evaluate the safety and efficacy of CM313 in adult patients with ITP. CM313 was administered intravenously at a dose of 16 mg per kilogram of body weight every week for 8 weeks, followed by a 16-week follow-up period. The primary outcomes were adverse events and documentation of two or more consecutive platelet counts of at least 50×10⁹ per liter within 8 weeks after the first dose of CM313. The status of peripheral-blood immune cells in patients and changes in the mononuclear phagocytic system in passive mouse models of ITP receiving anti-CD38 therapy were monitored.

Results: Of the 22 patients included in the study, 21 (95%) had two consecutive platelet counts of at least 50×10⁹ per liter during the treatment period, with a median cumulative response duration of 23 weeks (interquartile range, 17 to 24). The median time to the first platelet count of at least 50×10⁹ per liter was 1 week (range, 1 to 3). The most common adverse events that occurred during the study were infusion-related reaction (in 32% of the patients) and upper respiratory tract infection (in 32%). After CD38-targeted therapy, the percentage of CD56^dimCD16+ natural killer cells, the expression of CD32b on monocytes in peripheral blood, and the number of macrophages in the spleen of the passive mouse models of ITP all decreased.

Conclusions: In this study, anti-CD38 targeted therapy rapidly boosted platelet levels by inhibiting antibody-dependent cell-mediated cytotoxicity on platelets, maintained long-term efficacy by clearing plasma cells, and was associated with mainly low-grade toxic effects. (Funded by the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences and others; ClinicalTrials.gov number, NCT05694767).