A Novel Anti-CD20 Monoclonal Antibody for Treating Relapsed Immune Thrombocytopenia

Background and Objective: The anti-CD20 monoclonal antibody, such as rituximab, is a guideline-recommended reagent for refractory/relapsed immune thrombocytopenia (ITP) treatment. As a novel anti-CD20 monoclonal antibody developed in China, Ripertamab (chemical name) has the amino acid threonine replacing alanine at position 219 in the constant region, which is the most common sequence extracted from Chinese blood cells. It has lower immunogenicity and is more suitable for Chinese patients. Compared with rituximab, Ripertamab has demonstrated comparable efficacy and safety in patients with B-cell non-Hodgkin's lymphoma. However, there are currently no reports of Ripertamab in the treatment of relapsed ITP; therefore, the purpose of this study is to observe the efficacy and safety of this domestically produced novel anti-CD20 monoclonal antibody in the treatment of ITP.

Methods: From September 2022 to July 2024, relapsed ITP patients were enrolled and treated with Ripertamab (200 mg weekly for four consecutive weeks). The primary observation indicator is platelet response, and the secondary outcome is adverse reactions. Response criteria were: complete response (CR), platelet count ≥100 ×10⁹/L; partial response (PR), 30-99×10⁹/L, or at least double the baseline level, with no bleeding symptoms; no response (NR), platelet count <30×10⁹/L, less than double the baseline level, or bleeding symptoms present.

Results: The median follow-up was 5 months (1-23 months). 14 adult patients (6 males and 8 females; median age 38 [13-77] years old) were analyzed. Four patients (28.6%) had previously received treatment with two medications, while ten patients (71.4%) had been treated with three or more different medications, including immunoglobulins, all-trans retinoic acid (ATRA), cyclosporine, sirolimus, and thrombopoietin receptor agonists (TPO-RAs), etc. Before Ripertamab treatment, the average platelet count was 20×10⁹/L. The median time of initial response was 2 weeks (1-8 weeks), and the average platelet count reached 52×10⁹/L.

The median response duration was 3 months (range: 2-16 months). One month after the first Ripertamab dose, 11 responses (3 CR, 8 PR; ORR 78.6%) and 3 NR (21.4%) were recorded. Two months after the first dose, 12 responses (5 CR, 7 PR; ORR 85.7%) and 2 NR (14.3%) were observed, and the median platelet count reached 94×10⁹/L. During the follow-up period, a total of 4 patients relapsed, with three of them occurring in the third month after the initial treatment and one in the first month after the initial treatment. Adverse events included an infusion-related reaction (fever in 14.2% of patients) during the first dose and an upper respiratory tract infection (7.1%).

Conclusion: Ripertamab can effectively induce remission of relapsed ITP and demonstrate tolerable safety, although more data is required to verify this.

No relevant conflicts of interest to declare.