PB0702 - Real-World Use of Daratumumab for Children Refractory Chronic Immune Thrombocytopenia

Background: Refractroy chronic immune thrombocytopenia (RCITP) defined as refractory to multiple therapeutic, faced with the the bleeding and required treatment. Daratumumab, an anti-CD38 monoclonal antibody has demonstrated targeted depletion of CD38-positive cells, including plasma cells secreting antibodies in ITP.

Aims: The purpose of this study was to investigate the effect of the daratumumab of RCITP in children．

Methods: Daratumumab initially dosed at 16 mg/kg once a week for 4 or 5 weeks, accompanied by methylprednisolone 1 mg/kg . In order to avoid severe infection, IVIG 200 mg/kg was given monthly for 6 months.

Results: we report retrospectively a case-series the use of daratumumab for RCITP children at our center, with at least 23 weeks of follow-up. The 3 patients consisted of 2 males and 1 females, with a median age of 7 ((5-12) years, a median duration of ITP of 4 (1.4-9) years,a median baseline platelet count of 6( 4-9)×10 9/L, and the bleeding score were above level 2. All the three patients had previously accepted at least one more third-line therapy such as cyclosporine, vincristine and mycophenolate. We eventually selected the CD38 antibody daratumumab via compassionate use access. Patient 1 was treated with 5 doses of daratumumab, while the others were 4 doses. Three patients were treated with TPO-RAs simultaneously. The median time to response was 2 (1-6) weeks. The median follow-up time is 23 (28-41) weeks, and the time of complete response was 9 (8-18) weeks. The bleeding symptoms of all 3 were reduced, with bleeding score of 0-1. All the three patients had a grade 1or 2 infusion-related reaction (IRR) including rash and mild abdominal pain at the first dose but none at subsequent doses. There have been no serious infections have occurred up to now.

Conclusion(s): Daratumumab can be a safe and efficacious therapy for children with RCITP .