Among patients with immune thrombocytopenia (ITP), orelabrutinib appears to be both a safe and effective treatment, according to research presented at the EHA 2023 Hybrid Congress.
A previous murine model suggested that orelabrutinib, an oral, selective, and irreversible inhibitor of Bruton’s tyrosine kinase, suppressed the activation and differentiation of B cells. Platelet counts were also increased in the model.
For this ongoing phase 2 study, researchers are assessing the safety and efficacy of orelabrutinib as a therapy among patients with persistent or chronic primary ITP. The study’s primary endpoint is the proportion of patients who reach at least 2 consecutive platelet counts of at least 50 x 109/L without rescue medication within a predefined timeframe.
By the data cutoff point of February 2023, 33 patients were randomly assigned to receive orelabrutinib 50 mg (15 patients) or 30 mg (18 patients). The mean patient age was 41.9 years overall, and 63.6% of patients were female. At baseline, the mean count was 13.4 x 109/L.
The median treatment time was 13.7 weeks; 12 patients in the 30 mg arm transferred to the 50 mg arm because of no primary response. Analysis showed that 36.4% of patients met the primary endpoint (22.2% in the 30 mg arm and 40% in the 50 mg arm); 2 patients reached the primary endpoint after transferring to the 50 mg arm. Nine (27.3%) patients had a durable response by the study’s predefined criteria.
Among patients who had received prior glucocorticoids or intravenous immunoglobulin, 75% in the 50 mg group reached the primary endpoint (28.6% in the 30 mg arm).
The median time to first platelet count at 50 x 109/L or higher was 9 days where the initial dose was 50 mg. All treatment-related events were grade 1 or 2.
The study’s presenter noted that both doses of orelabrutinib were safe, although the 50 mg dose led to rapid responses and generally had greater efficacy, particularly among those who had received prior glucocorticoids or intravenous immunoglobulin.
Shi Y, Zhou H, Huang R, et al. Orelabrutinib, an irreversible inhibitor of Bruton’s tyrosine kinase, for treatment of primary immune thrombocytopenia: results of a randomized, open-label phase II study. EHA 2023. June 8-11, 2023. Abstract S299.