Bruton's Tyrosine Kinase Inhibition for Patients with ITP

The pathophysiology of immune thrombocytopenia (ITP) includes peripheral platelet destruction as well as impaired platelet production. The list of available options to treat ITP continues to expand based on a better understanding of the pathophysiology of this condition. Despite increasing therapeutic options, some patients have multiple relapses or refractory disease. One potential treatment target includes inhibition of Bruton's tyrosine kinase (BTK), which can result in a decrease in autoantibody production as well as reduction in macrophage-induced phagocytosis in the spleen and liver. Here, investigators conducted an industry-sponsored, dose-finding, phase 1–2 study to evaluate the safety and efficacy of the BTK inhibitor rilzabrutinib.

Key findings include:

• The 60 study participants had a median age of 50 years (57% female) and a median baseline platelet count of 15×10⁹/L.
• Participants had ITP for a median of 6.3 years and had received a median of four prior therapies.
• Platelet response, defined as at least two consecutive platelet counts of at least 50×10⁹/L, was noted in 40% of patients.
• While 52% of patients experienced treatment-associated adverse events, all events were grade 1 or 2; the most common included diarrhea (32%) and fatigue (10%).
• Based on safety and efficacy, a dose of 400 mg twice daily was suggested for further testing.