A recent study reported rapid and durable responses with oral Bruton’s tyrosine kinase (BTK) inhibitor, Rilzabrutirib, in pretreated patients with immune thrombocytopenia (ITP). The clinical study’s findings were recently published in The New England Journal of Medicine.
An enzyme called Bruton kinase is critical for the function of macrophages that are primarily responsible for destroying antibody-coated platelets in ITP. Oral rilzabrutinib is a new and promising Bruton kinase inhibitor that reduces macrophage activity without affecting platelet function. Its efficacy for ITP patients was evaluated by researchers from Harvard Medical School.
An international, open-label, phase1/2 clinical study enrolled 60 pre-treated ITP patients. The participants received an escalated dose of rilzabrutinib (200 mg once daily to 400 mg twice daily) over 24 weeks. The study’s primary endpoint was safety and platelet response.
After a median follow-up of 5.5 months post-treatment, 40% of patients overall (24/60) and 40% (18/45) treated with the highest dose of rilzabrutinib experienced significant platelet response. Patients developed healthy platelet count in a median time of 10.5 days. Also, the mean percentage of weeks with patients having a healthy platelet count was 65%.
Rilzabrutinib demonstrated a durable response with low-level toxic effects in ITP patients. Further, the study identified 400 mg as an optimal dose for further testing.