Autoimmune Cytopenias

At the 63rd annual meeting of the American Society of Hematology, an international multicenter team of investigators reported updated results of a phase 1/2 study of the oral Bruton tyrosine kinase (BTK) inhibitor rilzabrutinib in the setting of relapsed/refractory (R/R) immune thrombocytopenia (ITP), in which durable response to therapies remains a clinical challenge. Rilzabrutinib is the first oral, reversible, covalent BTK inhibitor that can target immune-mediated pathways in ITP without inhibiting normal aggregation of platelets. As of June 1, 2021, among 60 enrolled patients, 45 initiated rilzabrutinib at 400 mg bid and to date, 16 patients with durable, stable response proceeded to LTE at 400 mg bid, the researchers reported. Overall, 18 of the 45 LTE patients (40%) achieved the primary endpoint. All 18 maintained platelet counts of ≥30×10⁹/L, ≥30×10⁹/L with ≥20×10⁹/L above baseline, and ≥50×10⁹/L, for a median of 100%, 96%, and 90% of weeks, respectively, during the LTE period. The magnitude and durability of rilzabrutinib’s clinical benefit in ITP will be assessed further in the ongoing randomized phase III LUNA3 trial, the investigators said.