Dr. Coombs on the Efficacy Results of the BRUIN Study With Pirtobrutinib in CLL

Catherine Callaghan Coombs, MD, assistant professor of medicine, Division of Hematology, University of North Carolina (UNC) School of Medicine, UNC Lineberger Comprehensive Cancer Center, discusses the efficacy results of the ongoing phase 1/2 BRUIN study (NCT03740529) with pirtobrutinib (LOXO-305) in chronic lymphocytic leukemia (CLL).

The BRUIN study evaluated the clinical efficacy and safety of pirtobrutinib, a next-generation, highly selective, non-covalent BTK inhibitor, in patients with previously treated B-cell malignancies. During the 2021 SOHO Annual Meeting, findings from the CLL/small lymphocytic lymphoma (SLL) cohort of the BRUIN study were presented virtually.

The efficacy results demonstrated an overall response rate (ORR) of 63% in patients with CLL/SLL and 62% in patients with BTK inhibitor–exposed CLL/SLL, Coombs says. As such, the ORR did not appear to be affected by prior BTK inhibitor treatment nor reasons for discontinuation of prior BTK inhibitor treatment, such as progression or intolerance.

Additionally, the results showed that responses to pirtobrutinib deepened over time, Coombs explains. The median time on therapy was 6 months; however, patients who remained on pirtobrutinib for more than 10 months achieved an ORR of over 80%, Coombs says.

Finally, only 5 responding patients discontinued treatment. Four of these patients had progressive disease, and 1 patient electively discontinued pirtobrutinib to undergo transplant. Additionally, 1.5% of patients (n = 5) discontinued treatment because of treatment-related adverse effects, Coombs concludes.