Switching Rates Lower With Zanubrutinib Versus Other BTK Inhibitors in CLL, SLL

A retrospective study presented at the Society of Hematologic Oncology 2024 Annual Meeting examined the real-world switching and sequencing of Bruton tyrosine kinase inhibitors (BTKis) in patients with chronic lymphocytic leukemia (CLL) or small lymphocytic lymphoma (SLL).

Patients initiating zanubrutinib, acalabrutinib, or ibrutinib as either first- or second-line therapy between January 1, 2020, and February 28, 2023, were included in the analysis. Using the Integra Connect PrecisionQ database, the researchers identified adult patients with at least one diagnosis of CLL or SLL who initiated treatment with a BTKi. To be included, patients had to be continuously enrolled for at least 30 days before and after the start of their BTKi treatment.

The primary outcomes were treatment switching and sequencing to the next line of therapy. Treatment switching was defined as initiation of another treatment within the same line or advancement to the next line of therapy within 90 days. Sequencing to the next line was measured with Kaplan-Meier curves, reporting the proportion of patients who required a next-line therapy at 180 days.

The study included 2,816 patients who started a BTKi as first-line therapy (zanubrutinib: 157; acalabrutinib: 1,238; ibrutinib: 1,421) and 1,253 patients who initiated a BTKi as second-line therapy (zanubrutinib: 107, acalabrutinib: 672, ibrutinib: 474). Baseline demographic and clinical characteristics were similar between groups. The median follow-up periods for the first-line therapy groups were 123 days for zanubrutinib, 406 days for acalabrutinib, and 637 days for ibrutinib.

Switching rates within 60 days were lower for patients treated with zanubrutinib compared with acalabrutinib and ibrutinib, in both first-line and second-line therapies. Specifically, in first-line therapy, the switching rates within 60 days were 10.2% for zanubrutinib, 17.1% for acalabrutinib, and 13.1% for ibrutinib. Similarly, the proportion of patients moving to the next line of therapy at 180 days was also lower for zanubrutinib compared with the other BTKis. In second-line therapy, 9.1% of zanubrutinib patients progressed to a new therapy by 180 days versus 18.6% for acalabrutinib and 29.9% for ibrutinib.

“Longer follow-up and larger zanubrutinib sample size are required for a comprehensive assessment of treatment outcomes associated with use of BTKis in CLL/SLL,” the researchers concluded.

Reference

Pinilla-Ibarz J, Xue M, Wu E, et al. Real-world treatment switching and sequencing to next line of therapy of zanubrutinib, acalabrutinib, and ibrutinib in chronic/small lymphocytic leukemia (CLL/SLL). Abstract #CLL-534. Presented at the Society of Hematologic Oncology 2024 Annual Meeting; September 4-7, 2024; Houston, Texas.