Zanubrutinib is well tolerated and effective in CLL/SLL patients intolerant of ibrutinib/acalabrutinib: Updated results

• Only 40% of intolerance AEs in Cohort 1 (ibrutinib intolerance) and 28% in Cohort 2 (acalabrutinib intolerance) recurred with zanubrutinib

• After switching to zanubrutinib, 71% of patients in Cohort 1 and 63% in Cohort 2 maintained or had improved clinical benefit from treatment

Bruton tyrosine kinase (BTK) inhibitors such as ibrutinib revolutionized chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) treatment, although treatment-related toxicities limit the use of some BTK inhibitors. Zanubrutinib, a potent next-generation BTK inhibitor, has higher selectivity than ibrutinib or acalabrutinib. The ongoing phase 2, single-arm BGB-3111-215 study investigates the safety and efficacy of zanubrutinib in patients with B-cell malignancies who are intolerant of ibrutinib and/or acalabrutinib. Here, results in patients with CLL/SLL are presented. Patients received zanubrutinib 160 mg BID or 320 mg QD. With a 34.5-month median follow-up, 71 patients (ibrutinib intolerant only, n=44; acalabrutinib intolerant only, n=17; ibrutinib and acalabrutinib intolerant, n=10) received ≥1 zanubrutinib dose. On zanubrutinib, 54% (28/52) of ibrutinib-intolerant patients and 70% (19/27) of acalabrutinib-intolerant patients experienced no recurrence of intolerance AEs; 60% and 72% of intolerance AEs did not recur, respectively. Of recurrent ibrutinib-intolerance AEs, 64% were lower grade; 44% of acalabrutinib-intolerance AEs were lower grade. No intolerance AEs recurred at a higher grade with zanubrutinib. The most common recurrent ibrutinib-intolerance and acalabrutinib-intolerance AEs were fatigue and diarrhea, respectively. The most common TEAEs with zanubrutinib were fatigue (32%), COVID-19 (28%), and diarrhea and contusion (each 24%). Grade ≥3 TEAEs occurred in 61%, serious TEAEs in 32%, and TEAEs leading to discontinuation in 11%. Of 67 efficacy-evaluable patients, 94% experienced disease control: 30% had a best response of stable disease and 64% had a partial or complete response. These data demonstrate that patients intolerant of ibrutinib/acalabrutinib may benefit from switching to zanubrutinib therapy. ClinicalTrials.gov: NCT04116437.