Ibrutinib in Advanced Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma: Lower Risk of Hepatitis B Virus Reactivation

Introduction: Therapy of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) with drugs such as ibrutinib and rituximab is often associated with immune suppression, opportunistic infections, and reactivation of virus infections such as hepatitis B virus (HBV). This risk is especially important in geographical regions like Asia where many potential therapy recipients have HBV infection. Also, whether safety and efficacy of ibrutinib in Asians and Europeans with advanced CLL/SLL are similar is unknown. We determined the safety and efficacy of ibrutinib compared with rituximab in advanced CLL/SLL including persons with HBV infection. We compared outcomes with data published from trials in persons of European descent. Methods: This is a post hoc analysis of a multicenter, phase-3 trial (NCT01973387). Subjects with advanced CLL/SLL were randomized 2:1 to receive ibrutinib, 420 mg/day, or rituximab, 500 mg/mE + 2, for 6 cycles. Subjects with resolved HBV infection were included. Endpoints were progression-free survival (PFS), overall response rate (ORR), survival, and adverse events including resolved HBV reactivation. Results: 131 subjects received ibrutinib (N = 87) or rituximab (N = 44) including 53 with resolved HBV infection. Median follow-up was 31 months (95% confidence interval: 28, 32 months). ORR was 61% (50, 71%) versus 7% (2, 18%; p < 0.001). Median PFS was not reached in the ibrutinib cohort but must be >40 months versus 8 months (7, 9 months; p < 0.0001) in the rituximab cohort. Median survival was not reached but must be >40 months versus 27 months (17 months, NE; p = 0.0006). In multivariable analyses, receiving ibrutinib increased PFS (hazard rate [HR] for failure = 0.12 [0.06, 0.23]; p < 0.001) and decreased risk of death (HR = 0.31 [0.15, 0.63]; p < 0.001). Median duration of exposure to ibrutinib was significantly longer than exposure to rituximab (28 vs. 5 months). The safety profile of ibrutinib was consistent with that observed in previous studies with no new safety signal. No subject receiving ibrutinib had HBV reactivation versus 2 receiving rituximab, despite much greater use of drugs to prevent HBV reactivation in the rituximab cohort. Outcomes were like those reported in persons of European descent, except ORR which, was unreliably correlated with PFS in Asians. Conclusion: Ibrutinib is safe and effective in persons with advanced CLL/SLL and better than rituximab in all therapy outcomes including risk of HBV reactivation. Outcomes with ibrutinib in Chinese were like those reported in persons of predominately European descent.