Acalabrutinib Plus Bendamustine-Rituximab in Untreated Mantle Cell Lymphoma

BACKGROUND: The combination of the Bruton tyrosine kinase inhibitor ibrutinib with bendamustine-rituximab for first-line treatment of mantle cell lymphoma (MCL) prolonged progression-free survival, but without improvement to overall survival likely due to toxicity. Acalabrutinib was shown to be efficacious and less toxic than ibrutinib in a head-to-head trial in chronic lymphocytic leukemia and therefore might lead to better outcomes in MCL. METHODS: Patients aged ≥65 years with previously untreated mantle cell lymphoma received acalabrutinib (100 mg twice daily) or placebo (until disease progression or unacceptable toxicity), plus 6 cycles of bendamustine (90 mg/m²; days 1 and 2) and rituximab (375 mg/m²; day 1) followed by rituximab maintenance in responding patients for 2 years. Crossover to acalabrutinib at disease progression was permitted. Primary endpoint was progression-free survival per independent review committee; overall response rate and overall survival were secondary endpoints. RESULTS: In total, 598 patients were randomized, with 299 in each arm. At a median followup of 44.9 months, median progression-free survival was 66.4 months in the acalabrutinib arm and 49.6 months in the placebo arm (hazard ratio, 0.73; 95% confidence interval, 0.57 to 0.94; P = .0160). Benefit was seen across all subgroups, including those with high-risk features. Overall response/complete response rates were 91.0%/66.6% and 88.0%/53.5% in the acalabrutinib and placebo arms, respectively. Overall survival was not significantly different (hazard ratio, 0.86; 95% confidence interval, 0.65 to 1.13; P = .27). Grade 3 or greater adverse events were reported in 88.9% and 88.2% in the acalabrutinib and placebo arms, respectively. CONCLUSIONS: Combination of acalabrutinib with bendamustine-rituximab significantly improved progression-free survival. Clinical benefit of acalabrutinib with bendamustine-rituximab was achieved with manageable toxicity.