The MCL elderly III trial protocol: an international, randomized, open-label phase II trial to investigate the combinations of venetoclax, ibrutinib and rituximab or bendamustine, ibrutinib and rituximab in patients with treatment naive mantle cell lymphoma not eligible for dose-intensive treatment

Background: Mantle cell lymphoma (MCL) is a rare B-cell Non-Hodgkin-lymphoma that predominantly affects elderly patients. While younger and fit patients receive an intensive first-line treatment, older or comorbid patients have limited options of chemo-immunotherapy (CIT) alone followed by anti-CD20-antibody maintenance. Targeted oral agents as Bruton`s tyrosine kinase inhibitors (BTKi, e.g. ibrutinib) - and B-cell lymphoma 2 (Bcl2) – inhibitors (e.g. venetoclax) have revolutionized the treatment especially for relapsed patients, with apparent synergistic effects. The MCL elderly III trial of the European MCL Network is an international phase II trial evaluating the efficacy of the combination of ibrutinib, venetoclax and rituximab as well as the CIT bendamustine and rituximab in combination with ibrutinib in elderly patients with untreated MCL. Methods: The primary trial objective is to evaluate efficacy in both treatment arms as measured by failure-free survival at 30 months separately in both treatment arms. Secondary endpoints include progression-free survival, response rates, overall survival, adverse events as well as quality of life and impact of frailty and sarcopenia on treatment outcome through geriatric and body composition assessments via imaging. Exploratory endpoints comprise the rate of minimal residual disease negativity and kinetics of immune reconstitution. Current status: The first patient was included in May 2023, with full site activation achieved in Q1 2025. Until May 15th 2025, 75 of 150 planned patients were enrolled in 27 German and Italian trial sites. Discussion: This is the first randomized trial to exploratively compare a BTKi-Bcl2i-anti-CD20 triplet to a BTK-CIT combination in older MCL patients. Trial registration: The trial is registered on EU Clinical Trial Register (20225018089600).