The AIM study is a Phase II study of venetoclax (ABT-199) in combination with ibrutinib in the treatment of patients with relapsed or refractory mantle cell lymphoma (MCL). The trial tests the effects of the combination of the two newly developed drugs, and is one of the first trials worldwide to study the combination together (NCT02471391). The study has two Phases: first is the Primary Evaluation Phase, which closely monitors the effects of ibrutinib and ABT-199. Patients who complete the full 13 months of treatment and continue benefiting from the trial are then allowed to progress into the Continuation Phase, where patients are given access to use of both ibrutinib and ABT-199. AIM recruited 24 participants over the age of 18, with a confirmed diagnosis of MCL according to WHO (2008), and have received at least one prior line of systemic therapy for MCL. The subject must also have an Eastern Cooperative Oncology Group (ECOG) performance score equal or less than 2, with adequate bone marrow, coagulation, renal and hepatic function at screening.