Bendamustine and Rituximab Plus Venetoclax in Untreated Mantle Cell Lymphoma over 60 Years of Age (PrE0405): A Phase II Study

Background:

Mantle Cell Lymphoma (MCL) is an aggressive form of Non Hodgkin Lymphoma (NHL) and typically presents in patients over the age of 60 years. Bendamustine and rituximab (BR) combination is one of the standard treatments for MCL and is given to patients for whom high dose chemotherapy with autologous stem cell rescue is planned in the first remission. Progression free survival (PFS) with BR is approximately 36 months (Rummel M Lancet 2013; Flinn IW Blood 2014) and the regimen is overall well tolerated.

Venetoclax (VEN) is an orally available inhibitor of BCL2, an anti-apoptotic protein highly expressed in several NHL. Single agent activity has mostly been studied in a Phase I study (in various NHL histologies) where 28 MCL patients were enrolled. Overall response rate was 75% (21 of 28) but complete response (CR) rate was only 21% (6 of 28). Tumor lysis syndrome (TLS) has been associated with VEN and initial dosing requires a ramp up period (Davids MS JCO 2018). VEN has also been combined with other agents in MCL with promising activity (Tam CS NEJM 2018)

VEN has been studied as a chemotherapy sensitizer and has shown pre-clinical synergy with chemotherapy. In Follicular lymphoma, BR+VEN was studied at 800mg PO continuous daily dosing and showed an excessive Grade 3-4 adverse event (AE) rate of 78% compared to historical studies of 46% (Zinzani ASH 2016). We hypothesize that, in MCL, VEN can be safely combined with BR at a lower dose and intermittent dosing with improvements to the response rate based on historical controls and maintain a better safety profile.

Study Design:

This Phase II single arm, multicenter study evaluates VEN at a max dose of 400mg with BR (Bendamustine 90mg/m2 IV day 1 and 2; rituximab 375mg/m2 IV or SQ equivalent day 1) for six 28-day cycles in untreated patients with MCL over the age of 60 years (NCT03834688). Cycle 1 will include a VEN dose titration over the 4 week course (20mg D1-7, 50mg D8-14, 100mg D15-21, and 200mg D22-28). For Cycles 2-6, VEN will be given at 400mg daily x 10 days starting with day 1. Participants are followed for 6 cycles, though will be followed for progression and survival afterward. Participants may receive maintenance rituximab at investigator's discretion.

Eligible participants, age 60 years or older, must have biopsy proven untreated MCL with t(11;14) or cyclin D1 expression, though a short course of steroids is allowed for symptomatic MCL. They must have adequate organ function and not require any prohibited concomitant medications.

Primary outcome is CR rate as assessed by the Lugano criteria. We estimate a historical CR rate of BR after induction of about 70%. A 15% increase in this rate, to 85% CR, is considered promising for the combination. To achieve this goal, the study will enroll 56 participants (53 eligible) to achieve a 90% power to detect the difference with a 10% Type I error rate. We will also evaluate PFS and overall survival. TLS is an AE of interest and will be evaluated after 19 participants have been enrolled and treated during cycle 1.

Minimal residual disease (MRD) will be assessed throughout the study. MRD from peripheral blood will be compared to bone marrow aspirates in all participants undergoing bone marrow aspirate at the end of treatment. Tumor samples at screening and progression will be collected for future study.

This study is conducted through PrECOG and is funded by Genentech, a member of the Roche Group. Venetoclax is co-developed by Genentech and AbbVie. The study is slated to open in Fall of 2019 at 10 US sites.

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