Pts commenced treatment with IB 560mg/d for 4 weeks, followed by weekly ramp-up of VEN to 400mg/d...For pts with TP53 aberrant MCL (n=12), the CRR was 50% (95% CI 21-79) with and without PET. In this group the ORR was 58% (95% CI 28-85) without PET and 50% (CI 21-79%) with PET. The DOR in 6 responders with TP53 aberrant MCL (excluding one pt with CRu) was 12+, 24+, 26+, 35+, 36+ and 38+ months from study commencement. In contrast, pts with ATM aberrant MCL (n=10) the CRR was 90% (95% CI 55-100) with and without PET, and the ORR was 90% (95% CI 55-100) with and without PET. Of the 9 responders with ATM aberrant MCL, the DOR was 9+, 9+, 12+, 24+, 31+, 35+, 36+, 37+ and 38+ months from study commencement.