The compound activated apoptosis in CLL and MCL patient samples and induced tumor regression in xenograft models at a comparable level to venetoclax.336 In marked contrast to venetoclax, S55746 binds via a different binding mode and mainly occupies pockets P1, P2 and P3 but not P4 of BCL2 (Fig. 5c). This evidence concerns the gene BCL2 and mantle cell lymphoma.