Protein–protein interactions (PPIs) are ubiquitous in cellular signalling mechanisms, and provide a rich source of potential targets for drug discovery.1 Aberrant PPIs have prompted the discovery of PPI inhibitors including small molecules, peptides and peptidomimetics.2 A recent success is the BCL‐2 inhibitor venetoclax (ABT‐199),3 which was discovered using a fragment‐based discovery approach, and is now used clinically to treat chronic lymphocytic leukaemia and small lymphocytic lymphoma. Here, BCL2 is linked to B-cell chronic lymphocytic leukemia.