Successful crystallographic structure-based drug-discovery (SBDD) support of early-stage pharmaceutical research programs requires the timely establishment of a robust crystallization system for the target protein. This enables structure determination of early high-throughput screening or fragment-screening hits, in turn maximizing the impact of SBDD on hit optimization. Here, a collection of complementary case studies are presented that demonstrate typical strategies to achieve this goal.

A surface-entropy reduction approach for human Polo-like kinase 1 (PLK1) enabled a reproducible and robust crystallization system for this cancer drug target. Co-crystal structures with representatives of three different small-molecule inhibitor classes were elucidated. For two of them, co-crystal structures with PLK1 were also determined via a previously published crystallization approach using a designed ankyrin-repeat protein (DARPin), and the two approaches are compared.