Building in molecular diversity for targeted libraries.

The use of gene-focussed libraries for screening against protein targets can improve timelines for drug discovery projects. This is especially true when the library is based on a novel core scaffold, avoiding the potential need to scaffold hop from early hits. Identification of an appropriate novel scaffold is therefore integral to the success of such a library. In this article we outline a new method to aid scaffold design that combines structure- based virtual screening (VS) with a second phase in which fragmentation of the output is made before the final scaffold design step. Through consideration of a refined set of bound fragments, in the context of the compounds from which they originated, appropriate vectors for appended R-groups can be assigned before validation of the final library.

Discovery of selective and potent inhibitors of gram-positive bacterial thymidylate kinase (TMK).

Thymidylate kinase (TMK) is an essential enzyme in bacterial DNA synthesis. The deoxythymidine monophosphate (dTMP) substrate binding pocket was targeted in a rational-design, structure-supported effort, yielding a unique series of antibacterial agents showing a novel, induced-fit binding mode. Lead optimization, aided by X-ray crystallography, led to picomolar inhibitors of both Streptococcus pneumoniae and Staphylococcus aureus TMK. MICs < 1 µg/mL were achieved against methicillin-resistant S. aureus (MRSA), S. pneumoniae, and vancomycin-resistant Enterococcus (VRE). Log D adjustments yielded single diastereomers 14 (TK-666) and 46, showing a broad antibacterial spectrum against Gram-positive bacteria and excellent selectivity against the human thymidylate kinase ortholog.