Structure-based design of nitrogen-linked macrocyclic kinase inhibitors leading to the clinical candidate SB1317/TG02, a potent inhibitor of cyclin dependant kinases (CDKs), Janus kinase 2 (JAK2), and Fms-like tyrosine kinase-3 (FLT3)

A high-throughput screen against Aurora A kinase revealed several promising submicromolar pyrimidine-aniline leads. The bioactive conformation found by docking these leads into the Aurora A ATP-binding site had a semicircular shape. Macrocycle formation was proposed to achieve novelty and selectivity via ring-closing metathesis of a diene precursor. The nature of the optimal linker and its size was directed by docking. In a kinase panel screen, selected macrocycles were active on other kinase targets, mainly FLT3, JAK2, and CDKs. These compounds then became leads in a CDK/FLT3/JAK2 inhibitor project. Macrocycles with a basic nitrogen in the linker form a salt bridge with Asp86 in CDK2 and Asp698 in FLT3. Interaction with this residue explains the observed selectivity. The Asp86 residue is conserved in most CDKs, resulting in potent pan-CDK inhibition by these compounds. Optimized macrocycles generally have good DMPK properties, and are efficacious in mouse models of cancer. Compound 5 (SB1317/TG02), a pan-CDK/FLT3/JAK2 inhibitor, was selected for preclinical development, and is now in phase 1 clinical trials. Figure Structure of SB1317 (left). SB1317 docked into CDK2 (right)