Protein kinases are linked to numerous disease states, including cancer, arthritis, diabetes, cardiovascular diseases and neurological disorders. Gleevec from Novartis was the first compound active against a kinase (the Abl kinase) to be approved as a treatment — for certain gastrointestinal tumours and chronic myeloid leukaemia.

R&D Systems' Phospho-MAPK array tracks phosphorylated kinases. Credit: R&D SYSTEMS

The market for kinases is large. “More than 25% of new drugs being developed today are based on kinase technology,” says Jeff Linton, president of Upstate of Charlottesville, Virginia, which offers one of the largest collections of kinases. A flagship of Upstate's operation is its KinaseProfiler service, run from Dundee in Scotland. This provides quantitative characterization of compounds against an ever-expanding panel of human protein kinases in a direct radiometric assay. The panel currently contains around 230 kinases, almost 50% of the total number of human kinases in the genome. A new focus for Upstate is the addition of naturally occurring mutant kinases as they are identified.

Attention is also focusing on the newly emerging Gleevec-resistant mutants of Abl, and mutant forms of other kinases including the epithelial growth factor (EGF) receptor, as these mutations can alter an inhibitor's efficacy. One of these mutations involves a single ‘gatekeeper’ amino acid. Mutations in this amino acid can prevent therapeutic compounds from binding effectively without affecting the enzyme's activity. “The search is on for successful inhibitors that are not sensitive to changes at the gatekeeper site,” says Steve Davies, director of Upstate's drug discovery segment.

Upstate is helping this search by adding eight different mutant kinases to their portfolio, including ones for Kit, EGFR, Abl, Flt3 and p38/SAPK2a — and, says Davies, there are more in the pipeline.

A highly specific set of anti-kinase antibodies makes up R&D Systems' Proteome Profiler Phospho-MAPK Array. This allows analysis of the phosphorylation status of 19 key signalling proteins, including members of all three major families of mitogen-activated protein kinases — the extracellular signal-regulated kinases, c-Jun N-terminal kinases, and the p38 kinases. These enzymes play essential roles in numerous signalling pathways that underlie cell function and disease.

Signalling pathway analysis products from Beckman Coulter of Fullerton, California, are also devoted to looking at intracellular activated (phosphorylated) kinases. One strength is that these reagents can be used on many different types of specimen including whole blood, and can resolve activated and inactivated kinases in whole blood cells, according to Michel Herbert, marketing manager for Beckman Coulter.

P.M.