||Vandetanib is incubated with enzyme, 10 mM MnCl2, and 2 μM ATP in 96-well plates coated with a poly(Glu, Ala, Tyr) 6:3:1 random copolymer substrate. Phosphorylated tyrosine is then detected by sequential incubation with a mouse IgG anti-phosphotyrosine 4G10 antibody, a horseradish peroxidase-linked sheep antimouse immunoglobulin antibody, and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid). This methodology is adapted to examine selectivity versus tyrosine kinases associated with EGFR, PDGFRβ, Tie-2, FGFR1, c-kit, erbB2, IGF-1R, and FAK. All enzyme assays (tyrosine or serine-threonine) used appropriate ATP concentrations at or just below the respective Km (0.2–14 μM). Selectivity versus serine-threonine kinases (CDK2, AKT, and PDK1) is examined using a relevant scintillation proximity-assay (SPA) in 96-well plates. CDK2 assays contained 10 mM MnCl2, 4.5 μM ATP, 0.15 μCi of [γ-33 P]ATP/reaction, 50 mM HEPES (pH 7.5), 1 mM DTT, 0.1 mM sodium orthovanadate, 0.1 mM sodium fluoride, 10 mM sodium glycerophosphate, 1 mg/mL BSA fraction V, and a retinoblastoma substrate (part of the retinoblastoma gene, 792–928, expressed in a glutathione S-transferase expression system; 0.22 μM final concentration). Reactions are allowed to proceed at room temperature for 60 minutes before quenching for 2 hours with 150 μL of a solution containing EDTA (62 mM final concentration), 3 μg of a rabbit immunoglobulin anti-glutathione S-transferase antibody and protein A SPA-polyvinyltoluene beads (0.8 mg/reaction). Plates are then sealed, centrifuged (1200× g for 5 minutes), and counted on a Microplate scintillation counter for 30 seconds.