CH5424802

This molecule is a potent, selective and orally bioavailable. It is highly selective (1.9 nM biochemical assay; 2.4 nM Kd) against target, with only 2 other kinases showing >50% inhibition at 10 uM (out of a panel of 402). Extensive cell-based data, target engagement, and downstream-marker level changes have been recorded. This molecule has been designed for greater selectivity and to overcome resistance mutations. As such, care should be taken when using as probe in checking the relevance of the mutated ALK form being studied. The original publication contains convincing data including protein-drug co-crystal structure. PK data included in mice: half-life (8.6 hr), oral bioavailability (70.8%). ED50 = 0.46 mg/kg in NCI-H2228 model using once daily, oral delivery.

CH5424802 (alectinib) is a second generation ALK inhibitor. The compound inhibits the ALK gate-keeper mutation L1196M, one of the commonly seen secondary mutations leading to resistance to crizotibib, with an IC₅₀ of 1.5 nM. 

This is an ATP-competitive inhibitor of ALK kinase with IC50=1.9nM and KD=2.4 nM. It is active on the wild-type protein and the L1196M gatekeeper mutant that confers resistance to other inhibitors. The compound binds with one H-bond (crystal structure) to the kinase hinge region (as opposed to two or three found with other inhibitors), which might explain its selectivity. The inhibitor was selective in a small panel of 24 kinases and in the Ambit panel with 402 kinases. Only GAK and TLK were inhibited as well (window of ca. 5). The compound is active in NSCLC- and other tumor cell lines expressing the EML4-ALK fusion oncogene but not in ALK-fusion-negative cells. The inhibitor induces tumor regression in mouse tumor cell xenografts expressing native EML4-ALK or the L1196M gatekeeper mutation. This molecule is recommended for isolated enzyme, cell, 3D-cell spheroid and animal work for the specific ALK mutant described (ALK L1196M). There is a convincing package of on- and off-target selectivity, cell, biophysical and mouse data. Multiple lines of evidence demonstrate direct inhibition of the enzyme (biochemical, competition experiments, biophysical and X-ray) and exceptional selectivity for this ATP-competitive kinase inhibitor (only 3 kinases - ALK, GAK, LTK are inhibited >50% at 10 nM across a 402 kinase panel). Extended exposure results from a single dose in mice (high 70% oral bioavailability with 8.6 h half life).