The Discovery of Orally Bioavailable Tyrosine Threonine Kinase (TTK) Inhibitors: 3‑(4-(heterocyclyl)phenyl)‑1<i>H</i>‑indazole-5-carboxamides as Anticancer Agents
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Abstract
The
acetamido and carboxamido substituted 3-(1<i>H</i>-indazol-3-yl)benzenesulfonamides
are potent TTK inhibitors. However, they display modest ability to
attenuate cancer cell growth; their physicochemical properties, and
attendant pharmacokinetic parameters, are not drug-like. By eliminating
the polar 3-sulfonamide group and grafting a heterocycle at the 4
position of the phenyl ring, potent inhibitors with oral exposure
were obtained. An X-ray cocrystal structure and a refined binding
model allowed for a structure guided approach. Systematic optimization
resulted in novel TTK inhibitors, namely 3-(4-(heterocyclyl)phenyl)-1<i>H</i>-indazole-5-carboxamides. Compounds incorporating the 3-hydroxy-8-azabicyclo[3.2.1]octan-8-yl
bicyclic system were potent (TTK IC<sub>50</sub> < 10 nM, HCT116
GI<sub>50</sub> < 0.1 μM), displayed low off-target activity
(>500×), and microsomal stability (<i>T</i><sub>1/2</sub> > 30 min). A subset was tested in rodent PK and mouse
xenograft models of human cancer. Compound <b>75</b> (CFI-401870)
recapitulated the phenotype of TTK RNAi, demonstrated in vivo tumor
growth inhibition upon oral dosing, and was selected for preclinical
evaluation