Discovery, Structure-Activity Relationship, and Biological Characterization of a Novel Series of 6-((1 H-Pyrazolo[4,3- b]pyridin-3-yl)amino)-benzo[ d]isothiazole-3-carboxamides as Positive Allosteric Modulators of the Metabotropic Glutamate Receptor 4 (mGlu 4 ).

This work describes the discovery and characterization of novel 6-(1 H-pyrazolo[4,3- b]pyridin-3-yl)amino-benzo[ d]isothiazole-3-carboxamides as mGlu ₄ PAMs. This scaffold provides improved metabolic clearance and CYP1A2 profiles compared to previously discovered mGlu ₄ PAMs. From this work, 27o (VU6001376) was identified as a potent (EC ₅₀ = 50.1 nM, 50.5% GluMax) and selective mGlu ₄ PAM with an excellent rat DMPK profile ( in vivo rat CL _p = 3.1 mL/min/kg, t _1/2 = 445 min, CYP1A2 IC ₅₀ > 30 μM). Compound 27o was also active in reversing haloperidol induced catalepsy in a rodent preclinical model of Parkinson's disease.