Discovery of highly selective and orally available benzimidazole-based phosphodiesterase 10 inhibitors with improved solubility and pharmacokinetic properties for treatment of pulmonary arterial hypertension

Optimization efforts were devoted to discover novel PDE10 A inhibitors in order to improve solubility and pharmacokinetics properties for a long-term therapy against pulmonary arterial hypertension(PAH)starting from the previously synthesized inhibitor A.As a result,a potent and highly selective PDE10 A inhibitor,14·3 HC1(half maximal inhibitory concentration,IC50=2.8 nmol/L and>3500-fold selectivity)exhibiting desirable solubility and metabolic stability with a remarkable bioavailability of50%was identified with the aid of efficient methods of binding free energy predictions.Animal PAH studies showed that the improvement offered by 14·3 HCl[2.5 mg/kg,oral administration(p.o.)]was comparable to tadalafil(5.0 mg/kg,p.o.),verifying the feasibility of PDE10 A inhibitors for the antiPAH treatment.The crystal structure of the PDE10 A-14 complex illustrates their binding pattern,which provided a guideline for rational design of highly selective PDE10 A inhibitors.