Discovery and SAR of a novel series of Natriuretic Peptide Receptor-A (NPR-A) agonists.

Novel thienopyrimidine compounds 2 and 3 were discovered from high-throughput screening as Natriuretic Peptide Receptor A (NPR-A) agonists. Scaffold hopping of a thienopyrimidine ring to a quinazoline ring, introduction of the basic functional group and optimization of the substituent on the 6-position of the benzene ring of quinazoline led to improved agonistic activity. We discovered compound 48, which showed potent agonistic activity for NPR-A with an EC50 value of 0.073µM, indicating 350-fold potency compared to the hit compound 3.

Discovery and dimeric approach of novel Natriuretic Peptide Receptor A (NPR-A) agonists.

Novel agonists of the Natriuretic Peptide Receptor A (NPR-A) were obtained through random screening and subsequent structural modification of triazine derivatives. The key structural feature to improve in vitro activity was the dimerization of triazine monomer derivatives. The non peptide derivative 7c and 13a showed highly potent NPR-A agonistic activity in vitro and diuretic activity in vivo. These results implied that non-peptidic small molecules open the possibility of new therapy for congestive heart failure.

Discovery and in vivo effects of novel human natriuretic peptide receptor A (NPR-A) agonists with improved activity for rat NPR-A.

Natriuretic peptide receptor A (NPR-A) agonists were evaluated in vivo by optimizing the structure of quinazoline derivatives to improve agonistic activity for rat NPR-A. A 1,4-Cis-aminocyclohexylurea moiety at 4-position and hydroxy group of d-alaninol at 2-position on the quinazoline ring were found to be important factors in improving rat NPR-A activity. We identified potent quinazoline and pyrido[2,3-d]pyrimidine derivatives against rat NPR-A, with double-digit nanomolar EC50 values. The in vivo results showed that compound 56b administered at 1.0 mg/kg/min significantly increased plasma cGMP concentration and urine volume in rats. We discovered novel potent NPR-A agonists that showed agonistic effects similar to those of atrial natriuretic peptide.

2-Aminoalkyl nicotinamide derivatives as pure inverse agonists of the ghrelin receptor.

New inverse agonists of the ghrelin receptor (ghrelinR) were obtained through high-throughput screening and subsequent structural modification of 2-aminoalkyl nicotinamide derivatives. The key structural feature to improve in vitro activity was the introduction of a diazabicyclo ring at the 5-position of the pyridine ring. The final product showed potent inverse agonist activity and, despite its low brain permeability, reduced food intake in both normal and obese mice. These results implied that peripheral ghrelinR activity is important for appetite control and that a peripheral ghrelinR inverse agonist could be an anti-obesity drug with reduced risk of central nervous system (CNS)-related side effects.

Orally active ghrelin receptor inverse agonists and their actions on a rat obesity model.

A series of 2-alkylamino nicotinamide analogs was prepared as orally active ghrelin receptor (ghrelinR) inverse agonists. Starting from compound 1, oral bioavailability was improved by modifying metabolically unstable sites and reducing molecular weight. Brain-permeable compound 33 and compound 24 with low brain permeability were tested in rat models of obesity; 30 mg/kg of compound 33 suppressed weight gain. PK/PD analysis revealed that the anti-obesity effect of ghrelinR inverse agonists depends on their brain concentrations.