Evaluation of a non-nucleoside inhibitor of the RSV RNA-dependent RNA polymerase in translatable animals models.

Respiratory Syncytial Virus (RSV) causes severe respiratory infections and concomitant disease resulting in significant morbidity and mortality in infants, elderly, and immunocompromised adults. Vaccines, monoclonal antibodies, and small-molecule antivirals are now either available or in development to prevent and treat RSV infections. Although rodent and non-rodent preclinical animal models have been used to evaluate these emerging agents, there is still a need to improve our understanding of the pharmacokinetic (PK)-pharmacodynamic (PD) relationships within and between animal models to enable better design of human challenge studies and clinical trials.

Discovery of GS-7682, a Novel 4'-Cyano-Modified -Nucleoside Prodrug with Broad Activity against Pneumo- and Picornaviruses and Efficacy in RSV-Infected African Green Monkeys.

Acute respiratory viral infections, such as pneumovirus and respiratory picornavirus infections, exacerbate disease in COPD and asthma patients. A research program targeting respiratory syncytial virus (RSV) led to the discovery of GS-7682 (), a novel phosphoramidate prodrug of a 4'-CN-4-aza-7,9-dideazaadenosine -nucleoside GS-646089 () with broad antiviral activity against RSV (EC = 3-46 nM), human metapneumovirus (EC = 210 nM), human rhinovirus (EC = 54-61 nM), and enterovirus (EC = 83-90 nM). Prodrug optimization for cellular potency and lung cell metabolism identified 5'-methyl [()-hydroxy(phenoxy)phosphoryl]-l-alaninate in combination with 2',3'-diisobutyrate promoieties as being optimal for high levels of intracellular triphosphate formation and .