Novel hexahydropyrrolo[3,4-c]pyrrole CCR5 antagonists.

Starting with a high-throughput screening lead, a novel series of CCR5 antagonists was developed utilizing an information-based approach. Improvement of pharmacokinetic properties for the series was pursued by SAR exploration of the lead template. The synthesis, SAR and biological profiles of the series are described.

Spiropiperidine CCR5 antagonists.

A novel series of CCR5 antagonists has been identified, utilizing leads from high-throughput screening which were further modified based on insights from competitor molecules. Lead optimization was pursued by balancing opposing trends of metabolic stability and potency. Selective and potent analogs with good pharmacokinetic properties were successfully developed.

Transport of levovirin prodrugs in the human intestinal Caco-2 cell line.

The transport of 10 amino acid ester prodrugs of levovirin (LVV) was investigated in the human intestinal Caco-2 cell line in order to overcome the poor oral bioavailability of LVV, an investigational drug for the treatment of hepatitis C infection. The prodrugs were designed to improve the permeability of LVV across the intestinal epithelium by targeting the di/tri-peptide carrier, PepT1. Caco-2 cell monolayers were employed to study the transport and hydrolysis properties of the prodrugs. Among all mono amino acid ester prodrugs studied, the LVV-5'-(L)-valine prodrug (R1518) exhibited the maximum increase (48-fold) in permeability with nearly complete conversion to LVV within 1 h. Di-amino acid esters did not offer significant enhancement in permeability comparing with mono amino acid esters and exhibited slower conversion to LVV in Caco2 cell monolayers. Pharmacokinetic screening studies of the prodrugs in rats yielded the highest fold increase (6.9-fold) of AUC with R1518 and in general displayed a similar trend to that observed in increases of permeability in Caco-2 cells. Mechanisms involved in the Caco-2 cell transport of R1518 were also investigated. Results of bi-directional transport studies support the involvement of carrier-mediated transport mechanisms for R1518, but not for the LVV-5'-(D)-valine prodrug or LVV. Moreover, the permeability of R1518 was found to be proton dependent. PepT1-mediated transport of R1518 was supported by results of competitive transport studies of R1518 with the PepT1 substrates enalapril, Gly-Sar, valganciclovir, and cephalexin. R1518 was also found to inhibit the permeability of valganciclovir and cephalexin. These results suggest that R1518 is a PepT1 substrate as well as an inhibitor.

Single- and multiple-dose pharmacokinetics of levovirin valinate hydrochloride (R1518) in healthy volunteers.

R1518 is a valine ester prodrug of levovirin as an investigational new drug for the treatment of hepatitis C virus. Two phase 1, single- and multiple-dose studies were conducted to investigate the pharmacokinetics of R1518 in healthy volunteers. After oral dosing, R1518 was rapidly and exclusively converted to levovirin. Levovirin plasma concentrations peaked at 2 hours, with T(1/2) ranging from 6 to 8 hours. The T(1/2) of R1518 was less than 1 hour, with relative exposures (R1518/levovirin) less than 6%. A high-fat meal did not affect the pharmacokinetics. The female groups in both studies had higher plasma levels than males did due to age and renal function difference. An accumulation ratio of 1.3 to 1.5 was observed with the twice-daily regimen. About 75% to 90% of the levovirin equivalent dose was recovered in urine. Increase in exposure was slightly disproportionate to increase in dose. Significantly improved oral absorption of levovirin was achieved following administration of R1518.