GW873140 is a CCR5 antagonist that is in Phase I clinical development as a viral entry inhibitor for the treatment of HIV infection. GW873140 has demonstrated in vitro antiviral activity with an IC50 against CCR5-tropic HIV-1 of 1nM equals about 0.5ng/mL), that is shifted 8-10 fold (10nM equals about 0.5ng/mL) in the presence of physiological concentrations of human plasma proteins. A study to investigate the safety, tolerability, and pharmacokinetics of escalating single (50-1200mg) and repeat (200-800mg BID) doses of GW873140 has been conducted in 70 healthy volunteers (GW873140/001). Preliminary results indicate that GW873140 is well-tolerated up to a dose of 1200 mg following single dose and 800 mg BID following multiple-dose. Additionally, food was shown to increase the AUC and Cmax of a 400 mg single dose by 1.7-and 2.2-fold, respectively.