2-Bromo-5,6-dichloro-1-(-D-ribofuranosyl)benzimidazole (BDCRB) is a potent and selective inhibitor of human cytomegalovirus (HCMV), but it lacks clinical utility due to rapid in vivo metabolism. We hypothesized that amino acid ester prodrugs of BDCRB may enhance both in vitro potency and systemic exposure of BDCRB through evasion of BDCRB-metabolizing enzymes. To this end, eight different amino acid prodrugs of BDCRB were tested for N-glycosidic bond stability, ester bond stability, Caco-2 cell uptake, antiviral activity, and cytotoxicity. The prodrugs were resistant to metabolism by BDCRBmetabolizing enzymes, and ester bond cleavage was ratelimiting in metabolite formation from prodrug. Thus, BDCRB metabolism could be controlled by the selection of promoiety. In HCMV plaque-formation assays, L-Asp-BDCRB exhibited 3-fold greater selectivity than BDCRB for inhibition of HCMV replication. This potent and selective antiviral activity in addition to favorable stability profile made L-Asp-BDCRB an excellent candidate for in vivo assessment and pharmacokinetic comparison with BDCRB. In addition to rapid absorption and sufficient prodrug activation after oral administration to mice, LAsp-BDCRB exhibited a 5-fold greater half-life than BDCRB. Furthermore, the sum of area under the concentration-time profile (AUC) BDCRB and AUC prodrug after L-Asp-BDCRB administration was roughly 3-fold greater than AUC BDCRB after BD-CRB administration, suggesting that a reservoir of prodrug was delivered in addition to parent drug. Overall, these findings demonstrate that amino acid prodrugs of BDCRB exhibit evasion of metabolizing enzymes (i.e., bioevasion) in vitro and provide a modular approach for translating this in vitro stability into enhanced in vivo delivery of BDCRB.Benzimidazole D-ribonucleosides such as BDCRB were identified as potent inhibitors of HCMV replication over a decade ago (Townsend and Drach, 1992;Townsend et al., 1995). In addition to excellent potency, BDCRB exhibited low toxicity to uninfected cells due to its viral-specific mechanism of action (Krosky et al., 1998;Underwood et al., 1998;Scheffczik et al., 2002;Scholz et al., 2003). Despite these desirable attributes, the clinical development of BDCRB was restricted due to rapid N-glycosidic bond cleavage after oral and intravenous administration to rats and monkeys (Good et al., 1994). The enzymes 8-oxoguanine DNA glycosylase (OGG1), and N-methylpurine DNA glycosylase (MPG), were recently implicated in cleavage of the BDCRB glycosidic bond (P. L. Lorenzi, C. P. Landowski, X. Song, L. B. Townsend, J. C. Drach, and G. L. Amidon, manuscript submitted for publication). Thus, the main limitation to use of BDCRB in HCMV therapy seems to be metabolism by these and possibly additional enzymes.