Bob D. Rush

Broad-spectrum antiviral activity of PNU-183792, a 4-oxo-dihydroquinoline, against human and animal herpesviruses.

We identified a novel class of 4-oxo-dihydroquinolines represented by PNU-183792 which specifically inhibit herpesvirus polymerases. PNU-183792 was highly active against human cytomegalovirus (HCMV, IC(50) value 0.69 microM), varicella zoster virus (VZV, IC(50) value 0.37 microM) and herpes simplex virus (HSV, IC(50) value 0.58 microM) polymerases but was inactive (IC(50) value >40 microM) against human alpha (alpha), gamma (gamma), or delta (delta) polymerases. In vitro antiviral activity against HCMV was determined using cytopathic effect, plaque reduction and virus yield reduction assays (IC(50) ranging from 0.3 to 2.4 microM). PNU-183792 antiviral activity against both VZV (IC(50) value 0.1 microM) and HSV (IC(50) ranging from 3 to 5 microM) was analyzed using plaque reduction assays. PNU-183792 was also active (IC(50) ranging 0.1-0.7 microM) in cell culture assays against simian varicella virus (SVV), murine cytomegalovirus (MCMV) and rat cytomegalovirus (RCMV). Cell culture activity was compared with the appropriate licensed drugs ganciclovir (GCV), cidofovir (CDV) and acyclovir (ACV). PNU-183792 was also active against both GCV-resistant and CDV-resistant HCMV and against ACV-resistant HSV. Toxicity assays using four different species of proliferating mammalian cells indicated PNU-183792 was not cytotoxic at relevant drug concentrations (CC(50) value >100 microM). PNU-183792 was inactive against unrelated DNA and RNA viruses indicating specificity for herpesviruses. In animals, PNU-183792 was orally bioavailable and was efficacious in a model of lethal MCMV infection.

Desolvation Energy: A Major Determinant of Absorption, But Not Clearance, of Peptides in Rats

The oral delivery of peptidic drugs is problematic because of their degradation in the gastrointestinal tract and low absorption through the intestinal mucosa. Earlier in vitro studies with two series of digestion-resistant, radiolabeled peptides that varied in physical properties (molecular weight, lipophilicity, and hydrogen bonding sites) had suggested that intestinal transport of these peptides was most influenced by the number of hydrogen bonding sites, the major determinant of desolvation energy. To determine whether this correlation could be confirmed in vivo, intestinal absorption was determined by comparing the biliary and urinary recovery of these radiolabeled peptides in rats given intravenous or intraduodenal doses. Absorption was inversely correlated to the number of calculated hydrogen bonding sites for the model peptides, similar to what had been found in vitro. Clearance by liver and kidneys appeared to be unaffected by desolvation energy but was well correlated with lipophilicity.

Development of Activity Assays for High-Volume Evaluation of Human Immunodeficiency Virus (HIV) Protease Inhibitors in Rat Serum: Results with Ditekiren

We showed previously that a commercially available synthetic tetradecapeptide, Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Leu-Val-Tyr-Ser, produces authentic angiotensin I (Ang I) upon incubation with the HIV-1 protease (S. K. Sharma et al., Anal. Biochem. 198:363, 1991). Therefore, we developed an Ang-I based activity assay for HIV protease inhibitors based on the technology developed earlier (M. J. Ruwart et al., Pharm. Res. 7:407, 1990; S. K. Sharma et al., Anal. Biochem. 186:24, 1990) for tracking renin inhibitors in rat sera. Ditekiren was either extracted from sera with ethyl acetate or assayed after the interfering substances in sera were precipitated with acetonitrile. Purified recombinant HIV-1 protease was added to extracted rat serum and the enzymatic reaction was initiated in the presence of the tetradecapeptide substrate. The inhibition of Ang I production was measured by a commercially available RIA kit. The cleanup methodology also enabled a commercially available Proteinase Scintillation Proximity Assay (SPA, Amersham) to quantify ditekiren in rat serum through the addition of recombinant HIV-1 protease and cleavage of substrate from SPA beads. Results were confirmed by HPLC or by the renin assay for ditekiren, which inhibits both aspartyl proteases. These technologies should prove useful for assessing serum levels of HIV protease inhibitors in rat.