Review Article
Factors Important to the Prioritization and Development of Successful Topical Microbicides for HIV-1
Table 1
Comparison of EC50 and EC99 values determined in the standard transmission inhibition assay to MTSA defined sterilizing concentration.
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The dual acting (entry inhibition and NNRTI) pyrimidinediones IQP-0528, IQP-0410, IQP-1187 [69] nonnucleoside RT inhibitors UC781 and efavirenz, nucleoside RT inhibitor AZT, entry inhibitor cyanovirin-N (CVN), and nucleotide RT inhibitor tenofovir (TFV) were evaluated in the MTSA, and the sterilizing concentration was compared to the EC50 and EC90 determined in a standard virus transmission assay. The concentrations utilized for each compound in the MTSA were derived from their respective EC50 concentrations in a cytopathic effect assay and their TIs (EC50/TC50). The concentrations which were utilized are as follows: IQP-0528, IQP-0410, and IQP-1187: 10 through 31,250 times the EC50 concentration; AZT and UC781: 10 through 31,250 times the EC50 concentration; cyanovirin-N: 10 through 6,250 times the EC50 concentration; efavirenz: 10 through 31,250 times the EC50 concentration; tenofovir: 2.5 through 97.7 times the EC50 concentration. All concentrations evaluated represented 5-fold serial increases in drug concentration with the exception of tenofovir which was in 2.5-fold increments. Passages which were positive for virus production were defined by detection of virus in the cell-free supernatant by RT assay. Cells were passaged for 10 passages in the continuous presence of the fixed compound concentration and for an additional 5 passages in the absence of compound. All tested concentrations were significantly below the defined toxic concentration to CEM-SS cells. Passages which were positive for virus production were defined by detection of virus in the cell-free supernatant by RT assay.
The entry assay results used for comparison to the MTSA results were generated from an assay utilizing HeLa-CD4-LTR--Gal Cells with HIV-. Compound is added to the preplated cells approximately 15 minutes prior to the addition of virus. Following a 2-hour incubation at 37°/5% CO2, residual virus and compound are removed through washing. The culture is incubated for an additional 48 hours at which time compound efficacy is determined by evaluating -galactosidase in the lysate using a chemiluminescent endpoint. |