Development of topical microbicides to prevent the sexual transmission of HIV

Abstract

Women comprise almost 50% of the population of people living with HIV and the majority of these women contracted the virus through sexual transmission in monogamous relationships in the developing world. In these environments, where women are not empowered to protect themselves through the negotiation of condom use, effective means of preventing HIV transmission are urgently needed. In the absence of an approved and effective vaccine, microbicides have become the strategy of choice to provide women with the ability to prevent HIV transmission from their infected partners. Topical microbicides are agents specifically developed and formulated for use in either the vaginal or rectal environment that prevent infection by sexually transmitted infectious organisms, including pathogenic viruses, bacteria and fungi. Although a microbicidal product will have many of the same properties as other anti-infective agents and would be similarly developed through human clinical trials, microbicide development bears its own challenges related to formulation and delivery and the unique environment in which the product must act, as well as the requirement to develop a product that is acceptable to the user. Herein, perspectives based on preclinical and clinical microbicide development experience, which have led to an evolving microbicide development algorithm, will be discussed. This article forms part of a special issue of Antiviral Research marking the 25th anniversary of anti-retroviral drug discovery and development, Vol 85, issue 1, 2010.

Figure 1. Evaluation of Pyrimidinediones in a Specialized Transmission Inhibition Assay

Figure 1A: Sterilizing Concentration Determinations for Pyrimidinedione Inhibitors: SJ-3991, SJ-3366 and SJ-3339 were evaluated in the MTSA and the results are presented as the number of passages which were positive for virus replication at each compound concentration. The results of two replicate assays for each compound are presented. Each pyrimidinedione was evaluated at concentrations that were 10-, 50-, 250-, 1,250-, 6,250- and 31,250-times the EC₅₀ concentration that was defined in the CPE inhibition assay. 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. Cells were passaged for 10 passages and in the absence of compound for an additional 5 passages. Figure 1B: Sterilizing Concentration Determinations for Control Compounds: The entry inhibitor cynovirin –N, the nucleotide RT inhibitors AZT and 3TC, the nucleotide RT inhibitor Tenofovir and the nonnucleoside RT inhibitors UC781 and efavirenz were evaluated in the MTSA and the results are presented as the number of passages which were positive for virus replication at each compound concentration. The results of two replicate assays for each compound are presented. The concentrations utilized for each compound in the series are as follows: AZT: 10 to 31,250 nM (10- through 31,250-times the EC₅₀ concentration); 3TC: 100 to 62,500 nM (10- through 6,250-times the EC₅₀ concentration); Efavirenz: 10 to 6,250 nM (10- through 6,250-times the EC₅₀ concentration); UC781: 15 to 46,875 nM (10- through 31,250-times the EC₅₀ concentration); cyanovirin N: 0.1 to 62.5 μg/mL (10- through 6,250-times the EC₅₀ concentration); Tenofovir: 2.5 to 97.7 μM (2.5- through 97.7-times the EC₅₀ concentration). All concentrations were in 5-fold increments 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 and in the absence of compound for an additional 5 passages.

Figure 1. Evaluation of Pyrimidinediones in a Specialized Transmission Inhibition Assay

Figure 1A: Sterilizing Concentration Determinations for Pyrimidinedione Inhibitors: SJ-3991, SJ-3366 and SJ-3339 were evaluated in the MTSA and the results are presented as the number of passages which were positive for virus replication at each compound concentration. The results of two replicate assays for each compound are presented. Each pyrimidinedione was evaluated at concentrations that were 10-, 50-, 250-, 1,250-, 6,250- and 31,250-times the EC₅₀ concentration that was defined in the CPE inhibition assay. 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. Cells were passaged for 10 passages and in the absence of compound for an additional 5 passages. Figure 1B: Sterilizing Concentration Determinations for Control Compounds: The entry inhibitor cynovirin –N, the nucleotide RT inhibitors AZT and 3TC, the nucleotide RT inhibitor Tenofovir and the nonnucleoside RT inhibitors UC781 and efavirenz were evaluated in the MTSA and the results are presented as the number of passages which were positive for virus replication at each compound concentration. The results of two replicate assays for each compound are presented. The concentrations utilized for each compound in the series are as follows: AZT: 10 to 31,250 nM (10- through 31,250-times the EC₅₀ concentration); 3TC: 100 to 62,500 nM (10- through 6,250-times the EC₅₀ concentration); Efavirenz: 10 to 6,250 nM (10- through 6,250-times the EC₅₀ concentration); UC781: 15 to 46,875 nM (10- through 31,250-times the EC₅₀ concentration); cyanovirin N: 0.1 to 62.5 μg/mL (10- through 6,250-times the EC₅₀ concentration); Tenofovir: 2.5 to 97.7 μM (2.5- through 97.7-times the EC₅₀ concentration). All concentrations were in 5-fold increments 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 and in the absence of compound for an additional 5 passages.

Figure 2. Evaluation of Combination Drug Interactions in Three Cell System

Combination anti-HIV activity interactions of pyrimidinedione IQP-0410 (SAR 62) and Chicago Sky Blue in CEM-SS cells infected with a laboratory strain of HIV-1 (Panel A), in PBMCs infected with a low passage clinical strain of HIV-1 (Panel B) and in the microbicide-like attachment inhibition assay (Panel C). Slightly synergistic and additive interactions were observed with the CEM-SS and PBMC cultures, while significant synergy was observed in the microbicide-like attachment assay in MAGI cells.

Figure 2. Evaluation of Combination Drug Interactions in Three Cell System

Combination anti-HIV activity interactions of pyrimidinedione IQP-0410 (SAR 62) and Chicago Sky Blue in CEM-SS cells infected with a laboratory strain of HIV-1 (Panel A), in PBMCs infected with a low passage clinical strain of HIV-1 (Panel B) and in the microbicide-like attachment inhibition assay (Panel C). Slightly synergistic and additive interactions were observed with the CEM-SS and PBMC cultures, while significant synergy was observed in the microbicide-like attachment assay in MAGI cells.

Figure 2. Evaluation of Combination Drug Interactions in Three Cell System

Combination anti-HIV activity interactions of pyrimidinedione IQP-0410 (SAR 62) and Chicago Sky Blue in CEM-SS cells infected with a laboratory strain of HIV-1 (Panel A), in PBMCs infected with a low passage clinical strain of HIV-1 (Panel B) and in the microbicide-like attachment inhibition assay (Panel C). Slightly synergistic and additive interactions were observed with the CEM-SS and PBMC cultures, while significant synergy was observed in the microbicide-like attachment assay in MAGI cells.