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Background:  A small series of non-nucleoside reverse transcriptase inhibitors (NNRTI), belonging to the diaryltriazine (DATA) and diarylpyrimidine (DAPY) classes of compounds, was shown previously to possess potent antiviral activity (EC₅₀ between 0.05 and 3 nM) in co-cultures of monocyte-derived dendritic (MO-DC) and CD4⁺ T cells. These cells represent primary targets of sexual HIV transmission and, therefore, the long-term exposure activity of these compounds in this system can be indicative for their use as microbicides. Here we report on structure-activity relationships from a more extensive series of DATA/DAPY compounds.

Methods:  The present study involves 35 compounds, comprising 30 DATA/DAPY compounds and 5 reference compounds (TIBO, α-APA, an iminoylthiourea (ITU) compound, UC781, and DPC083). Of the 22 DAPY compounds, 13 are of the p-cyanovinyl-phenyl DAPY type. The described DATA/DAPY potently inhibit wild type HIV-1 IIIB in a standard MT-4 cell test (EC₅₀ between 0.3 and 8 nM). For the MO-DC/CD4⁺ T cell co-cultures, MO-DC were infected with HIV-1 BaL and cultured with CD4⁺ T cells and test compound for 14 days. Culture supernatants were analysed in HIV p24 ELISA for EC₅₀ calculations.

Results:  The range of antiviral activities in MO-DC/CD4⁺ T cell co-cultures appeared to be about 10-fold larger than that obtained in the MT-4 test. The correlation coefficient between the 2 types of tests is about 0.6 (Spearman, p < 0.001). On average, the DAPY compounds are more active in the MO-DC/CD4⁺ T cell test than the DATA compounds. The reference compounds (except DPC083) are markedly less active than the DATA/DAPY. Within the subseries of p-cyanovinyl-phenyl DAPY, double substitutions at the ortho positions of the p-cyanovinyl-phenyl ring by methyl in combination with methyl, chlorine or bromine tend to enhance long-term exposure microbicidal activity of these compounds. Additional substitution of hydrogen by methyl at the alpha position of the cyanovinyl side chain tends to reduce long-term microbicidal activity.

Conclusions:  The present study on 30 DATA/DAPY NNRTI shows that the results produced by our MO-DC/CD4⁺ T-cell model are consistent with a standard MT-4 cell model. The variation of activities in MO-DC/CD4⁺ T cell co-cultures allows deduction of structure-activity relationships. Specific double substitutions at the ortho positions of the p-cyanovinyl-phenyl ring enhance long-term exposure microbicidal activity of these compounds.

Keywords: nonnucleoside reverse transcriptase inhibitor; dendritic cells; structure-activity relationship