| Summary: | A number of 5′-<i>O</i>-fatty acyl derivatives of 3′-fluoro-2′,3′-dideoxythymidine (FLT, <b>1</b>) were synthesized. These conjugates were evaluated for their potential as topical microbicides with anti-HIV activity against cell-free (X4 and R5), cell-associated, and multidrug-resistant viruses. Compared to FLT and 3′-azido-2′,3′-dideoxythymidine (AZT), 5′-<i>O</i>-(12-azidododecanoyl) (<b>5</b>), 5′-<i>O</i>-myristoyl (<b>6</b>), and 5′-<i>O</i>-(12-thioethyldodecanoyl) (<b>8</b>) derivatives of FLT were found to be more active against both cell-free viruses (lymphocytotropic and monocytotropic strains) with EC<sub>50</sub> values of 0.4 μM, 1.1 μM, and <0.2 μM, respectively, as well as cell-associated virus with EC<sub>50</sub> values of 12.6, 6.4, and 2.3 μM, respectively. Conjugates <b>5</b>, <b>6</b>, and <b>8</b> exhibited >4 and >30 times better antiviral index than FLT and AZT, respectively. Conjugates <b>5</b> and <b>8</b> were significantly more potent than FLT against many multidrug-resistant strains. A comparison of the anti-HIV activity with the corresponding non-hydrolyzable ether conjugates suggested that ester hydrolysis to FLT and fatty acids is critical to enable anti-HIV activity. Cellular uptake studies were conducted using fluorescent derivatives of FLT attached with 5(6)-carboxyfluorescein through either β-alanine (<b>23</b>) or 12-aminododecanoic acid (<b>24</b>) spacers. The lipophilic fluorescent analog with a long chain (<b>24</b>) showed more than 12 times higher cellular uptake profile than the fluorescent analog with a short chain (<b>23</b>). These studies further confirmed that the attachment of fatty acids improved the cellular uptake of nucleoside conjugates. In addition, <b>5</b>, <b>6</b>, and <b>8</b> were the least cytotoxic and did not alter vaginal cell and sperm viability compared to the positive control, a commercial topical spermicide (N-9), which significantly decreased sperm and vaginal cell viability inducing the generation of proinflammatory cytokines.
|
|---|