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Background:  PRO 2000/5, a naphthalene sulfonic acid polymer, inhibits HIV and herpes simplex virus (HSV) in cell culture and in animal models. However, no data demonstrating antiviral activity in humans exists. A prospective, randomized, double-blind placebo-controlled study was conducted among 20 HIV-infected women to assess the anti-HIV and anti-HSV activity in cervicovaginal lavage (CVL) fluid collected 1 hour after a 2-g intravaginal dose of 0.5% PRO 2000/5 gel or a matched placebo gel. The acute inflammatory response was examined by measuring inflammatory cells interleukin (IL)-1b and IL-8.

Methods:  The antiviral activity in CVL was assessed using a spiking strategy and quantifying the virus recovered. A single cycle replication defective virus containing a luciferase-indicator gene and pseudotyped with the R5 envelope JRFL or an envelope derived from a primary viral isolate was diluted 1:2 in CVL and inoculated onto CCR5-expressing HeLa cells or primary human macrophages. Luciferase activity was measured 72 hours post-infection. Human cervical cells (CaSki) were exposed to CVL (diluted 1:2 in PBS) and challenged with serial dilutions of HSV-2(G) and the viral titer determined (pfu/mL). A peroxidase test was used to quantify PMNs and cytokines were measured by ELISA. Drug levels were measured by fluorescence assay.

Results:  Unblinding occurred after completion of all laboratory studies. CVL obtained after application of 0.5% PRO 2000/5 gel significantly inhibited HIV infection of CCR5-expressing HeLa cells and macrophages and HSV infection of human cervical cells, whereas the placebo gel had little or no antiviral activity. The fold reduction in HIV infection on HeLa cells was 1291 ± 383 for drug compared to 2.745 ± 0.8 for placebo (p = 0.0035 by unpaired 2-tailed t-test) and for HSV infection, 2642 ± 1066 for drug compared to 10.10 ± 5.877 for placebo (p = 0.0238). The concentration of 0.5% PRO 2000/5 Gel in CVL post-application ranged from 114 to 341 mg/mL, a concentration that exceeds the IC90 of the drug. No increase in PMNs, IL-1b, IL-8, or secretory leukocyte protease inhibitor was observed. Three adverse events were reported in each group. None was serious or unexpected.

Conclusions:  The results demonstrate that 0.5% PRO 2000/5 Gel is sufficiently bioavailable and retains substantial antiviral activity 1 hour after intravaginal application. Moreover, this strategy provides a mechanism for testing in vivo the efficacy of a microbicide before embarking on large-scale clinical trials.

Keywords: microbicides; HIV; HSV