A recent Phase 1 trial demonstrated that PC-1005 gel containing 50µM MIV-150, 14mM zinc acetate dihydrate and carrageenan (CG) applied daily vaginally for up to 14 days is safe and well tolerated. Additionally, cervico-vaginal lavage samples (CVLs) collected 4h or 24h after last gel application showed MIV-150 and CG dose-dependent inhibition of HIV-1 and HPV in cell-based assays (Friedland et al, in preparation). We aimed to determine anti-HIV and anti-HSV-2 activity of CVLs in human ectocervical explants ex vivo.
CVLs collected at the baseline and 4h (n=6 PC-1005 and n=2 hydroxycellulose (HEC) placebo) or 24h (n=6 PC-1005 and n=1 HEC placebo) post last vaginal gel administration during Phase 1 trial were utilized. CG and MIV-150 concentrations in CVLs were measured by ELISA and LC-MS/MS, respectively. Human ectocervical explants were prepared from tissues received from National Disease Research Interchange. Explants (n=3 per condition) were incubated with CVLs (1:1) for 4h, washed with PBS and then challenged with 500 TCID50 HIV-1BaL or co-challenged with 500 TCID50 HIV-1BaL and 106 pfu HSV-2 per explant for ~18h, washed and then cultured for 14d. The activity of each baseline and corresponding post-gel exposure CVL was tested in tissues from the same donor. To determine contribution of CG to anti-HIV activity of CVLs, tissues were challenged with HIV-1Bal after exposure to baseline CVLs spiked with CG concentrations detected in the study (n=3 experiments). Infections were monitored by one step HIV gag RT-qPCR and HSV-2 pol qPCR on culture supernatants (individual replicate analysis). SOFT and CUM endpoint analyses were performed. Tissue viability post exposure to CVLs was tested using MTT assay. Log-normal generalized linear mixed models were used for statistical analysis.
MIV-150 and CG in CVLs inhibited HIV and HSV-2 infection (single HIV challenge or co-challenge with HSV-2) in the explants in a dose-dependent manner (p≤0.01), with stronger inhibition using CVLs collected 4h post last gel administration. CG concentrations (>250 µg/ml; n=4 CVLs) could have contributed to the observed anti-HIV activity based on >55% HIV-1Bal infection inhibition in the CG spiking experiments.
The anti-HIV and anti-HSV-2 activity of CVLs in human ectocervical explants warrants the further development of PC-1005 gel as a broad-spectrum on demand microbicide.