Effects of gel volume on pharmacokinetics for vaginal and rectal applications of combination DuoGel-IQB4012, a dual chamber-dual drug HIV microbicide gel, in pigtailed macaques.

This study evaluated effects of differing gel volumes on pharmacokinetics (PK). IQB4012, a gel containing the non-nucleoside reverse transcriptase inhibitor IQP-0528 and tenofovir (TFV), was applied to the pigtailed macaque vagina and rectum. Vaginal gel volumes (1% loading of both drugs) were 0.5 or 1.5 ml; following wash-out, 1 or 4 ml of gel were then applied rectally. Blood, vaginal, and rectal fluids were collected at 0, 2, 4, and 24 h. Vaginal and rectal tissue biopsies were collected at 4 and 24 h. There were no statistically significant differences in concentrations for either drug between gel volumes within compartments at matched time points. After vaginal gel application, median IQP-0528 concentrations were ~ 104-105 ng/g, 105-106 ng/ml, and 103-105 ng/ml in vaginal tissues, vaginal fluids, and rectal fluids, respectively (over 24 h). Median vaginal TFV concentrations were 1-2 logs lower than IQP-0528 levels at matched time points. After rectal gel application, median IQP-0528 and TFV concentrations in rectal fluids were ~ 103-105 ng/ml and ~ 102-103 ng/ml, respectively. Concentrations of both drugs sampled in rectal tissues were low (~ 101-103 ng/g). For 1 ml gel, half of sampled rectal tissues had undetectable concentrations of either drug, and over half of sampled rectal fluids had undetectable TFV concentrations. These results indicate differences in drug delivery between the vaginal and rectal compartments, and that smaller vaginal gel volumes may not significantly compromise microbicide PK and prophylactic potential. However, effects of rectal gel volume on PK for both drugs were less definitive.

Current Concepts for the IND-Directed Development of Microbicide Products to Prevent the Sexual Transmission of HIV.

In the absence of an approved and effective vaccine, topical microbicides have become the strategy of choice to provide women with the ability to prevent the sexual transmission of HIV. Topical microbicides are chemical and physical agents specifically developed and formulated for use in either the vaginal or rectal environment to prevent the sexual transmission of infectious organisms. Although a microbicide product will have many of the same properties as other anti-infective therapeutic agents, the microbicide development pathway has significant differences which reflect the complex biological environment in which the products must act. These challenges to the development of an effective microbicide are reflected in the recently released FDA Guidance document which defines the microbicide development algorithm and includes the evaluation of preclinical efficacy and toxicity, and safety and toxicology, and indicates the necessity of testing of the active pharmaceutical product as well as an optimal formulation for delivery of the microbicide product. The microbicide development algorithm requires evaluation of the potential microbicidal agent and final formulated product in assays which mimic the microenvironment of the vagina and rectum during the sexual transmission of HIV, including the evaluation of activity and cytotoxicity in the appropriate biological matrices, toxicity testing against normal vaginal flora and at standard vaginal pH, testing in ectocervical and colorectal explant tissue, and irritation studies to vaginal, rectal and penile tissue. Herein, we discuss currently accepted practices required for the development of a successful microbicide product which will prevent virus transmission in the vaginal and rectal vaults.

The rational design and development of a dual chamber vaginal/rectal microbicide gel formulation for HIV prevention.

The DuoGel™ was developed for safe and effective dual chamber administration of antiretroviral drugs to reduce the high incidence of HIV transmission during receptive vaginal and anal intercourse. The DuoGel™s containing IQP-0528, a non-nucleoside reverse transcriptase inhibitor (NNRTI), were formulated from GRAS excipients approved for vaginal and rectal administration. The DuoGel™s were evaluated based upon quantitative physicochemical and biological evaluations defined by a Target Product Profile (TPP) acceptable for vaginal and rectal application. From the two primary TPP characteristics defined to accommodate safe rectal administration three DuoGel™ formulations (IQB3000, IQB3001, and IQB3002) were developed at pH 6.00 and osmolality ⩽400mmol/kg. The DuoGel™s displayed no in vitro cellular or bacterial toxicity and no loss in viability in ectocervical and colorectal tissue. IQB3000 was removed from consideration due to reduced NNRTI delivery (∼65% reduction) and IQB3001 was removed due to increase spread resulting in leakage. IQB3002 containing IQP-0528 was defined as our lead DuoGel™ formulation, possessing potent activity against HIV-1 (EC50=10nM). Over 12month stability evaluations, IQB3002 maintained formulation stability. This study has identified a lead DuoGel™ formulation that will safely deliver IQP-0528 to prevent sexual HIV-1 transmission in the vagina and rectum.

Novel preclinical models of topical PrEP pharmacodynamics provide rationale for combination of drugs with complementary properties.

BACKGROUND: The limited success of recent HIV topical pre-exposure prophylaxis clinical trials highlights the need for more predictive models of drug efficacy that better simulate what may happen during sexual exposure. To address this gap, we developed complementary in vitro models to evaluate the ability of drugs to retain anti-HIV activity if cells were washed with seminal plasma (simulating what may happen following exposure to ejaculate), and to protect drug-naive T cells (representing newly recruited immune cells) co-cultured with explants that had been pretreated with drug. We focused on tenofovir disoproxil fumarate (TDF), the non-nucleoside reverse transcriptase inhibitors dapivirine (DPV) and IQP-0528, and the entry inhibitors maraviroc (MVC) and the D-peptide chol-PIE-12 trimer (PIE12). Studies were extended to macaques and the ability of cervical biopsies obtained from animals treated with an intravaginal ring formulation of IQP-0528 to protect ex vivo co-cultured T cells was determined. The antiviral activity of cervicovaginal lavage samples against a primary Clade C isolate was also measured and correlated with drug levels. RESULTS: Cells exposed to TDF were equally protected from HIV whether or not the drug-treated cells were washed with medium or seminal plasma prior to challenge. In contrast, several-fold higher concentrations of NNRTIs and entry inhibitors were needed to attain similar levels of HIV inhibition following a wash with seminal plasma. Conversely, the NNRTIs and PIE12, but not TDF or MVC, were effectively transferred from ex vivo treated explants and protected co-cultured T cells. Biopsies obtained from IQP-0528 ring-treated macaques also protected co-cultured T cells with viral inhibition ranging from 42-72%. Antiviral activity correlated with the concentration of drug recovered. Combinations of TDF with IQP-0528 protected in both in vitro models. CONCLUSIONS: Together, these models suggest that intracellularly retained drugs such as TDF may protect resident immune cells following coitus but sustained delivery may be required to protect immune cells subsequently recruited into the genital tract. Sustained delivery may also be critical for NNRTIs, which are rapidly transported out of cells and could be lost following sexual intercourse. An ideal approach may be a combination of drugs with complementary bioavailability profiles formulated for sustained delivery.

Safety and efficacy of tenofovir/IQP-0528 combination gels - a dual compartment microbicide for HIV-1 prevention.

Tenofovir (TFV) is a nucleotide reverse transcriptase inhibitor and IQP-0528 is a non-nucleoside reverse transcriptase inhibitor that also blocks virus entry. TFV and IQP-0528 alone have shown antiviral activity as microbicide gels. Because combination therapy will likely be more potent than mono-therapy, these drugs have been chosen to make a combination microbicide gel containing 2.5% TFV/1% IQP-0528. Safety and efficacy testing was done to evaluate five prototype combination gels. The gels retained TZM-bl cell and ectocervical and colorectal tissue viability. Further, the epithelium of the ectocervical and colorectal tissue remained intact after a 24h exposure. The ED(50) calculated from the formulations for IQP-0528 was ~32nM and for TFV was ~59nM and their inhibitory activity was not affected by semen. The ED(50) of TFV in the combination gels was ~100-fold lower than when calculated for the drug substance alone reflecting the activity of the more potent IQP-0528. When ectocervical and colorectal tissue were treated with the combination gels, HIV-1 p24 release was reduced by ≥1log(10) and ≥2log(10), respectively. Immunohistochemistry for the ectocervical tissues treated with combination gels showed no HIV-1 infected cells at study end. With the increased realization of receptive anal intercourse among heterosexual couples often in conjunction with vaginal intercourse, having a safe and effective microbicide for both mucosal sites is critical. The safety and efficacy profiles of the gels were similar for ectocervical and colorectal tissues suggesting these gels have the potential for dual compartment use.