Intravaginal Ring Delivery of Safe & Effective Microbicides to Prevent HIV & HSV

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DESCRIPTION (provided by applicant): The growing HIV pandemic and its increasing burden on women highlights the urgent need for novel safe and effective preventative strategies such as topical microbicides. We hypothesize that a truly safe and effective microbicide will require sustained, local delivery of a combination of drugs that target different steps in the HIV life cycle and a delivery system that addresses the challenges related to adherence. A safe microbicide should not interfere with host defenses nor increase the risk of selecting for drug resistant viruses. Achieving this goal requires more stringent pre-clinical and clinical evaluation of microbicides, focusing on their interactions with the genital tract mucosal environment. The goal of this iterative Program is to develop a combination microbicide delivered via intravaginal ring (IVR) to prevent the sexual transmission of HIV. This will be accomplished either through IVR formulation of a dual-active single agent, a pyrimidinedione, which is both a potent reverse transcriptase and entry inhibitor, or by combining two distinct antiretroviral (ARV) drugs. We will address the importance of the biological synergy between HIV and HSV by also combining acyclovir with ARV drugs to provide local sustained suppression of HSV. The safety of the microbicides and formulations will be explored using novel assays designed to assess their impact on the epithelial barrier and mucosal immunity. Exploratory clinical studies to evaluate the genital tract mucosal environment of Rwandan women will be conducted as defining the healthy genital tract environment will provide crucial information for establishing clinical biomarkers of microbicide safety. Pilot studies to examine the safety and tolerability of three different polyurethane rings will be conducted to identify the optimal composition for formulation of microbicide rings. Results of this study will guide the IVR formulation of our lead drugs, which will be advanced for further safety and regulatory studies including macaque PK and safety studies. A pre-Phase I clinical study is proposed to evaluate PK and safety of our lead IVR formulated microbicide and to determine if the released drug retains its antiviral activity using a spiking strategy. RELEVANCE: These studies will provide crucial information for advancement of safe and effective IVR combination microbicides to prevent HIV and to suppress HSV. These studies will also address critical gaps in microbicide science focusing on the development of sustained delivery systems and safety biomarkers. PROJECT 1: Efficacy & Safety of Multitargeted Combination Microbicides to Prevent HIV & HSV (Herold, B) PROJECT 1 DESCRIPTION (provided by applicant): Topical microbicides, a female-controlled strategy to prevent HIV, are crucial in stemming the pandemic. An optimal microbicide should protect against infection without disrupting the mucosal environment or its mediators of host defense. This project focuses on the preclinical evaluation of combination microbicides with the goal of identifying safe and effective prevention strategies. Combinations that target at least two steps in the HIV life cycle will be prioritized, thus providing protection against circulating resistant viruses and reducing the risk that the drugs will select for resistant variants. This will be accomplished through the dual activities of a single antiretroviral drug (ARV), a pyrimidinedione, which is a potent reverse transcriptase inhibitor and also blocks HIV entry, or by combining two different ARV microbicides. The biological synergy between HIV and HSV will be addressed by evaluating the possibility of delivering acyclovir in combination with the ARV microbicides to provide local sustained suppression of HSV replication. The rationale for focusing on HSV suppression reflects the pre-existing high prevalence of HSV-2 (60-90%) in the developing world and the overwhelming biological and epidemiological evidence demonstrating that subclinical HSV recurrences, which are quite common, increase the risk for HIV acquisition. Critical gaps in microbicide development are the lack of biomarkers predictive of safety and efficacy. This project will address these gaps by developing and expanding novel assays, which focus on the interactions between microbicides and the vaginal environment, using primary cells, explant cultures, and a dual chamber culture system and murine models. The proposed safety models focus on the impact of sustained drug delivery on epithelial integrity and genital tract mucosal immunity. The biological significance of any observed changes will be assessed by examining changes in the ability of HIV to traverse the epithelial barrier in the dual culture model and changes in the susceptibility to genital herpes in the mouse. Results obtained from these studies will provide crucial information for the advancement of novel safe and effective combination microbicides.