Highly Acidifying Intravaginal Rings with Lactobacillus Probiotics to Treat Bacterial Vaginosis

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Abstract Millions of women in the U.S. suffer from bacterial vaginosis (BV), a vaginal condition initiated by marked overgrowth of polymicrobial bacterial populations that can suppress protective lactobacilli. Healthy lactobacilli (LB), in particular lactobacillus crispatus, secrete lactic acid (LA) that acidifies the vagina and acts as a broad- spectrum microbicide that protects against many types of pathogens and also can suppress polymicrobial communities of BV species that produce little or no lactic acid. We do not know what initiates episodes of BV, but we do know that BV strongly increases risks of many sexually transmitted infections including HIV, and increases risks of premature births. At any given time, about 1/3 of sexually active women in the U.S. and world-wide have BV. Antibiotics can provide transient relief from the foul-smelling discharge caused by BV but they do not prevent BV from recurring (sometimes at a frequency up to twice a month). There is no product on the market that can provide sustained protection against BV. We and others have shown that LA can potently inactivate many types of BV-associated bacteria as well as many types of pathogens that cause sexually transmitted infections. Since LA is abundant in the healthy vaginas of women with protective LB, particularly in women with Lactobacillus crispatus (L.c), it has the potential to serve as a safe, non-antibiotics microbicide. We have recently determined the rate at which healthy lactobacilli continuously produce LA and hence for the first time know the rate at which lactic acid should be supplied to the vagina to treat and prevent BV. This in turn guided our development of an LA-releasing intravaginal ring (LA-IVR) that can provide sustained release of LA over 30 days at the rate needed to treat and prevent BV while not suppressing healthy LB. We have further synthesized macaque-sized LA-IVR that, when inserted into the macaque vagina, could lower the vaginal pH substantially without causing any toxicity. Building on our promising work, we seek to combine this LA-IVR with a L.c probiotics in the form of capsules containing lyophilized L.c powder, in order to achieve a synergistic alteration to the vaginal environment to best promote the re-establishment of a L.c-dominated microflora. In Aim 1, we plan to identify a lead strain of L.c based on growth rates as well as acidification rates and extent, then formulate them into lyophilized powders and load into capsules. In Aim 2, we will fabricate the macaque-sized LA-IVRs, and test whether combinatorial treatment of sustained LA release by this IVR with the L.c probiotics capsules can suppress BV-like bacterial species in pigtail macaques. Successful demonstration of safety and efficacy in this highly relevant large animal model would support the design requirements of an optimal LB-LA-IVR that Mucommune can advance through IND-enabling activities. The simplicity of our LA-IVR and L.c loaded capsule designs ensures both ease of production and likely very low manufacturing costs of the eventual product, which in turn should maximize potential public health impact and commercial viability of the product both in the U.S. and in low and middle income countries worldwide.