One of the important unresolved problems in fungal antimicrobial chemotherapy is the ineffectiveness of existing therapeutics against cells that do no exist in a rapidly-growing, planktonic population. Upon attachment to abiotic surface or tissue, C. albicans produces quiescent, drug-tolerant persister cells. Subsequent development of a biofilm protects the pathogen from the immune system. Non-growing stationary cells are also tolerant to antimicrobials. Candida biofilms are responsible for infections of catheters;our data point to involvement of persister cells in oral thrush;and relapsing vaginitis is likely due to the presence of drug-tolerant cells as well. Our in vitro studies showed that amphotericin B or miconazole applied even at high, topical concentrations are not effective against a mature biofilm of C. albicans and persister cells. The goal of this Phase II project is to develop lead compounds that potentiate conventional antifungals and are capable of eradicating all forms of the pathogen, be it exponentially growing, stationary, biofilm or persister cells. We reasoned that a compound that can interfere with the formation or maintenance of quiescent forms of infection would synergize with conventional antifungals and produce a sterilizing therapeutic. In Phase I, we developed a screen for compounds that act synergistically with antifungals and successfully identified compounds that eradicated C. albicans biofilms in vitro in the presence of miconazole. The compounds have no activity alone. This is the first observation of effective action against Candida biofilms and persister cells for any anti-fungal agent. One of the compounds, AC17, has good drug-like properties and serves as proof-of principle for developing a combination therapeutic to eradicate fungal infections. In Phase II, we will introduce a large-scale drug discovery program to identify additional attractive leads for developing potentiators of antifungals. Together with AC17, the hits from the HTS will undergo a detailed in vitro validation, medicinal chemistry optimization, and animal studies. We plan to target currently untreatable diseases: Recurrent Vulvovaginal Candidiasis (RVC), refractory Oropharyngeal Candidiasis (OPC) and biofilm infection of central venous catheters with a sterilizing combination therapeutic. Essentially 100% of women experience vaginitis due to Candida at some point in life, and the disease is treatable with azole antifungals in most cases. However, 5-8% of women suffer from relapsing vaginitis that is recalcitrant to currently available therapies. Similarly, mild cases of oropharyngeal candidiasis are usually cured with antifungal therapy, however the infection is recurrent in immunocompromised patients with HIV and cancer. C. albicans biofilm infection of central venous catheters is untreatable with currently available antifungals, requiring device removal. If left untreated, catheter biofilm infection can develop into disseminated candidemia with mortality of 38-50%. We intend to salvage biofilm- infected catheters using a lock therapy of miconazole and potentiators. This is a multidisciplinary project that brings together experts in drug development (Tom Dahl, PI); antimicrobial resistance and drug discovery (Kim Lewis, NEU);yeast molecular genetics (Carol Kumamoto, Tufts University);medicinal chemistry (Richard Lee, St. Jude Children's Research Hospital);and animal models of fungal infections (Paul Fidel, LSU;Mahmoud Ghannoum, Case Western;Saul Tzipori, Tufts). Obtaining 2 advanced leads with good efficacy in an animal model of disease will be the end-point of this Phase II project.
The aim of this project is to develop an effective therapeutic which will sterilize fungal infection caused by Candida albicans. Currently available therapeutics suppress, but do not sterilize the infection causing relapse and resistance. This project is based on preliminary data that describe a discovery of substances that potentiate existing antifungals and effectively eliminate the pathogen. The end result of the project will be lead therapeutics validated in an animal model of fungal infection.
|Lafleur, Michael D; Sun, Lingmei; Lister, Ida et al. (2013) Potentiation of azole antifungals by 2-adamantanamine. Antimicrob Agents Chemother 57:3585-92|