Repurposing Drugs to Discover Novel Antifungals for Coccidioidomycosis

PROJECT SUMMARY Coccidioides is a fungal pathogen from the American deserts that infects people who breathe in the spores. Inside the person’s lungs, the spores develop into spherules which fill with hundreds of endospores that are released into the lungs. The symptoms of this disease, called Valley Fever, occur in a third of exposed individuals

and resemble the flu or pneumonia leading to misdiagnosis. In 7% of infected individuals the fungus will leave the lungs and spread or disseminate to the rest of the body, including the brain, joints, skin, and other organs. Treatments include two classes of drugs and may be needed for years: oral Triazoles like Fluconazole (to which

there is increasing resistance) or IV Amphotericin B which is generally reserved for disseminated disease since it is toxic to the kidneys. Due to limited therapies, risk of drug resistance, and the rapidly increasing spread of coccidioidomycosis from desertification, the need for novel anti-Coccidioides drugs is very urgent. Our proposal

will address this urgency by repurposing drugs that have already received FDA-approval as new antifungals, a practice best described as “teaching old drugs new tricks”. In a screening of 7962 compounds, we discovered 254 potential drugs, 30 were qualified as excellent candidates due to their strong inhibiting action. We tested 13

of these drugs in a combination matrix with three clinical antifungals, Amphotericin B, Fluconazole, and Caspofungin, to see if there were any synergistic effects where the drugs worked better together than alone. Excitingly, 6 compounds demonstrated synergy with Amphotericin B, resulting in lower concentrations of both

drugs inhibiting Coccidioides growth more than either drug individually. Therefore, we propose that these six compounds are strong candidates for a synergistic approach for treating Valley Fever by using combination therapy of these drugs with Amphotericin B. Aim 1 will investigate the properties of Coccidioides exposed to

drugs in vitro. In Aim 1.1, we measure the potential synergy of the six drugs with the other azole and echinocandin drugs. Next, in Aim 1.2, we will determine their fungicidal or fungistatic properties to guide our in vivo dosing. Aim 1.3 investigates pan-morphologic antifungal efficacy. Aim 1.4 assesses pan-isolate drug

efficacy across Coccidioides species, informing collaborative investigations into pan-fungal potential. In Aim 2, we will test the efficacy of the drugs in two animal models. In Aim 2.1, doses of the drugs individually and in combination will first be optimized in a Galleria larvae model of coccidioidomycosis to determine the most

effective dose for the mouse model. In the murine model (Aim 2.2) we will compare the efficacy of daily treatments of the combination therapy versus monotherapy in mice infected with a lethal dose of spores in short, 14d trials and longer, 30d trials where success will be measured both by fungal burden and survival. This

research addresses the unmet need for novel anti-Coccidioides drugs, offering a combination therapy approach to enhance efficacy, reduce toxicity, and mitigate resistance risks. The results of my combination therapy experiments with these novel drugs with known medications may change the future of Valley Fever treatments.