Implementing a new paradigm for antifungal drug development - about 30% of the drugs currently in clinical use function through covalent modification of their target

The National Institute of Allergy and Infectious Diseases awarded the University of Toledo $216,770 on June 11, 2026, under the Allergy and Infectious Diseases Research program (CFDA 93.855) to develop a new class of covalent antifungal drug candidates. The award, designated R21AI195315, funds research through May 31, 2028, and is performed at the University of Toledo in Ottawa Hills, Ohio.

The project aims to optimize and test novel covalent enzyme inactivators targeting a microbial pathway essential for fungal survival. Research activities include three specific aims: optimization of potency and selectivity of enzyme inactivators to overcome barriers in converting them to advanced drug candidates; enhancement of antifungal capability through incorporation of conjugate partners that exploit fungal nutrient uptake systems to achieve toxic levels in Candida species; and examination of target selectivity through fungal growth inhibition and killing assays. The research addresses the rising threat of drug-resistant pathogenic fungi and the limited efficacy of existing antifungal agents against virulent species.

Yet, until recently, none of these covalent drugs were specifically designed to utilize this irreversible mode of action. IT is our hypothesis that the production of a new class of covalent inactivators, designed to selectively modify new drug targets, will lead to novel agents with efficacy against both native and drug-resistant pathogenic fungal species. Because of their novelty these agents will also offer a greater opportunity to bypass the existing mechanisms of drug resistance. Pathogenic fungal infections remain among the leading causes of human mortality, and this threat is rising due to the increasing prevalence of drug- resistance strains and the paucity of effective antifungal drugs against the more virulent fungal species. Our proposed new drug target is an enzyme that plays a critical role in a uniquely microbial pathway that is essential for the survival of fungal organisms. To test our hypothesis and achieve the goals of this project we plan to complete the following specific aims during the initial R21 phase of this project: (1) optimization of the potency of novel enzyme inactivators. Our goals here are to use our strong preliminary results to address critical barriers that must be overcome to convert potent enzyme inactivators into advanced drug candidates, thereby achieving higher target selectivity and increasing compound reactivity once bound to the target; (2) enhance the antifungal capability of these enzyme inactivators. Our strategy for this aim is focused on the incorporation of conjugate partners into this new class of covalent inactivators, enabling them to potentially utilize the existing nutrient uptake systems to achieve toxic levels in candida species; (3) examine the target selectivity of our new antifungal agents. Results from fungal growth inhibition and fungal killing assays will be used to evaluate and rank the efficacy of our compounds against both wild-type and drug-resistant candida strains. Specific milestones are presented to evaluate our achievement of these initial aims. Once accomplished we will immediately proceed to the R33 phase of this project, with the aims of: (4) pharmacological evaluation of lead candidates, though ranking the drug candidates based on their adme, pharmacokinetic and toxicity properties; and then (5) evaluate the efficacy of our candidates against pathogenic fungal infections. A systematic infection animal model will be utilized for candidate screening to identify the best agents against disseminated fungal infections, followed by further efficacy screening in an oral infection model. Completion of these aims will produce, refine and evaluate a new class of antifungal agents with a novel mode of action against an unexplored but essential fungal target. The agents with the most promising drug profiles will then be moved into advanced preclinical trials used to select the most effective new antifungal agents.