Investigating MCE Chemical Library Drugs for Combinational Therapies for Clinical Aspergillus fumigatus isolates

Aspergillus fumigatus is a globally present pathogen capable of inflicting debilitating and life-threatening opportunistic infections in individuals, primarily those who are immunocompromised. Diagnosing A. fumigatus infections is often difficult, leading to a delay in treatment which can greatly impact patient outcomes. Furthermore, our lessening of antifungal development combined with increasing resistance generates a feasible scenario where only last resort options are viable. This has prompted the World Health Organization (WHO) to declare this pathogen a "critical priority" due to increased resistance and rising mortality rates. Azoles are utilized as primary treatment options for Aspergillus fumigatus infections such as voriconazole (VRC), itraconazole (ITC), and posaconazole (POS) with a reserve of Amphotericin B (AmB). In the past two decades, the emergence of resistance to azoles has contributed to a 90% mortality rate in resistant cases globally. In this report, we investigated the MedChem Express (MCE) Drug Repurposing Compound Library (4,226 compounds) in conjunction with itraconazole at 0.06 µg/mL against A. fumigatus CDC #738. After the initial screening, we identified compounds known to be antifungals or antiseptics and deselected them. The remaining thirty selected compounds were evaluated through published literature and clinical trial data to determine those candidates with favorable characteristics/properties. Criteria for candidate selection consisted of evaluating the compounds; plasma concentration peak, the time to reach peak, protein binding, oral availability, and drug class. Six candidates were ranked the highest of the previous round –surprisingly 50% of those compounds were HIV drugs, cobicistat, elvitegravir, lopinavir. The remaining three selected compounds are penfluridol, rilapladib, and rolapitant. The combination of itraconazole (ITC), posaconazole (POS), and voriconazole (VRC), with the identified compounds demonstrated promising amounts of synergy, in resistant and susceptible isolates. Further investigation revealed novel properties of ITC and POS when in combination with our compounds of interest. Rilapladib was able to reverse POS, ITC, and VRC resistant strain(s) to a sensitive profile. Growth kinetic assays demonstrate potent anti-germination properties not seen before in the sub-inhibitory doses of azoles. This work demonstrates that high-throughput screening as a viable technique to identify robust antifungal synergizers, allowing for tenable translation to a clinical setting.