Promising Antifungal Molecules against Mucormycosis Agents Identified from Pandemic Response Box(®): In Vitro and In Silico Analyses

New Strategies to Combat Human Fungal Infections

Over the past few decades, numerous reports have highlighted the significant rise in fungal infections worldwide, contributing to considerable morbidity, mortality, and escalating healthcare costs [...].

In vitro antifungal activity of MMV Pathogen Box® compounds alone or in combination with antifungal drugs against mucormycosis agents

Mucormycosis is a severe fungal infection that demands immediate and decisive intervention upon suspicion. The causative agents of mucormycosis exhibit inherent resistance to echinocandins and voriconazole, and their in vitro susceptibility to terbinafine is highly variable and species-specific. Considering these factors and the limitations of currently available antifungal therapies, the identification of novel antifungals with potent activity against mucormycosis is of paramount importance. This study aims to identify compounds from the MMV Pathogen Box® presenting antifungal activity against selected mucormycosis agents and to evaluate their potential synergistic effects when combined with antifungal drugs. A screening of the Pathogen Box® compounds was conducted, isolated or in combination with sub-inhibitory concentrations of amphotericin B, isavuconazole or posaconazole, against a Rhizopus oryzae strain. Hits from the screenings were further evaluated against eight Mucoralean strains for minimal inhibitory and fungicidal concentration determinations and to confirm synergistic interactions using the checkerboard method. Ultrastructural studies were performed using scanning electron microscopy. MMV675968 exhibited fungicidal activity against a R. oryzae strain. All but one Rhizopus spp. strains presented MIC ≤ 1 μg/mL, with a geometric mean of 0.78 μg/mL observed across all isolates for this compound, which did not change significantly the cellular structure of this fungus. The combination screening with antifungal drugs revealed six additional compounds potentially active against the R. oryzae strain, two of them demonstrated proven synergism through the checkerboard assay. This first study with the MMV Pathogen Box® and Zigomycetes highlights promising new treatment options for mucormycosis in the future.

Comprehensive Review on the Virulence Factors and Therapeutic Strategies with the Aid of Artificial Intelligence against Mucormycosis

Mucormycosis, a rare but deadly fungal infection, was an epidemic during the COVID-19 pandemic. The rise in cases (COVID-19-associated mucormycosis, CAM) is attributed to excessive steroid and antibiotic use, poor hospital hygiene, and crowded settings. Major contributing factors include diabetes and weakened immune systems. The main manifesting forms of CAM─cutaneous, pulmonary, and the deadliest, rhinocerebral─and disseminated infections elevated mortality rates to 85%. Recent focus lies on small-molecule inhibitors due to their advantages over standard treatments like surgery and liposomal amphotericin B (which carry several long-term adverse effects), offering potential central nervous system penetration, diverse targets, and simpler dosing owing to their small size, rendering the ability to traverse the blood-brain barrier via passive diffusion facilitated by the phospholipid membrane. Adaptation and versatility in mucormycosis are facilitated by a multitude of virulence factors, enabling the pathogen to dynamically respond to various environmental stressors. A comprehensive understanding of these virulence mechanisms is imperative for devising effective therapeutic interventions against this highly opportunistic pathogen that thrives in immunocompromised individuals through its angio-invasive nature. Hence, this Review delineates the principal virulence factors of mucormycosis, the mechanisms it employs to persist in challenging host environments, and the current progress in developing small-molecule inhibitors against them.

Identifying Fast and Slow-Acting Antimalarial Compounds of Pandemic Response Box Against Blood-Stage Culture of Plasmodium falciparum 3D7

The evolving clinical resistance in Plasmodium falciparum and the spike in malarial cases after the COVID-19 outbreak has triggered a search for new antimalarials effective against multi-drug-resistant P. falciparum strains. In this study, we assessed the timing of action, either fast or slow-acting of 13 potent compounds of Pandemic Response Box (PRB) against blood-stage Pf3D7 strain by SYBR Green-I assay. The asynchronous culture of Pf3D7 was exposed to varying concentrations of 13 compounds, and IC50 values were determined at 12, 24, 48, 72, and 96 h. We identified four fast-acting compounds (MMV000008, MMV1593541, MMV020752, MMV396785) with rapid-growth inhibitory activity having IC50 values ≤ 0.3 µM at 12 and 24 h. Similarly, we determined nine slow-acting compounds (MMV159340, MMV1634492, MMV1581558, MMV689758, MMV1593540, MMV394033, MMV019724, MMV000725, MMV1557856) having IC50 values ≤ 0.5 µM at 72 and 96 h. Furthermore, the stage-specific action of the two most potent fast-acting compounds (MMV1593541 and MMV020752) against rings, trophozoites, and schizonts at 48 h of exposure revealed that ring-stage parasites showed reduced IC50 values compared to mature stage forms. Therefore, our study demonstrates for the first time the identification of the most potent fast and slow-acting compounds from PRB against blood-stage infection, suggesting its utility in clinics and considering it as a partner drug in combination therapies.

Miltefosine: A Repurposing Drug against Mucorales Pathogens

Mucorales are a group of non-septated filamentous fungi widely distributed in nature, frequently associated with human infections, and are intrinsically resistant to many antifungal drugs. For these reasons, there is an urgent need to improve the clinical management of mucormycosis. Miltefosine, which is a phospholipid analogue of alkylphosphocholine, has been considered a promising repurposing drug to be used to treat fungal infections. In the present study, miltefosine displayed antifungal activity against a variety of Mucorales species, and it was also active against biofilms formed by these fungi. Treatment with miltefosine revealed modifications of cell wall components, neutral lipids, mitochondrial membrane potential, cell morphology, and the induction of oxidative stress. Treated Mucorales cells also presented an increased susceptibility to SDS. Purified ergosterol and glucosylceramide added to the culture medium increased miltefosine MIC, suggesting its interaction with fungal lipids. These data contribute to elucidating the effect of a promising drug repurposed to act against some relevant fungal pathogens that significantly impact public health.

Screening the medicine for malaria venture's Pandemic Response Box to identify novel inhibitors of Candida albicans and Candida auris biofilm formation

Candida spp. are opportunistic yeasts capable of forming biofilms, which contribute to resistance, increasing the urgency for new effective antifungal therapies. Repurposing existing drugs could significantly accelerate the development of novel therapies against candidiasis. We screened the Pandemic Response Box containing 400 diverse drug-like molecules active against bacteria, viruses or fungi, for inhibitors of Candida albicans and Candida auris biofilm formation. Initial hits were identified based on the demonstration of >70% inhibitory activity. Dose-response assays were used to confirm the antifungal activity of initial hits and establish their potency. The spectrum of antifungal activity of the leading compounds was determined against a panel of medically important fungi, and the in vivo activity of the leading repositionable agent was evaluated in murine models of C. albicans and C. auris systemic candidiasis. The primary screening identified 20 hit compounds, and their antifungal activity and potency against C. albicans and C. auris were validated using dose-response measurements. From these experiments, the rapalog everolimus, emerged as the leading repositionable candidate. Everolimus displayed potent antifungal activity against different Candida spp., but more moderate levels of activity against filamentous fungi. Treatment with everolimus increased survival of mice infected with C. albicans, but not those with C. auris. The screening of the Pandemic Response Box resulted in the identification of several drugs with novel antifungal activity, with everolimus emerging as the main repositionable candidate. Further in vitro and in vivo studies are needed to confirm its potential therapeutic use.