Antimicrobial effects of Medicines for Malaria Venture Pathogen Box compounds on strains of Neisseria gonorrhoeae

Therapeutic options for Neisseria gonorrhoeae are limited due to emerging global resistance. New agents and treatment options to treat patients with susceptible and multi-extensively drug-resistant N. gonorrhoeae is a high priority. This study used an in vitro approach to explore the antimicrobial potential, as well as synergistic effects of Medicine for Malaria Venture (MMV) Pathogen Box compounds against ATCC and clinical N. gonorrhoeae strains. Microbroth dilution assay was used to determine pathogen-specific minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the Pathogen Box compounds against susceptible and resistant N. gonorrhoeae strains, with modification, by adding PrestoBlue HS Cell Viability Reagent. A checkerboard assay was used to determine synergy between the active compounds and in conjunction with ceftriaxone. Time-kill kinetics was performed to determine if the compounds were either bactericidal or bacteriostatic. The Pathogen Box compounds: MMV676501, MMV002817, MMV688327, MMV688508, MMV024937, MMV687798 (levofloxacin), MMV021013, and MMV688978 (auranofin) showed potent activity against resistant strains of N. gonorrhoeae at an MIC and MBC of ≤10 µM. Besides the eight compounds, MMV676388 and MMV272144 were active against susceptible N. gonorrhoeae strains, also at MIC and MBC of ≤10 µM. All the compounds were bactericidal and were either synergistic or additive with fractional inhibitory concentration index ranging between 0.40 and 1.8. The study identified novel Pathogen Box compounds with potent activity against N. gonorrhoeae strains and has the potential to be further investigated as primary or adjunctive therapy to treat gonococcal infections.

Leveraging the MMV Pathogen Box to Engineer an Antifungal Compound with Improved Efficacy and Selectivity against Candida auris

Fungal infections pose a significant and increasing threat to human health, but the current arsenal of antifungal drugs is inadequate. We screened the Medicines for Malaria Venture (MMV) Pathogen Box for new antifungal agents against three of the most critical Candida species (Candida albicans, Candida auris, and Candida glabrata). Of the 14 identified hit compounds, most were active against C. albicans and C. auris. We selected the pyrazolo-pyrimidine MMV022478 for chemical modifications to build structure-activity relationships and study their antifungal properties. Two analogues, 7a and 8g, with distinct fluorine substitutions, greatly improved the efficacy against C. auris and inhibited fungal replication inside immune cells. Additionally, analogue 7a had improved selectivity toward fungal killing compared to mammalian cytotoxicity. Evolution experiments generating MMV022478-resistant isolates revealed a change in morphology from oblong to round cells. Most notably, the resistant isolates blocked the uptake of the fluorescent dye rhodamine 6G and showed reduced susceptibility toward fluconazole, indicative of structural changes in the yeast cell surface. In summary, our study identified a promising antifungal compound with activity against high-priority fungal pathogens. Additionally, we demonstrated how structure-activity relationship studies of known and publicly available compounds can expand the repertoire of molecules with antifungal efficacy and reduced cytotoxicity to drive the development of novel therapeutics.

Preliminary Structure-Activity Relationship Study of the MMV Pathogen Box Compound MMV675968 (2,4-Diaminoquinazoline) Unveils Novel Inhibitors of Trypanosoma brucei brucei

New drugs are urgently needed for the treatment of human African trypanosomiasis (HAT). In line with our quest for novel inhibitors of trypanosomes, a small library of analogs of the antitrypanosomal hit (MMV675968) available at MMV as solid materials was screened for antitrypanosomal activity. In silico exploration of two potent antitrypanosomal structural analogs (7-MMV1578647 and 10-MMV1578445) as inhibitors of dihydrofolate reductase (DHFR) was achieved, together with elucidation of other antitrypanosomal modes of action. In addition, they were assessed in vitro for tentative inhibition of DHFR in a crude trypanosome extract. Their ADMET properties were also predicted using dedicated software. Overall, the two diaminoquinazoline analogs displayed approximately 40-fold and 60-fold more potency and selectivity in vitro than the parent hit, respectively (MMV1578445 (10): IC₅₀ = 0.045 µM, SI = 1737; MMV1578467 (7): IC₅₀ = 0.06 µM; SI = 412). Analogs 7 and 10 were also strong binders of the DHFR enzyme in silico, in all their accessible protonation states, and interacted with key DHFR ligand recognition residues Val32, Asp54, and Ile160. They also exhibited significant activity against trypanosome protein isolate. MMV1578445 (10) portrayed fast and irreversible trypanosome growth arrest between 4–72 h at IC₉₉. Analogs 7 and 10 induced in vitro ferric iron reduction and DNA fragmentation or apoptosis induction, respectively. The two potent analogs endowed with predicted suitable physicochemical and ADMET properties are good candidates for further deciphering their potential as starting points for new drug development for HAT.

In Vitro Screening of the Open-Source Medicines for Malaria Venture Malaria and Pathogen Boxes To Discover Novel Compounds with Activity against Balamuthia mandrillaris

Balamuthia mandrillaris is an under-reported, pathogenic free-living amoeba that causes Balamuthia amoebic encephalitis (BAE) and cutaneous skin infections. Although cutaneous infections are not typically lethal, BAE with or without cutaneous involvement is usually fatal. This is due to the lack of drugs that are both efficacious and can cross the blood-brain barrier. We aimed to discover new leads for drug discovery by screening the open-source Medicines for Malaria Venture (MMV) Malaria Box and MMV Pathogen Box, with 800 compounds total. From an initial single point screen at 1 and 10 μM, we identified 54 hits that significantly inhibited the growth of B. mandrillaris in vitro Hits were reconfirmed in quantitative dose-response assays and 23 compounds (42.6%) were confirmed with activity greater than miltefosine, the current standard of care.

Screening the Medicines for Malaria Venture Pathogen Box across Multiple Pathogens Reclassifies Starting Points for Open-Source Drug Discovery

Open-access drug discovery provides a substantial resource for diseases primarily affecting the poor and disadvantaged. The open-access Pathogen Box collection is comprised of compounds with demonstrated biological activity against specific pathogenic organisms. The supply of this resource by the Medicines for Malaria Venture has the potential to provide new chemical starting points for a number of tropical and neglected diseases, through repurposing of these compounds for use in drug discovery campaigns for these additional pathogens. We tested the Pathogen Box against kinetoplastid parasites and malaria life cycle stages in vitro Consequently, chemical starting points for malaria, human African trypanosomiasis, Chagas disease, and leishmaniasis drug discovery efforts have been identified. Inclusive of this in vitro biological evaluation, outcomes from extensive literature reviews and database searches are provided. This information encompasses commercial availability, literature reference citations, other aliases and ChEMBL number with associated biological activity, where available. The release of this new data for the Pathogen Box collection into the public domain will aid the open-source model of drug discovery. Importantly, this will provide novel chemical starting points for drug discovery and target identification in tropical disease research.

In vitro screening of the open source Pathogen Box identifies novel compounds with profound activities against Neospora caninum

Neospora caninum is a major cause of abortion in cattle and represents an important veterinary health problem of great economic significance. The Medicines for Malaria Venture (MMV) Pathogen Box, an open-source collection of 400 compounds with proven anti-infective properties against a wide range of pathogens, was screened against a N. caninum beta-galactosidase reporter strain grown in human foreskin fibroblasts. A primary screening carried out at 1µM yielded 40 compounds that were effective against N. caninum tachyzoites. However, 30 of these compounds also affected the viability of the host cells. The 10 remaining compounds exhibited IC₅₀ values between 4 and 43nM. Three compounds with IC₅₀ values below 10nM, namely MMV676602, MMV688762 and MMV671636, were further characterized in vitro in more detail with respect to inhibition of invasion versus intracellular proliferation, and only MMV671636 had an impact on intracellular proliferation of tachyzoites. This was confirmed by transmission electron microscopy, showing that the primary target of MMV671636 was the mitochondrion. MMV671636 treatment of experimentally infected mice significantly reduced the number of animals with lung and brain infection, and these mice also exhibited a significantly reduced titer of antibodies directed against N. caninum antigens. Thus, MMV671636 is a promising starting point for the development of a future neosporosis therapy.