NIKKOMYCIN Z AGAINST DISSEMINATED COCCIDIOIDOMYCOSIS IN A MURINE MODEL OF SUSTAINED RELEASE DOSING

Introduction. Nikkomycin Z (nikZ) is a chitin synthase inhibitor. Efficacy against Coccidioides has been demonstrated in animal models of pulmonary or brain infection. Its short half-life, in mice and humans, would necessitate divided daily dosing. We assayed nikZ efficacy in disseminated coccidioidomycosis (in a reduction of CFU design), and whether sustained release might be useful. Methods. Mice were challenged intravenously, with low or high arthroconidial inocula. Fluconazole, clinically the most commonly used anti-coccidioidal drug, was compared (gavage) at high dose to a dose range of nikZ administered intraperitoneally or, to mimic sustained release, administered continuously in drinking water. Therapy was given for 5 days. Results. In vitro, both fluconazole and nikZ inhibited the isolate studied; nikZ was fungicidal. Oral nikZ therapy gave similar results to intraperitoneal nikZ, and sterilized infection in most animals after low inoculum challenge. In both challenges, oral nikZ produced greater reduction of CFU in organs (lung, liver, spleen) than fluconazole. Oral nikZ doses ≥200 mg/kg/day were particularly effective, in all organs, and were well tolerated. This efficacy occurred even though, after severe challenge, mice had reduced water intake, resulting in ingesting less than the desired dose, particularly initially after infection. Summary . This study shows, for the first time, efficacy of nikZ against disseminated coccidioidomycosis. Efficacy was shown after challenges producing different levels of severity of disease. This study also suggests the likely benefits of developing an extended release formulation, supplying continuous systemic concentrations of nikZ.

Antifungal activity of nikkomycin Z against Candida auris

Background Nikkomycin Z is a competitive inhibitor of chitin synthase—an enzyme needed for synthesis of the fungal cell wall. Nikkomycin Z shows promise as a treatment for coccidioidomycoses and mixed activity has been described against other fungi and yeast. To our knowledge, it has not previously been tested against the emerging fungal pathogen Candida auris. Objectives To determine the in vitro activity of nikkomycin Z against C. auris. Methods Nikkomycin Z was tested by broth microdilution against a panel of 100 isolates of genetically diverse C. auris from around the world. Results Nikkomycin Z showed mixed activity against the tested isolates, with an MIC range of 0.125 to >64 mg/L. The MIC50 and MIC90 were 2 and 32 mg/L, respectively. Conclusions These findings suggest nikkomycin Z has in vitro activity against some, but not all isolates of C. auris.

Nikkomycin Z—Ready to Meet the Promise?

Nikkomycin Z (NikZ) has fungicidal activity against some fungal species which currently requires patients to endure chronic therapy, sometimes for years. This review highlights reports of NikZ activity against fungal species for which current therapeutics are still inadequate, as a potential roadmap for continuing investigation. The possibility of faster and more complete clinical resolution by using NikZ has attracted scientific attention for decades. NikZ inhibits chitin structure formation, which is important for fungi, but not found in mammals. NikZ raised no safety concerns in a human Phase 1 trial or in extensive toxicology studies. NikZ showed strong clinical benefit in dogs with natural Coccidioides infection. NikZ has protected animals against fatal infections of Candida albicans. NikZ provides high protection in synergistic combination with several agent classes against Candida and Aspergillus species.

In silico Binding Profile Analysis and in vitro Investigation on Chitin Synthase Substrate and Inhibitors from Maize stem Borer, Chilo partellus

Introduction: Insect growth and metamorphosis are strictly dependent on the structural changes that occur in chitin containing tissues and organs. Chitin synthase catalyzes chitin polymerization by β-(1, 4) glycosidic linkage of Nacetyl-D-glucosamine (GlcNAc) monomers; the major component of insect cuticles. Targeting this enzyme could be a promising strategy to control insect pests while avoiding adverse effects on coexisting populations. Nikkomycin Z and polyoxins are commercially available fungal inhibitors known to bind to the nucleotide-binding sites of insects and fungal chitin synthase. But the binding mode of chitin synthase has not been explored to date as its structure is not available yet. Methods: To understand the structural features of the Chilo partellus chitin synthase enzyme (CpCHS), the threedimensional (3D) structure of the CpCHS catalytic domain was modeled using ROBETTA webserver. The obtained model was used to investigate the binding mode of its substrate, uridine diphosphate-N-acetyl-D-glucosamine (UDPGlcNAc), and inhibitors (nikkomycin Z and polyoxins) by molecular docking approach using Schrödinger Suite-Maestro v9.2. The docked complexes were further investigated for their interaction stability by performing molecular dynamics (MD) simulations using GROMACS v5.1.2. Results: Our study highlighted the significance of various interactions made by CHS residues present in the Walker-B loop and donor-binding motifs with the substrate (UDP-GlcNAc), and GEDR motif with an acceptor (GlcNAc). Also, the interactions of the QRRRW motif while forming chitin polymer were explored. We observed that the inhibitors exhibited good binding affinity with these motifs, indicated by their docking and binding affinity scores. Conclusion: In vitro analysis suggested that nikkomycin Z showed higher inhibition of chitin synthase activity at a concentration of 2.5 µg.L-1 . Our study provided insights into the crucial interactions of chitin synthase while designing inhibitors against insect pests.

Potential use of Nikkomycin Z as an anti- Sporothrix spp. drug

Sporotrichosis, the most common subcutaneous mycosis in several countries, is caused by the dimorphic fungus, Sporothrix spp. Given some limitations in the treatment of this disease, and the high potential of nikkomycin Z (NikZ) as an antifungal against dimorphic fungi, this study aimed to evaluate the in vitro susceptibility of Sporothrix spp. to NikZ alone and with the drug of choice, itraconazole (ITZ). Seventeen clinical isolates of three Sporothrix spp. species (10 S. brasiliensis, six S. schenckii sensu stricto and one S. globosa) were tested in microdilution and checkerboard assays. Minimal inhibitory concentration (MIC), minimal fungicidal concentration (MFC), fractional inhibitory and fungicidal concentration indexes (FICi and FFCi) were analyzed. MIC of NikZ alone could be determined against S. globosa (12.5 μg/ml) and against 67% (4/6) and 30% (3/10) of the S. schenckii sensu stricto and S. brasiliensis isolates, respectively (≤ 400 μg/ml). Synergism with ITZ was showed against almost all the isolates tested (94%; 16/17), including reversing resistance to ITZ alone in some isolates. Our study shows the potential of NikZ in sporotrichosis treatment. Further studies in experimental models are needed to understand the possible future application of this drug as an alternative therapy or as an adjuvant in sporotrichosis treatment. Lay Abstract Sporotrichosis is a subcutaneous and lymphatic infection, caused by fungi of Sporothrix spp. Our study shows the potential of NikZ to inhibiting Sporothrix species in vitro. Further studies are needed to understand the future application of this drug to sporotrichosis treatment.

Effects of Echinocandins in Combination with Nikkomycin Z against Invasive Candida albicans Bloodstream Isolates and the fks Mutants

ABSTRACT We evaluated the in vitro and in vivo effects of nikkomycin Z combined with an echinocandin (anidulafungin or micafungin) against two Candida albicans isolates and their lab-derived echinocandin-resistant fks mutants with FKS1 S645Y and FKS1 S645P. Synergistic effects were observed in all tested strains (fractional inhibitory concentration index, <0.5). Enhanced survival was observed in an immunocompromised murine model (log-rank test, P < 0.02). Our study demonstrated the therapeutic potential of nikkomycin Z-echinocandin combinations in managing echinocandin resistance.