Water-Soluble Nystatin and Derivative

A Study on the Effect of Quaternization of Polyene Antibiotics' Structures on Their Activity, Toxicity, and Impact on Membrane Models

Polyene antibiotics have been used in antifungal therapy since the mid-twentieth century. They are highly valued for their broad spectrum of activity and the rarity of pathogen resistance to their action. However, their use in the treatment of systemic mycoses often results in serious side-effects. Recently, there has been a renewed interest in the development of new antifungal drugs based on polyenes, particularly due to the emergence of highly dangerous pathogenic strains of fungi, such as Candida auris, and the increased incidence of mucormycosis. Considerable understanding has been established regarding the structure-biological activity relationships of polyene antifungals. Yet, no previous studies have examined the effect of introducing quaternized fragments into their molecular structure. In this study, we present a series of amides of amphotericin B, nystatin, and natamycin bearing a quaternized group in the side chain, and discuss their biological properties: antifungal activity, cytotoxicity, and effects on lipid bilayers that mimic fungal and mammalian cell membranes. Our research findings suggest that the nature of the introduced quaternized residue plays a more significant role than merely the introduction of a constant positive charge. Among the tested polyenes, derivatives 4b, 5b, and 6b, which contain a fragment of N-methyl-4-(aminomethyl)pyridinium in their structure, are particularly noteworthy due to their biological activity.

Microemulsions, nanoemulsions and emulgels as carriers for antifungal antibiotics

According to estimates, up to 25% of the world's population has fungal skin diseases, making them the most prevalent infectious disease. Several chemical classes of antifungal drugs are available to treat fungal infections. However, the major challenges of conventional formulations of antifungal drugs include poor pharmacokinetic profiles like solubility, low permeability, side effects and decreased efficacy. Novel drug delivery is a promising approach for overcoming pharmacokinetic limitations and increasing the effectiveness of antibiotics. In this review, we have shed light on microemulsions, nanoemulsions, and emulgels as novel drug delivery approaches for the topical delivery of antifungal antibiotics. We believe these formulations have potential translational value and could be developed for treating fungal infections in humans.

Reviving the interest in the versatile drug nystatin: A multitude of strategies to increase its potential as an effective and safe antifungal agent

Nystatin is an antifungal molecule with a remarkable yet squandered versatility. In this review, its mechanism of action is explored, along with its extensive action spectrum and toxicity. A multitude of methodologies to tackle the drug's physical and chemical hurdles are outlined along with some proven-effective strategies to increase its activity and/or decrease its toxicity. A separate detailed section focused on micro and nanotechnology solutions addresses new drug delivery systems made of polymeric, metallic or lipid materials. Although the topical route depicts greater representativeness amongst these formulations, the intravenous, dental, oral, vaginal and inhalation routes are also mentioned. The unsuccessful previous attempts at developing parenteral formulations of nystatin or even the withdrawal of a nystatin-loaded multilamellar liposome should not divert research away from this drug. In fact, the interest in nystatin ought to be reawakened with the ongoing clinical trials on the promising nystatin-like genetically engineered derivate BSG005.

Semisynthetic Amides of Polyene Antibiotic Natamycin

Natamycin is a macrolide polyene antibiotic, characterized by a potent broad spectrum antifungal activity and low toxicity. However, it is not used for the treatment of systemic mycoses due to its low bioavailability and low solubility in aqueous solutions. In order to create new semisynthetic antifungal agents for treatment of mycoses, a series of water-soluble amides of natamycin were synthesized. Antifungal activities of natamycin derivatives were investigated against Candida spp., including a panel of Candida auris clinical isolates and filamentous fungi. Toxicity for mammalian cells was assayed by monitoring antiproliferative activity against human postnatal fibroblasts (HPF) and human embryonic kidney cells (HEK293). By comparing leakage of contents from ergosterol versus cholesterol containing vesicles, a ratio that characterizes the efficacy and safety of natamycin and its derivatives was determined (EI, efficiency index). Ability of all tested semisynthetic natamycines to prevent proliferation of the yeast Candida spp. cells was comparable or even slightly higher to those of parent antibiotic. Interestingly, amide 8 was more potent than natamycin (1) against all tested C. auris strains (MIC values 2 μg/mL vs 8 μg/mL, respectively). Among 7 derivatives, amide 10 with long lipophilic side chains showed the highest EI and strong antifungal activity in vitro but was more toxic against HPF. In vivo experiments with amide 8 showed in vivo efficacy on a mouse candidemia model with a larger LD₅₀/ED₅₀ ratio in comparison to amphotericin B.

Semisynthetic Amides of Amphotericin B and Nystatin A1: A Comparative Study of In Vitro Activity/Toxicity Ratio in Relation to Selectivity to Ergosterol Membranes

Polyene antifungal amphotericin B (AmB) has been used for over 60 years, and remains a valuable clinical treatment for systemic mycoses, due to its broad antifungal activity and low rate of emerging resistance. There is no consensus on how exactly it kills fungal cells but it is certain that AmB and the closely-related nystatin (Nys) can form pores in membranes and have a higher affinity towards ergosterol than cholesterol. Notably, the high nephro- and hemolytic toxicity of polyenes and their low solubility in water have led to efforts to improve their properties. We present the synthesis of new amphotericin and nystatin amides and a comparative study of the effects of identical modifications of AmB and Nys on the relationship between their structure and properties. Generally, increases in the activity/toxicity ratio were in good agreement with increasing ratios of selective permeabilization of ergosterol- vs. cholesterol-containing membranes. We also show that the introduced modifications had an effect on the sensitivity of mutant yeast strains with alterations in ergosterol biosynthesis to the studied polyenes, suggesting a varying affinity towards intermediate ergosterol precursors. Three new water-soluble nystatin derivatives showed a prominent improvement in safety and were selected as promising candidates for drug development.