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.

The overexpression and activity of carbonic anhydrase (CA, EC 4.2.1.1) isoforms CA IX and CA XII promote the accumulation of exceeding protons and acidosis in the extracellular tumor environment. Sulfonamides are effective inhibitors of most families of CAs. In this study, using scaffold-hopping, indoline-5-sulfonamide analogs 4a–u of the CA IX-selective inhibitor 3 were designed and synthesized to evaluate their biological properties. 1-Acylated indoline-5-sulfonamides demonstrated inhibitory activity against tumor-associated CA IX and XII with K_I values up to 132.8 nM and 41.3 nM. Compound 4f, as one of the most potent inhibitors of CA IX and XII, exhibits hypoxic selectivity, suppressing the growth of MCF7 cells at 12.9 µM, and causes partial inhibition of hypoxia-induced CA IX expression in A431 skin cancer cells. 4e and 4f reverse chemoresistance to doxorubicin of K562/4 with overexpression of P-gp.

The sustained rise of antimicrobial resistance (AMR) causes a strong need to develop new antibacterial agents. One of the methods for addressing the problem of antibiotic resistance is through the design of hybrid antibiotics. In this work, we proposed a synthetic route for the conjugation of an azithromycin derivative with chloramphenicol and metronidazole hemisuccinates and synthesized two series of new hybrid molecules 4a–g and 5a–g. While a conjugation did not result in tangible synergy for wild-type bacterial strains, new compounds were able to overcome AMR associated with the inducible expression of the ermC gene on a model E. coli strain resistant to macrolide antibiotics. The newly developed hybrids demonstrated a tendency to induce premature ribosome stalling, which might be crucial since they will not induce a macrolide-resistant phenotype in a number of pathogenic bacterial strains. In summary, the designed structures are considered as a promising direction for the further development of hybrid molecules that can effectively circumvent AMR mechanisms to macrolide antibiotics.

Objectives: In 2022, the World Health Organization highlighted the necessity for the development of new antifungal agents. Polyene antibiotics are characterized by a low risk of drug resistance; however, their use is limited by low solubility and severe side effects. Methods: A series of N-alkylated derivatives of amphotericin B and nystatin A₁ as well as their N-(2-hydroxyethyl)amides were synthesized. Their antifungal activity was evaluated against various Candida strains and Aspergillus fumigatus using the broth microdilution method. Cytotoxicity was assessed using an MTT assay on human embryonic kidney cells HEK293 and human skin fibroblast cells hFB-hTERT6, as well as a hemolysis assay on erythrocytes. Membrane activity was analyzed by fluorimetric measurement of calcein leakage from model liposomes. Results: Derivatives containing the N-(hydroxyethyl)amino)ethyl fragment (compounds 3 and 4) exhibited relatively high antifungal activity, as did N-(2-hydroxyethyl)amides 5 and 9. Bis-modified compounds 6 and 10 did not outperform their mono-modified analogues in terms of activity or cytotoxicity. The mono-N-alkylated compound 3 showed the highest activity/toxicity ratio, which correlated well with its selectivity for ergosterol-containing model membranes. Discussion: Combining two successful modifications does not necessarily improve the activity/toxicity ratio of polyenes. Further studies can be performed for the optimization of carboxyl group of 3.

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.

The increasing threat of antimicrobial resistance (AMR) has driven the need for novel antibacterial agents. Conjugating antibiotics with siderophores may expand their spectrum of activity or enhance their efficacy against AMR strains. In this study, we developed a synthetic route for azithromycin derivatives bound with siderophore moieties containing one or two 2,3-dihydroxybenzamide residues, yielding two series of hybrid molecules (5a-b, 6a-b, 7a-b, and 8a-b, 9a-b, 10a-b). Derivatives 5a, 6a-b, and 7a-b, which bear a single siderophore fragment, exhibited MIC values comparable to those of azithromycin against the majority of tested pathogens. Notably, compounds 7a-b demonstrated increased activity under iron-deficient conditions against Gram-negative Pseudomonas aeruginosa and Escherichia coli strains. In contrast, azotochelin-containing conjugates (9ab and 10a-b) were found to be completely inactive. Although the introduction of a siderophore did not significantly enhance the potency of macrolides in this study, further optimization of the conjugation strategy, linker structure, or chelating moieties may lead to more effective siderophore-macrolide antibiotics.