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Decades of previous efforts to develop renal-sparing polyene antifungals were misguided by the classic membrane permeabilization model 1 . Recently, the clinically vital but also highly renal-toxic small-molecule natural product amphotericin B was instead found to kill fungi primarily by forming extramembraneous sponge-like aggregates that extract ergosterol from lipid bilayers 2 – 6 . Here we show that rapid and selective extraction of fungal ergosterol can yield potent and renal-sparing polyene antifungals. Cholesterol extraction was found to drive the toxicity of amphotericin B to human renal cells. Our examination of high-resolution structures of amphotericin B sponges in sterol-free and sterol-bound states guided us to a promising structural derivative that does not bind cholesterol and is thus renal sparing. This derivative was also less potent because it extracts ergosterol more slowly. Selective acceleration of ergosterol extraction with a second structural modification yielded a new polyene, AM-2-19, that is renal sparing in mice and primary human renal cells, potent against hundreds of pathogenic fungal strains, resistance evasive following serial passage in vitro and highly efficacious in animal models of invasive fungal infections. Thus, rational tuning of the dynamics of interactions between small molecules may lead to better treatments for fungal infections that still kill millions of people annually 7 , 8 and potentially other resistance-evasive antimicrobials, including those that have recently been shown to operate through supramolecular structures that target specific lipids 9 . A study reports the development of a structural derivative of amphotericin B with broad antifungal activity in mice but without the renal toxicity associated with amphotericin B.

COVID-19 patients often develop serious fungal infections like Aspergillosis, Candidiasis, and Mucormycosis, which are treated with antifungal drugs like Amphotericin B, Posaconazole, and Isavuconazole. However, these treatments are often insufficient, leading researchers to explore drug combinations and analogs. In theoretical chemistry, a chemical molecule is converted into an isomorphic molecular graph, represented as G (V, E) by considering atom set V as vertices and bond set E as edges. Quantitative structure–activity/property/toxicity relationships (QSAR, QSPR, QSTR) modelling is a widely recognized discipline that correlates physicochemical and molecular descriptors with a drug’s bioactivity to predict its standard pharmacological properties. In this article, the aforementioned drugs, as well as some Amphotericin B analogs, with their properties, are considered for QSPR/QSTR analysis. The QSPR/QSTR analysis is carried out using linear regression between the computed topological indices (based on degree and neighbourhood degree sum) and pharmacokinetic (ADMET) and toxicity properties (LD 50 ) of these drugs. The analysis reveals a strong correlation between the topological indices and the pharmacokinetic and toxicity properties of the drugs and their analogs. These insights are crucial for advancing more effective antifungal treatments, especially for COVID-19-related infections.

An amphotericin antifungal that is less toxic to human cells due to its increased capacity for binding the fungal ergosterol over the human cholesterol can still evade resistance mechanisms, challenging the resistance-toxicity yin-yang of antimicrobials. Drugs that act more promiscuously provide fewer routes for the emergence of resistant mutants. This benefit, however, often comes at the cost of serious off-target and dose-limiting toxicities. The classic example is the antifungal amphotericin B (AmB), which has evaded resistance for more than half a century. We report markedly less toxic amphotericins that nevertheless evade resistance. They are scalably accessed in just three steps from the natural product, and they bind their target (the fungal sterol ergosterol) with far greater selectivity than AmB. Hence, they are less toxic and far more effective in a mouse model of systemic candidiasis. To our surprise, exhaustive efforts to select for mutants resistant to these more selective compounds revealed that they are just as impervious to resistance as AmB. Thus, highly selective cytocidal action and the evasion of resistance are not mutually exclusive, suggesting practical routes to the discovery of less toxic, resistance-evasive therapies.

Amphotericin B (AMB) is a highly hydrophobic antifungal, whose use is limited by its toxicity and poor solubility. To improve its solubility, AMB was reacted with a functionalized polyethylene glycol (PEG), yielding soluble complex AmB-PEG formulations that theoretically comprise of chemically conjugated AMB-PEG and free AMB that is physically associated with the conjugate. Reverse-phase chromatography and size exclusion chromatography methods using HPLC were developed to separate conjugated AMB-PEG and free AmB, enabling the further characterization of these formulations. Using HPLC and dynamic light scattering analyses, it was observed that the AMB-PEG 2 formulation, having a higher molar ratio of 2 AMB: 1 PEG, possesses more free AMB and has relatively larger particle diameters compared to the AMB-PEG 1 formulation, that consists of 1 AMB: 1 PEG. The identity of the conjugate was also verified using mass spectrometry. AMB-PEG 2 demonstrates improved antifungal efficacy relative to AMB-PEG 1, without a concurrent increase in in vitro toxicity to mammalian cells, implying that the additional loading of free AMB in the AMB-PEG formulation can potentially increase its therapeutic index. Compared to unconjugated AMB, AMB-PEG formulations are less toxic to mammalian cells in vitro, even though their MIC50 values are comparatively higher in a variety of fungal strains tested. Our in vitro results suggest that AMB-PEG 2 formulations are two times less toxic than unconjugated AMB with antifungal efficacy on Candida albicans and Cryptococcus neoformans.

Streptomyces nodosus produces the antifungal polyene amphotericin B. Numerous modifications of the amphotericin polyketide synthase have yielded new analogues. However, previous inactivation of the ketoreductase in module 10 resulted in biosynthesis of truncated polyketides. Here we show that modules downstream of this domain remain intact. Therefore, loss of ketoreductase-10 activity is sufficient to cause early chain termination. This modification creates a labile point in cycle 11 of the polyketide biosynthetic pathway. Non-extendable intermediates are released to accumulate as polyenyl-pyrones.

HIV-1 virions are highly enriched in cholesterol relative to the cellular plasma membrane. We recently reported that a cholesterol-binding compound, amphotericin B methyl ester (AME), blocks HIV-1 entry and that single amino acid substitutions in the cytoplasmic tail of the transmembrane envelope glycoprotein gp41 confer resistance to AME. In this study, we defined the mechanism of resistance to AME. We observed that the gp41 in AME-resistant virions is substantially smaller than wild-type gp41. Remarkably, we found that this shift in gp41 size is due to cleavage of the gp41 cytoplasmic tail by the viral protease. We mapped the protease-mediated cleavage to two sites in the cytoplasmic tail and showed that gp41 truncations in this region also confer AME resistance. Thus, to escape the inhibitory effects of AME, HIV-1 evolved a mechanism of protease-mediated envelope glycoprotein cleavage used by several other retroviruses to activate envelope glycoprotein fusogenicity. In contrast to the mechanism of AME resistance observed for HIV-1, we demonstrate that simian immunodeficiency virus can escape from AME via the introduction of premature termination codons in the gp41 cytoplasmic tail coding region. These findings demonstrate that in human T cell lines, HIV-1 and simian immunodeficiency virus can evolve distinct strategies for evading AME, reflecting their differential requirements for the gp41 cytoplasmic tail in virus replication. These data reveal that HIV-1 can escape from an inhibitor of viral entry by acquiring mutations that cause the cytoplasmic tail of gp41 to be cleaved by the viral protease.

A new derivative of amphotericin B named amphotericin B(5) has been obtained under the following condition: amphotericin B powder was first dissolved in N,N -dimethylformamide at room temperature to obtain a solution of concentration of 2.0 mg ml −1 . Then, the solution was kept at 60 °C in an electric-heated thermostatic water bath for 48–60 h for the purpose of accelerating the degradation. Amphotericin B(5) was isolated by preparative HPLC. Its structure has been identified by means of UV, NMR and LCMS-IT-TOF as (1R, 3S, 5R, 6R, 9R, 11R, 15S, 16R, 17R, 18S, 19E, 21E, 23E, 25E, 27E, 29E, 31E, 33R, 35S, 36R, 37S)-33-[3-form-amide-3,6-dideoxy-β--mannopy-ran-osyl)oxy]-1,3,5,6,9,11,17,37-octahydroxy-15,16,18-trimethyl-13-oxo-14,39-di-oxabicyclo [33.3.1] nonatriaconta-19,21,23,25,27,29,31-heptaene-36-carboxylic acid named according to the International Union of Pure and Applied Chemistry. The activity of amphotericin B(5) was tested against Saccharomyces cerevisiae based on microbiological potency using cylinder-plate method, and the toxicities of amphotericin B and amphotericin B(5) were determined simultaneously in zebrafish embryo. The results showed that the toxicity of amphotericin B(5), as revealed by its LD 50 value, was lower than amphotericin B.

Comparative studies were performed to determine the activity and cytotoxicity of amphotericin B (AmB) and its derivatives on standard strain of Saccharomyces cerevisiae and its transformants with cloned genes from Candida albicans encoding multidrug resistance (MDR) pumps of ATP-binding cassette and major facilitator superfamilies. The AmB derivatives: amphotericin B 3-dimethylaminopropyl amide and N -methyl- N - D -fructopyranosylamphotericin B methyl ester were shown to be fungistatic and fungicidal towards MDR strains, by membrane permeabilization mechanism. Antibiotic-cell interaction monitored by energy transfer method indicates similar membrane affinity in parent strain and its MDR transformants. Experiments with fungal cells loaded with rhodamine 6G point to lack of competition between this dye and AmB and its derivatives for efflux driven by CDR2p. It can be thus assumed that AmB and its derivatives overcome fungal MDR by not being substrates of the multidrug exporting pumps, presumably due to their large molecular volumes.

Amphotericin B colloidal dispersion (ABCD; Amphocil) was evaluated in a phase I dose-escalation study in 75 marrow transplant patients with invasive fungal infections (primarily Aspergillus or Candida species) to determine the toxicity profile, maximum tolerated dose, and clinical response. Escalating doses of 0.5–8.0 mg/kg in 0.5-mg/kg/patient increments were given up to 6 weeks. No infusion-related toxicities were observed in 32% of the patients; 52% had grade 2 and 5% had grade 3 toxicity. No appreciable renal toxicity was observed at any dose level. The estimated maximum tolerated dose was 7.5 mg/kg, defined by rigors and chills and hypotension in 3 of 5 patients at 8.0 mg/kg. The complete or partial response rate across dose levels and infection types was 52%. For specific types of infections, 53% of patients with fungemia had complete responses, and 52% of patients with pneumonia had complete or partial responses. ABCD was safe at doses to 7.5 mg/kg and had tolerable infusion-related toxicity and demonstrable antifungal activity.

Enoyl reductase (ER) domains in module 5 of nystatin and amphotericin polyketide synthase (PKS) are responsible for reduction of the C28-C29 unsaturated bond on the nascent polyketide chain during biosynthesis of both macrolides, resulting in production of tetraenes nystatin A(1) and amphotericin A, respectively. Data obtained in fermentations under glucose limitation conditions demonstrated that the efficiency of the ER5 domain can be influenced by carbon source availability in the amphotericin producer Streptomyces nodosus, but not in the nystatin producer Streptomyces noursei. Two S. noursei ER5 domain mutants were constructed, GG5073SP and S5016N, both producing the heptaene nystatin analogue S44HP with unsaturated C28-C29 bond. While the GG5073SP mutant, with altered ER5 NADPH binding site, produced S44HP exclusively, the S5016N mutant synthesized a mixture of nystatin and S44HP. Comparative studies on the S5016N S. noursei mutant and S. nodosus, both producing mixtures of tetraenes and heptaenes, revealed that the ratio between these two types of metabolites was significantly more affected by glucose limitation in S. nodosus. These data suggest that mutation S5016N in NysC \"locks\" the ER5 domain in a state of intermediate activity which, in contrast to the ER5 domain in the amphotericin PKS, is not significantly influenced by physiological conditions.