Erythromycin Formulations—A Journey to Advanced Drug Delivery

Discovery, characterization, and engineering of an advantageous Streptomyces host for heterologous expression of natural product biosynthetic gene clusters

BACKGROUND

Streptomyces is renowned for its robust biosynthetic capacity in producing medically relevant natural products. However, the majority of natural products biosynthetic gene clusters (BGCs) either yield low amounts of natural products or remain cryptic under standard laboratory conditions. Various heterologous production hosts have been engineered to address these challenges, and yet the successful activation of BGCs has still been limited. In our search for a valuable addition to the heterologous host panel, we identified the strain Streptomyces sp. A4420, which exhibited rapid initial growth and a high metabolic capacity, prompting further exploration of its potential.

RESULTS

We engineered a polyketide-focused chassis strain based on Streptomyces sp. A4420 (CH strain) by deleting 9 native polyketide BGCs. The resulting metabolically simplified organism exhibited consistent sporulation and growth, surpassing the performance of most existing Streptomyces based chassis strains in standard liquid growth media. Four distinct polyketide BGCs were chosen and expressed in various heterologous hosts, including the Streptomyces sp. A4420 wild-type and CH strains, alongside Streptomyces coelicolor M1152, Streptomyces lividans TK24, Streptomyces albus J1074, and Streptomyces venezuelae NRRL B-65442. Remarkably, only the Streptomyces sp. A4420 CH strain demonstrated the capability to produce all metabolites under every condition outperforming its parental strain and other tested organisms. To enhance visualization and comparison of the tested strains, we developed a matrix-like analysis involving 15 parameters. This comprehensive analysis unequivocally illustrated the significant potential of the new strain to become a popular heterologous host.

CONCLUSION

Our engineered Streptomyces sp. A4420 CH strain exhibits promising attributes for the heterologous expression of natural products with a focus on polyketides, offering an alternative choice in the arsenal of heterologous production strains. As genomics and cloning strategies progress, establishment of a diverse panel of heterologous production hosts will be crucial for expediting the discovery and production of medically relevant natural products derived from Streptomyces.

Erythromycin for myotonic dystrophy type 1: a multicentre, randomised, double-blind, placebo-controlled, phase 2 trial

Background

Myotonic dystrophy type 1 (DM1) is a devastating multisystemic disorder caused by a CTG repeat expansion in the DMPK gene, which subsequently triggers toxic RNA expression and dysregulated splicing. In a preclinical study, we demonstrated that erythromycin reduces the toxicity of abnormal RNA and ameliorates the aberrant splicing and motor phenotype in DM1 model mice.

Methods

This multicentre, randomised, double-blind, placebo-controlled, phase 2 trial was conducted at three centres in Japan to translate preclinical findings into practical applications in patients with DM1 by evaluating the safety and efficacy of erythromycin. Between Nov 29, 2019, and Jan 20, 2022, a total of 30 adult patients with DM1 were enrolled and randomly assigned in a 1:2:2 ratio to receive either placebo or erythromycin at two daily doses (500 mg or 800 mg) for 24 weeks. The primary outcome included the safety and tolerability of erythromycin. The secondary efficacy measures included splicing biomarkers, 6-min walk test results, muscle strength, and serum creatinine kinase (CK) values. This trial is registered with the Japan Registry of Clinical Trials, jRCT2051190069.

Findings

Treatment-related gastrointestinal symptoms occurred more frequently in the erythromycin group, but all adverse events were mild to moderate and resolved spontaneously. No serious safety concerns were identified. The CK levels from baseline to week 24 decreased in the overall erythromycin group compared with the placebo group (mean change of -6.4 U/L [SD 149] vs +182.8 [SD 228]), although this difference was not statistically significant (p = 0.070). Statistically significant improvements in the overall erythromycin treated groups compared to placebo were seen for two of the eleven splicing biomarkers that were each evaluated in half of the trial sample. These were MBNL1 (p = 0.048) and CACNA1S (p = 0.042).

Interpretation

Erythromycin demonstrated favourable safety and tolerability profiles in patients with DM1. A well-powered phase 3 trial is needed to evaluate efficacy, building on the preliminary findings from this study.

Funding

Japan Agency for Medical Research and Development.

"Sandwich-like" structure electrostatic spun micro/nanofiber polylactic acid-polyvinyl alcohol-polylactic acid film dressing with metformin hydrochloride and puerarin for enhanced diabetic wound healing

A diabetic wound is a typical chronic wound with a long repair process and poor healing effects. It is an effective way to promote diabetic wound healing to design electrospinning nanofiber films with drug-assisted therapy, good air permeability and, a multilayer functional structure. In this paper, a diabetic wound dressing with a "sandwich-like" structure was designed. Metformin hydrochloride, loaded in the hydrophilic PVA inner layer, could effectively promote diabetic wound healing. The drug release was slowed down by osmosis. The laminate film dressing had good mechanical properties, with tensile strength and elongation at break reaching 5.91 MPa and 90.47 %, respectively, which was close to human skin. The laminate film loaded with erythromycin and puerarin in the hydrophobic PLA outer layer had good antibacterial properties. In addition, due to the high specific surface of the electrostatic spun film, it exhibited high water vapor permeability. It facilitates the gas exchange between the wound and the outside world. The cell experiments proved that the laminate film dressing had good biocompatibility. There was no toxic side effect on cell proliferation. In the diabetic animal wound model, it was shown that the closure rate of diabetic wound repair by laminate film reached 91.11 % in the second week. Our results suggest that the "sandwich-like" nanofiber film dressing could effectively promote the healing process and meet the various requirements of diabetic wound dressing as a promising candidate for future clinical application of chronic wound dressings.

Low-dose erythromycin in pediatrics: Formulation and stability of 20 mg hard gelatin capsules

OBJECTIVE

Erythromycin is a macrolide antibiotic that is also prescribed off-label in premature neonates as a prokinetic agent. There is no oral formulation with dosage and/or excipients adapted for these high-risk patients.

METHODS

Clinical studies of erythromycin as a prokinetic agent were reviewed. Capsules of 20 milligrams of erythromycin were compounded with microcrystalline cellulose. Erythromycin capsules were analyzed using the chromatographic method described in the United States Pharmacopoeia which was found to be stability-indicating. The stability of 20 mg erythromycin capsules stored protected from light at room temperature was studied for one year.

RESULTS

20 mg erythromycin capsules have a beyond use date not lower than one year.

CONCLUSION

20 milligrams erythromycin capsules can be compounded in batches of 300 unities in hospital pharmacy with a beyond-use-date of one year at ambient temperature protected from light.

Development and Optimization of Erythromycin Loaded Transethosomes Cinnamon Oil Based Emulgel for Antimicrobial Efficiency

Erythromycin (EM) is a macrolide antibiotic that is frequently used to treat skin bacterial infections. It has a short half-life (1-1.5 h), instability in stomach pH, and a low oral bioavailability. These foregoing factors limit its oral application; therefore, the development of topical formulations loaded with erythromycin is an essential point to maximize the drug's concentration at the skin. Accordingly, the current study's goal was to boost the antimicrobial activity of EM by utilizing the advantages of natural oils such as cinnamon oil. Erythromycin-loaded transethosomes (EM-TE) were generated and optimized using a Box-Behnken design employing, phospholipid concentration (A), surfactant concentration (B), and ethanol content (C) as independent variables. Their effects on entrapment efficiency, EE, (Y₁) and the total amount of erythromycin that penetrated the skin after 6 h, Q6h (Y₂), were assessed. The optimized transethosome showed a particle size of 256.2 nm, EE of 67.96 ± 0.59%, and Q6h of 665.96 ± 5.87 (µg/cm²) after 6 h. The TEM analysis revealed that, the vesicles are well-known packed structures with a spherical shape. The optimized transethosomes formulation was further transformed into a cinnamon oil-based emulgel system using HPMC as a gelling agent. The generated EM-TE-emulgel was characterized by its physical features, in vitro, ex vivo studies, and antimicrobial activities. The formulation showed sufficient characteristics for effective topical application, and demonstrated a great stability. Additionally, EM-TE-Emulgel had the highest transdermal flux (120.19 μg/cm²·h), and showed considerably (p < 0.05) greater antimicrobial activity, than EM-TE-gel and placebo TE-Emulgel. The action of EM was subsequently augmented with cinnamon oil, which eventually showed a notable effect against bacterial growth. Finally, these results demonstrate that the transethosomes-loaded cinnamon oil-based emulgel is an alternative way to deliver erythromycin for the treatment of topical bacterial infections.

Design, Characterization, and Biological Activities of Erythromycin-Loaded Nanodroplets to Counteract Infected Chronic Wounds Due to Streptococcus pyogenes

Streptococcus pyogenes causes a wide spectrum of diseases varying from mild to life threatening, despite antibiotic treatment. Nanoparticle application could facilitate the foreign pathogen fight by increasing the antimicrobial effectiveness and reducing their adverse effects. Here, we designed and produced erythromycin-loaded chitosan nanodroplets (Ery-NDs), both oxygen-free and oxygen-loaded. All ND formulations were characterized for physico-chemical parameters, drug release kinetics, and tested for biocompatibility with human keratinocytes and for their antibacterial properties or interactions with S. pyogenes. All tested NDs possessed spherical shape, small average diameter, and positive Z potential. A prolonged Ery release kinetic from Ery-NDs was demonstrated, as well as a favorable biocompatibility on human keratinocytes. Confocal microscopy images showed ND uptake and internalization by S. pyogenes starting from 3 h of incubation up to 24 h. According to cell counts, NDs displayed long-term antimicrobial efficacy against streptococci significantly counteracting their proliferation up to 24 h, thanks to the known chitosan antimicrobial properties. Intriguingly, Ery-NDs were generally more effective (10⁴-10³ log₁₀ CFU/mL), than free-erythromycin (10⁵ log₁₀ CFU/mL), in the direct killing of streptococci, probably due to Ery-NDs adsorption by bacteria and prolonged release kinetics of erythromycin inside S. pyogenes cells. Based on these findings, NDs and proper Ery-NDs appear to be the most promising and skin-friendly approaches for the topical treatment of streptococcal skin infections allowing wound healing during hypoxia.