Construction of a New Class of Tetracycline Lead Structures with Potent Antibacterial Activity through Biosynthetic Engineering

Abstract

Antimicrobial resistance and the shortage of novel antibiotics have led to an urgent need for new antibacterial drug leads. Several existing natural product scaffolds (including chelocardins) have not been developed because their suboptimal pharmacological properties could not be addressed at the time. It is demonstrated here that reviving such compounds through the application of biosynthetic engineering can deliver novel drug candidates. Through a rational approach, the carboxamido moiety of tetracyclines (an important structural feature for their bioactivity) was introduced into the chelocardins, which are atypical tetracyclines with an unknown mode of action. A broad‐spectrum antibiotic lead was generated with significantly improved activity, including against all Gram‐negative pathogens of the ESKAPE panel. Since the lead structure is also amenable to further chemical modification, it is a platform for further development through medicinal chemistry and genetic engineering.

Progress in Understanding the Genetic Information and Biosynthetic Pathways behind Amycolatopsis Antibiotics, with Implications for the Continued Discovery of Novel Drugs

“…The next steps are cyclization and aromatization of the CHD backbone, likely carried out by a number of proteins. The final step involves modifications to the core, including C‐9 methylation and a C‐4 hydroxylation . The chd cluster contains a number of features related to the classification of CHD as atypical: an additional gene for a putative two‐component cyclase/aromatase that might be responsible for the unique aromatization pattern, a gene for a putative aminotransferase for C‐4 (opposite stereochemistry to that of TCs), and a gene for a putative C‐9 methylase, a unique feature of this biosynthetic cluster.…”

Rapid identification of atypical tetracyclines using tandem mass spectrometric fragmentation patterns

“…Remarkably, they also differ in their mechanism of action which is believed to involve interference with the bacterial membrane and disruption of its function . CHD is produced by a rare actinomycete strain Amycolatopsis sulphurea NRRL 2822 and displays potent broad‐spectrum antibacterial activity . CHD has been shown to be highly active against Gram‐positive and some Gram‐negative pathogens including Staphylococcus aureus strains and shows potent activity against multi‐resistant pathogens .…”

“…CHD is produced by a rare actinomycete strain Amycolatopsis sulphurea NRRL 2822 and displays potent broad‐spectrum antibacterial activity . CHD has been shown to be highly active against Gram‐positive and some Gram‐negative pathogens including Staphylococcus aureus strains and shows potent activity against multi‐resistant pathogens . Although its chemical structure resembles that of typical TCs it has been demonstrated that CHD is likely not a translation inhibitor .…”

“…In our recent studies, a large number of engineered actinomycete strains potentially producing target TC analogues had to be rapidly analysed. The structures of the novel analogues could be predicted based on the targeted genetic modifications of the producing strains; however, there was a critical need for rapid confirmation of biosynthesised molecules in the fermentation broths.…”

“…Besides these compounds, two atypical TCs: anhydrotetracycline (ATC) and 4‐epianhydrotetracycline (epiATC), were also studied because of their similarity to the novel CHD analogues. The novel compounds (CDCHD and DMCHD) used in the presented study have also been characterised with HRMS, NMR and 2D NMR experiments in our previous studies . Analysis of differences in CID spectra of epimers will also enable determination of the stereochemistry of synthesised and isolated TC compounds.…”