Efficacy of epetraborole against Mycobacterium abscessus is increased with norvaline

Abstract

Mycobacterium abscessus is the most common rapidly growing non-tuberculous mycobacteria to cause pulmonary disease in patients with impaired lung function such as cystic fibrosis. M. abscessus displays high intrinsic resistance to common antibiotics and inducible resistance to macrolides like clarithromycin. As such, M. abscessus is clinically resistant to the entire regimen of front-line M. tuberculosis drugs, and treatment with antibiotics that do inhibit M. abscessus in the lab results in cure rates of 50% or less. Here, we identified epetraborole (EPT) from the MMV pandemic response box as an inhibitor against the essential protein leucyl-tRNA synthetase (LeuRS) in M. abscessus. EPT protected zebrafish from lethal M. abscessus infection and did not induce self-resistance nor against clarithromycin. Contrary to most antimycobacterials, the whole-cell activity of EPT was greater against M. abscessus than M. tuberculosis, but crystallographic and equilibrium binding data showed that EPT binds LeuRSMabs and LeuRSMtb with similar residues and dissociation constants. Since EPT-resistant M. abscessus mutants lost LeuRS editing activity, these mutants became susceptible to misaminoacylation with leucine mimics like the non-proteinogenic amino acid norvaline. Proteomic analysis revealed that when M. abscessus LeuRS mutants were fed norvaline, leucine residues in proteins were replaced by norvaline, inducing the unfolded protein response with temporal changes in expression of GroEL chaperonins and Clp proteases. This supports our in vitro data that supplementation of media with norvaline reduced the emergence of EPT mutants in both M. abscessus and M. tuberculosis. Furthermore, the combination of EPT and norvaline had improved in vivo efficacy compared to EPT in a murine model of M. abscessus infection. Our results emphasize the effectiveness of EPT against the clinically relevant cystic fibrosis pathogen M. abscessus, and these findings also suggest norvaline adjunct therapy with EPT could be beneficial for M. abscessus and other mycobacterial infections like tuberculosis.

The Pandemic Response Box─Accelerating Drug Discovery Efforts after Disease Outbreaks

“…Screening of the Pandemic Response Box has resulted in 11 publications so far. − Such a lag is similar to what was observed for earlier boxes with the peak 2–3 years after launch, as seen in Figure . Throughout 2020 and early 2021, the pandemic has shifted research, with a focus on SARS-CoV2, impacting the number and delaying publications.…”

L-norvaline affects the proliferation of breast cancer cells based on the microbiome and metabolome analysis

“…By metabolic analysis, we found that norvaline was the top 1 differentially ranked metabolite. Norvaline could interact with the gut microbiota to influence disease development (Coker et al, 2022; Sullivan et al, 2021). L‐norvaline is a type of norvaline.…”

A Novel Leucyl-tRNA Synthetase Inhibitor, MRX-6038, Expresses Anti-Mycobacterium abscessus Activity In Vitro and In Vivo

“…There are numerous reports regarding the anti- M. abscessus activity of LeuRS inhibitors, most of which belong to a new class of LeuRS inhibitors: benzoxaborole (including epetraborole), GSK2251052, EC/11770, and GSK656 ( 16 , 17 , 22 – 24 ). Epetraborole, a nonhalogenated benzoxaborole, was active against M. abscessus with a MIC ranging from 0.014 to 0.046 mg/L in vitro and a 1 log 10 decrease in bacteria in mice administered a 300 mg/kg dose orally ( 19 , 25 ). Notably, GSK2251052-related experiments were terminated following the development of resistance in a phase II clinical trial ( 26 ).…”