Multicentre preclinical profiling of apramycin for the treatment of nontuberculous mycobacteria.

Abstract

BACKGROUND: Current treatment regimens for nontuberculous mycobacteria (NTM) infections, especially Mycobacterium abscessus, have suboptimal clinical outcomes, demanding novel therapeutic options. The aminoglycoside apramycin (APR) has been suggested as a therapeutic alternative to amikacin (AMK). Here, we report experimental data as part of an ongoing preclinical assessment of APR. METHODS: Antimicrobial activity against 828 isolates comprising the clinically most relevant NTM species were determined by broth microdilution. Bactericidal activity and killing kinetics of APR were determined across a variety of assay conditions against rough and smooth M. abscessus isolates in vitro and in vivo. FINDINGS: Both the MICand tentative epidemiological cutoff (TECOFF) of APR was 4 μg/mL for 358 M. abscessus isolates and thus eight-fold lower than the 32 μg/mL determined for AMK. For 25 Mycobacterium chelonae isolates, the MICand TECOFF of APR was 4 μg/mL and thus four-fold lower than the 16 μg/mL determined for AMK. For 360 Mycobacterium avium complex (MAC) isolates the MICwas 32 μg/mL and the TECOFF was 64 μg/mL for both APR and AMK. The MICs of APR and AMK were largely indifferent to mucin, DNA, sputum or standard of care antimicrobials except bedaquiline, which appeared to exert an additive effect. 16 μg/mL of APR resulted in a multi-log CFU reduction of M. abscessus within 12 h, in contrast to AMK, which was bacteriostatic for at least 24 h up to a concentration of 256 μg/mL. This difference in bacterial killing was consistent across pH 6.0-7.4 in 7H9 and CAMHB culture medium, respectively. APR resulted in multi-log CFU reduction in surrogate caseum and, unlike AMK, demonstrated intracellular killing of M. abscessus and M. avium in macrophages. Concentrations of 16 μg/mL of APR or ≥128 μg/mL of AMK suppressed the dose-dependent M. abscessus frequency of spontaneous resistance to near below the detection limit. In a cystic fibrosis surrogate CFTRmouse infection model, APR demonstrated dose dependent CFU reduction of pulmonary M. abscessus 4530, by up to 2 logs at 64 mg/kg. INTERPRETATION: For M. abscessus and M. chelonae, the APR MICwas four-to eight-fold lower than that of AMK, and demonstrated enhanced bacterial killing. Collectively, our findings suggest APR has potent activity against NTM and warrants consideration for further clinical development. FUNDING: This study was supported by the Cystic Fibrosis Foundation (CFF) Therapeutic Development Award JUVABIS22W0 and CFF grant HOBBIE19I0.