Pharmacodynamic Evaluation of MRX-8, a Novel Polymyxin, in the Neutropenic Mouse Thigh and Lung Infection Models against Gram-Negative Pathogens
MRX-8 is a novel polymyxin analogue in development for the treatment of infections caused by Gram-negative pathogens, including those resistant to other antibiotic classes. In the present study, we examined the pharmacodynamic activity of MRX-8 against a variety of common Gram-negative pathogens in...
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Published in | Antimicrobial agents and chemotherapy Vol. 64; no. 11 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
American Society for Microbiology
20.10.2020
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Subjects | |
Online Access | Get full text |
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Summary: | MRX-8 is a novel polymyxin analogue in development for the treatment of infections caused by Gram-negative pathogens, including those resistant to other antibiotic classes. In the present study, we examined the pharmacodynamic activity of MRX-8 against a variety of common Gram-negative pathogens in the neutropenic mouse thigh and lung models. Additionally, we examined polymyxin B (PMB) as a comparator. Plasma pharmacokinetics of MRX-8 and PMB were linear over a broad dosing range of 0.156 to 10 mg/kg of body weight and had similar AUC
(area under the drug concentration-time curve from 0 h to infinity) exposures of MRX-8, 0.22 to 12.64 mg · h/liter, and PMB, 0.12 to 13.22 mg · h/liter. Dose fractionation was performed for MRX-8 using a single
isolate, and the results demonstrated that both
(maximum concentration of drug in serum)/MIC and AUC/MIC ratios were strongly associated with efficacy. In the thigh model, dose-ranging studies included strains of
(
= 3),
(
= 2),
(
= 3), and
(
= 1). Both MRX-8 and PMB exhibited increased effects with increasing doses. MRX-8 and PMB free AUC/MIC exposures for net stasis were similar for
and
at 20 to 30. Notably, for
and
, the free AUC/MIC ratio for stasis was numerically much smaller for MRX-8 at 6 to 8 than for PMB at 16 to 37. In the lung model, MRX-8 was also more effective than PMB when dosed to achieve similar free-drug AUC exposures over the study period. MRX-8 is a promising novel polymyxin analogue with
activity against many different clinically relevant species in both the mouse thigh and lung models. |
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ISSN: | 0066-4804 1098-6596 |
DOI: | 10.1128/AAC.01517-20 |