The 12-month therapy duration for the treatment of Mycobacterium kansasii pulmonary disease calls for more efficacious drugs for better treatment outcomes and to shorten the therapy duration. We performed (i) omadacycline MIC with M. kansasii ATCC 12478 strain and 21 clinical isolates, (ii) dose-response study in the hollow fiber system model of M. kansasii (HFS-Mkn) with six human equivalent omadacycline daily doses to determine the optimal drug exposure for the maximal kill, and (iii) a second HFS-Mkn study to determine the efficacy of omadacycline (300 mg/day) plus moxifloxacin (600 mg/day) plus tedizolid (200 mg/day) combination regimen with standard regimen as comparator. GraphPad Prism was used for data analysis and graphing. MIC of the reference strain was 4 mg/L but ranged from 8 to 32 mg/L among the 21 clinical isolates. In the HFS-Mkn, the exposure required for 50% of the maximal effect (EC50) was an omadacycline area under the concentration-time curve to MIC (AUC0-24/MIC) ratio of 1.95. The optimal exposure was an AUC0-24/MIC of 3.05, which could be achieved with 300 mg/day clinical dose. The omadacycline-moxifloxacin-tedizolid combination sterilized the HFS-Mkn in 14 days with a linear-regression based kill rate of -0.309 ± 0.044 log10 CFU/mL/day compared to the kill rate of -0.084 ± 0.036log10 CFU/mL/day with the standard regimen or 3.7-times faster. Omadacycline has efficacy against M. kansasii and could be used at 300 mg/day in combination with moxifloxacin and tedizolid for the treatment of M. kansasii pulmonary diseases with the potential to shorten the currently recommended 12-month therapy duration.
Keywords: combination regimen; nontuberculous mycobacteria; omadacycline.