Multiparameter Responses to Tedizolid Monotherapy and Moxifloxacin Combination Therapy Models of Children with Intracellular Tuberculosis

Background. Children are often neglected during early development of antituberculosis agents, and most receive treatment after it is first tested in adults. However, very young children have tuberculosis that differs in many respects from adult cavitary pneumonia and could have different toxicity profiles to drugs. Linezolid is effective against intracellular tuberculosis, a common manifestation in young children. However, linezolid has considerable toxicity due to inhibition of mitochondrial enzymes. Tedizolid could be a replacement if it shows equal efficacy and reduced toxicity. Methods. We performed tedizolid dose-effect studies in the hollow fiber system model of intracellular tuberculosis. We measured linezolid concentrations, colony-forming units (CFU), time-to-positivity, and monocyte viability and performed RNA sequencing on infected cells collected from repetitive sampling of each system. We also compared efficacy of tedizolid vs linezolid and vs tedizolid-moxifloxacin combination. Results. There was no downregulation of mitochondrial enzyme genes, with a tedizolid 0-24 hour area under the concentration-time curve (AUC_0-24) of up to 90 mg∗h/L. Instead, high exposures led to increased mitochondrial gene expression and monocyte survival. The AUC_0-24 to minimum inhibitory concentration ratio associated with 80% of maximal bacterial kill (EC₈₀) was 184 by CFU/mL (r² = 0.96) and 189 by time-to-positivity (r² = 0.99). Tedizolid EC₈₀ killed 4.0 log₁₀ CFU/mL higher than linezolid EC80. The tedizolid-moxifloxacin combination had a bacterial burden elimination rate constant of 0.27 ± 0.05 per day. Conclusions. Tedizolid demonstrated better efficacy than linezolid, without the mitochondrial toxicity gene or cytotoxicity signatures encountered with linezolid. Tedizolid-moxifloxacin combination had a high bacterial elimination rate.