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• Steady-state concentrations of contezolid in serum and cerebrospinal fluid (CSF) were measured in a patient with tuberculous meningoencephalitis. • The observed concentrations in CSF were above the minimum inhibitory concentration of contezolid against Mycobacterium tuberculosis. • The concentrations of contezolid in CSF were close to the estimated serum unbound fraction of contezolid. Central nervous system (CNS) tuberculosis (TB) is a devastating and often life-threatening disease caused by Mycobacterium tuberculosis. Contezolid, a new oxazolidinone, has demonstrated potent antimycobacterial activity in both in-vivo and in-vitro studies, with lower toxicity than linezolid. However, pharmacokinetic data are still not available for contezolid in the CNS of patients with CNS TB. This article reports the steady-state concentrations of contezolid in serum and cerebrospinal fluid (CSF) of a patient receiving contezolid as part of multi-drug treatment for tuberculous meningoencephalitis. At weeks 7 and 11 (7 h post-dose) after initiation of contezolid therapy, the serum concentrations of contezolid were 9.64 mg/L and 9.36 mg/L, respectively. In CSF, the observed concentrations of contezolid were 0.54 mg/L and 1.15 mg/L, respectively. The CSF:serum concentration ratios were 0.056 and 0.123 at weeks 7 and 11, respectively. The observed concentrations in CSF were above the minimum inhibitory concentration of contezolid against M. tuberculosis , and were close to the estimated serum unbound fraction of contezolid (10%), suggesting that unbound contezolid has high CSF permeability. [ABSTRACT FROM AUTHOR]

• Information on analytical methods in biological samples is limited. • Reliable UPLC-MS/MS methods for simultaneous determination of contezolid and M2. • Successful application of the validated assays to a clinical pharmacokinetic study. Contezolid is a novel oxazolidinone antibiotic with good antibacterial activity against gram-positive bacteria including methicillin-resistant Staphylococcus aureus. For the purpose to further characterize the pharmacokinetics of contezolid and its major metabolite M2, accurate and rapid ultra-performance liquid chromatography-tandem mass spectrometric assays (UPLC-MS/MS) were developed and validated for simultaneous quantification of contezolid and M2 in human plasma and urine. The plasma samples were pretreated by liquid–liquid extraction. The automated solid phase extraction method was used to preprocess urine samples. ACQUITY UPLC® BEH C8 (2.1 mm × 100 mm, 1.7 µm) column was used to separate the analytes with a gradient mobile phase of acetonitrile and water at a flow rate of 0.4 mL/min. The calibration curves showed good linearity over the concentration ranges of 0.0100–5.00 µg/mL for contezolid in plasma and urine, 0.00200–1.00 µg/mL in plasma and 0.0200–10.0 µg/mL in urine for M2, respectively. For both plasma and urine assays, the intra- and inter-batch accuracy and precision were within 15% for all quality control levels, including the lower limit of quantitation. The methods were fully validated and successfully applied to a pharmacokinetic study of contezolid tablets in subjects with moderate hepatic impairment. [ABSTRACT FROM AUTHOR]

This study assessed the tolerability and pharmacokinetic (PK) properties of a new-generation oxazolidinone, contezolid (MRX-I), and its major inactive metabolite, M2, after single oral administrations of 800, 1200, and 1600 mg in the fed state, and compared the efficacy of 3 dosing regimens in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection based on PK/pharmacodynamic (PD) analysis. A Phase I study at a single study center was conducted with 2 parts. In the first part, 20 healthy subjects received a single oral dose of 1200 or 1600 mg of contezolid or placebo in the fed state in a double-blind, placebo-controlled, dose-escalation tolerance study. In the second part of the study, 52 subjects received a single oral dose of 800 mg of contezolid in the fed state in a single-center, randomized, blinded, 4-period, crossover, thorough QT study. Noncompartmental analyses were used to evaluate the PK properties of contezolid and M2. Steady-state concentrations of contezolid following the 3 dosing regimens (800, 1200, and 1600 mg q12h) were simulated by employing a newly developed 2-compartmental PK model. The minimum inhibitory concentration (MIC) distributions of contezolid were analyzed in 178 Staphylococcus , Enterococcus, and Streptococcus clinical isolates. Monte Carlo simulations were conducted to predict the efficacy of the 3 dosing regimens to obtain probability of target attainment and cumulative fraction of response. Single-dose oral administrations of 800, 1200, and 1600 mg of contezolid were well tolerated in healthy subjects in the fed state, and nonlinear PK was observed. The mean plasma exposures to M2 exceeded 17.3% of contezolid exposure in the 3 groups. Both MIC 50 and MIC 90 (MICs that inhibit the growth of 50% and 90% of microorganisms, respectively) of contezolid against MRSA were 1 mg/L with clinical isolates from China. PK/PD analysis and Monte Carlo simulations predicted that 800 mg q12h of oral contezolid would be efficacious against MRSA infection, with a MIC of ≤4 mg/L (probability of target attainment, >90%; cumulative fraction of response, >90%). Contezolid is a well-tolerated treatment option for MRSA infection, including at supratherapeutic doses up to 1600 mg. The regimen of 800 mg q12h could achieve efficacy in treating bacterial infection with MRSA. To our knowledge, this is the first PK study to predict that a dosing regimen of 800 mg q12h of oral contezolid is sufficient for treating MRSA infection, with a MIC of ≤4 mg/L. A Phase III study of this suggested dosing regimen is being conducted. Chinadrugtrials.org.cn identifier: CTR20161074. [ABSTRACT FROM AUTHOR]