Antibacterial activity of the novel oxazolidinone contezolid (MRX-I) against Mycobacterium abscessus

Background Patients with extensively drug resistant tuberculosis (TB) have limited treatment options with historically poor outcomes. We investigated treatment with 3 oral drugs, bedaquiline (B), pretomanid (Pa) and linezolid (L), (B-Pa-L), with TB bactericidal activity and little pre-existing resistance. Methods Nix-TB is an open label single arm study ongoing at three South African sites evaluating the safety and efficacy of B-Pa-L for 26 weeks for extensively drug-resistant TB or treatment intolerant /non-responsive multidrug-resistant TB. We present the efficacy and safety outcomes for all 109 patients enrolled in the trial followed to the predefined primary endpoint, six months after the end of treatment. Results In the intent to treat analysis, 98 patients (90%), (95% CI 82.7-94.9%) had a favourable outcome at 6 months after the end of treatment. Six patients died during the early stages of treatment, one withdrew during treatment, one died during follow-up without evidence of relapse, one relapsed, one relapsed and subsequently died during follow up and one was lost to follow-up. The expected linezolid toxicities of peripheral neuropathy (experienced by 81% of patients) and myelosuppression (48%), while common, were manageable, often requiring reductions of dose and/or interruptions in linezolid. Conclusions These results suggest that B-Pa-L is a viable option for tuberculosis patients with highly resistant forms of TB, provided adequate safety management is available. Trial registration: ClinicalTrials.gov Identifier: NCT02333799 Sponsor: Global Alliance for TB Drug Development (TB Alliance)

The entry of anti-infectives into the central nervous system (CNS) depends on the compartment studied, molecular size, electric charge, lipophilicity, plasma protein binding, affinity to active transport systems at the blood-brain/blood-cerebrospinal fluid (CSF) barrier, and host factors such as meningeal inflammation and CSF flow. Since concentrations in microdialysates and abscesses are not frequently available for humans, this review focuses on drug CSF concentrations. The ideal compound to treat CNS infections is of small molecular size, is moderately lipophilic, has a low level of plasma protein binding, has a volume of distribution of around 1 liter/kg, and is not a strong ligand of an efflux pump at the blood-brain or blood-CSF barrier. When several equally active compounds are available, a drug which comes close to these physicochemical and pharmacokinetic properties should be preferred. Several anti-infectives (e.g., isoniazid, pyrazinamide, linezolid, metronidazole, fluconazole, and some fluoroquinolones) reach a CSF-to-serum ratio of the areas under the curves close to 1.0 and, therefore, are extremely valuable for the treatment of CNS infections. In many cases, however, pharmacokinetics have to be balanced against in vitro activity. Direct injection of drugs, which do not readily penetrate into the CNS, into the ventricular or lumbar CSF is indicated when other effective therapeutic options are unavailable.