Conditions: Pulmonary Tuberculosis Multidrug Resistant Tuberculosis Extensively Drug Resistant Tuberculosis
Keywords: XDR-TB Linezolid Drug Resistance Computed Tomography Pharmacokinetics Tuberculosis Drug Resistance Tuberculosis MDR-TB
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 41
Healthy volunteers: no

Brief summary:
This study, conducted in Masan and Seoul, South Korea, investigated the effectiveness of linezolid (LZD) in treating patients with extensively drug resistant tuberculosis (XDR TB). Because regular medicines do not work well against XDR TB, many more people die from it than from regular TB, which can be successfully treated by taking TB medication for 6 months. Linezolid has been used to treat other kinds of infections, but has not been well studied for TB. This study examined the side effects and effectiveness of prolonged treatment with linezolid at two different doses.

People 20 years of age and older who have XDR TB were eligible for this 3-year study.

Participants underwent the following tests and procedures:

* LZD treatment: Patients were randomly assigned to one of two study groups. Group 1 patients were observed for 2 months before starting LZD, while group 2 patients begin taking LZD right away. Both groups began with a 600 mg daily dose of LZD. After patients stopped coughing up TB germs (or after 4 months on LZD) they were randomly assigned either to continue taking 600 mg of LZD for the rest of the study or to take a decreased dose of 300 mg. In addition to LZD, patients continued to take their currently prescribed TB medications.
* Medical history.
* Physical examinations each month during treatment.
* Sputum collections once a week or more until 3 weeks after the patient was no longer contagious.
* Blood draws every week for 16 to 24 weeks and then once a month.
* Urine collections at several time points.
* Nerve and eye examinations before starting treatment and then monthly to look for possible LZD side effects.
* CT scans of the lungs three to four times the first year and once more later in the study. For this test the patient lay on a table within the doughnut-shaped CT scanner while special X-ray pictures are taken.

Patients who participated in a substudy had PET scans instead of the CT scans. For this test, the patient was given an injection into a vein of a radioactive chemical that can be detected by a special camera and viewed on a screen. The patient lay on a table within the doughnut-shaped scanner while pictures were taken.

Detailed description:
World-wide, there is an increasing incidence of multi-drug resistant tuberculosis (MDR-TB) and extensively drug-resistant TB (XDR-TB). For patients diagnosed with either of these deadly diseases, effective drug treatment options are sub-optimal or non-existent. In South Korea, there are a growing number of patients not responding to any therapy who have little hope for survival without new drugs. Linezolid (LZD), an antimicrobial approved for gram positive bacterial infections, has been used off-label for drug resistant TB and is quickly becoming a sought after drug for this population, despite lack of clinical evidence of efficacy. At the present time the prohibitive cost of LZD limits widespread use; however, when patent exclusivity expires in May of 2015 it will be imperative to have examined the benefits versus risks of LZD for TB in a controlled setting. The National Masan Tuberculosis Hospital (NMTH) in Masan, South Korea and the National Medical Center in Seoul, South Korea provide us with an opportunity to systematically address questions about LZD in a highly drug-resistant population.

This is a Phase 2a, randomized, 2-arm study of LZD, which evaluated the efficacy, safety, and tolerability of LZD in subjects whose isolates have shown resistance to all known active TB drugs or who have failed to respond to any active drugs to which they are susceptible. Subjects were required to have been on a failing regimen for at least 6 months prior to study entry, with persistent sputum smear positivity, culture positivity and no significant clinical sign of response to therapy. To be considered for the study, a subject's treatment plan must have been stable without the addition of drugs to which the subjects isolate was suspected to be sensitive: however drugs may have been discontinued during this time. Subjects were stratified based upon a diagnosis of diabetes mellitus (type I and II included) using block randomization. At the primary randomization, subjects were randomly assigned either to immediately add 600 mg LZD once daily to their existing regimen or to a delay of 2 months before adding 600 mg LZD once daily to their existing regimen. A second randomization occurred after 2 consecutive negative sputum smears or at 4 months after the start of LZD therapy (whichever came first), when subjects either stayed with their current 600 mg LZD once daily or de-escalated to 300 mg LZD once daily (see Section 4.1.4 Study Schema). The second randomization was stratified on diabetes. The primary objective of this study was to evaluate the efficacy of LZD therapy, as measured by sputum culture conversion. Secondary aims of this study included: investigation of the pharmacokinetic and pharmacodynamic profiles of LZD in blood; tolerability and toxicity of prolonged LZD administration at doses of 300 mg and 600 mg daily; the rate of change of radiological findings by computed tomography (CT); the rate of relapse 12 months after discontinuation of therapy; the rate of development of drug resistance to LZD; changes in immunologic and bacterial lipid markers during LZD therapy; the correlation of whole-blood killing assays with response to LZD therapy; and effects of LZD on mitochondrial function, a potential early indicator of LZD toxicity. In a substudy, we aimed to investigate the changes in lung architecture and cellular activity during treatment using F-fluoro-2-deoxy-D-glucose - positron emission tomography-computed tomography (FDG-PET-CT) of 20 subjects on LZD therapy. Estimated total study duration for each subject was approximately 3 years.

Arms:
arm 1: Subjects continued their existing regimen for 2 months after which LZD (600 mg once daily) was added. After 2 consecutive AFB negative sputum smears (not to exceed 4 months of LZD therapy), subjects were randomized to continue on 600 mg LZD once daily or to de-escalate to 300 mg once daily. Regardless of the dosage, subjects remained on LZD treatment for 18 months after sputum culture conversion or until they could no longer tolerate therapy. arm 2: Upon completion of entry criteria, subjects had LZD (600 mg once daily) added to their regimen. After 2 consecutive AFB negative sputum smears (or at 4 months) subjects were randomized to continue on 600 mg LZD once daily or to de-escalate to 300 mg once daily. Regardless of the dosage, subjects remained on LZD treatment for 18 months after sputum culture conversion or until they could no longer tolerate therapy.

Interventions: intervention 1: Immediate Start Linezolid intervention 2: Delayed Start Linezolid
Intervention descriptions: intervention 1: None intervention 2: None

Protocol document: