A strategy for the
“We found that if we use the strategy of a bedaquiline-linezolid five-drug regimen for 8 weeks and then followed patients for 96 weeks, [the regimen] was noninferior, clinically, to the standard regimen in terms of the number of people alive, free of TB disease, and not on treatment,” said lead author Nicholas Paton, MD, of the National University of Singapore, in a press conference held during the Conference on Retroviruses & Opportunistic Infections.
“The total time on treatment was reduced by half – instead of 160 days, it was 85 days for the total duration.”
Commenting on the study, which was published concurrently in the New England Journal of Medicine, Richard E. Chaisson, MD, noted that, although more needs to be understood, the high number of responses is nevertheless encouraging.
“Clinicians will not feel comfortable with the short regimens at this point, but it is remarkable that so many patients did well with shorter treatments,” Dr. Chaisson, who is a professor of medicine, epidemiology, and international health and director of the Johns Hopkins University Center for Tuberculosis Research, Baltimore, said in an interview.
Importantly, the study should help push forward “future studies [that] will stratify patients according to their likelihood of responding to shorter treatments,” he said.
The current global standard for TB treatment, practiced for 4 decades, has been a 6-month rifampin-based regimen. Although the regimen performs well, curing more than 95% of cases in clinical trials, in real-world practice, the prolonged duration can be problematic, with issues of nonadherence and loss of patients to follow-up.
Previous research has shown that shorter regimens have potential, with some studies showing as many as 85% of patients cured with 3- and 4-month regimens, and some promising 2-month regimens showing efficacy specifically for those with smear-negative TB.
These efforts suggest that “the current 6-month regimen may lead to overtreatment in the majority of persons in order to prevent relapse in a minority of persons,” the authors asserted.
TRUNCATE-TB
To investigate a suitable shorter-term alternative, the authors conducted the phase 2-3, prospective, open-label TRUNCATE-TB trial, in which 674 patients with rifampin-susceptible pulmonary TB were enrolled at 18 sites in Asia and Africa.
The patients were randomly assigned to receive either the standard treatment regimen (rifampin and isoniazid for 24 weeks with pyrazinamide and ethambutol for the first 8 weeks; n = 181), or one of four novel five-drug regimens to be administered over 8 weeks, along with extended treatment for persistent clinical disease of up to 12 weeks, if needed, and a plan for retreatment in the case of relapse (n = 493).
Two of the regimens were dropped because of logistic criteria; the two remaining shorter-course groups included in the study involved either high-dose rifampin plus linezolid or bedaquiline plus linezolid, each combined with isoniazid, pyrazinamide, and ethambutol.
Of the patients, 62% were male, and four withdrew or were lost to follow-up by the end of the study at a final follow-up at week 96.
Among patients assigned to the 8-week regimens, 80% stopped at exactly 8 weeks, while 9% wound up having extended treatment to 10 weeks and 3% were extended to 12 weeks.
For the primary endpoint, a composite of death, ongoing treatment, or active disease at week 96, the rate was lowest in the standard 24-week therapy group, occurring in 7 of 181 patients (3.9%), compared with 21 of 184 patients (11.4%) in the rifampin plus linezolid group (adjusted difference, 7.4 percentage points, which did not meet noninferiority criterion), and 11 of 189 (5.8%) in the group in the bedaquiline plus linezolid group (adjusted difference, 0.8 percentage points, meeting noninferiority criterion).
The mean total duration of treatment through week 96 in the standard treatment group was 180 days versus 106 days in the rifampin–linezolid group, and 85 days in the bedaquiline-linezolid group.
The results were consistent across multiple subgroups defined according to baseline characteristics, including some that could be linked to severe disease and a high risk for relapse.
In terms of safety, there were no significant differences between the groups in terms of grade 3 or 4 adverse events.
Of note, only two patients (1.1%) in the bedaquiline plus linezolid group acquired a resistance, which Dr. Paton said was “encouraging,” because of concerns about resistance to that drug.