Two short-course bedaquiline-containing treatment regimens for rifampicin-resistant tuberculosis showed “robust evidence” for superior efficacy and less ototoxicity compared to a 9-month injectable control regimen, researchers report.
The findings validate the World Health Organization’s current recommendation of a 9-month, bedaquiline-based oral regimen, “which was based only on observational data,” noted lead author Ruth Goodall, PhD, from the Medical Research Council Clinical Trials Unit at University College London, and colleagues.
The study was published in The Lancet.
The Standard Treatment Regimen of Anti-tuberculosis Drugs for Patients With MDR-TB (STREAM) stage 2 study was a randomized, phase 3, noninferiority trial conducted at 13 hospital clinics in seven countries that had prespecified tests for superiority if noninferiority was shown. The study enrolled individuals aged 15 years or older who had rifampicin-resistant TB without fluoroquinolone or aminoglycoside resistance.
The study’s first stage, STREAM stage 1, showed that The 9-month regimen was recommended by the WHO in 2016. That recommendation was superceded in 2020 when concerns of hearing loss associated with aminoglycosides prompted the WHO to endorse a 9-month bedaquiline-containing, injectable-free alternative, the authors write.
Seeking shorter treatment for better outcomes
STREAM stage 2 used a 9-month injectable regimen as its control. The investigators measured it against a fully oral 9-month bedaquiline-based treatment (primary comparison), as well as a 6-month oral bedaquiline regimen that included 8 weeks of a second-line injectable (secondary comparison).
The 9-month fully oral treatment included levofloxacin, clofazimine, ethambutol, and pyrazinamide for 40 weeks; bedaquiline, high-dose isoniazid, and prothionamide were given for the 16-week intensive phase.
The 6-month regimen included bedaquiline, clofazimine, pyrazinamide, and levofloxacin for 28 weeks, supplemented by high-dose isoniazid with kanamycin for an 8-week intensive phase.
For both comparisons, the primary outcome was favorable status at 76 weeks, defined as cultures that were negative for Mycobacterium tuberculosis without a preceding unfavorable outcome (defined as any death, bacteriologic failure or recurrence, or major treatment change).
Among 517 participants in the modified intention-to-treat population across the study groups, 62% were men, and 38% were women (median age, 32.5 years).
For the primary comparison, 71% of the control group and 83% of the oral regimen group had a favorable outcome.
In the secondary comparison, 69% had a favorable outcome in the control group, compared with 91% of those receiving the 6-month regimen.
Although the rate of grade 3 or 4 adverse events was similar in all three groups, there was significantly less ototoxicity among patients who received the oral regimen, compared with control patients (2% vs. 9%); 4% of those taking the 6-month regimen had hearing loss, compared with 8% of control patients.
Exploratory analyses comparing both bedaquiline-containing regimens revealed a significantly higher proportion of favorable outcomes among participants receiving the 6-month regimen (91%), compared with patients taking the fully oral 9-month regimen (79%). There were no significant differences in the rate of grade 3 or 4 adverse events.
The trial’s main limitation was its open-label design, which might have influenced decisions about treatment change, note the investigators.
“STREAM stage 2 has shown that two short-course, bedaquiline-containing regimens are not only non-inferior but superior to a 9-month injectable-containing regimen,” they conclude.
“The STREAM stage 2 fully oral regimen avoided the toxicity of aminoglycosides, and the 6-month regimen was highly effective, with reduced levels of ototoxicity. These two regimens offer promising treatment options for patients with MDR or rifampicin-resistant tuberculosis,” the authors write.
Dr. Goodall added, “Although both STREAM regimens were very effective, participants experienced relatively high levels of adverse events during the trial (though many of these were likely due to the close laboratory monitoring of the trial).
“While hearing loss was reduced on the 6-month regimen, it was not entirely eliminated,” she said. “Other new regimens in the field containing the medicine linezolid report side effects such as anemia and peripheral neuropathy. So more work needs to be done to ensure the treatment regimens are as safe and tolerable for patients as possible. In addition, even 6 months’ treatment is long for patients to tolerate, and further regimen shortening would be a welcome development for patients and health systems.”