Some cases of tuberculosis (TB) can be successfully treated in as little as two months – a third of the current standard of six months in South Africa and most other countries. This is according to early findings from the landmark TRUNCATE TB trial presented at last week’s Union World Conference on Lung Health.
Nick Paton, a professor of Infectious Diseases at the National University of Singapore and the chief investigator of the TRUNCATE trial, explains that the standard six-month treatment for drug-susceptible TB (DS-TB) is actually overtreating a lot of people who have the disease. The reason for the six-month mark for TB treatment is that a minority of TB patients need the long treatment regimen to avoid relapse, but the majority would be cured before the six-month mark.
Essentially, it’s a blunt, but generally, effective instrument used to protect a minority of TB patients.
Short initial treatment
The TRUNCATE trial set out to see if a two-month (eight weeks) novel combination of TB regimens would be feasible when compared to the standard six-month (24 weeks) treatment regimen. According to Paton, trial participants in the experimental arms of the study were initially given eight weeks of treatment, with the option of extending treatment to 10 to 12 weeks if they had persistent clinical disease after the eight-week treatment. If there was still active TB after that, participants were switched to the standard six-month treatment.
Breaking: 2 months+ Bdq/Lzd treatment for DSTB is non-inferior to standard care. #IDtwitter @UnionConference #truncateTB pic.twitter.com/g6CJqbRAhT
— Catherine Berry 🆔 (@catherineeberry) November 9, 2022
Study participants were monitored regularly through follow-up visits, which included TB symptom screening once a month and sputum smear tests every one to three months.
“The core [of the strategy] is it’s a very short period of initial treatment, plus you then do the monitoring and pick up people [who relapsed] early,” Paton says.
A total of 674 trial participants were recruited from March 2018 to March 2022 across 18 sites in Thailand, Indonesia, the Philippines, Uganda, and India. Four patients withdrew from the trial and 10 participants died during the trial.
Paton tells Spotlight that the overall death rate was low and there was no difference in the death rate between the standard treatment arm and the TRUNCATE strategy arms. The causes of death were mixed, he adds, and often the precise cause was unknown
For the final results, 660 participants were evaluated at week 96. In other words, about two years of follow-up occurred.
Paton explains that the trial used the TRUNCATE strategy, which initially involved using four treatment arms containing a novel combination of TB drugs and comparing the results to a control arm consisting of the standard six-month treatment. Later, two TRUNCATE strategy arms were selected to complete the latter half of the study. He notes that it was a pragmatic decision to stop two of the arms, to ensure better data.
In the first of the two remaining experimental arms, 184 study participants received a regimen consisting of high-dose rifampicin (35mg per kg, reduced to 20mg per kg as a precaution following a liver injury-related death), isoniazid, pyrazinamide, ethambutol, and linezolid (600mg). In the second, 189 study participants received a regimen consisting of bedaquiline (400mg/d for two weeks then 200mg three times a week), isoniazid, pyrazinamide, ethambutol, and linezolid (600mg). The standard treatment arm had 181 participants.
In the standard treatment arm, 98% completed treatment and 3% had to be re-treated before week 96.
In the TRUNCATE strategy arms, overall, 91% completed the eight-week treatment and stopped treatment by week 12. 17%, (ranging from 13 to 23% by arm) had re-treatment, and 2% of participants did not complete initial treatment due to withdrawing from the trial, death, or defaulting on treatment.
A comparison of the two experimental TRUNCATE arms with the standard treatment arm showed that the TRUNCATE arm with bedaquiline and linezolid was non-inferior to the standard treatment arm, while the high dose rifampicin and linezolid arm fell just short of meeting the non-inferiority criteria. Efficacy was calculated based on the proportion of unsatisfactory outcomes at week 96. Unsatisfactory outcomes were classified as death, still having active TB, or still being on TB treatment at week 96.
“The idea was that if we added those [unsatisfactory outcomes] up and that was the same in the standard treatment arm as the TRUNCATE strategy arm then that shows that this strategy in principle, can work,” Paton tells Spotlight.
The mean total days on treatment were reduced in the TRUNCATE strategy arms when compared to the standard treatment arm, which was 180 days. For high-dose rifampicin-linezolid, the average total days on treatment was 106 days, and in the bedaquiline-linezolid arm, it was 85 days.
“So, clearly the net effect is to decrease the average time on treatment,” Paton says. “You do substantially cut down the amount of time on treatment overall.”
He adds that the proportion of participants that had Grade 3 or 4 adverse events, serious adverse events, or who died did not differ between the standard treatment arm and the TRUNCATE strategy arm. The proportion of participants with respiratory disability at week 96 also did not differ.
The only cases of acquired drug resistance were two cases observed in the bedaquiline and linezolid arm. This is a frequency of 1.1% according to Paton. One of these participants missed several treatment doses, while the other did not miss any doses. Both were successfully re-treated.
Initially, they wanted to enroll participants who were co-infected with HIV in the later stages of the trial, but none could be enrolled in time, so currently there is no data on how well it works in people living with HIV who also have TB, says Paton.
“The trial has shown that alternatives to systematically over-treating the large majority of people with TB can be successful. This is an important new research direction which has the promise to improve outcomes for patients and programmes,” Paton says. “The strategy may be refined in future to improve outcomes using alternative drug regimens or alternative approaches to monitoring. Ongoing analysis from the trial will further enhance our understanding.”
PK and safety data
At last week’s conference, Christopher Cousins, project leader of the TRUNCATE trial presented the first level of pharmacokinetic (PK) analysis from the trial. The PK results were taken from week eight of the study.
After fasting overnight, participants took an observed dose of their medication at the trial site and had blood sampling done over a 12-hour period. The data is based on 96 participants in the two experimental arms.
He says the AUC (which represents total drug exposure over time – AUC = area under the curve) for the high-dose rifampicin was four to six times higher than in the standard dose and exceeded the proposed efficacy targets in the majority of patients. This supports the hypothesis that high-dose rifampicin would enhance treatment sterilisation in the eight-week regimen.
The data also showed what seems to be a drug-drug interaction between rifampicin and linezolid, but this didn’t appear to be significant enough to abolish anti-mycobacterial efficacy.
According to Cousins, the bedaquiline concentrations at the end of week eight in the bedaquiline and linezolid arm were comparable to the concentrations seen after 24 weeks of treatment for drug-resistant TB (currently both bedaquiline and linezolid are part of the standard treatment for DR-TB, but not for DS-TB).
When asked how well monitoring participants in the TRUNCATE arms after they stopped treatment was able to detect those who still had active TB disease, Paton tells Spotlight that further analysis of the sputum smears samples will be able to tell us more. The trial used a relatively low-technology approach where a symptom screening and a sputum smear test were used to determine if a participant still had active TB and needed to be re-treated.
“We need to run additional biomarkers, interrogate the data set in more detail to figure out who was cured, who wasn’t cured, over what duration and how well do these other things [sputum smear test and symptom screening] pick it [TB] up,” he says.
He adds that this was a starting point, “but we are likely to be able to do better if we use some of the new biomarker technologies for monitoring”.
Implications of findings
“These results are very exciting as proof of concept – they show it’s possible to shorten treatment for drug-sensitive TB even further,” says Lindsay McKenna, TB Project Co-Director at New York-based Treatment Action Group (TAG). “But we need to optimise the regimen and study this treatment strategy in broader populations, including people living with HIV – none were enrolled in the study – and [in] programme contexts,” she says.
“There are other trials that are being planned that look to proactively (for example, at time of treatment initiation) determine who might benefit from shorter versus longer treatment based on available indicators or risk factors known to be correlated with treatment outcomes, such as disease severity, BMI, and HIV status (called a stratified medicine approach), and to tailor the duration of treatment accordingly,” she adds. “If the latter stratified medicine approach is proven, it will be very interesting to see how these two approaches compare and are viewed by programmes and affected communities.”
Feasibility of shortened regimens
Nerissa Donato the site co-investigator for the Truncate TB trial from the Lung Centre in the Philippines outlined the feasibility and acceptability of the TRUNCATE strategy at last week’s conference. This was based on participant questionnaires, clinician surveys, description data from the trial, and observations from Donato.
“The TRUNCATE strategies were acceptable and feasible in the context of the clinical trial. It can be successfully implemented provided that it is supported by the NTP (national treatment programme) and embraced by trained clinicians,” she says.
She explains the main challenges to implementing the strategy were patients’ concerns about potential side effects and the greater pill burden, but after some discussion participants were comfortable with the regimen due to the possibility of a much shorter treatment regimen. The close following up of participants and follow-up visits required was different from the normal procedure of treating for six months and being discharged from care. But she says participants were generally happy to come back for the follow-up visits.
Clinicians who participated were initially sceptical of whether the regimen was safe and would work but after the trial, they had a more positive view, according to Donato.
She says that in order to implement the strategy in the real world, it would need to be adopted by the NTPs, which will likely require more data on cost-effectiveness.
Need better treatment approaches and regimens
Paton tells Spotlight that somewhere between the two extremes of overtreating TB patients and personalised medicine as seen in high-income countries, there can lie a better treatment option for TB patients. An approach that is less monolithic and instead based on reacting to individual patient needs and responses.
“We need to look at how do we personalise it [TB treatment], but in a way that’s not so high tech so it becomes impossible for programmes,” he says. “At least if you’re monitoring [patients] you’ve got a safety net. If you get it wrong, you just make sure you pick the person up early and re-treat and there shouldn’t be serious harm from that.”
Additional data from the trial will be released in the coming months.