In ZeNix study, there were four groups of people, all of whom had drug-resistant forms of TB, and who were treated using the all-oral, six-months-long BPaL regimen of Bedaquiline, Pretomanid and Linezolid. The only difference among these four groups was in the duration and/or dosing of Linezolid.
The first group received 1200mg of Linezolid for six months; second group received 1200mg of Linezolid for two months; third group received 600mg of Linezolid for six months, and the fourth group received 600mg of Linezolid for two months, shared Dr Tweed.
Overall treatment efficacy across the four groups ranged between 93% and 84% - with 93% among those who received 1200mg of Linezolid for six months and 84% among those who received 600mg of Linezolid for two months. It is important to note that the group with 600mg of Linezolid for six months had 91% efficacy - very similar to the highest efficacy of 93% - but drastically reduced levels of Linezolid-related toxicity - such as peripheral neuropathy, which was reported in only 24%, and myelosuppression reported in only 2% of patients in the study.
Dr Tweed shared that this study had had a life-influencing impact on those enrolled. There were 181 people who took part in ZeNix study (about 20% of them in each of the four groups were people living with HIV). All of them had highly drug-resistant TB - a form of TB that previously required 20 to 24 months to treat with associated cure rates between 40% to 50% in the field, and alarmingly high rates of toxicity. This study demonstrated that treatment success rate with the all-oral BPaL regimen was over 90%, treatment duration was reduced to one-fourth of the previous regimen (6 months compared to 20-24 months), and much reduced drug-related toxicities. There is still work to be done for even better treatments.
The BPaL regimen to treat highly drug-resistant forms of TB has been endorsed by the UN health agency, the World Health Organization (WHO) for use under operational research conditions. Earlier, United States FDA and European regulators had already given the green signal for the use of this regimen. Recently the Indian regulators have also given a thumbs up to Pretomanid and shorter regimens.
However, we have to remember that the number of participants in ZeNix study was relatively small, given the burden of TB in the real world. Dr Conor cautioned that "We do not think we feel comfortable making a definitive casual statement about the relationship between the different doses of Linezolid and the incidence of toxicity, but I think we would feel confident to draw attention to the association between higher rates of toxicity with the higher doses of Linezolid."
He added that "it is unacceptable for people to die from an infection that could theoretically be treated".
TB could also be prevented as we have the tools to prevent TB but are failing to do so because of which over 10 million people suffer from active TB disease every year.
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