The regimen proposed is based on the NIX-TB and ZeNIX trial regimen with modification in the Linezolid doses. The rationale is -~While the EBA study showed that a modestly greater bactericidal effect over 14 days at the highest 1200 mg daily, this dose appears to be associated with a greater incidence of neuropathic and myelosuppressive effects than the 600 mg daily dose in the NIXTB trial.~Linezolid EBA study showed similar bactericidal activity over 14 days irrespective of the single daily dose or twice-daily doses. A single daily dose will enhance patient adherence and will reduce the total time of exposure to the drug concentration that is greater than the calculated concentration associated with mitochondrial toxicity (likely mechanism for the toxicities of peripheral neuropathy and myelosuppression).~While a full 6 months of linezolid therapy in the regimen may give greater culture conversion and avoid relapse, the mouse model found that linezolid dosing only for one or two months, when B and Pa were given continuously for a total of 3 months, maximized relapse-free cure.~More than 2 months of linezolid, when combined with B and Pa, does not increase relapse-free cure in the mouse model. Thus, the treatment arms in this study will give randomized comparative information about the optimal duration and dose of linezolid in the regimen relative to efficacy and toxicity.~The ZeNIX study with consistent dosing of bedaquilline and pretomanid reported 93% success rate with linezolid 1200 mg for 6 months and 91% with linezolid 600mg for 6 months. However 2 months of 600mg linezolid showed a success rate of 84%. Adverse reactions were reported in 38 % of those receiving 1200mg linezolid for 6 months, 24% of those receiving 600mg of linezolid for 6 months and 13% of those receiving 600mg linezolid for 2 months.~Interim analysis of BEAT study (personal communication/52nd UNION abstract) with 6 month regimen of bedaquilline, delaminid, clofazimine and linezolid (600mg daily for 6 months) reported 89.6% success rate at the end of 6 months of treatment. Adverse reactions such as peripheral neuropathy were reported in 39% and myelosuppression in 47% of the patients.~Learning from ZeNIX and BEAT study, a planned reduction of Linezolid along with BDQ and Pretomanid is planned as BDQ+Pa+LZD 600mg for 9 weeks followed by 300 mg for 17 weeks and BDQ+Pa+LZD 600mg for 13 weeks followed by 300mg for 13 weeks. This will help in deciding the effective dosing of Lzd to be combined with Bdq and Pa for drug resistant TB in the program.
Existing problem with DR TB management:~Injectable regimens for longer duration with toxicity Poor adherence, treatment failures, continued transmission~Need of the study:~Oral regimens of shorter duration Improved treatment adherence Implementation of community-based models of care Reduction in direct costs and indirect costs of patients Improved treatment outcomes~Need for shorter, tolerable and effective regimen~Hence modified BPaL regimen is designed to study the newer shorter oral in varying doses of Linezolid for pre XDR Tb patients and MDR TI/NR patients