Animal experiment:

Rats: Sprague Dawley rats are used for pharmacokinetic studies. Compounds (Q203) are given at a dose of 2 mg per kg body weight intravenously or 10 mg per kg body weight orally. The compounds (Q203) are formulated in 20% TPGS (d-α tocopheryl polyethylene glycol 1000 succinate) for repeated-dose studies and in 40% PEG400, pH4 for single-dose studies. Blood samples are taken through the caudal vena cava using 1-mL syringes before perfusion. Samples are collected from three mice or rats at 0.5, 1, 2, 6, 12, 24 and 48 h post-dose. Blood samples are centrifuged at 3,200g for 10 min at 4 ℃. Following centrifugation, plasma is collected and frozen until further analysis. Compound concentrations are determined by LC-MS[1]. Mice: Efficacy of Q203 in a mouse model of established tuberculosis is studied. Bacterial loads are enumerated in the lung of infected mice after 14 d and 28 d of treatment. Q203 is used at 0.4, 2 and 10 mg per kg body weight. Bedaquiline and isoniazid (INH) are used as positive controls at 6.5 and 15 mg per kg body weight, respectively. Five mice per group and per time point are used[1].

Q203 (IAP6) is a midazopyridine amide compound. Q203 is active against Mycobacterium tuberculosis H37Rv with an MIC50 of 2.7 nM in culture broth medium.

Imidazopyridine amide (IPA) compounds block Mycobacterium tuberculosis growth by targeting the respiratory cytochrome bc1 complex. The optimized IPA compound Q203 inhibits the growth of MDR and XDR Mycobacterium tuberculosis clinical isolates in culture broth medium in the low nanomolar range. Q203 is active against the reference strain Mycobacterium tuberculosis H37Rv with MIC50s of 2.7 nM in culture broth medium and 0.28 nM inside macrophages[1].

Q203 is efficacious in a mouse model of tuberculosis at a dose less than 1 mg per kg body weight. Q203 displays pharmacokinetic and safety profiles compatible with once-daily dosing. Q203 has a bioavailability of 90% and a terminal half-life of 23.4 h. The volume of distribution is moderate (5.27 l per kg body weight), and the systemic clearance is low (4.03 mL/min per kg). After 4 weeks of treatment, reductions of 90%, 99% and 99.9% in M. tuberculosis H37Rv bacterial load is observed in the groups treated with Q203 at 0.4, 2 and 10 mg per kg body weight, respectively[1].

References:
[1]. Pethe K, et al. Discovery of Q203, a potent clinical candidate for the treatment of tuberculosis. Nat Med. 2013 Sep;19(9):1157-60.