Nonclinical pharmacokinetics and relative efficacy of the first 25 novel tuberculosis drug combinations from the PAN-TB consortium: Use of the BALB/c relapsing mouse model and combination pharmacokinetics within a modeling-based framework

The Project to Accelerate New Treatments for Tuberculosis (PAN-TB) aims to accelerate development of shorter, simpler and safer pan-TB combinations, effective for use in both Drug Susceptible (DS)- and Drug Resistant (DR)- TB patients. Towards this aim, bactericidal and sterilizing activity of 25 priority 4-drug combinations was evaluated at doses targeting clinically relevant exposures, in the BALB/c relapsing mouse model of TB. The combinations comprised 8 PAN-TB drugs and candidates: bedaquiline (B), pretomanid (Pa), delamanid (Del), quabodepistat (Q), sutezolid (Sut), GSK2556286 (286), GSK3211830 (830) and ganfeborole (GSK3036656, (656)). Combination PK studies in infected mice enabled dose selection and a population-PK approach guided dosing so that compounds should achieve mean AUC _0-24 within 2-fold of their clinical target exposures during the efficacy studies. All test combinations showed time-dependent bactericidal activity, with six regimens reducing lung bacterial burdens below the limit of detection with 8 weeks’ treatment, similar to the comparator BPaMZ (M is moxifloxacin and Z as pyrazinamide). Cure/Relapse data were modelled to derive population time to cure 90% mice (T90) values. Fifteen PAN-TB combinations had T90s of less than 5 months, sterilizing mice faster than the standard of care for drug susceptible TB, RHZE/RH. The best-performing PAN-TB combinations, BPa830Sut, BPa286Sut and BQSut286, cured 90% of mice in less than 3 months. These 3 top-ranked 4-drug combinations are all centered on a diarylquinoline (B)/oxazolidinone (Sut) core, together with the nitroimidazole (Pa) or a DprE1 inhibitor (Q) plus a novel agent such as the LeuRS inhibitor (830) or the Rv1625c agonist (286).