The Tuberculosis Drug Accelerator at year 10: what have we learned?

Background Patients with extensively drug resistant tuberculosis (TB) have limited treatment options with historically poor outcomes. We investigated treatment with 3 oral drugs, bedaquiline (B), pretomanid (Pa) and linezolid (L), (B-Pa-L), with TB bactericidal activity and little pre-existing resistance. Methods Nix-TB is an open label single arm study ongoing at three South African sites evaluating the safety and efficacy of B-Pa-L for 26 weeks for extensively drug-resistant TB or treatment intolerant /non-responsive multidrug-resistant TB. We present the efficacy and safety outcomes for all 109 patients enrolled in the trial followed to the predefined primary endpoint, six months after the end of treatment. Results In the intent to treat analysis, 98 patients (90%), (95% CI 82.7-94.9%) had a favourable outcome at 6 months after the end of treatment. Six patients died during the early stages of treatment, one withdrew during treatment, one died during follow-up without evidence of relapse, one relapsed, one relapsed and subsequently died during follow up and one was lost to follow-up. The expected linezolid toxicities of peripheral neuropathy (experienced by 81% of patients) and myelosuppression (48%), while common, were manageable, often requiring reductions of dose and/or interruptions in linezolid. Conclusions These results suggest that B-Pa-L is a viable option for tuberculosis patients with highly resistant forms of TB, provided adequate safety management is available. Trial registration: ClinicalTrials.gov Identifier: NCT02333799 Sponsor: Global Alliance for TB Drug Development (TB Alliance)

Finding new treatment-shortening antibiotics to improve cure rates and curb the alarming emergence of drug resistance is the major objective of tuberculosis (TB) drug development. Using a MALDI mass spectrometry imaging suite in a biosafety containment facility, we show that the key sterilizing drugs rifampicin and pyrazinamide efficiently penetrate the sites of TB infection in lung lesions. Rifampicin even accumulates in necrotic caseum, a critical lesion site where persisting tubercle bacilli reside 1 . In contrast, moxifloxacin which is active in vitro against persisters, a sub-population of Mycobacterium tuberculosis that persists in specific niches under drug pressure, and achieved treatment shortening in mice 2 , does not diffuse well in caseum, concordant with its failure to shorten therapy in recent clinical trials. We also suggest that such differential spatial distribution and kinetics of accumulation in lesions may create temporal and spatial windows of monotherapy in specific niches, allowing the gradual development of multidrug resistant TB. We propose an alternative working model to prioritize new antibiotic regimens based on quantitative and spatial distribution of TB drugs in the major lesion types found in human lungs. The finding that lesion penetration contributes to treatment outcome has wide implications for TB.

With the aim of fuelling open-source, translational, early-stage drug discovery activities, the results of the recently completed antimycobacterial phenotypic screening campaign against Mycobacterium bovis BCG with hit confirmation in M. tuberculosis H37Rv were made publicly accessible. A set of 177 potent non-cytotoxic H37Rv hits was identified and will be made available to maximize the potential impact of the compounds toward a chemical genetics/proteomics exercise, while at the same time providing a plethora of potential starting points for new synthetic lead-generation activities. Two additional drug-discovery-relevant datasets are included: a) a drug-like property analysis reflecting the latest lead-like guidelines and b) an early lead-generation package of the most promising hits within the clusters identified.