Efficacy and safety of a 4-month quabodepistat, delamanid, and bedaquiline regimen for drug-susceptible pulmonary tuberculosis: a multicentre, open-label, randomised, proof-of-concept, non-inferiority, phase 2b/c trial.

backgroundCombined therapy with delamanid, bedaquiline, and quabodepistat (DBQ) showed potent early bactericidal activity and was well tolerated in a phase 2a, 14-day early bactericidal activity trial in participants with drug-susceptible pulmonary tuberculosis. This subsequent proof-of-concept trial evaluated the efficacy and safety of a 4-month, three-dose level regimen of DBQ in participants with drug-susceptible pulmonary tuberculosis compared with 6 months of the standard of care.

methodsThis open-label, randomised, proof-of-concept, non-inferiority, phase 2b/c trial was conducted at six clinical research sites in South Africa. Adults aged 18-65 years with newly diagnosed, drug-susceptible pulmonary tuberculosis were recruited by research sites from community tuberculosis clinics. Participants were randomly assigned (1:2:2:1) by balanced block randomisation (block size six) to receive oral delamanid (300 mg once a day) and bedaquiline (400 mg once a day for 2 weeks then 200 mg three times a week) plus quabodepistat at once-daily doses of 10 mg (DBQ10 group), 30 mg (DBQ30 group), or 90 mg (DBQ90 group) for 4 months; or 6 months of RHEZ (rifampicin, isoniazid, ethambutol, and pyrazinamide for 8 weeks followed by 18 weeks of rifampin and isoniazid). All drugs were administered orally. Masking procedures were not used, although microbiology laboratory staff were masked to treatment assignment. The primary endpoints were the proportion of participants reaching sputum culture conversion by the end of the treatment period in the modified intention-to-treat (mITT) analysis set and safety in the safety analysis set. Non-inferiority, with a margin of 12%, was assessed for the primary endpoint in the mITT analysis set, comparing the pooled DBQ group and the RHEZ group using a two-sided 80% CI. This study was registered at ClinicalTrials.gov, NCT05221502, and is complete.

findingsBetween April 12, 2022, and May 19, 2024, 306 individuals were screened, of whom 122 were enrolled and randomly assigned: 20 to the DBQ10 group, 42 to the DBQ30 group, 39 to the DBQ90 group, and 21 to the RHEZ group. 121 participants received at least one dose of study drug and comprised the mITT analysis set. At the end of the treatment period, the proportion of participants with sputum culture conversion was 100·0% (95% CI 83·2-100·0, all 20 participants) in the DBQ10 group, 92·9% (80·5-98·5, 39 of 42 participants) in the DBQ30 group, 97·4% (86·2-99·9, 37 of 38 participants) in the DBQ90 group, 96·0% (90·1-98·9, 96 of 100 participants) in the pooled DBQ group, and 100·0% (83·9-100·0, all 21 participants) in the RHEZ group. The comparison between the pooled DBQ group and the RHEZ group met non-inferiority for the primary endpoint (difference -4·0% [80% CI -7·4 to 3·4]). Adverse events were mostly mild to moderate, with no serious adverse events or discontinuations attributed to trial medications. Rates of adverse events of grade 3 or higher were 20% (four of 20 participants) in the DBQ10 group, 14% (six of 42 participants) in the DBQ30 group, 11% (four of 38 participants) in the DBQ90 group, and 5% (one of 21 participants) in the RHEZ group. One participant (in the DBQ90 group) died after worsening pulmonary tuberculosis with pneumonia, which was assessed as not related to study treatment. 105 (87%) of 121 participants had at least one treatment-emergent adverse event: 17 (85%) of 20 in the DBQ10 group, 37 (88%) of 42 in the DBQ30 group, 30 (79%) of 38 in the DBQ90 group, and all 21 (100%) participants in the RHEZ group. The most common treatment-emergent adverse events in the total population of 121 participants were upper respiratory tract infection (n=36, 30%), headache (n=24, 20%), and diarrhoea (n=12, 10%).

interpretationIn this proof-of-concept study, 4 months of DBQ showed a promising end-of-treatment non-inferiority signal versus 6 months of RHEZ and was generally well tolerated. Our results support further studies of quabodepistat as a potential component of new treatment-shortening regimens for tuberculosis.

fundingOtsuka Pharmaceutical Development & Commercialization, with partial funding from the Gates Foundation.