Tuberculosis (TB) remains a significant global health threat, causing 1.6 million deaths in 2021. The current standard of care (SOC) for drug-susceptible TB involves a 6-month course of four first-line drugs: rifampicin, isoniazid, pyrazinamide, and ethambutol. However, drug resistance, lengthy treatment duration, and adverse reactions necessitate new treatment options. The emergence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB) further highlights this urgent need. While new agents like bedaquiline, delamanid, and pretomanid have been approved, their optimal use and potential for treatment shortening remain areas of ongoing research. The development of new drugs with novel mechanisms of action is crucial to combat the growing threat of drug-resistant TB. This study focuses on ganfeborole, a novel benzoxaborole that inhibits *Mycobacterium tuberculosis* leucyl-tRNA synthetase, a promising target for TB drug development. Preclinical studies demonstrated ganfeborole's potent in vitro and in vivo activity against various *M. tuberculosis* strains, including drug-resistant isolates. A phase 1 study confirmed its safety and tolerability in healthy participants, paving the way for this phase 2a trial to evaluate its efficacy and safety in patients with TB.

Extensive research has been dedicated to the development of new anti-TB drugs to address the limitations of current therapies. The challenges posed by drug resistance, long treatment durations, and adverse effects have driven the search for novel targets and mechanisms of action. The literature highlights the success of bedaquiline, delamanid, and pretomanid in treating drug-resistant TB, but also points to the ongoing need for optimization of regimens and exploration of combination therapies to improve outcomes. Several studies have demonstrated the efficacy of various drug combinations in reducing bacterial loads and shortening treatment duration. The literature supports the potential of targeting essential bacterial processes like protein synthesis as a strategy for effective TB treatment. Ganfeborole's unique mechanism of targeting leucyl-tRNA synthetase, a critical enzyme in protein synthesis, distinguishes it from existing TB drugs and potentially mitigates the risk of cross-resistance. Preclinical studies cited in this paper have already shown the promise of ganfeborole in laboratory and animal models.

This single-center, open-label, randomized, phase 2a trial was conducted in Cape Town, South Africa, enrolling 76 male participants with newly diagnosed, rifampicin-susceptible pulmonary TB. Participants were randomized 3:1 to receive ganfeborole (at doses of 1, 5, 15, or 30 mg once daily (QD)) or SOC (weight-based Rifafour e-275 or generic equivalent) for 14 days. A dose-escalation approach was employed, with safety and pharmacokinetic (PK) data from previous cohorts informing subsequent dose selections. The primary endpoint was the early bactericidal activity (EBA), measured as the change in log10 colony-forming units (CFU)/ml sputum from baseline to day 14. Secondary endpoints included EBA at days 0-2 and 2-14, and changes in time to sputum culture positivity (TTP). Safety and PK assessments were conducted throughout the study. Post-hoc exploratory analyses included computational analysis of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) scans (available for a subset of participants) and transcriptional profiling of whole blood samples. Statistical analysis involved mixed-effects modeling for EBA and descriptive summaries for safety data. PET/CT scans were analyzed manually and computationally to assess changes in lesion volume, total glycolytic activity, and impact on various lesion types. Transcriptomic analysis was performed to assess gene expression changes in response to treatment.

A total of 76 participants were enrolled, with 58 receiving ganfeborole and 18 receiving SOC. Treatment completion rates were high across all groups (87-100%). Numerical reductions in log10 CFU/ml sputum from baseline to day 14 were observed in the ganfeborole 5, 15, and 30 mg groups, indicating EBA. The 1 mg dose showed minimal reduction. All adverse events (AEs) were grade 1 or 2, with no serious AEs reported. AE rates were similar across treatment groups. The most common AEs were hemoptysis and pruritus. Pharmacokinetic analysis showed that ganfeborole absorption was rapid, with plasma PK parameters approximately dose-proportional for doses 1-15 mg, and a more than dose-proportional increase in AUC0-24 at the 30 mg dose. Post-hoc exploratory PET/CT analysis (in a subset of participants receiving 1 mg or 30 mg ganfeborole) showed a reduction in lesion-associated radiodensity and total glycolytic activity in participants receiving 30 mg ganfeborole, whereas the 1 mg group showed no significant change. Transcriptional profiling of whole blood revealed a strong association between the treatment response to ganfeborole (30 mg) and neutrophil-dominated transcriptional modules.

This phase 2a trial provides evidence of ganfeborole's EBA in participants with rifampicin-susceptible pulmonary TB. The observed dose-response relationship supports further investigation into ganfeborole as a potential new treatment for TB. The favorable safety profile with no serious AEs, and a low rate of grade 1 and 2 AEs, is encouraging. The post-hoc PET/CT and transcriptional analyses provide additional insights into the mechanism of action, suggesting that ganfeborole may act in concert with the inflammatory response to contain the bacteria. While the study was limited to male participants with rifampicin-susceptible TB, the results suggest that ganfeborole warrants further investigation in larger, longer-term trials, including those evaluating its use in combination with other agents and in patients with drug-resistant TB and those receiving co-medication with antiretroviral drugs. The findings support a proposed optimal dose of 20 mg QD for future combination therapy studies.

This phase 2a trial demonstrates that ganfeborole exhibits early bactericidal activity against *Mycobacterium tuberculosis* in patients with rifampicin-susceptible pulmonary TB, with a favorable safety profile. The findings support further investigation of ganfeborole, potentially at a dose of 20 mg QD, in combination regimens to address the global TB epidemic. Future studies should evaluate its efficacy and safety in larger populations, including those with drug-resistant TB and female patients, to confirm its potential as a valuable addition to TB treatment strategies.

This study has several limitations. It was conducted in a single center, enrolled only male participants due to preclinical teratogenicity data, and included only participants with rifampicin-susceptible TB. The open-label design and lack of a placebo group are also limitations. The post-hoc PET/CT and transcriptional analyses were performed on relatively small subsets of participants. These limitations highlight the need for further research in larger, more diverse populations with different forms of TB to confirm the findings and evaluate the drug's broader applicability.