Tuberculosis (TB) drug, regimen, and vaccine development rely heavily on preclinical animal experiments, and quantification of bacterial and immune response dynamics is essential for understanding drug and vaccine efficacy. A mechanism-based model was built to describe Mycobacterium tuberculosis H37Rv infection over time in BALB/c and athymic nude mice, which consisted of bacterial replication, bacterial death, and adaptive immune effects. The adaptive immune effect was best described by a sigmoidal function on both bacterial load and incubation time. Applications to demonstrate the utility of this baseline model showed (i) the important influence of the adaptive immune response on pyrazinamide (PZA) drug efficacy, (ii) a persistent adaptive immune effect in mice relapsing after chemotherapy cessation, and (iii) the protective effect of vaccines after M. tuberculosis challenge. These findings demonstrate the utility of our model for describing M. tuberculosis infection and corresponding adaptive immune dynamics for evaluating the efficacy of TB drugs, regimens, and vaccines.

Background

Linezolid (LZD) is bactericidal against Mycobacterium tuberculosis, but it has treatment-limiting toxicities. A better understanding of exposure-response relationships governing LZD efficacy and toxicity will inform dosing strategies. Because in vitro monotherapy studies yielded conflicting results, we explored LZD pharmacokinetic/pharmacodynamic (PK/PD) relationships in vivo against actively and nonactively multiplying bacteria, including in combination with pretomanid.

Methods

Linezolid multidose pharmacokinetics were modeled in mice. Dose-fractionation studies were performed in acute (net bacterial growth) and chronic (no net growth) infection models. In acute models, LZD was administered alone or with bacteriostatic or bactericidal pretomanid doses. Correlations between PK/PD parameters and lung colony-forming units (CFUs) and complete blood counts were assessed.

Results

Overall, time above minimum inhibitory concentration (T>MIC) correlated best with CFU decline. However, in growth-constrained models (ie, chronic infection, coadministration with pretomanid 50 mg/kg per day), area under the concentration-time curve over MIC (AUC/MIC) had similar explanatory power. Red blood cell counts correlated strongly with LZD minimum concentration (Cmin).

Conclusions

Although T>MIC was the most consistent correlate of efficacy, AUC/MIC was equally predictive when bacterial multiplication was constrained by host immunity or pretomanid. In effective combination regimens, administering the same total LZD dose less frequently may be equally effective and cause less Cmin-dependent toxicity.

Introduction

BTZ-043 is a promising novel drug candidate for anti-tuberculosis treatment. This study aimed to apply a previously developed mouse-to-human translational modeling platform for anti-tuberculosis drugs to predict phase IIA outcomes for BTZ-043 in humans and evaluate the impact of observed drug-drug interactions on the contribution of BTZ-043 to combotherapy in a mouse model.

Methods

The study utilized data from mouse experiments for BTZ-043 monotherapy and combotherapy with bedaquiline, pretomanid, and linezolid, and clinical information for BTZ-043 monotherapy. The translational models were applied to predict the colony-forming units as a measure of efficacy in humans treated with BTZ-043 monotherapy and evaluate the effect of BTZ-043 on the pharmacokinetics-pharmacodynamics of combotherapy bedaquiline, pretomanid, and linezolid.

Results

The mouse-pharmacokinetic and mouse-pharmacodynamic data for BTZ-043 monotherapy were best described by two-compartmental and direct Emax models, respectively. The model-based prediction of efficacy in humans was comparable to the observed phase IIA efficacy. Single-compartmental models, developed separately, best described the mouse-pharmacokinetic data for bedaquiline, pretomanid, and linezolid in combotherapy. Co-administration with BTZ-043 was associated with at least a 2-fold reduction in bedaquiline, pretomanid, and linezolid exposures in mice, and model-based simulations suggested that the observed decreases in exposure to these drugs would have resulted in even lower efficacy than what was observed when BPaL is co-administered with BTZ-043.

Conclusion

The translational modeling platform adequately predicted the efficacy of BTZ-043 monotherapy. In the absence of drug-drug interactions, co-administration of BTZ-043 with bedaquiline, pretomanid, and linezolid in combotherapy is predicted to improve treatment efficacy.

TBI-223, a novel oxazolidinone for tuberculosis, is designed to provide improved efficacy and safety compared to linezolid in combination with bedaquiline and pretomanid (BPaL). We aim to optimize the dosing of TBI-223 within the BPaL regimen for enhanced therapeutic outcomes. TBI-223 is investigated in preclinical monotherapy, multidrug therapy, and lesion penetration experiments to describe its efficacy and safety versus linezolid. A translational platform incorporating linezolid and BPaL data from preclinical experiments and 4 clinical trials (NCT00396084, NCT02333799, NCT03086486, NCT00816426) is developed, enabling validation of the framework. TBI-223 preclinical and Phase 1 data (NCT03758612) are applied to the translational framework to predict clinical outcomes and optimize TBI-223 dosing in combination with bedaquiline and pretomanid. Results indicate that daily doses of 1200-2400 mg TBI-223 may achieve efficacy comparable to the BPaL regimen, with >90% of patients predicted to reach culture conversion by two months.