Session: Session 3

Distribution of standard-of-care antituberculosis drugs in cynomolgus macaque lungs

INTRODUCTION

This study aimed to determine the tissue pharmacokinetics of isoniazid (H), rifampicin (R), pyrazinamide (Z), and ethambutol (E) in the lungs of cynomolgus macaques, preparing for future studies in Mycobacterium tuberculosis-infected animals. It was part of the ERA4TB consortium, an IMI-funded initiative, using Quantitative Mass Spectrometry Imaging (QMSI) for tissue PK of HRZE in NHP lungs.

METHODOLOGY

Six cynomolgus macaques received a single oral dose of H (15 mg/kg), R (15 mg/kg), Z (200 mg/kg), and E (75 mg/kg). Necropsies were conducted at intervals up to 24h post-administration. The upper right lung lobe was collected, inflated with agarose, snap-frozen, and shipped to Aliri. Lung samples were cryosectioned and mounted on ITO slides. Drug dilution series were spotted on control tissues and coated with MALDI matrices, solvents, and derivatization agents. Slides were imaged using a MALDI FTICR. Calibration curves were obtained using Multimaging software. Adjacent sections on Superfrost slides were stained with Hematoxylin-Eosin and overlayed with the MSI datasets.

RESULTS

Isoniazid was barely detected despite a detection limit of 2 µg/g of tissue. QMSI revealed ethambutol distribution up to 24h post-administration at around 30 µg/g. Pyrazinamide was imaged via its metabolite pyrazinoic acid, detected at all time points. Pyrazinoic acid's concentration-time profile and PK parameters were obtained, revealing unexpected production by a host enzyme. Significant inter-individual variation in drug exposure was observed, highlighting the need to consider such variations when building PBPK models with limited NHPs.

CONCLUSION

This study provided HRZE distribution data in cynomolgus macaque lungs, aiding the understanding of antituberculosis drug PK for further optimization of the dosing regimens. It also sets the stage for future determinations of drug concentrations in lesions in infected NHPs to support PK/PD investigations.