PII-038 - PK/PD OF RIFAMPICIN, ISONIAZID, PYRAZINAMIDE, AND ETHAMBUTOL IN MACROPHAGES INFECTED WITH M. TUBERCULOSIS.

J. B Ximenez¹, G. Balthazar Nardotto², A. Masson¹, T. Bachelli Riul¹, A. Rocha¹, E. M Svensson³, V. Lanchote¹, M. D Baruffi¹; ¹University of Sao Paulo, ²Roswell Park Comprehensive Cancer Center, ³Uppsala University.

Background: Current tuberculosis treatment consists of rifampicin (RIF), isoniazid (INH), pyrazinamide (PZA), and ethambutol (ETB) followed by four months of RIF and INH. Despite their extensive use, the knowledge of FLATDs dosing to ensure optimal drug exposure remains limited. The present study aims to evaluate the pharmacokinetics and pharmacodynamics of RIF, INH, PZA, and ETB in macrophages infected with M. tuberculosis.

Methods: THP-1 cells were differentiated into macrophages. THP-1 macrophages contaminated with M. tuberculosis H37Rv were cultured in a medium containing different concentrations of RIF (1, 3, 7 g/mL), INH (1, 3, 7g/mL), PZA (25, 40, 55 g/mL) and ETB (5; 10; 15 g/mL). Serial sampling (n=6 for each concentration and time) was performed at times 30 min and 1, 6, 24, 48, 72, 98, and 120 hours. Simultaneously, infected macrophages were also cultured in the treatment medium without antibiotics. The intracellular concentrations of RIF, INH, PZA, and ETB were quantified by LC-MS/MS. The activity of FLATDs against M. tuberculosis within macrophages was assessed using non-linear mixed effects models, utilizing the M. tuberculosis H37Rv CFU/mL count as a pharmacodynamic descriptors and the concentrations of FLATDs as kinetic measure using the NONMEM version 7.5.0.

Results: The pharmacodynamics of FLATDs evaluation included a first-order antibiotic reduction rate on the mycobacterium CFU (Kill), a first-order bacterial growth rate (KG) and drug effect explored by a linear model. RIF, INH, PZA, and ETB have shown half-lives (h) [Typical value (RSE %)] of 2.38 (12.9), 0.859 (13.4), 1.5 (24.1), and 2.58 (8.3), respectively. The kill rate (h-1) for all compounds were approximaly 0.015. For the concentration ratio cell/medium (CR), RIF, INH, PZA, and ETB have shown CR values of 0.44 (19.4), 0.26 (18.1), 1.86 (13.4), and 1.47 (2.4).

Conclusion: Therefore, PZA showed higher intra-cellular accumulation and, on the other hand, INH demonstrated the lower intra-cellular accumulation. Regarding the high ETB intra-cellular accumulation (1.47), the corresponding plasma concentration in the medium (2 ug/mL) was not sufficient to kill the M. tuberculosis H37Rv (Figure 1).