Pharmacokinetics and pharmacodynamics of clofazimine in a mouse model of tuberculosis

Abstract

The antileprosy drug clofazimine has shown potential for shortening tuberculosis treatment; however, the current dosing of the drug is not evidence based, and the optimal dosing is unknown. Our objective was to conduct a preclinical evaluation of the pharmacokinetics and pharmacodynamics of clofazimine in the mouse model of tuberculosis, with the goal of providing useful information on dosing for future studies. Pharmacokinetic parameters were evaluated in infected and uninfected BALB/c mice. Pharmacodynamic parameters were evaluated in Mycobacterium tuberculosis-infected mice that were treated for 12 weeks with one of six different clofazimine dosing regimens, i.e., doses of 6.25, 12.5, and 25 mg/kg of body weight/day and 3 regimens with loading doses. Clofazimine progressively accumulated in the lungs, livers, and spleens of the mice, reaching levels of greater than 50 μg/g in all tissues by 4 weeks of administration, while serum drug levels remained low at 1 to 2 μg/ml. Elimination of clofazimine was extremely slow, and the half-life was dependent on the duration of drug administration. Clofazimine exhibited dose-dependent tissue and serum concentrations. At any dose, clofazimine did not have bactericidal activity during the first 2 weeks of administration but subsequently demonstrated potent, dose-independent bactericidal activity. The antituberculosis activity of clofazimine was dependent on neither the dose administered nor the drug concentrations in the tissues, suggesting that much lower doses could be effectively used for tuberculosis treatment.

FIG 1

Clofazimine-induced discoloration in uninfected BALB/c mice. Photographs of the lungs, spleen, and subcutaneous adipose tissue were taken at each time point during the 20 weeks of clofazimine administration and during the 24 weeks after stopping administration. Postadministration photographs of the mice that received clofazimine for 4, 8, 12, and 16 weeks are presented in Fig. S1 in the supplemental material.

FIG 2

Nonlinear regression of clofazimine accumulation and elimination in the lungs (A), liver (B), and serum (C) of uninfected BALB/c mice. Elimination curves are included for each group of mice that discontinued clofazimine administration after 4, 8, 12, 16, and 20 weeks. Clofazimine concentration data for the lungs, liver, and serum are presented in Tables S3, S4, and S5 in the supplemental material, respectively. The dotted lines represent the MIC of clofazimine for M. tuberculosis.

FIG 3

Clofazimine accumulation and elimination in the spleens of uninfected BALB/c mice. The concentrations of clofazimine measured after stopping administration are represented by the dashed lines. The error bars represent standard deviations (3 mice per group per time point). Clofazimine concentration values are presented in Table S6 in the supplemental material. The dotted line represents the MIC of clofazimine for M. tuberculosis.

FIG 4

Mean clofazimine concentrations in the sera of M. tuberculosis-infected mice during the first 2 weeks (A) or weeks 2 to 12 (B) of treatment. The dashed lines represent the MIC of clofazimine for M. tuberculosis. The error bars represent standard deviations (5 mice per group per time point). The drug regimens are described in Table 1.

FIG 5

Mean clofazimine concentrations in the lungs (A and B), liver (C and D), and spleen (E and F) of M. tuberculosis-infected mice during the first 2 weeks (A, C, and E) or weeks 2 to 12 (B, D, and F) of treatment. The dashed lines represent the MIC of clofazimine for M. tuberculosis. The error bars represent standard deviations (5 mice per group per time point). The drug regimens are described in Table 1.

FIG 6

Mean log₁₀ CFU counts in the lungs (A and C) and spleens (B and D) of M. tuberculosis-infected mice during the first 2 weeks (A and B) and weeks 2 to 12 (C and D) of treatment. The error bars represent standard deviations (5 mice per group per time point). The drug regimens are described in Table 1.