PRACTECAL-PKPD Sub Study

PRACTECAL-PKPD is an exploratory pharmacokinetic and pharmacodynamic sub-study investigating the relationship between the patients' exposure to anti- tuberculosis (TB) drugs in the TB-PRACTECAL trial investigational regimens and their respective treatment outcomes.

PRACTECAL-PKPD is a sub-study of the main TB-PRACTECAL phase II-III trial for the treatment of biologically confirmed pulmonary multi drug or extensively drug-resistant TB (M/XDR-TB). TB-PRACTECAL is a multicentre, open label, phase 2-3 randomised controlled trial evaluating 6 months, exclusively oral regimens containing bedaquiline (B), pretomanid (Pa), linezolid (Lzd) +/- moxifloxacin (Mfx) or clofazimine (Cfz) for the treatment of microbiologically confirmed pulmonary M/XDR-TB.

Primary objective Measure the plasma concentrations of pretomanid, linezolid, bedaquiline, clofazimine and moxifloxacin in a sub-set of patients in the TB-PRACTECAL trial and using population pharmacokinetic (PK) models, estimate the population exposure metrics (minimum plasma concentration (Cmin), mean plasma concentration (Cmean), maximum plasma concentration (Cmax), plasma concentration versus time curve (AUC)) for the individual drugs in the TB-PRACTECAL trial.

Secondary objectives Develop a population pharmacodynamic model to explore the relationship between drug exposure, baseline minimum inhibitory concentrations and both mycobacteriological and clinical treatment success Develop a population pharmacodynamics model and identify PK parameters that are associated with treatment emergent toxicity Explore covariates specific to the regimens and study population Use results of above objectives to develop a hypothesis on the optimal dosing of linezolid and clofazimine Explore the pharmacogenomic factors associated with efficacy and toxicity of the investigational drugs Analyse adherence/exposure to the investigational regimen(s) by analysing anti-TB drug levels in small hair samples Assess the potential of using hair drug levels to develop safety and efficacy pharmacodynamic models Conduct clinical validation of a dried blood quantification method using volumetric absorptive microsampling.

Procedures:

4 ml (vacutainer tube, lithium heparin) of blood will be collected from the hand, forearm or antecubital vein at each sampling occasion and moment for the PK. The sampling occasions are on Day 1, Weeks 8, 12, 16, 20, 24, 32 and 72. On Day 1, blood will be collected just before drugs intake, then 2 and 23 hours after drugs intake. On week 8, blood will be collected just before drugs intake, then 6.5 and 23 hours post dose. At weeks 12, 16, 20 and 24 the blood will be collected within 30 minutes before taking the dose. Samples from week 32 and 72 will be collected whenever feasible after the patients have completed their treatment so blood collection is not relative to drug intake on that occasion. These have been included to capture the elimination phases of the drugs which have long terminal half-lives.

A subgroup of patients will also participate to the clinical validation study of a dried blood quantification method using volumetric absorptive microsampling. 2ml of blood and a drop of blood from the finger tips will be collected at the following sampling occasions: day 1, week 8, 12 and 16.

In the small hair study, a small thatch of hair will be cut as close as possible to the scalp from the occiput at weeks 8, 16, 24, 32 and 72.