Personalization of AntiTB Treatment: Evaluation of Pharmacological Determinants of Treatment Response

A longitudinal observational multicentred study will be conducted in patients with diagnosis of active pulmonary TB.

The following variables will be recorded:

• demographic variables: age, gender, ethnicity, SNPs for NAT2, SLCO1B1, ABCB1 and VDR;
• clinical variables: weight, height, renal function tests, liver function tests, vitamin D (25-OH vitamin D) level, albuminemia, serology for HIV, HCV, presence of comorbidities (e.g. diabetes mellitus), visual acuity test, presence of neuropathic symptoms;
• microbiological variables: phenotypic and genotypic drug sensitivity test results, sputum Mycobacterium tuberculosis DNA (PCR), microscopy, culture, Time To Positivity (TTP) in liquid culture, IGRA test (if performed), history of previous treatments, location of pulmonary lesions, presence of extra-pulmonary locations;
• therapeutic variables: start/end of treatment, treatment interruptions, dose mg/kg, route of administration.

The patients will received standard antitubercular drugs according to international guidelines (RIF 10 mg/kg, INH 5 mg/kg maximum dose 300 mg, ETB 15-20 mg/kg, PZA 25 mg/kg maximum dose 2000 mg) in fasten condition, once daily.

To measure plasma concentrations four blood samples (Lithium heparin 7 ml tubes) will be collected at 0, 2, 4 and 6 hours post dose. This analysis will be performed at 7 and 14 days after the beginning of anti-TB treatment.

For the pharmacogenetic analysis a blood sample (EDTA 4 ml tube) will be collected at the baseline.

Sputum samples will be collected at baseline, 7 and 14 days for Mycobacterial culture.

Medical visits and blood samples (for LFTs) will be performed at baseline, 7 and 14 days to investigate neuro and hepato- toxicity.

Pharmacokinetics After the collection the samples will be centrifugated (3000 rev min-1 at 4°C for 10 min) and plasma will be frozen at - 20°C in 2 aliquots (1 mL of volume) and will be delivered to the Laboratory of Pharmacokinetics and Pharmacogenetics of the University of Torino Amedeo di Savoia Hospital, ASLTO2, Torino, Italy.

Plasma concentrations of all four drugs will be measured using liquid chromatography coupled with tandem mass-spectroscopy (allowing high sensitivity despite small sample volumes). Collected concentration-time data will be evaluated by a non-compartmental approach to characterize the pharmacokinetic properties at steady-state. AUC, maximum (Cmax) and minimum (Cmin) drug levels and plasma elimination half-life will be used to assess the enzymatic induction properties of these drugs. Pharmacogenomics (PG) DNA will be extracted from whole blood using QIamp DNA Mini Kit (Quiagen, Valencia, CA). Purified and eluted DNA will be directly used for real-time PCR (BIORAD, Milano, Italia) reaction. The allelic discrimination analysis will be performed using the TaqMan assays (Applied Biosystems, Foster City, CA).

Analyzed SNPs will be:

ABCB1 3435C>T (rs1045642), OATP1B1 521T>C (rs4149056) e OATP1B1 85-7793T>C (rs4149032), PXR 63396C>T (rs2472677), BsmI G>A (rs1544410).

and NAT2 G>A (rs1799930). Dried blood spots (DBSs) and Dried plasma spots (DPSs) Method for the determination of plasma concentrations on DPSs will be developed and validated by our laboratory. In the study, the blood samples for evaluation on DPSs will be obtained only from subjects of our institute. After centrifugation (3000 rev min-1 at 4°C for 10 min) 100 μ l plasma will be spotted onto each glass filter (purchased from Laboratori Biomicron srl, Italy) and used for pharmacokinetic (PK) analysis. The remaining plasma will be used as controls in the analysis.

For the pharmacogenetic (PG) analysis venous blood samples will be obtained from all subjects and whole blood (50 μ l per spot) will be spotted on DBS Whatman 903 protein saver cards (VWR International, Milan, Italy).

DBS will be inserted in a foil bag with desiccant (Foil Bag and Desiccant Packs, purchased from Laboratori Biomicron srl, Italy) and then stored at room temperature. After a maximum of 30 days samples will be delivered to the Laboratory of Pharmacokinetics and Pharmacogenetics of the University of Torino Amedeo di Savoia Hospital, ASLTO2, Torino, Italy. They will be stored at - 20°C until analysis will be performed (within 3 months from collection).

Time To Positivity Time to positivity on sputum cultures at baseline, 7 and 14 days will be calculated using software BD Epicenter integrated in BACTEC MGIT System (Mycobacteria Growth Indication Tube) 960. Default time is 42 days.