Pradigastat disposition in humans: in vivo and in vitro investigations.

1. Pradigastat is a potent and specific diacylglycerol acyltransferase-1 (DGAT1) inhibitor effective in lowering postprandial triglycerides (TG) in healthy human subjects and fasting TG in familial chylomicronemia syndrome (FCS) patients. 2. Here we present the results of human oral absorption, metabolism and excretion (AME), intravenous pharmacokinetic (PK), and in vitro studies which together provide an overall understanding of the disposition of pradigastat in humans. 3. In human in vitro systems, pradigastat is metabolized slowly to a stable acyl glucuronide (M18.4), catalyzed mainly by UDP-glucuronosyltransferases (UGT) 1A1, UGT1A3 and UGT2B7. M18.4 was observed at very low levels in human plasma. 4. In the human AME study, pradigastat was recovered in the feces as parent drug, confounding the assessment of pradigastat absorption and the important routes of elimination. However, considering pradigastat exposure after oral and intravenous dosing, this data suggests that pradigastat was completely bioavailable in the radiolabeled AME study and therefore completely absorbed. 5. Pradigastat is eliminated very slowly into the feces, presumably via the bile. Renal excretion is negligible. Oxidative metabolism is minimal. The extent to which pradigastat is eliminated via metabolism to M18.4 could not be established from these studies due to the inherent instability of glucuronides in the gastrointestinal tract.

Metabolism and pharmacokinetics of indacaterol in humans.

The metabolism, pharmacokinetics, and excretion of [(14)C]indacaterol were investigated in healthy male subjects. Although indacaterol is administered to patients via inhalation, the dose in this study was administered orally. This was done to avoid the complications and concerns associated with the administration of a radiolabeled compound via the inhalation route. The submilligram doses administered in this study made metabolite identification and structural elucidation by mass spectrometry especially challenging. In serum, the mean t(max), C(max), and AUC(0-last) values were 1.75 h, 0.47 ng/ml, and 1.81 ng · h/ml for indacaterol and 2.5 h, 1.4 ngEq/ml, and 27.2 ngEq · h/ml for total radioactivity. Unmodified indacaterol was the most abundant drug-related compound in the serum, contributing 30% to the total radioactivity in the AUC(0-24h) pools, whereas monohydroxylated indacaterol (P26.9), the glucuronide conjugate of P26.9 (P19), and the 8-O-glucuronide conjugate of indacaterol (P37) were the most abundant metabolites, with each contributing 4 to 13%. In addition, the N-glucuronide (2-amino) conjugate (P37.7) and two metabolites (P38.2 and P39) that resulted from the cleavage about the aminoethanol group linking the hydroxyquinolinone and diethylindane moieties had a combined contribution of 12.5%. For all four subjects in the study, ≥90% of the radioactivity dose was recovered in the excreta (85% in feces and 10% in urine, mean values). In feces, unmodified indacaterol and metabolite P26.9 were the most abundant drug-related compounds (54 and 17% of the dose, respectively). In urine, unmodified indacaterol accounted for ∼0.3% of the dose, with no single metabolite accounting for >1.3%.