Role of P-glycoprotein and the intestine in the excretion of DPC 333 [(2R)-2-{(3R)-3-amino-3-[4-(2-methylquinolin-4-ylmethoxy)phenyl]-2-oxopyrrolidin-1-yl}-N-hydroxy-4-methylpentanamide] in rodents

Recent advances in the translation of drug metabolism and pharmacokinetics science for drug discovery and development

Drug metabolism and pharmacokinetics (DMPK) is an important branch of pharmaceutical sciences. The nature of ADME (absorption, distribution, metabolism, excretion) and PK (pharmacokinetics) inquiries during drug discovery and development has evolved in recent years from being largely descriptive to seeking a more quantitative and mechanistic understanding of the fate of drug candidates in biological systems. Tremendous progress has been made in the past decade, not only in the characterization of physiochemical properties of drugs that influence their ADME, target organ exposure, and toxicity, but also in the identification of design principles that can minimize drug-drug interaction (DDI) potentials and reduce the attritions. The importance of membrane transporters in drug disposition, efficacy, and safety, as well as the interplay with metabolic processes, has been increasingly recognized. Dramatic increases in investments on new modalities beyond traditional small and large molecule drugs, such as peptides, oligonucleotides, and antibody-drug conjugates, necessitated further innovations in bioanalytical and experimental tools for the characterization of their ADME properties. In this review, we highlight some of the most notable advances in the last decade, and provide future perspectives on potential major breakthroughs and innovations in the translation of DMPK science in various stages of drug discovery and development.

Intestinal Excretion, Intestinal Recirculation, and Renal Tubule Reabsorption Are Underappreciated Mechanisms That Drive the Distribution and Pharmacokinetic Behavior of Small Molecule Drugs

Drug reabsorption following biliary excretion is well-known as enterohepatic recirculation (EHR). Renal tubular reabsorption (RTR) following renal excretion is also common but not easily assessed. Intestinal excretion (IE) and enteroenteric recirculation (EER) have not been recognized as common disposition mechanisms for metabolically stable and permeable drugs. IE and intestinal reabsorption (IR:EHR/EER), as well as RTR, are governed by dug concentration gradients, passive diffusion, active transport, and metabolism, and together they markedly impact disposition and pharmacokinetics (PK) of small molecule drugs. Disruption of IE, IR, or RTR through applications of active charcoal (AC), transporter knockout (KO), and transporter inhibitors can lead to changes in PK parameters. The impacts of intestinal and renal reabsorption on PK are under-appreciated. Although IE and EER/RTR can be an intrinsic drug property, there is no apparent strategy to optimize compounds based on this property. This review seeks to improve understanding and applications of IE, IR, and RTR mechanisms.

Disposition and metabolism of 2',2'"-Dithiobisbenzanilide in rodents following intravenous and oral administration and dermal application

•

2′,2′′′-Dithiobisbenzanilide (DTBBA) is a chemical used as a peptizing agent for rubber.

•

Humane exposure to DTBBA is possible via oral and dermal routes.

•

DTBBA is well-absorbed in rodents following oral and dermal administration.

•

Absorbed DTBBA was extensively metabolized and excreted mainly via urine.

•

N-(2-mercaptophenyl)benzamide accounted for more than 50% of radioactivity in urine.

2′,2′′′-Dithiobisbenzanilide (DTBBA) is a high-production-volume chemical used as a peptizing agent for rubber. The disposition and metabolism of [¹⁴C]DTBBA were determined in male and female rats and mice following oral (4, 40, or 400 mg/kg) and intravenous (IV) (4 mg/kg) administration and dermal application (0.4 or 4 mg/kg). [¹⁴C]DTBBA was well absorbed following oral administration (> 60%) and dermal application (∼40–50%) in rats and mice. Following oral administration, the majority of radioactivity was excreted in urine (29 − 70%) and feces (16 − 45%). Unlike rats, mice excreted ∼1-5% of the dose as exhaled CO₂. The residual radioactivity in tissues was <1% in both species and sexes. The pattern of disposition following IV administration in male rats was similar to that following oral. When [¹⁴C]DTBBA was administered via IV to rats, a significant portion of the dose was recovered in bile (∼13%) suggesting that at least a portion of the dose recovered in feces following oral administration was likely the absorbed dose. The profiles of urine from rats and mice were similar and consisted of four major metabolites and three minor metabolites. The predominant metabolite in urine was the S-glucuronide of the thiol/sulfide cleavage product N-(2-mercaptophenyl)benzamide, which accounted for more than 50% of radioactivity in the radiochromatogram.

Radiosynthesis and preclinical evaluation of [11C]prucalopride as a potential agonist PET ligand for the 5-HT4 receptor

Background

Serotonin 5-HT₄ receptor (5-HT₄-R) agonists are potential therapeutic agents for enterokinetic and cognitive disorders and are marketed for treatment of constipation. The aim of this study was to develop an agonist positron emission tomography (PET) ligand in order to label the active G-protein coupled 5-HT₄-R in peripheral and central tissues. For this purpose prucalopride, a high-affinity selective 5-HT₄-R agonist, was selected.

Methods

[¹¹C]Prucalopride was synthesized from [¹¹C]methyl triflate and desmethyl prucalopride, and its LogD_oct,pH7.4 was determined. Three distinct studies were performed with administration of IV [¹¹C]prucalopride in male rats: (1) The biodistribution of radioactivity was measured ex vivo; (2) the kinetics of radioactivity levels in brain regions and peripheral organs was assessed in vivo under baseline conditions and following pre-treatment with tariquidar, a P-glycoprotein efflux pump inhibitor; and (3) in vivo stability of [¹¹C]prucalopride was checked ex vivo in plasma and brain extracts using high-performance liquid chromatography.

Results

[¹¹C]Prucalopride was synthesized in optimised conditions with a yield of 21% ± 4% (decay corrected) and a radiochemical purity (>99%), its LogD_oct,pH7.4 was 0.87. Ex vivo biodistribution studies with [¹¹C]prucalopride in rats showed very low levels of radioactivity in brain (maximal 0.13% ID·g⁻¹) and ten times higher levels in certain peripheral tissues. The PET studies confirmed very low brain levels of radioactivity under baseline conditions; however, it was increased three times after pre-treatment with tariquidar. [¹¹C]Prucalopride was found to be very rapidly metabolised in rats, with no parent compound detectable in plasma and brain extracts at 5 and 30 min following IV administration. Analysis of levels of radioactivity in peripheral tissues revealed a distinct PET signal in the caecum, which was reduced following tariquidar pre-treatment. The latter is in line with the role of the P-glycoprotein pump in the gut.

Conclusion

[¹¹C]Prucalopride demonstrated low radioactivity levels in rat brain; a combination of reasons may include rapid metabolism in the rat in particular, low passive diffusion and potential P-glycoprotein substrate. In humans, further investigation of [¹¹C]prucalopride for imaging the active state of 5-HT₄-R is worthwhile, in view of the therapeutic applications of 5-HT₄ agonists for treatment of gastrointestinal motility disorders.

Comparative metabolism of 14C-labeled apixaban in mice, rats, rabbits, dogs, and humans

The metabolism and disposition of [(14)C]apixaban, a potent, reversible, and direct inhibitor of coagulation factor Xa, were investigated in mice, rats, rabbits, dogs, and humans after a single oral administration and in incubations with hepatocytes. In plasma, the parent compound was the major circulating component in mice, rats, dogs, and humans. O-Demethyl apixaban sulfate (M1) represented approximately 25% of the parent area under the time curve in human plasma. This sulfate metabolite was present, but in lower amounts relative to the parent, in plasma from mice, rats, and dogs. Rabbits showed a plasma metabolite profile distinct from that of other species with apixaban as a minor component and M2 (O-demethyl apixaban) and M14 (O-demethyl apixaban glucuronide) as prominent components. The fecal route was a major elimination pathway, accounting for >54% of the dose in animals and >46% in humans. The urinary route accounted for <15% of the dose in animals and 25 to 28% in humans. Apixaban was the major component in feces of every species and in urine of all species except rabbit. M1 and M2 were common prominent metabolites in urine and feces of all species as well as in bile of rats and humans. In vivo metabolite profiles showed quantitative differences between species and from in vitro metabolite profiles, but all human metabolites were found in animal species. After intravenous administration of [(14)C]apixaban to bile duct-cannulated rats, the significant portion (approximately 22%) of the dose was recovered as parent drug in the feces, suggesting direct excretion of the drug from gastrointestinal tracts of rats. Overall, apixaban was effectively eliminated via multiple elimination pathways in animals and humans, including oxidative metabolism, and direct renal and intestinal excretion.