3 research outputs found
A Physiologically Based Modeling Strategy during Preclinical CNS Drug Development
Physiologically
based pharmacokinetic (PBPK) modeling of the central
nervous system (CNS) provides the opportunity to predict the relevant
drug concentrations at the therapeutic target site during preclinical
and clinical development. In order to successfully interpret model
results, and to provide confidence in the subsequent human predictions,
it is essential that an appropriate model structure is chosen at the
preclinical stage which takes into account both physiological and
drug-specific knowledge. However, the models published to date in
the literature show significant variation in the approaches applied
by different authors, which can lead to difficulties in the interpretation
of model parameter estimates. We aimed to develop a coherent PBPK
modeling approach in the rat, which would also be adaptable depending
on the quantity and quality of <i>in vivo</i> data obtained
during drug development. Based on a sensitivity analysis of the model
parameters, and using three CNS drugs as case studies (atomoxetine,
acetaminophen, and S 18986), we proposed a decision tree to aid in
the appropriate parametrization and structure of the model according
to the data available. We compared our parameter estimates to those
originally published, and considered the impact of the respective
approaches on the mechanistic interpretation of the parameter values.
Since the measurement of brain extracellular fluid (ECF) concentrations
using microdialysis is not routinely performed in the industrial environment,
we also evaluated the bottom-up scaling of <i>in vitro</i> permeability data from the Caco-2 cell line to predict BBB passive
permeability in the absence of measured ECF concentrations. Our strategy
demonstrates the value of PBPK as a prediction tool throughout the
development process of CNS-targeting drugs
Quantitative Atlas of Cytochrome P450, UDP-Glucuronosyltransferase, and Transporter Proteins in Jejunum of Morbidly Obese Subjects
Protein
expression levels of drug-metabolizing enzymes and transporters in
human jejunal tissues excised from morbidly obese subjects during
gastric bypass surgery were evaluated using quantitative targeted
absolute proteomics. Protein expression levels of 15 cytochrome P450
(CYP) enzymes, 10 UDP-glucuronosyltransferase (UGT) enzymes, and NADPH-P450
reductase (P450R) in microsomal fractions from 28 subjects and 49
transporters in plasma membrane fractions from 24 of the same subjects
were determined using liquid chromatography–tandem mass spectrometry.
Based on average values, UGT1A1, UGT2B15, UGT2B17, SGLT1, and GLUT2
exhibited high expression levels (over 10 fmol/μg protein),
though UGT2B15 expression was detected at a high level in only one
subject. CYP2C9, CYP2D6, CYP3A5, UGT1A6, P450R, ABCG2, GLUT5, PEPT1,
MCT1, 4F2 cell-surface antigen heavy chain (4F2hc), LAT2, OSTα,
and OSTβ showed intermediate levels (1–10 fmol/μg
protein), and CYP1A1, CYP1A2, CYP1B1, CYP2C18, CYP2C19, CYP2J2, CYP3A7,
CYP4A11, CYP51A1, UGT1A3, UGT1A4, UGT1A8, UGT2B4, ABCC1, ABCC4, ABCC5,
ABCC6, ABCG8, TAUT, OATP2A1, OATP2B1, OATP3A1, OATP4A1, OCTN1, CNT2,
PCFT, MCT4, GLUT4, and SLC22A18 showed low levels (less than 1 fmol/μg
protein). The greatest interindividual difference (364-fold) was detected
for UGT2B17. However, differences in expression levels of other quantified
UGTs (except UGT2B15 and UGT2B17), CYPs (except CYP1A1 and CYP3A5),
and P450R, and all quantified transporters, were within 10-fold. Expression
levels of CYP1A2 and GLUT4 were significantly correlated with body-mass
index. The levels of 4F2hc showed significant gender differences.
Smokers showed increased levels of UGT1A1 and UGT1A3. These findings
provide a basis for understanding the changes in molecular mechanisms
of jejunal metabolism and transport, as well as their interindividual
variability, in morbidly obese patients
Oral Morphine Pharmacokinetic in Obesity: The Role of P‑Glycoprotein, MRP2, MRP3, UGT2B7, and CYP3A4 Jejunal Contents and Obesity-Associated Biomarkers
The objective of our work was to
study the association between
the jejunal expression levels of P-gp, MRP2, MRP3, UGT2B7, CYP3A4,
the <i>ABCB1</i> c.3435C > T polymorphism, and several
obesity-associated
biomarkers, as well as oral morphine and glucuronides pharmacokinetics
in a population of morbidly obese subjects. The pharmacokinetics of
oral morphine (30 mg) and its glucuronides was performed in obese
patients candidate to bariatric surgery. A fragment of jejunal mucosa
was preserved during surgery. Subjects were genotyped for the <i>ABCB1</i> single nucleotide polymorphism (SNP) c.3435C >
T.
The subjects were 6 males and 23 females, with a mean body mass index
of 44.8 (35.4–61.9) kg/m<sup>2</sup>. The metabolic ratios
AUC<sub>0‑inf</sub> M3G/morphine and AUC<sub>0‑inf</sub> M6G/morphine
were highly correlated (rs = 0.8, <i>p</i> < 0.0001)
and were 73.2 ± 24.6 (34.7–137.7) and 10.9 ± 4.1
(3.8–20.6). The pharmacokinetic parameters of morphine and
its glucuronides were not associated with the jejunal contents of
P-gp, CYP3A4, MRP2, and MRP3. The jejunal content of UGT2B7 was positively
associated with morphine AUC<sub>0‑inf</sub> (rs = 0.4, <i>p</i> = 0.03). Adiponectin was inversely correlated with morphine <i>C</i><sub>max</sub> (rs = −0.44, <i>p</i> =
0.03). None of the factors studied was associated with morphine metabolic
ratios. The interindividual variability in the jejunal content of
drug transporters and metabolizing enzymes, the <i>ABCB1</i> gene polymorphism, and the low-grade inflammation did not explain
the variability in morphine and glucuronide exposure. High morphine
metabolic ratio argued for an increased morphine glucuronidation in
morbidly obese patients