Study design
This study was a repeated-dose, single-center, open-label, phase 1 study
conducted between November 2015 and June 2016 in Japan. The study
protocol and the informed consent form were approved by the
Institutional Review Board of Hakata Clinic. All participants gave
written informed consent before initiation of any study-specific
procedures. The study was conducted in accordance with the ethical
principles originating in or derived from the Declaration of Helsinki,
and Good Clinical Practice guidelines.
Subjects orally received 960 mg of carotegrast methyl three times daily
for 14 days from day 1 to day 14. Carotegrast methyl was administered 30
min after each meal, but under fasting conditions in the morning on the
day of blood collection. A single dose of midazolam (5 mg; po, 0.017 mg
kg-1; iv),
prednisolone (5 mg; po), or
atorvastatin (10 mg; po) was administered under fasting conditions on
day -1 (one day before the start of carotegrast methyl administration),
day 7 (coadministration with carotegrast methyl), day 14
(coadministration with carotegrast methyl), day 28 (14 days after the
end of carotegrast methyl administration) and day 48 (28 days after the
end of carotegrast methyl administration). Because the median time for
intravenous midazolam to reach the maximum drug concentration
(Tmax) was two hours, the drug was administered two
hours after the administration of carotegrast methyl. Each
coadministration cohort consisted of 20 subjects, 80 subjects in total,
and the cohort to which carotegrast methyl alone was administered
consisted of eight subjects. When the 90% confidence interval (CI) of
the geometric mean ratio of the area under the concentration‐time curve
from time of dosing to time of last measurable concentration
(AUC0-t) and maximum concentration
(Cmax) of oral midazolam both with and without
concomitant carotegrast methyl fell within the range of 0.80 − 1.25, it
was determined that there was no pharmacokinetic interaction between the
drugs, subsequent combination studies were not conducted.
Midazolam was selected for this study because it is a representative
substrate of CYP3A4 listed in the guideline13 and used
in many clinical studies as a sensitive probe for drug-drug interactions
mediated by human CYP3A4.14-16 When given orally,
midazolam is quickly metabolized via the first-pass effect, which is not
only associated with CYP3A4 in the liver, but also in the small
intestine.17 On the other hand, intravenous midazolam,
mainly metabolized in the liver by CYP3A4, is one of the most commonly
used medications for inducing anxiolysis or sedation or both, prior to
colonoscopy in patients with UC.18 Therefore, whether
carotegrast methyl interacted with intravenous midazolam was also
investigated. Prednisolone is used for inducing remission of
UC19 and it is known to be a substrate of
CYP3A4.20-22 Atorvastatin is a substrate of
CYP3A423-25 and a typical substrate of
OATP1B1/1B3.13 It has been
reported26,27 that the ratio of the contribution of
CYP3A4 to the oral clearance of midazolam, atorvastatin, and
prednisolone is 92%, 68%, and 18%, respectively.
In order to maximize the inhibitory effect of carotegrast methyl on
CYP3A4, carotegrast methyl should be administered for more than ten days
because the recovery half-life of CYP3A4 activity following 14-day
treatment with St. John’s Wort was reported to be 46.2
h,28 and five times its half-life is 231 h (9.6 days).
Therefore, we set a 14-day treatment period for carotegrast methyl. The
follow-up period was four weeks after the end of administration of
carotegrast methyl. Subjects were admitted to the study center on day -3
and discharged on day 15. The second admission was from day 27 to day
42.