CLINICAL PHARMACOLOGY
Mechanism Of Action
The mechanism by which suvorexant exerts its therapeutic
effect in insomnia is presumed to be through antagonism of orexin receptors.
The orexin neuropeptide signaling system is a central promoter of wakefulness.
Blocking the binding of wake-promoting neuropeptides orexin A and orexin B to
receptors OX1R and OX2R is thought to suppress wake drive.
Antagonism of orexin receptors may also underlie
potential adverse effects such as signs of narcolepsy/cataplexy. Genetic
mutations in the orexin system in animals result in hereditary narcolepsy; loss
of orexin neurons has been reported in humans with narcolepsy.
Pharmacodynamics
Evaluation Of QTc Interval
The effects of suvorexant on the QTc interval were
evaluated in a randomized, placebo-, and active-controlled (moxifloxacin 400
mg) crossover study in healthy subjects (n=53). The upper bound of the
one-sided 95% confidence interval for the largest placebo-adjusted,
baseline-corrected QTc interval was below 10 ms based on analysis of suvorexant
doses up to 240 mg, 12 times the maximum recommended dose. BELSOMRA thus does
not prolong the QTc interval to any clinically relevant extent.
Pharmacokinetics
Suvorexant exposure increases in a less than strictly
dose-proportional manner over the range of 10-80 mg because of decreased
absorption at higher doses. Suvorexant pharmacokinetics are similar in healthy
subjects and patients with insomnia.
Absorption
Suvorexant peak concentrations occur at a median Tmax of
2 hours (range 30 minutes to 6 hours) under fasted conditions. The mean
absolute bioavailability of 10 mg is 82%.
Ingestion of suvorexant with a high-fat meal resulted in
no meaningful change in AUC or Cmax but a delay in Tmax of approximately 1.5
hours. Suvorexant may be taken with or without food; however for faster sleep
onset, suvorexant should not be administered with or soon after a meal.
Distribution
The mean volume of distribution of suvorexant is
approximately 49 liters. Suvorexant is extensively bound (>99%) to human
plasma proteins and does not preferentially distribute into red blood cells.
Suvorexant binds to both human serum albumin and α1-acid glycoprotein.
Metabolism
Suvorexant is mainly eliminated by metabolism, primarily
by CYP3A with a minor contribution from CYP2C19. The major circulating entities
are suvorexant and a hydroxy-suvorexant metabolite. This metabolite is not
expected to be pharmacologically active.
Elimination
The primary route of elimination is through the feces,
with approximately 66% of radiolabeled dose recovered in the feces compared to
23% in the urine. The systemic pharmacokinetics of suvorexant are linear with
an accumulation of approximately 1-to 2-fold with once-daily dosing.
Steady-state is achieved by 3 days. The mean t½ is approximately 12 hours
(95% CI: 12 to 13).
Special Populations
Gender, age, body mass index (BMI), and race were
included as factors assessed in the population pharmacokinetic model to
evaluate suvorexant pharmacokinetics in healthy subjects and to predict
exposures in the patient population. Age and race are not predicted to have any
clinically meaningful changes on suvorexant pharmacokinetics; therefore, no
dose adjustment is warranted based upon these factors.
Suvorexant exposure is higher in females than in males.
In females, the AUC and Cmax are increased by 17% and 9%, respectively,
following administration of BELSOMRA 40 mg. The average concentration of
suvorexant 9 hours after dosing is 5% higher for females across the dose range
studied (10-40 mg). Dose adjustment of BELSOMRA is generally not needed based
on gender only.
Apparent oral clearance of suvorexant is inversely
related to body mass index. In obese patients, the AUC and Cmax are increased
by 31% and 17%, respectively. The average concentration of suvorexant
approximately 9 hours after a 20 mg dose is 15% higher in obese patients (BMI
> 30 kg/m²) relative to those with a normal BMI (BMI ≤ 25 kg/m²).
In obese females, the AUC and Cmax are increased by 46%
and 25%, respectively, compared to non-obese females. The higher exposure to suvorexant
in obese females should be considered before increasing dose [see DOSAGE AND
ADMINISTRATION].
The effects of renal and hepatic impairment on the
pharmacokinetics of suvorexant were evaluated in specific pharmacokinetic
studies.
Suvorexant exposure after a single dose was similar in
patients with moderate hepatic insufficiency (Child-Pugh category 7 to 9) and
healthy matched control subjects; however, the suvorexant apparent terminal
half-life was increased from approximately 15 hours (range 10 -22 hours) in
healthy subjects to approximately 19 hours (range 11 -49 hours) in patients
with moderate hepatic insufficiency [see Use In Specific Populations].
Suvorexant exposure (expressed as total and unbound concentrations)
was similar between patients with severe renal impairment (urinary creatinine
clearance ≤30 mL/min/1.73m²) and healthy matched control subjects. No
dose adjustment is required in patients with renal impairment [see Use In Specific
Populations].
Drug Interactions
CNS-Active Drugs
An additive effect on psychomotor performance was
observed when a single dose of 40 mg of suvorexant was co-administered with a
single dose of 0.7 g/kg alcohol. Suvorexant did not affect alcohol
concentrations and alcohol did not affect suvorexant concentrations [see WARNINGS
AND PRECAUTIONS and DRUG INTERACTIONS].
An interaction study with a single dose of 40 mg
suvorexant and paroxetine 20 mg at steady-state levels in healthy subjects did
not demonstrate a clinically significant pharmacokinetic or pharmacodynamic
interaction.
Effects Of Other Drugs On BELSOMRA
The effects of other drugs on the pharmacokinetics of
suvorexant are presented in Figure 1 as change relative to suvorexant
administered alone (test/reference). Strong (e.g., ketoconazole or
itraconazole) and moderate (e.g., diltiazem) CYP3A inhibitors significantly
increased suvorexant exposure. Strong CYP3A inducers (e.g., rifampin)
substantially decreased suvorexant exposure [see DRUG INTERACTIONS].
Figure 1: Effects of Co-Administered Drugs on the
Pharmacokinetics of Suvorexant
Effects Of BELSOMRA On Other Drugs
In vitro metabolism studies demonstrate that suvorexant
has the potential to inhibit CYP3A and intestinal P-gp; however, suvorexant is
unlikely to cause clinically significant inhibition of human CYP1A2, CYP2B6,
CYP2C8, CYP2C9, CYP2C19 or CYP2D6. In addition, no clinically meaningful
inhibition of OATP1B1, BCRP and OCT2 transporters is anticipated. Chronic
administration of suvorexant is unlikely to induce the metabolism of drugs
metabolized by major CYP isoforms. Specific in vivo effects on the
pharmacokinetics of midazolam, warfarin, digoxin and oral contraceptives are
presented in Figure 2 as a change relative to the interacting drug administered
alone (test/reference) [see DRUG INTERACTIONS].
Figure 2: Effects of Suvorexant* on the Pharmacokinetics
of Co-Administered Drugs
* Suvorexant 40 mg was evaluated in all studies, except
midazolam where 80 mg suvorexant was administered.
# Monitor digoxin concentrations as clinically indicated [see DRUG INTERACTIONS].
Animal Toxicology And/Or Pharmacology
In dogs, daily oral administration of suvorexant (5, 30
mg/kg) for 4-7 days resulted in behavior characteristic of cataplexy (e.g.,
transient limb buckling, prone posture) when presented with food enrichment, a
stimulus demonstrated to induce cataplexy in dogs with hereditary narcolepsy.
In the 2-year carcinogenicity study in rats, an increased
incidence of retinal atrophy was observed at all doses. Plasma AUCs at the
lowest dose tested were approximately 7 times that in humans at the MRHD.
In subsequent studies of suvorexant in albino and
pigmented rats, retinal atrophy was delayed in onset and, after approximately
one year of dosing, was of lower incidence and severity in pigmented rats.
Clinical Studies
Controlled Clinical Studies
BELSOMRA was evaluated in three clinical trials in
patients with insomnia characterized by difficulties with sleep onset and sleep
maintenance.
Two similarly designed, 3-month, randomized,
double-blind, placebo-controlled, parallel-group studies were conducted (Study
1 and Study 2). In both studies, non-elderly (age 18-64) and elderly (age
≥ 65) patients were randomized separately. For the studies together,
non-elderly adults (mean age 46 years; 465 females, 275 males) were treated
with BELSOMRA 20 mg (n=291) or placebo (n=449). Elderly patients (mean age 71
years, 346 females, 174 males) were treated with BELSOMRA 15 mg (n=202) or
placebo (n=318).
In Study 1 and Study 2, BELSOMRA 15 mg or 20 mg was
superior to placebo for sleep latency as assessed both objectively by
polysomnography (Table 3) and subjectively by patient-estimated sleep latency
(Table 4). BELSOMRA 15 mg or 20 mg was also superior to placebo for sleep
maintenance, as assessed both objectively by polysomnography (Table 5) and
subjectively by patient-estimated total sleep time (Table 6). The effects of
BELSOMRA at night 1 (objective) and week 1 (subjective) were generally consistent
with later time points. The efficacy of BELSOMRA was similar between women and
men and, based on limited data, between Caucasians and non-Caucasians. Twenty
seven percent of patients treated with BELSOMRA 15 mg or 20 mg in Study 1 and
Study 2 were non-Caucasians. The majority (69%) of the non-Caucasian patients
was Asian.
Table 3: Polysomnographic Assessment of Time to Sleep
Onset in Studies 1 and 2
|
Mean Baseline and Change from Baseline† After 1 and 3 Months (minutes) |
Difference* Between BELSOMRA and Placebo (minutes) |
Study 1 |
|
Placebo
(n=290) |
BELSOMRA 15-20 mg‡
(n=193) |
|
Baseline |
66 |
69 |
|
Change from Baseline |
Month 1 |
-23 |
- 34 |
- 10*** |
Month 3 |
-27 |
- 35 |
- 8** |
Study 2 |
|
Placebo
(n=286) |
BELSOMRA 15-20 mg‡
(n=145) |
|
Baseline |
69 |
65 |
|
Change from Baseline |
Month 1 |
-25 |
- 33 |
-8* |
Month 3 |
-29 |
-29 |
0 |
† Change from baseline and treatment differences based
upon estimated means.
‡ 15 mg in elderly and 20 mg in non-elderly patients
* p<0.05; **p<0.01; ***p<0.001 |
Table 4: Patient-Estimated Time to Sleep Onset in
Studies 1 and 2
|
Mean Baseline and Change from Baseline† After 1 and 3 Months (minutes) |
Difference† Between BELSOMRA and Placebo (minutes) |
Study 1 |
|
Placebo
(n=382) |
BELSOMRA 15-20 mg*
(n=251) |
|
Baseline |
67 |
64 |
|
Change from Baseline |
Month 1 |
-12 |
-17 |
-5 |
Month 3 |
-17 |
-23 |
-5* |
Study 2 |
|
Placebo
(n=369) |
BELSOMRA 15-20 mg‡
(n=231) |
|
Baseline |
83 |
86 |
|
Change from Baseline |
Month 1 |
-14 |
-21 |
-7* |
Month 3 |
-21 |
-28 |
-8* |
† Change from baseline and treatment differences based
upon estimated means.
‡ 15 mg in elderly and 20 mg in non-elderly patients
* p<0.05; **p<0.01; ***p<0.001 |
Table 5: Polysomnographic Assessment of Sleep
Maintenance (Wake After Sleep Onset) in Studies 1 and 2
|
Mean Baseline and Change from Baseline† After 1 and 3 Months (minutes) |
Difference† Between BELSOMRA and Placebo (minutes) |
Study 1 |
|
Placebo
(n=290) |
BELSOMRA 15-20 mg‡
(n=193) |
|
Baseline |
115 |
120 |
|
Change from Baseline |
Month 1 |
-19 |
-45 |
- 26*** |
Month 3 |
-25 |
-42 |
- 17*** |
Study 2 |
|
Placebo
(n=286) |
BELSOMRA 15-20 mg‡
(n=145) |
|
Baseline |
118 |
119 |
|
Change from Baseline |
Month 1 |
-23 |
-47 |
- 24*** |
Month 3 |
-25 |
-56 |
- 31*** |
† Change from baseline and treatment differences based
upon estimated means.
‡ 15 mg in elderly and 20 mg in non-elderly patients
* p<0.05; **p<0.01; ***p<0.001 |
Table 6: Patient-Estimated Total Sleep Time in Studies 1 and 2
|
Mean Baseline and Change from Baseline† After 1 and 3 Months (minutes) |
Difference†Between BELSOMRA and Placebo (minutes) |
Study 1 |
|
Placebo
(n=382) |
BELSOMRA 15-20 mg‡
(n=251) |
|
Baseline |
315 |
322 |
|
Change from Baseline |
Month 1 |
23 |
39 |
16*** |
Month 3 |
41 |
51 |
11* |
Study 2 |
|
Placebo
(n=369) |
BELSOMRA 15-20 mg‡
(n=231) |
|
Baseline |
307 |
299 |
|
Change from Baseline |
Month 1 |
22 |
43 |
21*** |
Month 3 |
38 |
60 |
22*** |
† Change from baseline and treatment differences based
upon estimated means.
‡ 15 mg in elderly and 20 mg in non-elderly patients
* p<0.05; **p<0.01; ***p<0.001 |
In the 1-month crossover study (Study 3), non-elderly
adults (age 18-64 years, mean age 44 years) were treated with placebo (n=249)
and BELSOMRA at a dose of 10 mg (n=62), 20 mg (n=61), or up to 80 mg. BELSOMRA
10 mg and 20 mg were superior to placebo for sleep latency and sleep
maintenance, as assessed objectively by polysomnography.
BELSOMRA was also evaluated at doses of 30 mg and 40 mg
in the 3-month placebo-controlled trials (Study 1 and Study 2). The higher
doses were found to have similar efficacy to lower doses, but significantly
more adverse reactions were reported at the higher doses.
Special Safety Studies
Effects On Driving
Two randomized, double-blind, placebo-and
active-controlled, four-period crossover studies evaluated the effects of
nighttime administration of BELSOMRA on next-morning driving performance 9
hours after dosing in 24 healthy elderly subjects (≥65 years old, mean
age 69 years; 14 men, 10 women) who received 15 mg and 30 mg BELSOMRA, and 28
non-elderly subjects (mean age 46 years; 13 men, 15 women) who received 20 mg
and 40 mg BELSOMRA. Testing was conducted after one night and after 8
consecutive nights of treatment with BELSOMRA at these doses.
The primary outcome measure was change in Standard
Deviation of Lane Position (SDLP), a measure of driving performance, assessed
using a symmetry analysis. The analysis showed clinically meaningful impaired
driving performance in some subjects. After one night of dosing, this effect
was observed in non-elderly subjects after either a 20 mg or 40 mg dose of
BELSOMRA. A statistically significant effect was not observed in elderly
subjects after a 15 mg or 30 mg dose of BELSOMRA. Across these two studies,
five subjects (4 non-elderly women on BELSOMRA; 1 elderly woman on placebo)
prematurely stopped their driving tests due to somnolence. Patients using the
20 mg dose of BELSOMRA should be cautioned against next-day driving and other
activities requiring full mental alertness. Patients taking lower doses of
BELSOMRA should also be cautioned about the potential for driving impairment
because there is individual variation in sensitivity to BELSOMRA [see WARNINGS
AND PRECAUTIONS].
Effects On Next-Day Memory And Balance In Elderly And Non-Elderly
Four placebo-controlled trials evaluated the effects of
nighttime administration of BELSOMRA on next-day memory and balance using word
learning tests and body sway tests, respectively. Three trials showed no
significant effects on memory or balance compared to placebo. In a fourth trial
in healthy non-elderly subjects, there was a significant decrease in word
recall after the words were presented to subjects in the morning following a
single dose of 40 mg BELSOMRA, and there was a significant increase on body
sway area in the morning following a single dose of 20 mg or 40 mg BELSOMRA.
Middle Of The Night Safety In Elderly Subjects
A double-blind, randomized, placebo-controlled trial
evaluated the effect of a single dose of BELSOMRA on balance, memory and psychomotor
performance in healthy elderly subjects (n=12) after being awakened during the
night. Nighttime dosing of BELSOMRA 30 mg resulted in impairment of balance
(measured by body sway area) at 90 minutes as compared to placebo. Memory was
not impaired, as assessed by an immediate and delayed word recall test at 4
hours post-dose.
Rebound Effects
In 3-month controlled safety and efficacy trials (Study
1, Study 2), rebound insomnia was assessed following discontinuation of
BELSOMRA relative to placebo and baseline in non-elderly adult patients
receiving BELSOMRA 40 mg or 20 mg and in elderly patients receiving BELSOMRA 30
mg or 15 mg. No clear effects were observed on measures of sleep onset or
maintenance.
Withdrawal Effects
In 3-month controlled safety and efficacy trials (Study
1, Study 2), withdrawal effects were assessed following discontinuation in
non-elderly adult patients who received BELSOMRA 40 mg or 20 mg and elderly
patients who received BELSOMRA 30 mg or 15 mg. The analysis showed no clear
evidence of withdrawal in the overall study population based on assessment of
patient responses to the Tyrer Withdrawal Symptom Questionnaire or assessment
of withdrawal-related adverse events following the discontinuation of BELSOMRA.
Respiratory Safety
Use In Healthy Subjects With Normal Respiratory Function
A randomized, placebo-controlled, double-blind, crossover
trial in healthy non-elderly subjects (n=12) evaluated the respiratory
depressant effect of BELSOMRA (40 mg and 150 mg) after one night of treatment.
At the doses studied, BELSOMRA had no respiratory depressant effect as measured
by oxygen saturation [see WARNINGS AND PRECAUTIONS and Use In Specific
Populations].