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June 13, 2012 7:00 am ET

• Suvorexant Achieved Statistical Significance on 15 of 16 Primary Endpoints
• Merck Remains on Track to File a New Drug Application for Suvorexant in 2012,
  One of the Six Major Pipeline Filings Merck Plans for 2012 and 2013

Merck (NYSE: MRK), known as MSD outside the United States and Canada,
today announced new data from two pivotal Phase III efficacy trials for
suvorexant, the investigational medicine Merck is developing for the
treatment of insomnia. In the studies, suvorexant significantly reduced
the time it took patients to fall asleep and increased the time that
patients stayed asleep as early as the first night and at the
three-month time point compared to placebo. The investigational medicine
met statistical significance for all primary endpoints except for one
measurement at Month 3 in one of the trials. These late-breaking data
were presented here today at SLEEP 2012, the 26^th Annual
Meeting of the Associated Professional Sleep Societies.

“This investigational drug targets insomnia in a way that is different
from other medicines,” said Andrew D. Krystal, M.D., professor of
Psychiatry and Behavioral Sciences, Duke University Medical Center. “The
potential for a new and different option would be welcome by patients
with insomnia who cannot sleep through the night.”

Further efficacy and safety results from the Phase III clinical program
for suvorexant were presented at the SLEEP meeting. In these two pivotal
Phase III efficacy trials, the most common adverse events (AEs) reported
at an incidence of greater than or equal to five percent and more often
than placebo were sleepiness and headache. Other data presented included
results that demonstrated the effects of suvorexant after daily dosing
for at least a year (abstract 0641, oral session O22). This is one of
the longest continuously dosed, placebo-controlled trials of a sleep
medication ever conducted. Results from a driving study in elderly
patients also were presented (abstract 0670, poster 192). Merck plans to
present additional results from its two pivotal Phase III efficacy
trials later this year.

Merck researchers developed suvorexant to target and block orexins,
chemical messengers that originate from the hypothalamus (an important
sleep center in the brain) that help to keep you awake. By blocking the
actions of orexins, suvorexant helps to facilitate sleep. Merck plans to
file a New Drug Application (NDA) for suvorexant with the U.S. Food and
Drug Administration (FDA) in 2012, making it one of the company’s six
major filings planned for 2012 and 2013. If approved, suvorexant would
be the first medicine approved in a new class of medicines, called
orexin receptor antagonists, for use in patients with difficulty falling
or staying asleep. Merck anticipates that suvorexant will be evaluated
by the Controlled Substance Staff of the FDA.

“We specifically focused our research efforts on insomnia because it is
an area of significant unmet medical need,” said Darryle D. Schoepp,
Ph.D., senior vice president and head of Neuroscience and Ophthalmology
franchise, Merck Research Laboratories. “Suvorexant approaches insomnia
differently than other medicines because it helps patients to sleep by
targeting and blocking orexins, which play a role in keeping people
awake. We’re excited about the Phase III results and the potential of
suvorexant to become the first in a new class of medicines to help
patients with insomnia.”

Studies Measured Effect of Suvorexant on Sleep Onset and Maintenance

Merck’s two pivotal Phase III efficacy studies were multicenter,
randomized, double-blind, placebo-controlled trials of suvorexant in
patients with primary insomnia (1,021 and 1,009 treated patients in
Trial 1 and Trial 2, respectively). Primary insomnia is defined as
difficulty falling or staying asleep or poor sleep quality that is the
main condition experienced (not caused by another medical problem). A
high and a low dose of suvorexant were studied in each trial. The high
dose evaluated suvorexant 40 mg in patients 18-64 years and suvorexant
30 mg in patients 65 years and older, and the low dose assessed
suvorexant 20 mg in patients 18-64 years and suvorexant 15 mg in
patients 65 years and older. Patients were randomized to receive one of
the suvorexant doses or placebo over a three-month period. The results
reported below are for the combined primary endpoint dose of 40 mg and
30 mg (383 patients in Trial 1 and 387 patients in Trial 2 were treated
with the high dose compared to 384 and 383 on placebo, respectively).

The endpoints for the studies included mean change from baseline for
suvorexant compared to placebo in both subjective (patient-reported) and
objective (polysomnographic, sleep lab-based, assessed in a subset of
patients) measures of sleep onset and sleep maintenance. The subjective
measures included time it took to fall asleep and total sleep time.
Subjective endpoints were measured after one and three months (primary
endpoints) and over the first week (a secondary endpoint) of taking
suvorexant or placebo. The objective measures included time it took to
fall into continuous sleep and time spent awake during the night.
Objective endpoints were measured after one and three months (primary
endpoints) and after the first night (a secondary endpoint) of taking
suvorexant or placebo.

Results for Objective and Subjective Measures

In both trials, on all primary subjective measures, patients who took
suvorexant fell asleep significantly faster and stayed asleep longer
compared to patients taking placebo at one month and three months
(p<0.003). On the objective measures, suvorexant also significantly reduced the time it took patients to fall into continuous sleep and decreased the time patients spent awake during the night at one month and three months (primary endpoints), and as early as night one (a secondary endpoint) (p<0.001), except for Month 3 in Trial 2, at which point the difference in time to fall into continuous sleep did not reach statistical significance.

Specifically, at three months in Trial 1, patients reported suvorexant
reduced the time it took them to fall asleep by 25.7 minutes (vs. 17.3
minutes with placebo) and helped them to sleep 60.3 minutes longer (vs.
40.6 minutes with placebo) compared to before they started taking
suvorexant. For the objective measures, patients taking suvorexant
entered into continuous sleep 36.0 minutes faster (vs. 26.6 minutes with
placebo) and spent less time awake during the night by 47.9 minutes (vs.
25.0 minutes with placebo) compared to before they started taking
suvorexant. (All of these differences between suvorexant and placebo
were statistically significant.)

At three months in Trial 2, patients reported suvorexant reduced the
time it took them to fall asleep by 33.7 minutes (vs. 20.5 minutes with
placebo) and helped them to sleep 62.8 minutes longer (vs. 37.7 minutes
with placebo) compared to before they started taking suvorexant. For the
objective measures at three months, suvorexant did not achieve
statistical significance on the measure of patients falling into
continuous sleep faster than with placebo (-32.2 minutes vs. -28.6
minutes, p=0.265). The objective data showed that patients taking
suvorexant spent less time awake during the night by 54.2 minutes (vs.
24.8 minutes with placebo) compared to before they started taking
suvorexant. (All of these differences were statistically significant
except for the one noted above.)

In these studies, secondary objective measurements included the time it
took patients to fall into continuous sleep and the time patients spent
awake during the night on night one. In Trial 1, patients taking
suvorexant entered into continuous sleep 30.6 minutes faster (vs. 20.3
minutes with placebo) and spent less time awake during the night by 58.0
minutes (vs. 19.6 minutes with placebo) compared to before they started
taking suvorexant. In Trial 2, patients taking suvorexant entered into
continuous sleep 34.7 minutes faster (vs. 13.0 minutes with placebo) and
spent less time awake during the night by 63.3 minutes (vs. 21.3 minutes
with placebo) compared to before they started taking suvorexant.

Safety Results

Over three months, the overall incidence of AEs reported as related to
the medicine in patients who took the high dose of suvorexant compared
to placebo was 25.1 percent versus 13.8 percent in Trial 1, and 22.2
percent versus 16.4 percent in Trial 2. The overall incidence of
discontinuations due to an AE in patients who received the high dose of
suvorexant compared to placebo was 4.7 percent versus 6.0 percent in
Trial 1, and 4.7 percent versus 4.4 percent in Trial 2. No serious
drug-related AEs were observed in either trial with the high dose of
suvorexant. The most common AEs that occurred at an incidence of greater
than or equal to five percent and more often than placebo in patients
who received the high dose of suvorexant were sleepiness (10.7 percent
vs. 3.4 percent with placebo in Trial 1; 10.3 percent vs. 3.1 percent
with placebo in Trial 2) and headache (6.8 percent vs. 6.0 percent with
placebo in Trial 1; 7.5 percent vs. 5.7 percent with placebo in Trial 2).

In the overall study population, there were no statistically significant
next day objective residual effects compared to placebo as measured by
the Digit Symbol Substitution Test (an assessment of memory, attention,
visual scanning and perceptual and motor speed). Additionally, patients
reported incidence of next day sleepiness at three months were 10.7
percent for high dose of suvorexant versus 3.4 percent for placebo in
Trial 1, and 10.3 percent versus 3.1 percent in Trial 2. Cataplexy, an
abrupt and temporary loss of muscle control, was not reported in either
study. Patients with narcolepsy or cataplexy were excluded from these
trials.

Suvorexant Briefing Webcast

Merck will hold a briefing in conjunction with SLEEP 2012 on June 13 at
2 p.m. EDT. Investors and journalists may access a live audio webcast of
the briefing on Merck’s website at http://www.merck.com/investors/events-and-presentations/home.html.
Software needed to listen to the webcast is available on the corporate
website and should be downloaded prior to the beginning of the webcast.
A replay of the webcast will be available at approximately 8 a.m. EDT on
June 14 and will remain on the website for 12 months.

About Merck

Today’s Merck is a global healthcare leader working to help the world be
well. Merck is known as MSD outside the United States and Canada.
Through our prescription medicines, vaccines, biologic therapies, and
consumer care and animal health products, we work with customers and
operate in more than 140 countries to deliver innovative health
solutions. We also demonstrate our commitment to increasing access to
healthcare through far-reaching policies, programs and partnerships. For
more information, visit www.merck.com
and connect with us on Twitter, Facebook and YouTube.

Forward-Looking Statement

This news release includes “forward-looking statements” within the
meaning of the safe harbor provisions of the United States Private
Securities Litigation Reform Act of 1995. Such statements may include,
but are not limited to, statements about the benefits of the merger
between Merck and Schering-Plough, including future financial and
operating results, the combined company’s plans, objectives,
expectations and intentions and other statements that are not historical
facts. Such statements are based upon the current beliefs and
expectations of Merck’s management and are subject to significant risks
and uncertainties. Actual results may differ from those set forth in the
forward-looking statements.

The following factors, among others, could cause actual results to
differ from those set forth in the forward-looking statements: the
possibility that all of the expected synergies from the merger of Merck
and Schering-Plough will not be realized, or will not be realized within
the expected time period; the impact of pharmaceutical industry
regulation and health care legislation in the United States and
internationally; Merck’s ability to accurately predict future market
conditions; dependence on the effectiveness of Merck’s patents and other
protections for innovative products; and the exposure to litigation
and/or regulatory actions.

Merck undertakes no obligation to publicly update any forward-looking
statement, whether as a result of new information, future events or
otherwise. Additional factors that could cause results to differ
materially from those described in the forward-looking statements can be
found in Merck’s 2011 Annual Report on Form 10-K and the company’s other
filings with the Securities and Exchange Commission (SEC) available at
the SEC’s Internet site (www.sec.gov).

Merck
Media:
Pam Eisele, 908-423-5042
Lesley Brown, 267-305-3545
or
Investors:
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