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June 4, 2017 9:00 am ET

Merck (NYSE: MRK), known as MSD outside the United States and Canada,
today announced findings from Cohort 1 of the phase 2 registrational
KEYNOTE-059 trial investigating KEYTRUDA^® (pembrolizumab),
the company’s anti-PD-1 therapy, as monotherapy in previously-treated
patients with advanced gastric or gastroesophageal junction
adenocarcinoma. Results showed an overall response rate (ORR) of 11.6
percent (95% CI, 8.0-16.1) in patients treated with KEYTRUDA who had
received two or more prior lines of treatment, with higher response
rates among patients with PD-L1 positive tumors. The results will be
presented at the 2017 American Society of Clinical Oncology (ASCO)
Annual Meeting in Chicago in an oral presentation on Sunday, June 4 from
9:00 – 9:12 a.m. CDT (Location: Hall D2) (Abstract #4003).

Data from this Cohort support Merck’s supplemental Biologics License
Application (sBLA) for KEYTRUDA – currently under Priority Review with
the U.S. Food and Drug Administration (FDA) – seeking approval for the
treatment of patients with recurrent or advanced gastric or
gastroesophageal junction adenocarcinoma who have already received two
or more lines of chemotherapy.

“Advanced gastric cancer is difficult to treat and there is a
significant need to identify new treatment options for these patients,”
said Charles S. Fuchs, M.D., MPH, lead investigator and director of Yale
Cancer Center. “The findings from this study showed meaningful response
rates for KEYTRUDA in heavily pre-treated patients, who have
historically faced poor outcomes.”

“The data we are observing from this trial are encouraging as they
demonstrate the potential for KEYTRUDA to address the serious unmet need
that currently exists for patients with advanced gastric cancer,” said
Dr. Roger Dansey, senior vice president and therapeutic area head,
oncology late-stage development, Merck Research Laboratories.

Merck is committed to investigating new approaches across the spectrum
of cancers with more than 500 clinical trials evaluating KEYTRUDA
(pembrolizumab) in more than 30 tumor types – including multiple
gastrointestinal disorders, such as gastric or gastroesophageal cancers
and MSI-H colorectal cancer, among others. Specific to gastric cancer,
Merck’s broad clinical development program encompasses all stages of
advanced disease and is investigating KEYTRUDA as monotherapy and in
combination with other cancer treatments across multiple lines of
therapy. To date, the program includes four gastric cancer
registration-enabling studies and numerous other gastrointestinal cancer
studies are underway.

Key Findings from KEYNOTE-059 Cohort 1

KEYNOTE-059 is a registrational, phase 2 non-randomized, multi-cohort
study investigating KEYTRUDA in patients with advanced gastric or
gastroesophageal junction adenocarcinoma. In patients who received at
least two prior chemotherapies (Cohort 1), KEYTRUDA is being
investigated as a monotherapy (200 mg every three weeks for up to 24
months). The primary endpoints are ORR as assessed by Blinded
Independent Central Review (BICR) using Response Evaluation Criteria in
Solid Tumors (RECIST) v1.1 and safety; secondary endpoints include
duration of response and overall survival. Data were further assessed
based on PD-L1 expression; tumors were considered to have positive PD-L1
expression if the combined positive score (CPS) – as examined by tumor
and immune cells – was equal to or greater than one.

The efficacy analysis in all patients (n=259) showed an ORR of 11.6
percent (95% CI, 8.0- 16.1) – with a complete response rate of 2.3
percent (95% CI, 0.9-5.0) and a partial response rate of 9.3 percent
(95% CI, 6.0-13.5). Data were further analyzed based on PD-L1
expression. In patients whose tumors expressed PD-L1 (CPS ≥1%) (n=148),
the ORR was 15.5 percent (95% CI, 10.1-22.4) – with a complete response
rate of two percent (95% CI, 0.4-5.8) and a partial response rate of
13.5 percent (95% CI, 8.5-20.1). In PD-L1 negative patients (n=109), the
ORR was 6.4 percent (95% CI, 2.6-12.8) – with a complete response rate
of 2.8 percent (95% CI, 0.6-7.8) and a partial response rate of 3.7
percent (95% CI, 1.0-9.1).

Analyses based on prior lines of therapy showed that in patients who
received two lines of prior chemotherapy (third-line treatment setting;
n=134), the ORR was 16.4 percent (95% CI, 10.6-23.8) – with a complete
response rate of 3.0 percent (95% CI, 0.8-7.5) and a partial response
rate of 13.4 percent (95% CI, 8.2-20.4). In patients who had received
three lines of prior chemotherapy (fourth-line treatment setting;
n=125), the ORR was 6.4 percent (95% CI, 2.8-12.2) – with a complete
response rate of 1.6 percent (95% CI, 0.2-5.7) and a partial response
rate of 4.8 percent (95% CI, 1.8-10.2).

The safety profile of KEYTRUDA (pembrolizumab) was consistent with that
observed in previously reported studies. The treatment-related adverse
events (any grade occurring in 5% or more of patients) were fatigue
(18.9%), pruritus (8.9%), rash (8.5%), hypothyriodism (7.7%), decreased
appetite (7.3%), anemia (6.9%), nausea (6.9%), diarrhea (6.6%), and
arthralgia (5.8%). Grade 3-4 treatment-related adverse events observed
(in all patients) were anemia (2.7%), fatigue (2.3%), diarrhea (1.2%),
rash (0.8%), nausea (0.8%), hypothyroidism (0.4%), and arthralgia
(0.4%). Two patients discontinued treatment due to treatment-related
adverse events (abnormal hepatic function and bile duct stenosis); Grade
5 treatment-related adverse events occurred in two patients (acute
kidney injury and pleural effusion). Immune-mediated adverse events of
Grade 3-4 occurred in 4.6 percent or less of patients and included:
colitis, pneumonitis, thyroiditis, hypothyroidism, and severe skin
reactions.

About Gastric Cancer

Gastric cancer, also called stomach cancer, is a type of cancer that
begins in the stomach and tends to develop slowly over many years. Most
gastric cancers are adenocarcinomas, which develop from the cells of the
innermost lining (mucosa) of the stomach. Risk factors for gastric
cancer include gender, age, ethnicity, geography and infection with Helicobacter
pylori. Worldwide, gastric cancer is the fifth most common type of
cancer and the third leading cause of cancer death. Each year there are
approximately 952,000 newly diagnosed cases of gastric cancer resulting
in approximately 723,000 deaths worldwide. It is estimated that in 2017,
more than 10,000 people will die from gastric cancer in the U.S. alone.

About KEYTRUDA

^®

(pembrolizumab) Injection

KEYTRUDA is an anti-PD-1 therapy that works by increasing the ability of
the body’s immune system to help detect and fight tumor cells. KEYTRUDA
is a humanized monoclonal antibody that blocks the interaction between
PD-1 and its ligands, PD-L1 and PD-L2, thereby activating T lymphocytes
which may affect both tumor cells and healthy cells.

Studies of KEYTRUDA – from the largest immuno-oncology program in the
industry with more than 500 trials – include a wide variety of cancers
and treatment settings. The KEYTRUDA clinical program seeks to
understand factors that predict a patient’s likelihood of benefitting
from treatment with KEYTRUDA, including the exploration of several
different biomarkers across a broad range of tumors.

KEYTRUDA is administered as an intravenous infusion over 30 minutes
every three weeks for the approved indications. KEYTRUDA (pembrolizumab)
for injection is supplied in a 100 mg single-dose vial.

KEYTRUDA (pembrolizumab) Indications and Dosing

Melanoma

KEYTRUDA is indicated for the treatment of patients with unresectable or
metastatic melanoma at a fixed dose of 200 mg every three weeks until
disease progression or unacceptable toxicity.

Lung Cancer

KEYTRUDA, as a single agent, is indicated for the first-line treatment
of patients with metastatic non-small cell lung cancer (NSCLC) whose
tumors have high PD-L1 expression [tumor proportion score (TPS) ≥50%] as
determined by an FDA-approved test, with no EGFR or ALK genomic tumor
aberrations.

KEYTRUDA, as a single agent, is also indicated for the treatment of
patients with metastatic NSCLC whose tumors express PD-L1 (TPS ≥1%) as
determined by an FDA-approved test, with disease progression on or after
platinum-containing chemotherapy. Patients with EGFR or ALK genomic
tumor aberrations should have disease progression on FDA-approved
therapy for these aberrations prior to receiving KEYTRUDA.

KEYTRUDA, in combination with pemetrexed and carboplatin, is indicated
for the first-line treatment of patients with metastatic nonsquamous
NSCLC. This indication is approved under accelerated approval based on
tumor response rate and progression-free survival. Continued approval
for this indication may be contingent upon verification and description
of clinical benefit in the confirmatory trials.

In metastatic NSCLC, KEYTRUDA is administered at a fixed dose of 200 mg
every three weeks until disease progression, unacceptable toxicity, or
up to 24 months in patients without disease progression.

When administering KEYTRUDA in combination with chemotherapy, KEYTRUDA
should be administered prior to chemotherapy when given on the same day.
See also the Prescribing Information for pemetrexed and carboplatin.

Head and Neck Cancer

KEYTRUDA is indicated for the treatment of patients with recurrent or
metastatic head and neck squamous cell carcinoma (HNSCC) with disease
progression on or after platinum-containing chemotherapy. This
indication is approved under accelerated approval based on tumor
response rate and durability of response. Continued approval for this
indication may be contingent upon verification and description of
clinical benefit in the confirmatory trials. In HNSCC, KEYTRUDA
(pembrolizumab) is administered at a fixed dose of 200 mg every three
weeks until disease progression, unacceptable toxicity, or up to 24
months in patients without disease progression.

Classical Hodgkin Lymphoma

KEYTRUDA is indicated for the treatment of adult and pediatric patients
with refractory classical Hodgkin lymphoma (cHL), or who have relapsed
after three or more prior lines of therapy. This indication is approved
under accelerated approval based on tumor response rate and durability
of response. Continued approval for this indication may be contingent
upon verification and description of clinical benefit in the
confirmatory trials. In adults with cHL, KEYTRUDA is administered at a
fixed dose of 200 mg every three weeks until disease progression or
unacceptable toxicity, or up to 24 months in patients without disease
progression. In pediatric patients with cHL, KEYTRUDA is administered at
a dose of 2 mg/kg (up to a maximum of 200 mg) every three weeks until
disease progression or unacceptable toxicity, or up to 24 months in
patients without disease progression.

Urothelial Carcinoma

KEYTRUDA is indicated for the treatment of patients with locally
advanced or metastatic urothelial carcinoma who are not eligible for
cisplatin-containing chemotherapy. This indication is approved under
accelerated approval based on tumor response rate and duration of
response. Continued approval for this indication may be contingent upon
verification and description of clinical benefit in the confirmatory
trials.

KEYTRUDA is also indicated for the treatment of patients with locally
advanced or metastatic urothelial carcinoma who have disease progression
during or following platinum-containing chemotherapy or within 12 months
of neoadjuvant or adjuvant treatment with platinum-containing
chemotherapy.

In locally advanced or metastatic urothelial carcinoma, KEYTRUDA is
administered at a fixed dose of 200 mg every three weeks until disease
progression or unacceptable toxicity, or up to 24 months in patients
without disease progression.

Microsatellite Instability-High (MSI-H) Cancer

KEYTRUDA is indicated for the treatment of adult and pediatric patients
with unresectable or metastatic microsatellite instability-high (MSI-H)
or mismatch repair deficient (dMMR)

• solid tumors that have progressed following prior treatment and who
  have no satisfactory alternative treatment options, or
• colorectal cancer that has progressed following treatment with
  fluoropyrimidine, oxaliplatin, and irinotecan.

This indication is approved under accelerated approval based on tumor
response rate and durability of response. Continued approval for this
indication may be contingent upon verification and description of
clinical benefit in the confirmatory trials. The safety and
effectiveness of KEYTRUDA (pembrolizumab) in pediatric patients with
MSI-H central nervous system cancers have not been established.

In adult patients with MSI-H cancer, KEYTRUDA is administered at a fixed
dose of 200 mg every three weeks until disease progression, unacceptable
toxicity, or up to 24 months in patients without disease progression. In
pediatric patients with MSI-H cancer, KEYTRUDA is administered at a dose
of 2 mg/kg (up to a maximum of 200 mg) every three weeks until disease
progression or unacceptable toxicity, or up to 24 months in patients
without disease progression.

Selected Important Safety Information for KEYTRUDA

^®
 (pembrolizumab)

KEYTRUDA can cause immune-mediated pneumonitis, including fatal cases.
Pneumonitis occurred in 94 (3.4%) of 2799 patients receiving KEYTRUDA,
including Grade 1 (0.8%), 2 (1.3%), 3 (0.9%), 4 (0.3%), and 5 (0.1%)
pneumonitis, and occurred more frequently in patients with a history of
prior thoracic radiation (6.9%) compared to those without (2.9%).
Monitor patients for signs and symptoms of pneumonitis. Evaluate
suspected pneumonitis with radiographic imaging. Administer
corticosteroids for Grade 2 or greater pneumonitis. Withhold KEYTRUDA
for Grade 2; permanently discontinue KEYTRUDA for Grade 3 or 4 or
recurrent Grade 2 pneumonitis.

KEYTRUDA can cause immune-mediated colitis. Colitis occurred in 48
(1.7%) of 2799 patients receiving KEYTRUDA, including Grade 2 (0.4%), 3
(1.1%), and 4 (<0.1%) colitis. Monitor patients for signs and symptoms
of colitis. Administer corticosteroids for Grade 2 or greater colitis.
Withhold KEYTRUDA for Grade 2 or 3; permanently discontinue KEYTRUDA for
Grade 4 colitis.

KEYTRUDA can cause immune-mediated hepatitis. Hepatitis occurred in 19
(0.7%) of 2799 patients receiving KEYTRUDA, including Grade 2 (0.1%), 3
(0.4%), and 4 (<0.1%) hepatitis. Monitor patients for changes in liver
function. Administer corticosteroids for Grade 2 or greater hepatitis
and, based on severity of liver enzyme elevations, withhold or
discontinue KEYTRUDA.

KEYTRUDA can cause hypophysitis. Hypophysitis occurred in 17 (0.6%) of
2799 patients receiving KEYTRUDA, including Grade 2 (0.2%), 3 (0.3%),
and 4 (<0.1%) hypophysitis. Monitor patients for signs and symptoms of
hypophysitis (including hypopituitarism and adrenal insufficiency).
Administer corticosteroids and hormone replacement as clinically
indicated. Withhold KEYTRUDA (pembrolizumab) for Grade 2; withhold or
discontinue for Grade 3 or 4 hypophysitis.

KEYTRUDA can cause thyroid disorders, including hyperthyroidism,
hypothyroidism, and thyroiditis. Hyperthyroidism occurred in 96 (3.4%)
of 2799 patients receiving KEYTRUDA, including Grade 2 (0.8%) and 3
(0.1%) hyperthyroidism. Hypothyroidism occurred in 237 (8.5%) of 2799
patients receiving KEYTRUDA, including Grade 2 (6.2%) and 3 (0.1%)
hypothyroidism. Thyroiditis occurred in 16 (0.6%) of 2799 patients
receiving KEYTRUDA, including Grade 2 (0.3%) thyroiditis. Monitor
patients for changes in thyroid function (at the start of treatment,
periodically during treatment, and as indicated based on clinical
evaluation) and for clinical signs and symptoms of thyroid disorders.
Administer replacement hormones for hypothyroidism and manage
hyperthyroidism with thionamides and beta-blockers as appropriate.
Withhold or discontinue KEYTRUDA for Grade 3 or 4 hyperthyroidism.

KEYTRUDA can cause type 1 diabetes mellitus, including diabetic
ketoacidosis, which have been reported in 6 (0.2%) of 2799 patients.
Monitor patients for hyperglycemia or other signs and symptoms of
diabetes. Administer insulin for type 1 diabetes, and withhold KEYTRUDA
and administer antihyperglycemics in patients with severe hyperglycemia.

KEYTRUDA can cause immune-mediated nephritis. Nephritis occurred in 9
(0.3%) of 2799 patients receiving KEYTRUDA, including Grade 2 (0.1%), 3
(0.1%), and 4 (<0.1%) nephritis. Monitor patients for changes in renal
function. Administer corticosteroids for Grade 2 or greater nephritis.
Withhold KEYTRUDA for Grade 2; permanently discontinue KEYTRUDA for
Grade 3 or 4 nephritis.

KEYTRUDA can cause other clinically important immune-mediated adverse
reactions. These immune-mediated reactions may occur in any organ
system. For suspected immune-mediated adverse reactions, ensure adequate
evaluation to confirm etiology or exclude other causes. Based on the
severity of the adverse reaction, withhold KEYTRUDA and administer
corticosteroids. Upon improvement to Grade 1 or less, initiate
corticosteroid taper and continue to taper over at least 1 month. Based
on limited data from clinical studies in patients whose immune-related
adverse reactions could not be controlled with corticosteroid use,
administration of other systemic immunosuppressants can be considered.
Resume KEYTRUDA when the adverse reaction remains at Grade 1 or less
following corticosteroid taper. Permanently discontinue KEYTRUDA for any
Grade 3 immune-mediated adverse reaction that recurs and for any
life-threatening immune-mediated adverse reaction.

The following clinically significant immune-mediated adverse reactions
occurred in less than 1% (unless otherwise indicated) of 2799 patients:
arthritis (1.5%), exfoliative dermatitis, bullous pemphigoid, rash
(1.4%), uveitis, myositis, Guillain-Barré syndrome, myasthenia gravis,
vasculitis, pancreatitis, hemolytic anemia, and partial seizures arising
in a patient with inflammatory foci in brain parenchyma. In addition,
myelitis and myocarditis were reported in other clinical trials,
including classical Hodgkin lymphoma, and postmarketing use.

Solid organ transplant rejection has been reported in postmarketing use
of KEYTRUDA (pembrolizumab). Treatment with KEYTRUDA may increase the
risk of rejection in solid organ transplant recipients. Consider the
benefit of treatment with KEYTRUDA vs the risk of possible organ
rejection in these patients.

KEYTRUDA can cause severe or life-threatening infusion-related
reactions, including hypersensitivity and anaphylaxis, which have been
reported in 6 (0.2%) of 2799 patients. Monitor patients for signs and
symptoms of infusion-related reactions, including rigors, chills,
wheezing, pruritus, flushing, rash, hypotension, hypoxemia, and fever.
For Grade 3 or 4 reactions, stop infusion and permanently discontinue
KEYTRUDA.

Immune-mediated complications, including fatal events, occurred in
patients who underwent allogeneic hematopoietic stem cell
transplantation (HSCT) after being treated with KEYTRUDA. Of 23 patients
with cHL who proceeded to allogeneic HSCT after treatment with KEYTRUDA
on any trial, 6 patients (26%) developed graft-versus-host-disease
(GVHD), one of which was fatal, and 2 patients (9%) developed severe
hepatic veno-occlusive disease (VOD) after reduced-intensity
conditioning, one of which was fatal. Cases of fatal hyperacute GVHD
after allogeneic HSCT have also been reported in patients with lymphoma
who received a PD-1 receptor–blocking antibody before transplantation.
These complications may occur despite intervening therapy between PD-1
blockade and allogeneic HSCT. Follow patients closely for early evidence
of transplant-related complications such as hyperacute GVHD, severe
(Grade 3 to 4) acute GVHD, steroid-requiring febrile syndrome, hepatic
VOD, and other immune-mediated adverse reactions, and intervene promptly.

Based on its mechanism of action, KEYTRUDA (pembrolizumab) can cause
fetal harm when administered to a pregnant woman. If used during
pregnancy, or if the patient becomes pregnant during treatment, apprise
the patient of the potential hazard to a fetus. Advise females of
reproductive potential to use highly effective contraception during
treatment and for 4 months after the last dose of KEYTRUDA.

In KEYNOTE-006, KEYTRUDA was discontinued due to adverse reactions in 9%
of 555 patients with advanced melanoma; adverse reactions leading to
discontinuation in more than one patient were colitis (1.4%), autoimmune
hepatitis (0.7%), allergic reaction (0.4%), polyneuropathy (0.4%), and
cardiac failure (0.4%). Adverse reactions leading to interruption of
KEYTRUDA occurred in 21% of patients; the most common (≥1%) was diarrhea
(2.5%). The most common adverse reactions with KEYTRUDA vs ipilimumab
were fatigue (28% vs 28%), diarrhea (26% with KEYTRUDA), rash (24% vs
23%), and nausea (21% with KEYTRUDA). Corresponding incidence rates are
listed for ipilimumab only for those adverse reactions that occurred at
the same or lower rate than with KEYTRUDA (pembrolizumab).

In KEYNOTE-002, KEYTRUDA was discontinued due to adverse reactions in
12% of 357 patients with advanced melanoma; the most common (≥1%) were
general physical health deterioration (1%), asthenia (1%), dyspnea (1%),
pneumonitis (1%), and generalized edema (1%). Adverse reactions leading
to interruption of KEYTRUDA occurred in 14% of patients; the most common
(≥1%) were dyspnea (1%), diarrhea (1%), and maculopapular rash (1%). The
most common adverse reactions with KEYTRUDA vs chemotherapy were fatigue
(43% with KEYTRUDA), pruritus (28% vs 8%), rash (24% vs 8%),
constipation (22% vs 20%), nausea (22% with KEYTRUDA), diarrhea (20% vs
20%), and decreased appetite (20% with KEYTRUDA). Corresponding
incidence rates are listed for chemotherapy only for those adverse
reactions that occurred at the same or lower rate than with KEYTRUDA.

KEYTRUDA monotherapy was discontinued due to adverse reactions in 8% of
682 patients with metastatic NSCLC. The most common adverse event
resulting in permanent discontinuation of KEYTRUDA was pneumonitis
(1.8%). Adverse reactions leading to interruption of KEYTRUDA occurred
in 23% of patients; the most common (≥1%) were diarrhea (1%), fatigue
(1.3%), pneumonia (1%), liver enzyme elevation (1.2%), decreased
appetite (1.3%), and pneumonitis (1%). The most common adverse reactions
(occurring in at least 20% of patients and at a higher incidence than
with docetaxel) were decreased appetite (25% vs 23%), dyspnea (23% vs
20%), and nausea (20% vs 18%).

When KEYTRUDA was administered in combination with carboplatin and
pemetrexed (carbo/pem), KEYTRUDA was discontinued in 10% of 59 patients.
The most common adverse reaction resulting in discontinuation of
KEYTRUDA (≥2%) was acute kidney injury (3.4%). Adverse reactions leading
to interruption of KEYTRUDA occurred in 39% of patients; the most common
(≥2%) were fatigue (8%), neutrophil count decreased (8%), anemia (5%),
dyspnea (3.4%), and pneumonitis (3.4%).The most common adverse reactions
(≥20%) with KEYTRUDA compared to carbo/pem alone were fatigue (71% vs
50%), nausea (68% vs 56%), constipation (51% vs 37%), rash (42% vs 21%),
vomiting (39% vs 27%), dyspnea (39% vs 21%), diarrhea (37% vs 23%),
decreased appetite (31% vs 23%), headache (31% vs 16%), cough (24% vs
18%), dizziness (24% vs 16%), insomnia (24% vs 15%), pruritus (24% vs
4.8%), peripheral edema (22% vs 18%), dysgeusia (20% vs 11%), alopecia
(20% vs 3.2%), upper respiratory tract infection (20% vs 3.2%), and
arthralgia (15% vs 24%). This study was not designed to demonstrate a
statistically significant difference in adverse reaction rates for
KEYTRUDA as compared to carbo/pem alone for any specified adverse
reaction.

KEYTRUDA (pembrolizumab) was discontinued due to adverse reactions in
17% of 192 patients with HNSCC. Serious adverse reactions occurred in
45% of patients. The most frequent serious adverse reactions reported in
at least 2% of patients were pneumonia, dyspnea, confusional state,
vomiting, pleural effusion, and respiratory failure. The most common
adverse reactions (reported in at least 20% of patients) were fatigue,
decreased appetite, and dyspnea. Adverse reactions occurring in patients
with HNSCC were generally similar to those occurring in patients with
melanoma or NSCLC, with the exception of increased incidences of facial
edema (10% all Grades; 2.1% Grades 3 or 4) and new or worsening
hypothyroidism.

KEYTRUDA was discontinued due to adverse reactions in 5% of 210 patients
with cHL, and treatment was interrupted due to adverse reactions in 26%
of patients. Fifteen percent (15%) of patients had an adverse reaction
requiring systemic corticosteroid therapy. Serious adverse reactions
occurred in 16% of patients. The most frequent serious adverse reactions
(≥1%) included pneumonia, pneumonitis, pyrexia, dyspnea, GVHD, and
herpes zoster. Two patients died from causes other than disease
progression; one from GVHD after subsequent allogeneic HSCT and one from
septic shock. The most common adverse reactions (occurring in ≥20% of
patients) were fatigue (26%), pyrexia (24%), cough (24%),
musculoskeletal pain (21%), diarrhea (20%), and rash (20%).

In KEYNOTE-052, KEYTRUDA (pembrolizumab) was discontinued due to adverse
reactions in 11% of 370 patients with locally advanced or metastatic
urothelial carcinoma. The most common adverse reactions (in ≥20% of
patients) were fatigue (38%), musculoskeletal pain (24%), decreased
appetite (22%), constipation (21%), rash (21%), and diarrhea (20%).
Eighteen patients (5%) died from causes other than disease progression.
Five patients (1.4%) who were treated with KEYTRUDA experienced sepsis
which led to death, and 3 patients (0.8%) experienced pneumonia which
led to death. Adverse reactions leading to interruption of KEYTRUDA
occurred in 22% of patients; the most common (≥1%) were liver enzyme
increase, diarrhea, urinary tract infection, acute kidney injury,
fatigue, joint pain, and pneumonia. Serious adverse reactions occurred
in 42% of patients, the most frequent (≥2%) of which were urinary tract
infection, hematuria, acute kidney injury, pneumonia, and urosepsis.

In KEYNOTE-045, KEYTRUDA was discontinued due to adverse reactions in 8%
of 266 patients with locally advanced or metastatic urothelial
carcinoma. The most common adverse reaction resulting in permanent
discontinuation of KEYTRUDA was pneumonitis (1.9%). Adverse reactions
leading to interruption of KEYTRUDA occurred in 20% of patients; the
most common (≥1%) were urinary tract infection (1.5%), diarrhea (1.5%),
and colitis (1.1%). The most common adverse reactions (≥20%) in patients
who received KEYTRUDA vs those who received chemotherapy were fatigue
(38% vs 56%), musculoskeletal pain (32% vs 27%), pruritus (23% vs 6%),
decreased appetite (21% vs 21%), nausea (21% vs 29%), and rash (20% vs
13%). Serious adverse reactions occurred in 39% of KEYTRUDA
(pembrolizumab)-treated patients, the most frequent (≥2%) of which were
urinary tract infection, pneumonia, anemia, and pneumonitis.

The most common adverse reactions (reported in ≥20% of patients) were
fatigue, pruritus, diarrhea, decreased appetite, rash, pyrexia, cough,
dyspnea, musculoskeletal pain, constipation, and nausea.

It is not known whether KEYTRUDA is excreted in human milk. Because many
drugs are excreted in human milk, instruct women to discontinue nursing
during treatment with KEYTRUDA and for 4 months after the final dose.

Our Focus on Cancer

Our goal is to translate breakthrough science into innovative oncology
medicines to help people with cancer worldwide. At Merck, helping people
fight cancer is our passion and supporting accessibility to our cancer
medicines is our commitment. Our focus is on pursuing research in
immuno-oncology and we are accelerating every step in the journey – from
lab to clinic – to potentially bring new hope to people with cancer.

As part of our focus on cancer, Merck is committed to exploring the
potential of immuno-oncology with one of the fastest-growing development
programs in the industry. We are currently executing an expansive
research program that includes more than 500 clinical trials evaluating
our anti-PD-1 therapy across more than 30 tumor types. We also continue
to strengthen our immuno-oncology portfolio through strategic
acquisitions and are prioritizing the development of several promising
immunotherapeutic candidates with the potential to improve the treatment
of advanced cancers.

For more information about our oncology clinical trials, visit www.merck.com/clinicaltrials.

About Merck

For more than a century, Merck, a leading global biopharmaceutical
company known as MSD outside of the United States and Canada, has been
inventing for life, bringing forward medicines and vaccines for many of
the world’s most challenging diseases. Through our prescription
medicines, vaccines, biologic therapies and animal health products, we
work with customers and operate in more than 140 countries to deliver
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and infectious diseases including HIV and Ebola. For more information,
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The company 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 the company’s 2016 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).

Please see Prescribing Information for KEYTRUDA (pembrolizumab) at 

http://www.merck.com/product/usa/pi_circulars/k/keytruda/keytruda_pi.pdf

 and

Patient Information/Medication Guide for KEYTRUDA at 

http://www.merck.com/product/usa/pi_circulars/k/keytruda/keytruda_mg.pdf

.

Merck
Media:
Pamela Eisele, 267-305-3558
or
Ann Bush, 908-740-6677
or
Investors:
Teri Loxam, 908-740-1986
or
Amy Klug, 908-740-1898