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October 14, 2024 8:00 am ET

ALAMEDA, CALIF. & RAHWAY, N.J., Oct. 14, 2024 – Exelixis, Inc. (Nasdaq: EXEL) and Merck (NYSE: MRK), known as MSD
outside of the United States and Canada, today announced that the companies have entered into a clinical development
collaboration to evaluate the combination of Exelixis’ investigational tyrosine kinase inhibitor (TKI) zanzalintinib
with Merck’s anti-PD-1 therapy KEYTRUDA^® (pembrolizumab) in a Phase 3 pivotal trial for the treatment of
patients with head and neck squamous cell carcinoma (HNSCC), and zanzalintinib with WELIREG^®
(belzutifan), Merck’s oral hypoxia-inducible factor-2 alpha (HIF-2α) inhibitor, in a Phase 1/2 trial and two Phase 3
pivotal trials for the treatment of patients with renal cell carcinoma (RCC).

“This collaboration underscores our belief in zanzalintinib’s potential to drive patient benefit in combination with
immunotherapy or targeted therapy in HNSCC and RCC indications that have unmet clinical need,” said Amy Peterson,
M.D., executive vice president, product development & medical affairs, and chief medical officer, Exelixis.
“KEYTRUDA and WELIREG are approved therapies that have led to improved outcomes for some cancer patients, and we are
pleased to collaborate with Merck’s clinical development organization to evaluate the potential of these therapies
in combination with zanzalintinib. This collaboration paves the way for further zanzalintinib development in RCC in
a pragmatic manner.”

“We look forward to working with our colleagues at Exelixis to advance these clinical trials,” said Dr. Marjorie
Green, senior vice president and head of oncology, global clinical development, Merck Research Laboratories. “Merck
remains committed to building upon the progress made to-date by strategically evaluating the potential of new
combination regimens to improve outcomes for more patients.”

Under the terms of the collaboration, Merck will supply KEYTRUDA for the ongoing, Exelixis-sponsored Phase 3
STELLAR-305 pivotal trial in previously untreated PD-L1 positive recurrent or metastatic HNSCC. In addition, Merck
will sponsor a Phase 1/2 trial and two Phase 3 pivotal trials in RCC. Merck will fund one of these Phase 3 studies,
and Exelixis will co-fund the Phase 1/2 trial and the other Phase 3 study, as well as supply zanzalintinib and
cabozantinib. Exelixis maintains all global commercial and marketing rights to zanzalintinib.

About head and neck cancer

Head and neck cancer describes a number of different tumors that develop in or around the throat, larynx, nose,
sinuses and mouth. Most head and neck cancers are squamous cell carcinomas that begin in the flat, squamous cells
that make up the thin surface layer of the structures in the head and neck. There are several factors that greatly
increase the risk of developing head and neck cancer, including tobacco and alcohol use and human papillomavirus
(HPV). It is estimated there were more than 891,500 new cases of head and neck cancer diagnosed and over 458,100
deaths from the disease in 2022 globally. In the U.S., it is estimated there will be more than 58,450 new cases of
head and neck cancer diagnosed and more than 12,230 deaths from the disease in 2024.

About renal cell carcinoma

Renal cell carcinoma is by far the most common type of kidney cancer; about nine out of 10 kidney cancer diagnoses
are RCCs. Renal cell carcinoma is about twice as common in men than in women. Most cases of RCC are discovered
incidentally during imaging tests for other abdominal diseases. Renal cell carcinoma is associated with a high risk
of recurrence, with up to 40% of newly diagnosed patients experiencing recurrence within five years following
surgery. In the U.S., it is estimated there will be approximately 81,600 new cases of kidney cancer diagnosed and
approximately 14,400 deaths from the disease in 2024. Worldwide, it is estimated there were approximately 434,840
new cases of kidney cancer diagnosed and more than 155,953 deaths from the disease in 2022.

About zanzalintinib

Zanzalintinib inhibits multiple cancer-related pathways that play a role in resistance to multiple therapies,
including immune checkpoint inhibitors. Encouraging results from the expansion cohort of the Phase 1b STELLAR-001
(NCT03845166) clinical trial evaluating zanzalintinib
in patients with previously treated clear cell RCC were reported at the 2023 International Kidney Cancer Symposium (IKCS): North America. 

About KEYTRUDA^® (pembrolizumab) injection, 100 mg

KEYTRUDA is an anti-programmed death receptor-1 (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.

Merck has the industry’s largest immuno-oncology clinical research program. There are currently more than 1,600
trials studying KEYTRUDA across a wide variety of cancers and treatment settings. The KEYTRUDA clinical program
seeks to understand the role of KEYTRUDA across cancers and the factors that may predict a patient’s likelihood of
benefitting from treatment with KEYTRUDA, including exploring several different biomarkers.

Selected KEYTRUDA^® (pembrolizumab) Indications in the U.S.

Head and Neck Squamous Cell Cancer

KEYTRUDA, in combination with platinum and fluorouracil (FU), is indicated for the first-line treatment of patients
with metastatic or with unresectable, recurrent head and neck squamous cell carcinoma (HNSCC).

KEYTRUDA, as a single agent, is indicated for the first-line treatment of patients with metastatic or with
unresectable, recurrent HNSCC whose tumors express PD-L1 [Combined Positive Score (CPS) ≥1] as determined by an
FDA-approved test.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with recurrent or metastatic HNSCC with
disease progression on or after platinum-containing chemotherapy.

Renal Cell Carcinoma

KEYTRUDA, in combination with axitinib, is indicated for the first-line treatment of adult patients with advanced
renal cell carcinoma (RCC).

KEYTRUDA is indicated for the adjuvant treatment of patients with RCC at intermediate-high or high risk of recurrence
following nephrectomy, or following nephrectomy and resection of metastatic lesions.

See additional selected KEYTRUDA indications in the U.S. after the Selected Important Safety Information.

Selected Important Safety Information for KEYTRUDA 

Severe and Fatal Immune-Mediated Adverse Reactions 

KEYTRUDA is a monoclonal antibody that belongs to a class of drugs that bind to either the programmed death
receptor-1 (PD-1) or the programmed death ligand 1 (PD-L1), blocking the PD-1/PD-L1 pathway, thereby removing
inhibition of the immune response, potentially breaking peripheral tolerance and inducing immune-mediated adverse
reactions. Immune-mediated adverse reactions, which may be severe or fatal, can occur in any organ system or tissue,
can affect more than one body system simultaneously, and can occur at any time after starting treatment or after
discontinuation of treatment. Important immune-mediated adverse reactions listed here may not include all possible
severe and fatal immune-mediated adverse reactions.

Monitor patients closely for symptoms and signs that may be clinical manifestations of underlying immune-mediated
adverse reactions. Early identification and management are essential to ensure safe use of anti–PD-1/PD-L1
treatments. Evaluate liver enzymes, creatinine, and thyroid function at baseline and periodically during treatment.
For patients with TNBC treated with KEYTRUDA in the neoadjuvant setting, monitor blood cortisol at baseline, prior
to surgery, and as clinically indicated. In cases of suspected immune-mediated adverse reactions, initiate
appropriate workup to exclude alternative etiologies, including infection. Institute medical management promptly,
including specialty consultation as appropriate. 

Withhold or permanently discontinue KEYTRUDA depending on severity of the immune-mediated adverse reaction. In
general, if KEYTRUDA requires interruption or discontinuation, administer systemic corticosteroid therapy (1 to 2
mg/kg/day prednisone or equivalent) until improvement to Grade 1 or less. Upon improvement to Grade 1 or less,
initiate corticosteroid taper and continue to taper over at least 1 month. Consider administration of other systemic
immunosuppressants in patients whose adverse reactions are not controlled with corticosteroid therapy. 

Immune-Mediated Pneumonitis 

KEYTRUDA can cause immune-mediated pneumonitis. The incidence is higher in patients who have received prior thoracic
radiation. Immune-mediated pneumonitis occurred in 3.4% (94/2799) of patients receiving KEYTRUDA, including fatal
(0.1%), Grade 4 (0.3%), Grade 3 (0.9%), and Grade 2 (1.3%) reactions. Systemic corticosteroids were required in 67%
(63/94) of patients. Pneumonitis led to permanent discontinuation of KEYTRUDA in 1.3% (36) and withholding in 0.9%
(26) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, 23% had
recurrence. Pneumonitis resolved in 59% of the 94 patients. 

Pneumonitis occurred in 8% (31/389) of adult patients with cHL receiving KEYTRUDA as a single agent, including Grades
3-4 in 2.3% of patients. Patients received high-dose corticosteroids for a median duration of 10 days (range: 2 days
to 53 months). Pneumonitis rates were similar in patients with and without prior thoracic radiation. Pneumonitis led
to discontinuation of KEYTRUDA in 5.4% (21) of patients. Of the patients who developed pneumonitis, 42% interrupted
KEYTRUDA, 68% discontinued KEYTRUDA, and 77% had resolution.

Pneumonitis occurred in 7% (41/580) of adult patients with resected NSCLC who received KEYTRUDA as a single agent for
adjuvant treatment of NSCLC, including fatal (0.2%), Grade 4 (0.3%), and Grade 3 (1%) adverse reactions. Patients
received high-dose corticosteroids for a median duration of 10 days (range: 1 day to 2.3 months). Pneumonitis led to
discontinuation of KEYTRUDA in 26 (4.5%) of patients. Of the patients who developed pneumonitis, 54% interrupted
KEYTRUDA, 63% discontinued KEYTRUDA, and 71% had resolution. 

Immune-Mediated Colitis 

KEYTRUDA can cause immune-mediated colitis, which may present with diarrhea. Cytomegalovirus infection/reactivation
has been reported in patients with corticosteroid-refractory immune-mediated colitis. In cases of
corticosteroid-refractory colitis, consider repeating infectious workup to exclude alternative etiologies.
Immune-mediated colitis occurred in 1.7% (48/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%),
Grade 3 (1.1%), and Grade 2 (0.4%) reactions. Systemic corticosteroids were required in 69% (33/48); additional
immunosuppressant therapy was required in 4.2% of patients. Colitis led to permanent discontinuation of KEYTRUDA in
0.5% (15) and withholding in 0.5% (13) of patients. All patients who were withheld reinitiated KEYTRUDA after
symptom improvement; of these, 23% had recurrence. Colitis resolved in 85% of the 48 patients. 

Hepatotoxicity and Immune-Mediated Hepatitis 

KEYTRUDA as a Single Agent 

KEYTRUDA can cause immune-mediated hepatitis. Immune-mediated hepatitis occurred in 0.7% (19/2799) of patients
receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (0.4%), and Grade 2 (0.1%) reactions. Systemic
corticosteroids were required in 68% (13/19) of patients; additional immunosuppressant therapy was required in 11%
of patients. Hepatitis led to permanent discontinuation of KEYTRUDA in 0.2% (6) and withholding in 0.3% (9) of
patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement; of these, none had
recurrence. Hepatitis resolved in 79% of the 19 patients. 

KEYTRUDA With Axitinib 

KEYTRUDA in combination with axitinib can cause hepatic toxicity. Monitor liver enzymes before initiation of and
periodically throughout treatment. Consider monitoring more frequently as compared to when the drugs are
administered as single agents. For elevated liver enzymes, interrupt KEYTRUDA and axitinib, and consider
administering corticosteroids as needed. With the combination of KEYTRUDA and axitinib, Grades 3 and 4 increased
alanine aminotransferase (ALT) (20%) and increased aspartate aminotransferase (AST) (13%) were seen at a higher
frequency compared to KEYTRUDA alone. Fifty-nine percent of the patients with increased ALT received systemic
corticosteroids. In patients with ALT ≥3 times upper limit of normal (ULN) (Grades 2-4, n=116), ALT resolved to
Grades 0-1 in 94%. Among the 92 patients who were rechallenged with either KEYTRUDA (n=3) or axitinib (n=34)
administered as a single agent or with both (n=55), recurrence of ALT ≥3 times ULN was observed in 1 patient
receiving KEYTRUDA, 16 patients receiving axitinib, and 24 patients receiving both. All patients with a recurrence
of ALT ≥3 ULN subsequently recovered from the event.

Immune-Mediated Endocrinopathies 

Adrenal Insufficiency

KEYTRUDA can cause primary or secondary adrenal insufficiency. For Grade 2 or higher, initiate symptomatic treatment,
including hormone replacement as clinically indicated. Withhold KEYTRUDA depending on severity. Adrenal
insufficiency occurred in 0.8% (22/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3
(0.3%), and Grade 2 (0.3%) reactions. Systemic corticosteroids were required in 77% (17/22) of patients; of these,
the majority remained on systemic corticosteroids. Adrenal insufficiency led to permanent discontinuation of
KEYTRUDA in <0.1% (1) and withholding in 0.3% (8) of patients. All patients who were withheld reinitiated
KEYTRUDA after symptom improvement.

Hypophysitis

KEYTRUDA can cause immune-mediated hypophysitis. Hypophysitis can present with acute symptoms associated with mass
effect such as headache, photophobia, or visual field defects. Hypophysitis can cause hypopituitarism. Initiate
hormone replacement as indicated. Withhold or permanently discontinue KEYTRUDA depending on severity. Hypophysitis
occurred in 0.6% (17/2799) of patients receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (0.3%), and Grade 2
(0.2%) reactions. Systemic corticosteroids were required in 94% (16/17) of patients; of these, the majority remained
on systemic corticosteroids. Hypophysitis led to permanent discontinuation of KEYTRUDA in 0.1% (4) and withholding
in 0.3% (7) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement. 

Thyroid Disorders

KEYTRUDA can cause immune-mediated thyroid disorders. Thyroiditis can present with or without endocrinopathy.
Hypothyroidism can follow hyperthyroidism. Initiate hormone replacement for hypothyroidism or institute medical
management of hyperthyroidism as clinically indicated. Withhold or permanently discontinue KEYTRUDA depending on
severity. Thyroiditis occurred in 0.6% (16/2799) of patients receiving KEYTRUDA, including Grade 2 (0.3%). None
discontinued, but KEYTRUDA was withheld in <0.1% (1) of patients.

Hyperthyroidism occurred in 3.4% (96/2799) of patients receiving KEYTRUDA, including Grade 3 (0.1%) and Grade 2
(0.8%). It led to permanent discontinuation of KEYTRUDA in <0.1% (2) and withholding in 0.3% (7) of patients. All
patients who were withheld reinitiated KEYTRUDA after symptom improvement. Hypothyroidism occurred in 8% (237/2799)
of patients receiving KEYTRUDA, including Grade 3 (0.1%) and Grade 2 (6.2%). It led to permanent discontinuation of
KEYTRUDA in <0.1% (1) and withholding in 0.5% (14) of patients. All patients who were withheld reinitiated
KEYTRUDA after symptom improvement. The majority of patients with hypothyroidism required long-term thyroid hormone
replacement. The incidence of new or worsening hypothyroidism was higher in 1185 patients with HNSCC, occurring in
16% of patients receiving KEYTRUDA as a single agent or in combination with platinum and FU, including Grade 3
(0.3%) hypothyroidism. The incidence of new or worsening hypothyroidism was higher in 389 adult patients with cHL
(17%) receiving KEYTRUDA as a single agent, including Grade 1 (6.2%) and Grade 2 (10.8%) hypothyroidism. The
incidence of new or worsening hyperthyroidism was higher in 580 patients with resected NSCLC, occurring in 11% of
patients receiving KEYTRUDA as a single agent as adjuvant treatment, including Grade 3 (0.2%) hyperthyroidism. The
incidence of new or worsening hypothyroidism was higher in 580 patients with resected NSCLC, occurring in 22% of
patients receiving KEYTRUDA as a single agent as adjuvant treatment (KEYNOTE-091), including Grade 3 (0.3%)
hypothyroidism. 

Type 1 Diabetes Mellitus (DM), Which Can Present With Diabetic Ketoacidosis

Monitor patients for hyperglycemia or other signs and symptoms of diabetes. Initiate treatment with insulin as
clinically indicated. Withhold KEYTRUDA depending on severity. Type 1 DM occurred in 0.2% (6/2799) of patients
receiving KEYTRUDA. It led to permanent discontinuation in <0.1% (1) and withholding of KEYTRUDA in <0.1% (1)
of patients. All patients who were withheld reinitiated KEYTRUDA after symptom improvement.

Immune-Mediated Nephritis With Renal Dysfunction

KEYTRUDA can cause immune-mediated nephritis. Immune-mediated nephritis occurred in 0.3% (9/2799) of patients
receiving KEYTRUDA, including Grade 4 (<0.1%), Grade 3 (0.1%), and Grade 2 (0.1%) reactions. Systemic
corticosteroids were required in 89% (8/9) of patients. Nephritis led to permanent discontinuation of KEYTRUDA in
0.1% (3) and withholding in 0.1% (3) of patients. All patients who were withheld reinitiated KEYTRUDA after symptom
improvement; of these, none had recurrence. Nephritis resolved in 56% of the 9 patients.

Immune-Mediated Dermatologic Adverse Reactions

KEYTRUDA can cause immune-mediated rash or dermatitis. Exfoliative dermatitis, including Stevens-Johnson syndrome,
drug rash with eosinophilia and systemic symptoms, and toxic epidermal necrolysis, has occurred with anti–
PD-1/PD-L1 treatments. Topical emollients and/or topical corticosteroids may be adequate to treat mild to moderate
nonexfoliative rashes. Withhold or permanently discontinue KEYTRUDA depending on severity. Immune-mediated
dermatologic adverse reactions occurred in 1.4% (38/2799) of patients receiving KEYTRUDA, including Grade 3 (1%) and
Grade 2 (0.1%) reactions. Systemic corticosteroids were required in 40% (15/38) of patients. These reactions led to
permanent discontinuation in 0.1% (2) and withholding of KEYTRUDA in 0.6% (16) of patients. All patients who were
withheld reinitiated KEYTRUDA after symptom improvement; of these, 6% had recurrence. The reactions resolved in 79%
of the 38 patients.

Other Immune-Mediated Adverse Reactions

The following clinically significant immune-mediated adverse reactions occurred at an incidence of <1% (unless
otherwise noted) in patients who received KEYTRUDA or were reported with the use of other anti–PD-1/PD-L1
treatments. Severe or fatal cases have been reported for some of these adverse reactions. Cardiac/Vascular:
Myocarditis, pericarditis, vasculitis; Nervous System: Meningitis, encephalitis, myelitis and demyelination,
myasthenic syndrome/myasthenia gravis (including exacerbation), Guillain-Barré syndrome, nerve paresis, autoimmune
neuropathy; Ocular: Uveitis, iritis and other ocular inflammatory toxicities can occur. Some cases can be associated
with retinal detachment. Various grades of visual impairment, including blindness, can occur. If uveitis occurs in
combination with other immune-mediated adverse reactions, consider a Vogt-Koyanagi-Harada-like syndrome, as this may
require treatment with systemic steroids to reduce the risk of permanent vision loss; Gastrointestinal:
Pancreatitis, to include increases in serum amylase and lipase levels, gastritis, duodenitis; Musculoskeletal and
Connective Tissue: Myositis/polymyositis, rhabdomyolysis (and associated sequelae, including renal failure),
arthritis (1.5%), polymyalgia rheumatica; Endocrine: Hypoparathyroidism; Hematologic/Immune: Hemolytic anemia,
aplastic anemia, hemophagocytic lymphohistiocytosis, systemic inflammatory response syndrome, histiocytic
necrotizing lymphadenitis (Kikuchi lymphadenitis), sarcoidosis, immune thrombocytopenic purpura, solid organ
transplant rejection, other transplant (including corneal graft) rejection.

Infusion-Related Reactions

KEYTRUDA can cause severe or life-threatening infusion-related reactions, including hypersensitivity and anaphylaxis,
which have been reported in 0.2% of 2799 patients receiving KEYTRUDA. Monitor for signs and symptoms of
infusion-related reactions. Interrupt or slow the rate of infusion for Grade 1 or Grade 2 reactions. For Grade 3 or
Grade 4 reactions, stop infusion and permanently discontinue KEYTRUDA.

Complications of Allogeneic Hematopoietic Stem Cell Transplantation (HSCT)

Fatal and other serious complications can occur in patients who receive allogeneic HSCT before or after
anti–PD-1/PD-L1 treatments. Transplant- related complications include hyperacute graft-versus-host disease (GVHD),
acute and chronic GVHD, hepatic veno-occlusive disease after reduced intensity conditioning, and steroid-requiring
febrile syndrome (without an identified infectious cause). These complications may occur despite intervening therapy
between anti–PD-1/PD-L1 treatments and allogeneic HSCT. Follow patients closely for evidence of these complications
and intervene promptly. Consider the benefit vs risks of using anti–PD-1/PD-L1 treatments prior to or after an
allogeneic HSCT.

Increased Mortality in Patients With Multiple Myeloma

In trials in patients with multiple myeloma, the addition of KEYTRUDA to a thalidomide analogue plus dexamethasone
resulted in increased mortality. Treatment of these patients with an anti–PD-1/PD-L1 treatment in this combination
is not recommended outside of controlled trials.

Embryofetal Toxicity

Based on its mechanism of action, KEYTRUDA can cause fetal harm when administered to a pregnant woman. Advise women
of this potential risk. In females of reproductive potential, verify pregnancy status prior to initiating KEYTRUDA
and advise them to use effective contraception during treatment and for 4 months after the last dose.

Adverse Reactions

In KEYNOTE-006, KEYTRUDA was discontinued due to adverse reactions in 9% of 555 patients with advanced melanoma;
adverse reactions leading to permanent 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%). The most common
adverse reactions (≥20%) with KEYTRUDA were fatigue (28%), diarrhea (26%), rash (24%), and nausea (21%).

In KEYNOTE-054, when KEYTRUDA was administered as a single agent to patients with stage III melanoma, KEYTRUDA was
permanently discontinued due to adverse reactions in 14% of 509 patients; the most common (≥1%) were pneumonitis
(1.4%), colitis (1.2%), and diarrhea (1%). Serious adverse reactions occurred in 25% of patients receiving KEYTRUDA.
The most common adverse reaction (≥20%) with KEYTRUDA was diarrhea (28%). In KEYNOTE-716, when KEYTRUDA was
administered as a single agent to patients with stage IIB or IIC melanoma, adverse reactions occurring in patients
with stage IIB or IIC melanoma were similar to those occurring in 1011 patients with stage III melanoma from
KEYNOTE-054.

In KEYNOTE-189, when KEYTRUDA was administered with pemetrexed and platinum chemotherapy in metastatic nonsquamous
NSCLC, KEYTRUDA was discontinued due to adverse reactions in 20% of 405 patients. The most common adverse reactions
resulting in permanent discontinuation of KEYTRUDA were pneumonitis (3%) and acute kidney injury (2%). The most
common adverse reactions (≥20%) with KEYTRUDA were nausea (56%), fatigue (56%), constipation (35%), diarrhea (31%),
decreased appetite (28%), rash (25%), vomiting (24%), cough (21%), dyspnea (21%), and pyrexia (20%).

In KEYNOTE-407, when KEYTRUDA was administered with carboplatin and either paclitaxel or paclitaxel protein-bound in
metastatic squamous NSCLC, KEYTRUDA was discontinued due to adverse reactions in 15% of 101 patients. The most
frequent serious adverse reactions reported in at least 2% of patients were febrile neutropenia, pneumonia, and
urinary tract infection. Adverse reactions observed in KEYNOTE-407 were similar to those observed in KEYNOTE-189
with the exception that increased incidences of alopecia (47% vs 36%) and peripheral neuropathy (31% vs 25%) were
observed in the KEYTRUDA and chemotherapy arm compared to the placebo and chemotherapy arm in KEYNOTE-407.

In KEYNOTE-042, KEYTRUDA was discontinued due to adverse reactions in 19% of 636 patients with advanced NSCLC; the
most common were pneumonitis (3%), death due to unknown cause (1.6%), and pneumonia (1.4%). The most frequent
serious adverse reactions reported in at least 2% of patients were pneumonia (7%), pneumonitis (3.9%), pulmonary
embolism (2.4%), and pleural effusion (2.2%). The most common adverse reaction (≥20%) was fatigue (25%).

In KEYNOTE-010, KEYTRUDA monotherapy was discontinued due to adverse reactions in 8% of 682 patients with metastatic
NSCLC; the most common was pneumonitis (1.8%). The most common adverse reactions (≥20%) were decreased appetite
(25%), fatigue (25%), dyspnea (23%), and nausea (20%).

In KEYNOTE-671, adverse reactions occurring in patients with resectable NSCLC receiving KEYTRUDA in combination with
platinum-containing chemotherapy, given as neoadjuvant treatment and continued as single-agent adjuvant treatment,
were generally similar to those occurring in patients in other clinical trials across tumor types receiving KEYTRUDA
in combination with chemotherapy.

The most common adverse reactions (reported in ≥20%) in patients receiving KEYTRUDA in combination with chemotherapy
were fatigue/asthenia, nausea, constipation, diarrhea, decreased appetite, rash, vomiting, cough, dyspnea, pyrexia,
alopecia, peripheral neuropathy, mucosal inflammation, stomatitis, headache, weight loss, abdominal pain,
arthralgia, myalgia, insomnia, palmar- plantar erythrodysesthesia, urinary tract infection, and hypothyroidism.

In the neoadjuvant phase of KEYNOTE-671, when KEYTRUDA was administered in combination with platinum-containing
chemotherapy as neoadjuvant treatment, serious adverse reactions occurred in 34% of 396 patients. The most frequent
(≥2%) serious adverse reactions were pneumonia (4.8%), venous thromboembolism (3.3%), and anemia (2%). Fatal adverse
reactions occurred in 1.3% of patients, including death due to unknown cause (0.8%), sepsis (0.3%), and
immune-mediated lung disease (0.3%). Permanent discontinuation of any study drug due to an adverse reaction occurred
in 18% of patients who received KEYTRUDA in combination with platinum-containing chemotherapy; the most frequent
adverse reactions (≥1%) that led to permanent discontinuation of any study drug were acute kidney injury (1.8%),
interstitial lung disease (1.8%), anemia (1.5%), neutropenia (1.5%), and pneumonia (1.3%).

Of the KEYTRUDA-treated patients who received neoadjuvant treatment, 6% of 396 patients did not receive surgery due
to adverse reactions. The most frequent (≥1%) adverse reaction that led to cancellation of surgery in the KEYTRUDA
arm was interstitial lung disease (1%).

In the adjuvant phase of KEYNOTE-671, when KEYTRUDA was administered as a single agent as adjuvant treatment, serious
adverse reactions occurred in 14% of 290 patients. The most frequent serious adverse reaction was pneumonia (3.4%).
One fatal adverse reaction of pulmonary hemorrhage occurred. Permanent discontinuation of KEYTRUDA due to an adverse
reaction occurred in 12% of patients who received KEYTRUDA as a single agent, given as adjuvant treatment; the most
frequent adverse reactions (≥1%) that led to permanent discontinuation of KEYTRUDA were diarrhea (1.7%),
interstitial lung disease (1.4%), increased aspartate aminotransferase (1%), and musculoskeletal pain (1%).

Adverse reactions observed in KEYNOTE-091 were generally similar to those occurring in other patients with NSCLC
receiving KEYTRUDA as a single agent, with the exception of hypothyroidism (22%), hyperthyroidism (11%), and
pneumonitis (7%). Two fatal adverse reactions of myocarditis occurred.

In KEYNOTE-048, KEYTRUDA monotherapy was discontinued due to adverse events in 12% of 300 patients with HNSCC; the
most common adverse reactions leading to permanent discontinuation were sepsis (1.7%) and pneumonia (1.3%). The most
common adverse reactions (≥20%) were fatigue (33%), constipation (20%), and rash (20%).

In KEYNOTE-048, when KEYTRUDA was administered in combination with platinum (cisplatin or carboplatin) and FU
chemotherapy, KEYTRUDA was discontinued due to adverse reactions in 16% of 276 patients with HNSCC. The most common
adverse reactions resulting in permanent discontinuation of KEYTRUDA were pneumonia (2.5%), pneumonitis (1.8%), and
septic shock (1.4%). The most common adverse reactions (≥20%) were nausea (51%), fatigue (49%), constipation (37%),
vomiting (32%), mucosal inflammation (31%), diarrhea (29%), decreased appetite (29%), stomatitis (26%), and cough
(22%).

In KEYNOTE-012, KEYTRUDA 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 (≥20%) 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 who received
KEYTRUDA as a monotherapy, with the exception of increased incidences of facial edema and new or worsening
hypothyroidism.

In KEYNOTE-204, KEYTRUDA was discontinued due to adverse reactions in 14% of 148 patients with cHL. Serious adverse
reactions occurred in 30% of patients receiving KEYTRUDA; those ≥1% were pneumonitis, pneumonia, pyrexia,
myocarditis, acute kidney injury, febrile neutropenia, and sepsis. Three patients died from causes other than
disease progression: 2 from complications after allogeneic HSCT and 1 from unknown cause. The most common adverse
reactions (≥20%) were upper respiratory tract infection (41%), musculoskeletal pain (32%), diarrhea (22%), and
pyrexia, fatigue, rash, and cough (20% each).

In KEYNOTE-087, KEYTRUDA was discontinued due to adverse reactions in 5% of 210 patients with cHL. Serious adverse
reactions occurred in 16% of patients; those ≥1% were pneumonia, pneumonitis, pyrexia, dyspnea, GVHD, and herpes
zoster. Two patients died from causes other than disease progression: 1 from GVHD after subsequent allogeneic HSCT
and 1 from septic shock. The most common adverse reactions (≥20%) were fatigue (26%), pyrexia (24%), cough (24%),
musculoskeletal pain (21%), diarrhea (20%), and rash (20%).

In KEYNOTE-170, KEYTRUDA was discontinued due to adverse reactions in 8% of 53 patients with PMBCL. Serious adverse
reactions occurred in 26% of patients and included arrhythmia (4%), cardiac tamponade (2%), myocardial infarction
(2%), pericardial effusion (2%), and pericarditis (2%). Six (11%) patients died within 30 days of start of
treatment. The most common adverse reactions (≥20%) were musculoskeletal pain (30%), upper respiratory tract
infection and pyrexia (28% each), cough (26%), fatigue (23%), and dyspnea (21%).

In KEYNOTE-A39, when KEYTRUDA was administered in combination with enfortumab vedotin to patients with locally
advanced or metastatic urothelial cancer (n=440), fatal adverse reactions occurred in 3.9% of patients, including
acute respiratory failure (0.7%), pneumonia (0.5%), and pneumonitis/ILD (0.2%). Serious adverse reactions occurred
in 50% of patients receiving KEYTRUDA in combination with enfortumab vedotin; the serious adverse reactions in ≥2%
of patients were rash (6%), acute kidney injury (5%), pneumonitis/ILD (4.5%), urinary tract infection (3.6%),
diarrhea (3.2%), pneumonia (2.3%), pyrexia (2%), and hyperglycemia (2%). Permanent discontinuation of KEYTRUDA
occurred in 27% of patients. The most common adverse reactions (≥2%) resulting in permanent discontinuation of
KEYTRUDA were pneumonitis/ILD (4.8%) and rash (3.4%). The most common adverse reactions (≥20%) occurring in patients
treated with KEYTRUDA in combination with enfortumab vedotin were rash (68%), peripheral neuropathy (67%), fatigue
(51%), pruritus (41%), diarrhea (38%), alopecia (35%), weight loss (33%), decreased appetite (33%), nausea (26%),
constipation (26%), dry eye (24%), dysgeusia (21%), and urinary tract infection (21%).

In KEYNOTE-052, KEYTRUDA was discontinued due to adverse reactions in 11% of 370 patients with locally advanced or
metastatic urothelial carcinoma. Serious adverse reactions occurred in 42% of patients; those ≥2% were urinary tract
infection, hematuria, acute kidney injury, pneumonia, and urosepsis. The most common adverse reactions (≥20%) were
fatigue (38%), musculoskeletal pain (24%), decreased appetite (22%), constipation (21%), rash (21%), and diarrhea
(20%).

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%). Serious adverse reactions occurred in 39% of KEYTRUDA-treated patients; those ≥2% were
urinary tract infection, pneumonia, anemia, and pneumonitis. The most common adverse reactions (≥20%) in patients
who received KEYTRUDA were fatigue (38%), musculoskeletal pain (32%), pruritus (23%), decreased appetite (21%),
nausea (21%), and rash (20%).

In KEYNOTE-057, KEYTRUDA was discontinued due to adverse reactions in 11% of 148 patients with high-risk NMIBC. The
most common adverse reaction resulting in permanent discontinuation of KEYTRUDA was pneumonitis (1.4%). Serious
adverse reactions occurred in 28% of patients; those ≥2% were pneumonia (3%), cardiac ischemia (2%), colitis (2%),
pulmonary embolism (2%), sepsis (2%), and urinary tract infection (2%). The most common adverse reactions (≥20%)
were fatigue (29%), diarrhea (24%), and rash (24%).

Adverse reactions occurring in patients with MSI-H or dMMR CRC were similar to those occurring in patients with
melanoma or NSCLC who received KEYTRUDA as a monotherapy.

In KEYNOTE-158 and KEYNOTE-164, adverse reactions occurring in patients with MSI-H or dMMR cancer were similar to
those occurring in patients with other solid tumors who received KEYTRUDA as a single agent.

In KEYNOTE-811, when KEYTRUDA was administered in combination with trastuzumab, fluoropyrimidine- and
platinum-containing chemotherapy, KEYTRUDA was discontinued due to adverse reactions in 6% of 217 patients with
locally advanced unresectable or metastatic HER2+ gastric or GEJ adenocarcinoma. The most common adverse reaction
resulting in permanent discontinuation was pneumonitis (1.4%). In the KEYTRUDA arm versus placebo, there was a
difference of ≥5% incidence between patients treated with KEYTRUDA vs standard of care for diarrhea (53% vs 44%) and
nausea (49% vs 44%).

In KEYNOTE-859, when KEYTRUDA was administered in combination with fluoropyrimidine- and platinum-containing
chemotherapy, serious adverse reactions occurred in 45% of 785 patients. Serious adverse reactions in >2% of
patients included pneumonia (4.1%), diarrhea (3.9%), hemorrhage (3.9%), and vomiting (2.4%). Fatal adverse reactions
occurred in 8% of patients who received KEYTRUDA including infection (2.3%) and thromboembolism (1.3%). KEYTRUDA was
permanently discontinued due to adverse reactions in 15% of patients. The most common adverse reactions resulting in
permanent discontinuation of KEYTRUDA (≥1%) were infections (1.8%) and diarrhea (1.0%). The most common adverse
reactions (reported in ≥20%) in patients receiving KEYTRUDA in combination with chemotherapy were peripheral
neuropathy (47%), nausea (46%), fatigue (40%), diarrhea (36%), vomiting (34%), decreased appetite (29%), abdominal
pain (26%), palmar-plantar erythrodysesthesia syndrome (25%), constipation (22%), and weight loss (20%). 

In KEYNOTE-590, when KEYTRUDA was administered with cisplatin and fluorouracil to patients with metastatic or locally
advanced esophageal or GEJ (tumors with epicenter 1 to 5 centimeters above the GEJ) carcinoma who were not
candidates for surgical resection or definitive chemoradiation, KEYTRUDA was discontinued due to adverse reactions
in 15% of 370 patients. The most common adverse reactions resulting in permanent discontinuation of KEYTRUDA (≥1%)
were pneumonitis (1.6%), acute kidney injury (1.1%), and pneumonia (1.1%). The most common adverse reactions (≥20%)
with KEYTRUDA in combination with chemotherapy were nausea (67%), fatigue (57%), decreased appetite (44%),
constipation (40%), diarrhea (36%), vomiting (34%), stomatitis (27%), and weight loss (24%).

Adverse reactions occurring in patients with esophageal cancer who received KEYTRUDA as a monotherapy were similar to
those occurring in patients with melanoma or NSCLC who received KEYTRUDA as a monotherapy.

In KEYNOTE-A18, when KEYTRUDA was administered with CRT (cisplatin plus external beam radiation therapy [EBRT]
followed by brachytherapy [BT]) to patients with FIGO 2014 Stage III-IVA cervical cancer, fatal adverse reactions
occurred in 1.4% of 292 patients, including 1 case each (0.3%) of large intestinal perforation, urosepsis, sepsis,
and vaginal hemorrhage. Serious adverse reactions occurred in 30% of patients; those ≥1% included urinary tract
infection (2.7%), urosepsis (1.4%), and sepsis (1%). KEYTRUDA was discontinued for adverse reactions in 7% of
patients. The most common adverse reaction (≥1%) resulting in permanent discontinuation was diarrhea (1%). For
patients treated with KEYTRUDA in combination with CRT, the most common adverse reactions (≥10%) were nausea (56%),
diarrhea (50%), vomiting (33%), urinary tract infection (32%), fatigue (26%), hypothyroidism (20%), constipation
(18%), decreased appetite and weight loss (17% each), abdominal pain and pyrexia (12% each), hyperthyroidism,
dysuria, rash (11% each), and pelvic pain (10%).

In KEYNOTE-826, when KEYTRUDA was administered in combination with paclitaxel and cisplatin or paclitaxel and
carboplatin, with or without bevacizumab (n=307), to patients with persistent, recurrent, or first-line metastatic
cervical cancer regardless of tumor PD-L1 expression who had not been treated with chemotherapy except when used
concurrently as a radio- sensitizing agent, fatal adverse reactions occurred in 4.6% of patients, including 3 cases
of hemorrhage, 2 cases each of sepsis and due to unknown causes, and 1 case each of acute myocardial infarction,
autoimmune encephalitis, cardiac arrest, cerebrovascular accident, femur fracture with perioperative pulmonary
embolus, intestinal perforation, and pelvic infection. Serious adverse reactions occurred in 50% of patients
receiving KEYTRUDA in combination with chemotherapy with or without bevacizumab; those ≥3% were febrile neutropenia
(6.8%), urinary tract infection (5.2%), anemia (4.6%), and acute kidney injury and sepsis (3.3% each).

KEYTRUDA was discontinued in 15% of patients due to adverse reactions. The most common adverse reaction resulting in
permanent discontinuation (≥1%) was colitis (1%).

For patients treated with KEYTRUDA, chemotherapy, and bevacizumab (n=196), the most common adverse reactions (≥20%)
were peripheral neuropathy (62%), alopecia (58%), anemia (55%), fatigue/asthenia (53%), nausea and neutropenia (41%
each), diarrhea (39%), hypertension and thrombocytopenia (35% each), constipation and arthralgia (31% each),
vomiting (30%), urinary tract infection (27%), rash (26%), leukopenia (24%), hypothyroidism (22%), and decreased
appetite (21%).

For patients treated with KEYTRUDA in combination with chemotherapy with or without bevacizumab, the most common
adverse reactions (≥20%) were peripheral neuropathy (58%), alopecia (56%), fatigue (47%), nausea (40%), diarrhea
(36%), constipation (28%), arthralgia (27%), vomiting (26%), hypertension and urinary tract infection (24% each),
and rash (22%).

In KEYNOTE-158, KEYTRUDA was discontinued due to adverse reactions in 8% of 98 patients with previously treated
recurrent or metastatic cervical cancer. Serious adverse reactions occurred in 39% of patients receiving KEYTRUDA;
the most frequent included anemia (7%), fistula, hemorrhage, and infections [except urinary tract infections] (4.1%
each). The most common adverse reactions (≥20%) were fatigue (43%), musculoskeletal pain (27%), diarrhea (23%), pain
and abdominal pain (22% each), and decreased appetite (21%).

In KEYNOTE-394, KEYTRUDA was discontinued due to adverse reactions in 13% of 299 patients with previously treated
hepatocellular carcinoma. The most common adverse reaction resulting in permanent discontinuation of KEYTRUDA was
ascites (2.3%). The most common adverse reactions in patients receiving KEYTRUDA (≥10%) were pyrexia (18%), rash
(18%), diarrhea (16%), decreased appetite (15%), pruritis (12%), upper respiratory tract infection (11%), cough
(11%), and hypothyroidism (10%). 

In KEYNOTE-966, when KEYTRUDA was administered in combination with gemcitabine and cisplatin, KEYTRUDA was
discontinued for adverse reactions in 15% of 529 patients with locally advanced unresectable or metastatic biliary
tract cancer. The most common adverse reaction resulting in permanent discontinuation of KEYTRUDA (≥1%) was
pneumonitis (1.3%). Adverse reactions leading to the interruption of KEYTRUDA occurred in 55% of patients. The most
common adverse reactions or laboratory abnormalities leading to interruption of KEYTRUDA (≥2%) were decreased
neutrophil count (18%), decreased platelet count (10%), anemia (6%), decreased white blood cell count (4%), pyrexia
(3.8%), fatigue (3.0%), cholangitis (2.8%), increased ALT (2.6%), increased AST (2.5%), and biliary obstruction
(2.3%).

In KEYNOTE-017 and KEYNOTE-913, adverse reactions occurring in patients with MCC (n=105) were generally similar to
those occurring in patients with melanoma or NSCLC who received KEYTRUDA as a single agent. 

In KEYNOTE-426, when KEYTRUDA was administered in combination with axitinib, fatal adverse reactions occurred in 3.3%
of 429 patients. Serious adverse reactions occurred in 40% of patients, the most frequent (≥1%) were hepatotoxicity
(7%), diarrhea (4.2%), acute kidney injury (2.3%), dehydration (1%), and pneumonitis (1%). Permanent discontinuation
due to an adverse reaction occurred in 31% of patients; KEYTRUDA only (13%), axitinib only (13%), and the
combination (8%); the most common were hepatotoxicity (13%), diarrhea/colitis (1.9%), acute kidney injury (1.6%),
and cerebrovascular accident (1.2%). The most common adverse reactions (≥20%) were diarrhea (56%), fatigue/asthenia
(52%), hypertension (48%), hepatotoxicity (39%), hypothyroidism (35%), decreased appetite (30%), palmar-plantar
erythrodysesthesia (28%), nausea (28%), stomatitis/mucosal inflammation (27%), dysphonia (25%), rash (25%), cough
(21%), and constipation (21%).

In KEYNOTE-564, when KEYTRUDA was administered as a single agent for the adjuvant treatment of renal cell carcinoma,
serious adverse reactions occurred in 20% of patients receiving KEYTRUDA; the serious adverse reactions (≥1%) were
acute kidney injury, adrenal insufficiency, pneumonia, colitis, and diabetic ketoacidosis (1% each). Fatal adverse
reactions occurred in 0.2% including 1 case of pneumonia. Discontinuation of KEYTRUDA due to adverse reactions
occurred in 21% of 488 patients; the most common (≥1%) were increased ALT (1.6%), colitis (1%), and adrenal
insufficiency (1%). The most common adverse reactions (≥20%) were musculoskeletal pain (41%), fatigue (40%), rash
(30%), diarrhea (27%), pruritus (23%), and hypothyroidism (21%).

In KEYNOTE-868, when KEYTRUDA was administered in combination with chemotherapy (paclitaxel and carboplatin) to
patients with advanced or recurrent endometrial carcinoma (n=382), serious adverse reactions occurred in 35% of
patients receiving KEYTRUDA in combination with chemotherapy, compared to 19% of patients receiving placebo in
combination with chemotherapy (n=377). Fatal adverse reactions occurred in 1.6% of patients receiving KEYTRUDA in
combination with chemotherapy, including COVID-19 (0.5%) and cardiac arrest (0.3%). KEYTRUDA was discontinued for an
adverse reaction in 14% of patients. Adverse reactions occurring in patients treated with KEYTRUDA and chemotherapy
were generally similar to those observed with KEYTRUDA alone or chemotherapy alone, with the exception of rash (33%
all Grades; 2.9% Grades 3-4).

Adverse reactions occurring in patients with MSI-H or dMMR endometrial carcinoma who received KEYTRUDA as a single
agent were similar to those occurring in patients with melanoma or NSCLC who received KEYTRUDA as a single agent.

Adverse reactions occurring in patients with TMB-H cancer were similar to those occurring in patients with other
solid tumors who received KEYTRUDA as a single agent.

Adverse reactions occurring in patients with recurrent or metastatic cSCC or locally advanced cSCC were similar to
those occurring in patients with melanoma or NSCLC who received KEYTRUDA as a monotherapy.

In KEYNOTE-522, when KEYTRUDA was administered with neoadjuvant chemotherapy (carboplatin and paclitaxel followed by
doxorubicin or epirubicin and cyclophosphamide) followed by surgery and continued adjuvant treatment with KEYTRUDA
as a single agent (n=778) to patients with newly diagnosed, previously untreated, high-risk early-stage TNBC, fatal
adverse reactions occurred in 0.9% of patients, including 1 each of adrenal crisis, autoimmune encephalitis,
hepatitis, pneumonia, pneumonitis, pulmonary embolism, and sepsis in association with multiple organ dysfunction
syndrome and myocardial infarction. Serious adverse reactions occurred in 44% of patients receiving KEYTRUDA; those
≥2% were febrile neutropenia (15%), pyrexia (3.7%), anemia (2.6%), and neutropenia (2.2%). KEYTRUDA was discontinued
in 20% of patients due to adverse reactions. The most common reactions (≥1%) resulting in permanent discontinuation
were increased ALT (2.7%), increased AST (1.5%), and rash (1%). The most common adverse reactions (≥20%) in patients
receiving KEYTRUDA were fatigue (70%), nausea (67%), alopecia (61%), rash (52%), constipation (42%), diarrhea and
peripheral neuropathy (41% each), stomatitis (34%), vomiting (31%), headache (30%), arthralgia (29%), pyrexia (28%),
cough (26%), abdominal pain (24%), decreased appetite (23%), insomnia (21%), and myalgia (20%).

In KEYNOTE-355, when KEYTRUDA and chemotherapy (paclitaxel, paclitaxel protein-bound, or gemcitabine and carboplatin)
were administered to patients with locally recurrent unresectable or metastatic TNBC who had not been previously
treated with chemotherapy in the metastatic setting (n=596), fatal adverse reactions occurred in 2.5% of patients,
including cardio-respiratory arrest (0.7%) and septic shock (0.3%). Serious adverse reactions occurred in 30% of
patients receiving KEYTRUDA in combination with chemotherapy; the serious reactions in ≥2% were pneumonia (2.9%),
anemia (2.2%), and thrombocytopenia (2%). KEYTRUDA was discontinued in 11% of patients due to adverse reactions. The
most common reactions resulting in permanent discontinuation (≥1%) were increased ALT (2.2%), increased AST (1.5%),
and pneumonitis (1.2%). The most common adverse reactions (≥20%) in patients receiving KEYTRUDA in combination with
chemotherapy were fatigue (48%), nausea (44%), alopecia (34%), diarrhea and constipation (28% each), vomiting and
rash (26% each), cough (23%), decreased appetite (21%), and headache (20%).

Lactation

Because of the potential for serious adverse reactions in breastfed children, advise women not to breastfeed during
treatment and for 4 months after the last dose.

Pediatric Use

In KEYNOTE-051, 173 pediatric patients (65 pediatric patients aged 6 months to younger than 12 years and 108
pediatric patients aged 12 years to 17 years) were administered KEYTRUDA 2 mg/kg every 3 weeks. The median duration
of exposure was 2.1 months (range: 1 day to 25 months).

Adverse reactions that occurred at a ≥10% higher rate in pediatric patients when compared to adults were pyrexia
(33%), leukopenia (31%), vomiting (29%), neutropenia (28%), headache (25%), abdominal pain (23%), thrombocytopenia
(22%), Grade 3 anemia (17%), decreased lymphocyte count (13%), and decreased white blood cell count (11%).

Geriatric Use

Of the 564 patients with locally advanced or metastatic urothelial cancer treated with KEYTRUDA in combination with
enfortumab vedotin, 44% (n=247) were 65-74 years and 26% (n=144) were 75 years or older. No overall differences in
safety or effectiveness were observed between patients 65 years of age or older and younger patients. Patients 75
years of age or older treated with KEYTRUDA in combination with enfortumab vedotin experienced a higher incidence of
fatal adverse reactions than younger patients. The incidence of fatal adverse reactions was 4% in patients younger
than 75 and 7% in patients 75 years or older.

Additional Selected KEYTRUDA Indications in the U.S.

Melanoma

KEYTRUDA is indicated for the treatment of patients with unresectable or metastatic melanoma.

KEYTRUDA is indicated for the adjuvant treatment of adult and pediatric (12 years and older) patients with Stage IIB,
IIC, or III melanoma following complete resection.

Non-Small Cell Lung Cancer

KEYTRUDA, in combination with pemetrexed and platinum chemotherapy, is indicated for the first-line treatment of
patients with metastatic nonsquamous non-small cell lung cancer (NSCLC), with no EGFR or ALK genomic tumor
aberrations.

KEYTRUDA, in combination with carboplatin and either paclitaxel or paclitaxel protein-bound, is indicated for the
first-line treatment of patients with metastatic squamous NSCLC.

KEYTRUDA, as a single agent, is indicated for the first-line treatment of patients with NSCLC expressing PD-L1 [Tumor
Proportion Score (TPS) ≥1%] as determined by an FDA-approved test, with no EGFR or ALK genomic tumor aberrations,
and is:

• Stage III where patients are not candidates for surgical resection or definitive chemoradiation, or
• metastatic.

KEYTRUDA, as a single agent, is 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 is indicated for the treatment of patients with resectable (tumors ≥4 cm or node positive) NSCLC in
combination with platinum-containing chemotherapy as neoadjuvant treatment, and then continued as a single agent as
adjuvant treatment after surgery. 

KEYTRUDA, as a single agent, is indicated as adjuvant treatment following resection and platinum-based chemotherapy
for adult patients with Stage IB (T2a ≥4 cm), II, or IIIA NSCLC.

Malignant Pleural Mesothelioma

KEYTRUDA, in combination with pemetrexed and platinum chemotherapy, is indicated for the first-line treatment of
adult patients with unresectable advanced or metastatic malignant pleural mesothelioma (MPM).

Classical Hodgkin Lymphoma

KEYTRUDA is indicated for the treatment of adult patients with relapsed or refractory classical Hodgkin lymphoma
(cHL).

KEYTRUDA is indicated for the treatment of pediatric patients with refractory cHL, or cHL that has relapsed after 2
or more lines of therapy.

Primary Mediastinal Large B-Cell Lymphoma

KEYTRUDA is indicated for the treatment of adult and pediatric patients with refractory primary mediastinal large
B-cell lymphoma (PMBCL), or who have relapsed after 2 or more prior lines of therapy. KEYTRUDA is not recommended
for treatment of patients with PMBCL who require urgent cytoreductive therapy.

Urothelial Cancer

KEYTRUDA, in combination with enfortumab vedotin, is indicated for the treatment of adult patients with locally
advanced or metastatic urothelial cancer.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with locally advanced or metastatic
urothelial carcinoma:

• who are not eligible for any platinum-containing chemotherapy, or
• who have disease progression during or following platinum-containing chemotherapy or within 12 months of
  neoadjuvant or adjuvant treatment with platinum-containing chemotherapy.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with Bacillus Calmette-Guerin
(BCG)-unresponsive, high-risk, non-muscle invasive bladder cancer (NMIBC) with carcinoma in situ (CIS) with or
without papillary tumors who are ineligible for or have elected not to undergo cystectomy.

Microsatellite Instability-High or Mismatch Repair Deficient 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, as determined by an
FDA-approved test, that have progressed following prior treatment and who have no satisfactory alternative treatment
options.

Microsatellite Instability-High or Mismatch Repair Deficient Colorectal Cancer

KEYTRUDA is indicated for the treatment of patients with unresectable or metastatic MSI-H or dMMR colorectal cancer
(CRC) as determined by an FDA-approved test.

Gastric Cancer 

KEYTRUDA, in combination with trastuzumab, fluoropyrimidine- and platinum containing chemotherapy, is indicated for
the first-line treatment of adults with locally advanced unresectable or metastatic HER2-positive gastric or
gastroesophageal junction (GEJ) adenocarcinoma whose tumors express PD-L1 (CPS ≥1) as determined by an FDA-approved
test.

This indication is approved under accelerated approval based on tumor response rate and durability of response.
Continued approval of this indication may be contingent upon verification and description of clinical benefit in the
confirmatory trials.

KEYTRUDA, in combination with fluoropyrimidine- and platinum-containing chemotherapy, is indicated for the first-line
treatment of adults with locally advanced unresectable or metastatic HER2-negative gastric or gastroesophageal
junction (GEJ) adenocarcinoma.

Esophageal Cancer

KEYTRUDA is indicated for the treatment of patients with locally advanced or metastatic esophageal or
gastroesophageal junction (GEJ) (tumors with epicenter 1 to 5 centimeters above the GEJ) carcinoma that is not
amenable to surgical resection or definitive chemoradiation either:

• in combination with platinum- and fluoropyrimidine-based chemotherapy, or
• as a single agent after one or more prior lines of systemic therapy for patients with tumors of squamous cell
  histology that express PD-L1 (CPS ≥10) as determined by an FDA-approved test.

Cervical Cancer

KEYTRUDA, in combination with chemoradiotherapy (CRT), is indicated for the treatment of patients with FIGO 2014
Stage III-IVA cervical cancer.

KEYTRUDA, in combination with chemotherapy, with or without bevacizumab, is indicated for the treatment of patients
with persistent, recurrent, or metastatic cervical cancer whose tumors express PD-L1 (CPS ≥1) as determined by an
FDA-approved test.

KEYTRUDA, as a single agent, is indicated for the treatment of patients with recurrent or metastatic cervical cancer
with disease progression on or after chemotherapy whose tumors express PD-L1 (CPS ≥1) as determined by an
FDA-approved test.

Hepatocellular Carcinoma

KEYTRUDA is indicated for the treatment of patients with hepatocellular carcinoma (HCC) secondary to hepatitis B who
have received prior systemic therapy other than a PD-1/PD-L1-containing regimen. 

Biliary Tract Cancer

KEYTRUDA, in combination with gemcitabine and cisplatin, is indicated for the treatment of patients with locally
advanced unresectable or metastatic biliary tract cancer (BTC). 

Merkel Cell Carcinoma

KEYTRUDA is indicated for the treatment of adult and pediatric patients with recurrent locally advanced or metastatic
Merkel cell carcinoma (MCC). 

Endometrial Carcinoma

KEYTRUDA, in combination with carboplatin and paclitaxel, followed by KEYTRUDA as a single agent, is indicated for
the treatment of adult patients with primary advanced or recurrent endometrial carcinoma.

KEYTRUDA, as a single agent, is indicated for the treatment of adult patients with advanced endometrial carcinoma
that is MSI-H or dMMR, as determined by an FDA-approved test, who have disease progression following prior systemic
therapy in any setting and are not candidates for curative surgery or radiation.

Tumor Mutational Burden-High Cancer

KEYTRUDA is indicated for the treatment of adult and pediatric patients with unresectable or metastatic tumor
mutational burden-high (TMB-H) [≥10 mutations/megabase (mut/Mb)] solid tumors, as determined by an FDA-approved
test, that have progressed following prior treatment and who have no satisfactory alternative treatment
options. 

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 in pediatric patients with TMB-H central nervous
system cancers have not been established.

Cutaneous Squamous Cell Carcinoma

KEYTRUDA is indicated for the treatment of patients with recurrent or metastatic cutaneous squamous cell carcinoma
(cSCC) or locally advanced cSCC that is not curable by surgery or radiation.

Triple-Negative Breast Cancer

KEYTRUDA is indicated for the treatment of patients with high-risk early-stage triple-negative breast cancer (TNBC)
in combination with chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant
treatment after surgery.

KEYTRUDA, in combination with chemotherapy, is indicated for the treatment of patients with locally recurrent
unresectable or metastatic TNBC whose tumors express PD-L1 (CPS ≥10) as determined by an FDA-approved test.

Please see Prescribing Information for KEYTRUDA (pembrolizumab) at http://www.merck.com/product/usa/pi_circulars/k/keytruda/keytruda_pi.pdf
and Medication Guide for KEYTRUDA at https://www.merck.com/product/usa/pi_circulars/k/keytruda/keytruda_mg.pdf. 

About WELIREG^® (belzutifan) 40 mg tablets, for oral use

Indications in the U.S.

Certain von Hippel-Lindau (VHL) disease-associated tumors

WELIREG (belzutifan) is indicated for the treatment of adult patients with von Hippel-Lindau (VHL) disease who
require therapy for associated renal cell carcinoma (RCC), central nervous system (CNS) hemangioblastomas, or
pancreatic neuroendocrine tumors (pNET), not requiring immediate surgery.

Advanced Renal Cell Carcinoma (RCC)

WELIREG is indicated for the treatment of adult patients with advanced renal cell carcinoma (RCC) following a
programmed death receptor-1 (PD-1) or programmed death ligand 1 (PD-L1) inhibitor and a vascular endothelial growth
factor tyrosine kinase inhibitor (VEGF-TKI).

Selected Safety Information for WELIREG

Warning: Embryo-Fetal Toxicity

Exposure to WELIREG during pregnancy can cause embryo-fetal harm. Verify pregnancy status prior to the initiation of
WELIREG. Advise patients of these risks and the need for effective non-hormonal contraception as WELIREG can render
some hormonal contraceptives ineffective.

Anemia 

WELIREG can cause severe anemia that can require blood transfusion. Monitor for anemia before initiation of, and
periodically throughout, treatment. Transfuse patients as clinically indicated. For patients with hemoglobin <8
g/dL, withhold WELIREG until ≥8 g/dL, then resume at the same or reduced dose or permanently discontinue WELIREG,
depending on the severity of anemia. For life-threatening anemia or when urgent intervention is indicated, withhold
WELIREG until hemoglobin ≥8 g/dL, then resume at a reduced dose or permanently discontinue WELIREG. 

In LITESPARK-004 (N=61), decreased hemoglobin occurred in 93% of patients with VHL disease and 7% had Grade 3 events.
Median time to onset of anemia was 31 days (range: 1 day to 8.4 months). 

The safety of erythropoiesis-stimulating agents (ESAs) for treatment of anemia in patients with VHL disease treated
with WELIREG has not been established. 

In LITESPARK-005 (n=372), decreased hemoglobin occurred in 88% of patients with advanced RCC and 29% had Grade 3
events. Median time to onset of anemia was 29 days (range: 1 day to 16.6 months). Of the patients with anemia, 22%
received transfusions only, 20% received ESAs only, and 12% received both transfusion and ESAs.

Hypoxia

WELIREG can cause severe hypoxia that may require discontinuation, supplemental oxygen, or hospitalization. 

Monitor oxygen saturation before initiation of, and periodically throughout, treatment. For decreased oxygen
saturation with exercise (e.g., pulse oximeter <88% or PaO2 ≤55 mm Hg), consider withholding WELIREG until pulse
oximetry with exercise is greater than 88%, then resume at the same or a reduced dose. For decreased oxygen
saturation at rest (e.g., pulse oximeter <88% or PaO2 ≤55 mm Hg) or when urgent intervention is indicated,
withhold WELIREG until resolved and resume at a reduced dose or discontinue. For life-threatening or recurrent
symptomatic hypoxia, permanently discontinue WELIREG. Advise patients to report signs and symptoms of hypoxia
immediately to a healthcare provider.

In LITESPARK-004, hypoxia occurred in 1.6% of patients.

In LITESPARK-005, hypoxia occurred in 15% of patients and 10% had Grade 3 events. Of the patients with hypoxia, 69%
were treated with oxygen therapy. Median time to onset of hypoxia was 30.5 days (range: 1 day to 21.1 months).

Embryo-Fetal Toxicity 

Based on findings in animals, WELIREG can cause fetal harm when administered to a pregnant woman. 

Advise pregnant women and females of reproductive potential of the potential risk to the fetus. Advise females of
reproductive potential to use effective non-hormonal contraception during treatment with WELIREG and for 1 week
after the last dose. WELIREG can render some hormonal contraceptives ineffective. Advise male patients with female
partners of reproductive potential to use effective contraception during treatment with WELIREG and for 1 week after
the last dose.

Adverse Reactions

In LITESPARK-004, serious adverse reactions occurred in 15% of patients, including anemia, hypoxia, anaphylaxis
reaction, retinal detachment, and central retinal vein occlusion (1 patient each).

WELIREG was permanently discontinued due to adverse reactions in 3.3% of patients for dizziness and opioid overdose
(1.6% each).

Dosage interruptions due to an adverse reaction occurred in 39% of patients. Those which required dosage interruption
in >2% of patients were fatigue, decreased hemoglobin, anemia, nausea, abdominal pain, headache, and
influenza-like illness.

Dose reductions due to an adverse reaction occurred in 13% of patients. The most frequently reported adverse reaction
which required dose reduction was fatigue (7%).

The most common adverse reactions (≥25%), including laboratory abnormalities, that occurred in patients who received
WELIREG were decreased hemoglobin (93%), fatigue (64%), increased creatinine (64%), headache (39%), dizziness (38%),
increased glucose (34%), and nausea (31%).

In LITESPARK-005, serious adverse reactions occurred in 38% of patients. The most frequently reported serious adverse
reactions were hypoxia (7%), anemia (5%), pneumonia (3.5%), hemorrhage (3%), and pleural effusion (2.2%). Fatal
adverse reactions occurred in 3.2% of patients who received WELIREG, including sepsis (0.5%) and hemorrhage (0.5%).

WELIREG was permanently discontinued due to adverse reactions in 6% of patients. Adverse reactions which resulted in
permanent discontinuation (≥0.5%) were hypoxia (1.1%) and hemorrhage (0.5%).

Dosage interruptions due to an adverse reaction occurred in 39% of patients. Of the patients who received WELIREG,
28% were 65 to 74 years, and 10% were 75 years and over. Dose interruptions occurred in 48% of patients ≥65 years of
age and in 34% of younger patients. Adverse reactions which required dosage interruption in ≥2% of patients were
anemia (8%), hypoxia (5%), COVID-19 (4.3%), fatigue (3.2%), and hemorrhage (2.2%).

Dose reductions due to an adverse reaction occurred in 13% of patients. Dose reductions occurred in 18% of patients
≥65 years of age and in 10% of younger patients. The most frequently reported adverse reactions which required dose
reduction (≥1.0%) were hypoxia (5%) and anemia (3.2%).

The most common (≥25%) adverse reactions, including laboratory abnormalities, were decreased hemoglobin (88%),
fatigue (43%), musculoskeletal pain (33%), increased creatinine (34%), decreased lymphocytes (34%), increased
alanine aminotransferase (32%), decreased sodium (31%), increased potassium (29%), and increased aspartate
aminotransferase (27%).

Drug Interactions 

Coadministration of WELIREG with inhibitors of UGT2B17 or CYP2C19 increases plasma exposure of belzutifan, which may
increase the incidence and severity of adverse reactions. Monitor for anemia and hypoxia and reduce the dosage of
WELIREG as recommended.

Coadministration of WELIREG with CYP3A4 substrates decreases concentrations of CYP3A4 substrates, which may reduce
the efficacy of these substrates or lead to therapeutic failures. Avoid coadministration with sensitive CYP3A4
substrates. If coadministration cannot be avoided, increase the sensitive CYP3A4 substrate dosage in accordance with
its Prescribing Information. Coadministration of WELIREG with hormonal contraceptives may lead to contraceptive
failure or an increase in breakthrough bleeding.

Lactation

Because of the potential for serious adverse reactions in breastfed children, advise women not to breastfeed during
treatment with WELIREG and for 1 week after the last dose. 

Females and Males of Reproductive Potential

WELIREG can cause fetal harm when administered to a pregnant woman. Verify the pregnancy status of females of
reproductive potential prior to initiating treatment with WELIREG. 

Use of WELIREG may reduce the efficacy of hormonal contraceptives. Advise females of reproductive potential to use
effective non-hormonal contraception during treatment with WELIREG and for 1 week after the last dose. Advise males
with female partners of reproductive potential to use effective contraception during treatment with WELIREG and for
1 week after the last dose. 

Based on findings in animals, WELIREG may impair fertility in males and females of reproductive potential and the
reversibility of this effect is unknown. 

Pediatric Use

Safety and effectiveness of WELIREG in pediatric patients under 18 years of age have not been established.

Please see Prescribing Information, including information for the Boxed Warning about embryo-fetal toxicity, for WELIREG (belzutifan) at https://www.merck.com/product/usa/pi_circulars/w/welireg/welireg_pi.pdf
and Medication Guide for WELIREG at https://www.merck.com/product/usa/pi_circulars/w/welireg/welireg_mg.pdf.

About Exelixis

Exelixis is a globally ambitious oncology company innovating next-generation medicines and regimens at the forefront
of cancer care. Powered by drug discovery and development excellence, we are rapidly evolving our product portfolio
to target an expanding range of tumor types and indications with our clinically differentiated pipeline of small
molecules, antibody-drug conjugates and other biotherapeutics. This comprehensive approach harnesses decades of
robust investment in our science and partnerships to advance our investigational programs and extend the impact of
our flagship commercial product, CABOMETYX® (cabozantinib). Exelixis is driven by a bold scientific pursuit to
create transformational treatments that give more patients hope for the future. For information about the company
and its mission to help cancer patients recover stronger and live longer, visit www.exelixis.com, follow @ExelixisInc
on X (Twitter), like Exelixis, Inc. on Facebook and follow Exelixis
on LinkedIn.

Merck’s focus on cancer

Every day, we follow the science as we work to discover innovations that can help patients, no matter what stage of
cancer they have. As a leading oncology company, we are pursuing research where scientific opportunity and medical
need converge, underpinned by our diverse pipeline of more than 25 novel mechanisms. With one of the largest
clinical development programs across more than 30 tumor types, we strive to advance breakthrough science that will
shape the future of oncology. By addressing barriers to clinical trial participation, screening and treatment, we
work with urgency to reduce disparities and help ensure patients have access to high-quality cancer care. Our
unwavering commitment is what will bring us closer to our goal of bringing life to more patients with cancer. For
more information, visit https://www.merck.com/research/oncology. 

About Merck

At Merck, known as MSD outside of the United States and Canada, we are unified around our
purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130
years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be
the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of
research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and
animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe,
sustainable and healthy future for all people and communities.
For more information, visit www.merck.com and connect with us on X (formerly Twitter), Facebook, Instagram, YouTube and LinkedIn.

Exelixis Forward-Looking Statements

This press release contains forward-looking statements, including, without limitation, statements related to the
therapeutic potential of zanzalintinib to drive patient benefit in combination with immunotherapy or targeted
therapy in HNSCC and RCC indications that have unmet clinical need and Exelixis’ scientific pursuit to create
transformational treatments that give more patients hope for the future. Any statements that refer to expectations,
projections or other characterizations of future events or circumstances are forward-looking statements and are
based upon Exelixis’ current plans, assumptions, beliefs, expectations, estimates and projections. Forward-looking
statements involve risks and uncertainties. Actual results and the timing of events could differ materially from
those anticipated in the forward-looking statements as a result of these risks and uncertainties, which include,
without limitation: the potential failure of the combination of zanzalintinib with each of pembrolizumab and
belzutifan, as applicable, to demonstrate safety and/or efficacy in clinical trials; complexities and the
unpredictability of the regulatory review and approval processes in the U.S. and elsewhere; Exelixis’ and Merck’s
continuing compliance with applicable legal and regulatory requirements; the costs of conducting clinical trials;
Exelixis’ dependence on third-party vendors for the development, manufacture and supply of zanzalintinib; Exelixis’
and Merck’s ability to protect its intellectual property rights; market competition; changes in economic and
business conditions; and other factors affecting Exelixis and its development programs detailed from time to time
under the caption “Risk Factors” in Exelixis’ most recent Annual Report on Form 10-K and subsequent Quarterly
Reports on Form 10-Q, and in Exelixis’ future filings with the Securities and Exchange Commission. All
forward-looking statements in this press release are based on information available to Exelixis as of the date of
this press release, and Exelixis undertakes no obligation to update or revise any forward-looking statements
contained herein, except as required by law.

Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA

This news release of Merck & Co., Inc., Rahway, N.J., USA (the “company”) includes “forward-looking statements”
within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These
statements are based upon the current beliefs and expectations of the company’s management and are subject to
significant risks and uncertainties. There can be no guarantees with respect to pipeline candidates that the
candidates will receive the necessary regulatory approvals or that they will prove to be commercially successful. If
underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially
from those set forth in the forward-looking statements.

Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic
factors, including interest rate and currency exchange rate fluctuations; the impact of pharmaceutical industry
regulation and health care legislation in the United States and internationally; global trends toward health care
cost containment; technological advances, new products and patents attained by competitors; challenges inherent in
new product development, including obtaining regulatory approval; the company’s ability to accurately predict future
market conditions; manufacturing difficulties or delays; financial instability of international economies and
sovereign risk; dependence on the effectiveness of the company’s patents and other protections for innovative
products; and the exposure to litigation, including patent litigation, and/or regulatory actions.

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 Annual Report on Form 10-K for the year
ended December 31, 2023 and the company’s other filings with the Securities and Exchange Commission (SEC) available
at the SEC’s Internet site (www.sec.gov).

Exelixis, the Exelixis logo and CABOMETYX are registered U.S. trademarks.

KEYTRUDA® and WELIREG® are registered trademarks of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., Rahway, N.J., USA.

###

Media Contacts:

Merck

Julie Cunningham

(617) 519-6264

Carly Myar

(917) 227-5957

Exelixis

Hal Mackins

For Exelixis, Inc.

(415) 994-0040

Investor Contacts:

Merck

Peter Dannenbaum

(732) 594-1579

Damini Chokshi

(732) 594-1577

Exelixis

Susan Hubbard

EVP, Public Affairs & Investor Relations

Exelixis, Inc.

(650) 837-8194