KEYTRUDA® (pembrolizumab) Plus Padcev® (enfortumab vedotin-ejfv) Reduced Risk of Event-Free Survival Events by 47% and Risk of Death by 35% for Cisplatin-Eligible Patients with Muscle-Invasive Bladder Cancer When Given Before and After Surgery

First and only immunotherapy plus antibody-drug conjugate regimen, used perioperatively, to significantly extend survival for these patients

KEYNOTE-B15 is the sixth study demonstrating overall survival with a KEYTRUDA-based regimen in an earlier-stage cancer

Late-breaking results from the Phase 3 KEYNOTE-B15 trial were selected for the official Press Program and will be presented at the 2026 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancers Symposium

RAHWAY, N.J.--(BUSINESS WIRE)--Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced KEYTRUDA^® (pembrolizumab) plus Padcev ^® (enfortumab vedotin-ejfv) reduced the risk of event-free survival (EFS) events by 47% and reduced the risk of death by 35% when given before and after surgery versus neoadjuvant chemotherapy and surgery in patients with muscle-invasive bladder cancer (MIBC) who are eligible for cisplatin-based chemotherapy. These late-breaking data will be presented for the first time today during an oral abstract session at the 2026 American Society of Clinical Oncology (ASCO) Genitourinary (GU) Cancers Symposium (abstract #LBA630) and are included in the official ASCO GU Press Program.

After a median follow-up of 33.6 months, KEYTRUDA plus Padcev, as perioperative treatment, demonstrated a statistically significant and clinically meaningful improvement in EFS, the trial’s primary endpoint, reducing the risk of EFS events by 47% (HR=0.53 [95% CI, 0.41-0.70]; p<0.0001) versus neoadjuvant chemotherapy and surgery in patients with MIBC who are eligible for cisplatin-based chemotherapy. Median EFS was not reached (NR) (95% CI, NR-NR) for the KEYTRUDA plus Padcev regimen versus 48.5 months (95% CI, 43.3-NR) for neoadjuvant chemotherapy and surgery. Approximately 79.4% of patients treated with KEYTRUDA plus Padcev were alive without disease progression or recurrence versus approximately 66.2% for patients treated with neoadjuvant chemotherapy and surgery at two years.

“These findings demonstrate the strength and consistency of KEYTRUDA plus Padcev in treating muscle-invasive bladder cancer,” said Dr. Marjorie Green, senior vice president and head of oncology, global clinical development, Merck Research Laboratories. “Showing a survival benefit in cisplatin-eligible patients in the perioperative setting reinforces the potential of this combination to play a foundational role in bladder cancer care.”

KEYTRUDA plus Padcev also demonstrated a statistically significant and clinically meaningful improvement in key secondary endpoints of overall survival (OS) and pathologic complete response (pCR) rate. KEYTRUDA plus Padcev reduced the risk of death by 35% (HR=0.65 [95% CI, 0.48-0.89]; p=0.0029) versus neoadjuvant chemotherapy and surgery. Median OS was NR (95% CI, NR-NR) for either regimen. Approximately 86.9% of patients treated with KEYTRUDA plus Padcev were alive versus approximately 81.3% of patients treated with neoadjuvant chemotherapy and surgery at two years. The pCR rate increased from 32.5% in patients treated with neoadjuvant chemotherapy and surgery to 55.8% in patients treated with perioperative KEYTRUDA plus Padcev, an estimated increase of 23.4% (95% CI, 16.7-29.8; p<0.0001).

"For almost 25 years, cisplatin-based neoadjuvant chemotherapy was the standard of care for approximately half of patients with muscle-invasive bladder cancer who were eligible to receive platinum-based treatment,” said Dr. Matthew Galsky, Lillian and Howard Stratton Professor of Medicine, director of genitourinary medical oncology, Mount Sinai Tisch Cancer Center. “Results from KEYNOTE-B15 further support that a perioperative approach with pembrolizumab plus enfortumab vedotin can significantly improve survival compared to neoadjuvant chemotherapy in cis-eligible patients with muscle-invasive bladder cancer – setting the stage for a new treatment standard in this disease setting.”

KEYNOTE-B15 evaluated Merck’s KEYTRUDA, an anti-PD-1 therapy, plus Padcev, an antibody-drug conjugate (ADC), and was conducted in collaboration with Pfizer and Astellas. The companies plan to share these results with regulatory authorities worldwide for potential regulatory filings. KEYTRUDA plus Padcev is currently approved for the treatment of adult patients with locally advanced or metastatic urothelial cancer (la/mUC) in the U.S., the European Union (EU), Japan and several other countries around the world. KEYTRUDA plus Padcev is also approved in the U.S. for the treatment of adult patients with MIBC who are ineligible for cisplatin-based chemotherapy. KEYTRUDA as a monotherapy is also approved in the U.S., EU, Japan and other countries for the treatment of certain patients with la/mUC or a type of non-muscle-invasive bladder cancer (NMIBC).

KEYTRUDA plus Padcev has now demonstrated an OS benefit across three Phase 3 trials bladder cancer. In addition to KEYNOTE-B15, these trials include KEYNOTE-905 for the treatment of patients with MIBC who are not eligible for or declined cisplatin-based chemotherapy and KEYNOTE-A39 for the treatment of adult patients with la/mUC. Three additional Phase 3 studies are currently evaluating KEYTRUDA across all stages of bladder cancer, including non-muscle-invasive, muscle-invasive and metastatic disease. Two of these studies are in MIBC including KEYNOTE-866 (NCT03924856) and KEYNOTE-992 (NCT04241185). KEYTRUDA is also being evaluated in combination with Bacillus Calmette-Guerin (BCG) in patients with NMIBC in KEYNOTE-676 (NCT03711032).

KEYNOTE-B15 is one of six Phase 3 studies of a KEYTRUDA-based regimen in an earlier stage of cancer to demonstrate an OS benefit. It is also the 14^th positive pivotal trial for a KEYTRUDA-based regimen in earlier-stage cancers.

Study design and additional data from KEYNOTE-B15/EV-304
KEYNOTE-B15, also known as EV-304, is an open-label, randomized Phase 3 trial (ClinicalTrials.gov, NCT04700124) evaluating perioperative KEYTRUDA in combination with Padcev and surgery (radical cystectomy and pelvic lymph node dissection) versus neoadjuvant chemotherapy (gemcitabine plus cisplatin) and surgery in patients with MIBC who are cisplatin-eligible. The trial enrolled 808 patients who were randomized to receive either:

• Four cycles (each cycle length is 21 days) of neoadjuvant KEYTRUDA intravenous (IV) infusion plus enfortumab vedotin IV infusion, followed by surgery, followed by 13 cycles of adjuvant KEYTRUDA IV infusion plus five cycles of enfortumab vedotin IV infusion, or;
• Four cycles (each cycle is 21 days) of standard of care neoadjuvant chemotherapy followed by surgery.

The primary endpoint is EFS, defined as the time from randomization to the first occurrence of the following events: radiographic disease progression precluding radical cystectomy and pelvic lymph node dissection, failure to undergo surgery in participants with residual disease, gross residual disease left behind at time of surgery, local or distant recurrence based on blinded independent central review or death due to any cause. The key secondary endpoints are OS and pCR rate.

The safety profile of KEYTRUDA plus Padcev in this study was consistent with the known safety profiles of each agent. Grade ≥3 treatment-emergent adverse events occurred in 75.7% of patients receiving KEYTRUDA plus Padcev versus 67.2% of patients receiving neoadjuvant chemotherapy and surgery.

About bladder cancer
In 2022, bladder cancer changed the lives of more than 600,000 people around the world. According to some clinical practice guidelines, about 25% of newly diagnosed bladder cancer cases are MIBC. The standard of care for patients with MIBC has been neoadjuvant cisplatin-based chemotherapy followed by surgery, which is shown to prolong survival. However, nearly half of patients who undergo this standard treatment experience recurrence.

About Merck’s early-stage cancer clinical program
Finding cancer at an earlier stage may give patients a greater chance of long-term survival. Many cancers are considered most treatable and potentially curable in their earliest stage of disease. Building on the strong understanding of the role of KEYTRUDA in later-stage cancers, Merck is evaluating our portfolio of medicines and pipeline candidates in earlier disease states, with more than 30 ongoing registrational studies across multiple types of cancer.

About Merck’s research in genitourinary cancers
Merck is advancing research aimed at helping transform the treatment landscape and broaden options for people with genitourinary (GU) cancers, including bladder, kidney and prostate cancers. Globally, GU cancers account for an estimated 2.6 million new cancer diagnoses each year, equaling over 1 in 8 of all cancer incidences. Through a robust clinical development program with more than 50 clinical trials evaluating more than 22,000 patients around the world, Merck is investigating the potential of several portfolio medicines and pipeline assets, leveraging multiple novel combination strategies, across various stages of disease, to help address unmet needs in GU cancers.

About KEYTRUDA^® (pembrolizumab) injection for intravenous use, 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.
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, in combination with enfortumab vedotin, as neoadjuvant treatment and then continued after cystectomy as adjuvant treatment, is indicated for the treatment of adult patients with muscle invasive bladder cancer (MIBC) who are ineligible for cisplatin-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.

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.

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