Merck’s KEYTRUDA® (pembrolizumab) Plus Chemotherapy Showed Statistically Significant Improvement in Pathological Complete Response (pCR) Rate as Neoadjuvant Therapy Versus Chemotherapy in High-Risk, Early-Stage ER+/HER2- Breast Cancer

KEYTRUDA plus chemotherapy before surgery significantly improved pCR rate compared to neoadjuvant placebo plus chemotherapy (24.3% vs. 15.6%, respectively)

KEYNOTE-756 is the first positive Phase 3 study with an immunotherapy regimen to demonstrate a statistically significant improvement in pCR rate in the neoadjuvant setting for this patient population

RAHWAY, N.J.–(BUSINESS WIRE)–Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced the first presentation of results from the neoadjuvant part of the Phase 3 KEYNOTE-756 trial investigating KEYTRUDA, Merck’s anti-PD-1 therapy, in combination with chemotherapy as neoadjuvant treatment, followed by KEYTRUDA plus endocrine therapy as adjuvant treatment, for patients with high-risk, early-stage estrogen receptor-positive, human epidermal growth factor receptor 2-negative (ER+/HER2-) breast cancer. KEYTRUDA plus chemotherapy before surgery met one of its dual primary endpoints of pathological complete response (pCR), demonstrating a statistically significant improvement in pCR rate compared to placebo plus chemotherapy. The pCR rate increased from 15.6% in patients treated with neoadjuvant chemotherapy alone (n=100/643) to 24.3% in patients treated with neoadjuvant KEYTRUDA plus chemotherapy (n=154/635), an estimated increase of 8.5 percentage points (p=0.00005). A pCR rate is defined as a lack of all signs of cancer in tissue samples analyzed following completion of neoadjuvant therapy and definitive surgery (ypT0/Tis ypN0). The trial is currently continuing without changes to evaluate event-free survival (EFS), the other dual primary endpoint of the study, per the trial design.

These pCR results are being featured today during a late-breaking proffered paper session at the European Society for Medical Oncology (ESMO) Congress 2023 (abstract #LBA21). The safety profile of KEYTRUDA in this trial was consistent with that observed in previously reported studies.

“Results from KEYNOTE-756, together with our work across our oncology portfolio, demonstrate the progress we are making in earlier stages of certain cancers, including breast cancer,” said Dr. Gursel Aktan, vice president, global clinical development, Merck Research Laboratories. “KEYNOTE-756 is the first positive Phase 3 trial with an immunotherapy regimen to demonstrate a statistically significant improvement in pCR rate in the neoadjuvant setting for patients with high-risk, early-stage ER-positive, HER2-negative breast cancer. These results support the potential of a KEYTRUDA-based regimen for more patients with difficult-to-treat types of early-stage breast cancer.”

“With high rates of recurrence, patients with high-risk, early-stage ER-positive, HER2-negative breast cancer are in need of new treatment options,” said Dr. Fatima Cardoso, director of the Breast Unit of the Champalimaud Clinical Centre, Lisbon, Portugal, and co-principal investigator. “While we await results from the dual primary endpoint of event-free survival, we are encouraged by data from KEYNOTE-756 in which the pembrolizumab-based regimen demonstrated a statistically significant improvement in pathological complete response rate compared to chemotherapy.”

“The goal of neoadjuvant therapy is to reduce the size of the tumor prior to surgery,” said Dr. Aditya Bardia, attending physician, medical oncology, Massachusetts General Hospital, director, breast cancer research, Massachusetts General Cancer Center, associate professor, Harvard Medical School and global co-principal investigator. “In KEYNOTE-756, 24.3% of patients treated with neoadjuvant pembrolizumab plus chemotherapy achieved a pathological complete response, a meaningful endpoint demonstrating there was no cancer in tissue samples analyzed and obtained at the time of definitive surgery following completion of neoadjuvant therapy for these patients. Overall, the study met one of its primary endpoints and we are looking forward to data for the other dual primary endpoint of event-free survival in the future.”

As announced, data spanning more than 15 types of cancer are being presented from Merck’s broad oncology portfolio and investigational pipeline at ESMO Congress 2023.

Study design and additional data from KEYNOTE-756

KEYNOTE-756 is a randomized, double-blind, Phase 3 trial (ClinicalTrials.gov, NCT03725059) that is fully accrued, evaluating KEYTRUDA in combination with chemotherapy as neoadjuvant treatment, followed by adjuvant treatment with KEYTRUDA plus endocrine therapy for the treatment of high-risk, early-stage ER+/HER2- breast cancer. The dual primary endpoints are pCR rate (ypT0/Tis ypN0) and EFS, and secondary endpoints include overall survival. The trial enrolled 1,240 patients who were randomized 1:1 to receive:

• KEYTRUDA (200 mg every three weeks [Q3W]) plus chemotherapy (paclitaxel weekly) for four cycles, followed by four additional cycles of KEYTRUDA in combination with chemotherapy (doxorubicin or epirubicin plus cyclophosphamide) as neoadjuvant therapy prior to surgery, followed by nine cycles of KEYTRUDA (Q3W) plus endocrine therapy (for up to 10 years) as adjuvant therapy post-surgery; or,
• Placebo (Q3W) plus chemotherapy (paclitaxel weekly) for four cycles, followed by four additional cycles of placebo in combination with chemotherapy (doxorubicin or epirubicin plus cyclophosphamide) as neoadjuvant therapy prior to surgery, followed by nine cycles of placebo (Q3W) plus endocrine therapy (for up to 10 years) as adjuvant therapy post-surgery.

Results from KEYNOTE-756 were consistent for secondary pCR definitions (ypT0 ypN0 and ypT0/Tis). In the neoadjuvant phase of the study, no new safety signals for KEYTRUDA were identified. Among all patients treated, 52.5% of those who received KEYTRUDA plus chemotherapy and 46.4% of those who received chemotherapy experienced Grade 3-5 adverse events (AEs). Treatment-related AEs in the neoadjuvant part of the study that led to discontinuation of any drug occurred in 19.1% of patients treated with KEYTRUDA plus chemotherapy and 10.1% who received chemotherapy. There was one death in the KEYTRUDA arm due to acute myocardial infarction; it was not related to KEYTRUDA.

About breast cancer

Breast cancer is one of the leading causes of cancer-related death in women worldwide, with more than two million patients diagnosed and approximately 685,000 deaths from the disease globally in 2020. In the U.S., it is estimated there will be approximately 298,000 patients diagnosed with breast cancer and 43,700 deaths from the disease in 2023. There are many different types of breast cancer and various subtypes. Of all breast cancer patients, about 70% will be diagnosed with hormone receptor-positive, HER2-negative disease. Cancer recurrence following surgery for this type of cancer is most common within five years, and patients with high-risk features have a greater chance of recurrence.

About Merck’s research in breast and gynecologic cancers

Merck is advancing research aimed at improving outcomes for patients affected by breast and gynecologic (ovarian, cervical and endometrial) cancers. Merck has a comprehensive clinical development program across these cancers comprised of more than 20 Merck-sponsored Phase 3 studies evaluating KEYTRUDA as monotherapy and in combination with other medicines. In the U.S., KEYTRUDA currently has two approved indications for triple-negative breast cancer, include one for high-risk early-stage disease, and four approved indications across certain types of advanced cervical and endometrial cancers (see indications below). Among Merck’s research efforts are trials focused on evaluating KEYTRUDA in earlier stages of these cancers, as well as identifying new combinations and coformulations with KEYTRUDA.

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 studying KEYTRUDA in earlier disease states, with more than 25 ongoing Phase 3 studies across multiple types of cancer.

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.

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.

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; Musculoske

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