Node-positive breast cancer

KEYTRUDA plus CRT is the first immunotherapy-based regimen to demonstrate a statistically significant improvement in OS in these patients RAHWAY, N.J.--(BUSINESS WIRE)-- Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced that the Phase 3 KEYNOTE-A18 trial, also known as ENGOT-cx11/GOG-3047, investigating KEYTRUDA, Merck’s anti-PD-1 therapy, in combination with chemoradiotherapy (CRT) met its primary endpoint of overall survival (OS) for the treatment of newly diagnosed patients with high-risk locally advanced cervical cancer. At a pre-specified interim analysis conducted by an independent Data Monitoring Committee, KEYTRUDA in combination with concurrent CRT showed a statistically significant and clinically meaningful improvement in OS versus concurrent CRT alone. The safety pro KEYTRUDA in this trial was consistent with that observed in previously reported studies; no new safety signals were identified. Results will be presented at an upcoming medical meeting and shared with regulatory authorities worldwide. As previously reported, KEYNOTE-A18 met its other primary endpoint of progression-free survival (PFS) in 2023. These PFS data were presented at the European Society for Medical Oncology (ESMO) Congress 2023 and supported the U.S. Food and Drug Administration's approval of KEYTRUDA in combination with CRT for the treatment of patients with FIGO (International Federation of Gynecology and Obstetrics) 2014 Stage III-IVA cervical cancer in January 2024. “This is the first Phase 3 trial in which an immunotherapy-based regimen has shown a statistically significant and clinically meaningful improvement in overall survival compared to chemoradiotherapy alone,” said Dr. Gursel Aktan, vice president, global clinical development, Merck Research Laboratories. “Building on the positive progression-free survival findings from this study, these results underscore our commitment to exploring the role of KEYTRUDA across different types of cancers in earlier stages of disease, where there is a greater potential for better outcomes.” “These findings are important for patients and the medical community alike and reinforce previous data from the KEYNOTE-A18 trial, now showing this regimen has the potential to extend the lives of patients with locally advanced cervical cancer,” said Prof. Domenica Lorusso, the study’s overall principal investigator, lead investigator for ENGOT, and professor of Obstetrics and Gynecology at Humanitas University. In the U.S., KEYTRUDA has two additional approved indications in cervical cancer: in combination with chemotherapy, with or without bevacizumab, for the treatment of patients with persistent, recurrent, or metastatic cervical cancer whose tumors express PD-L1 [Combined Positive Score (CPS) ≥1] as determined by an FDA-approved test; and as a single agent, 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. About KEYNOTE-A18/ENGOT-cx11/GOG-3047 KEYNOTE-A18, also known as ENGOT-cx11/GOG-3047, is a randomized, double-blind Phase 3 trial (ClinicalTrials.gov, NCT04221945) sponsored by Merck and conducted in collaboration with the European Network for Gynecological Oncology Trial (ENGOT) groups and the GOG Foundation, Inc. (GOG) investigating KEYTRUDA in combination with CRT (cisplatin and external beam radiotherapy [EBRT] followed by brachytherapy [BT]) compared to placebo plus concurrent CRT for the treatment of newly diagnosed high-risk (stage IB2-IIB with lymph node-positive disease, and stage III-IVA with and without lymph node-positive disease) locally advanced cervical cancer where patients are treated with definitive intent. The primary endpoints are PFS and OS, and secondary endpoints include complete response rate, objective response rate and safety. The trial enrolled 1,060 patients with cervical cancer who had not previously received any definitive surgery, radiation, or systemic therapy for cervical cancer. Patients were randomized (1:1) to receive either: KEYTRUDA (200 mg intravenously [IV]) every three weeks (Q3W) for five cycles concurrent with cisplatin (40 mg/m2 IV) weekly for five cycles (an optional sixth infusion could be administered per local practice) and radiotherapy (EBRT followed by BT), followed by KEYTRUDA (400 mg IV) every six weeks (Q6W) for 15 cycles; Placebo IV Q3W for five cycles concurrent with cisplatin (40 mg/m2 IV) weekly for five cycles (an optional sixth infusion could be administered per local practice) and radiotherapy (EBRT followed by BT), followed by placebo IV Q6W for 15 cycles. About cervical cancer Cervical cancer forms in the cells lining the cervix, which is the lower part of the uterus. All women are at risk for cervical cancer, and it is most frequently diagnosed between the ages of 35 and 44. While screenings and prevention have resulted in declining cervical cancer rates, the disease continues to affect many people in the U.S. and around the world. Cervical cancer is the fourth most common cancer in women globally. In the U.S., it is estimated there will be approximately 13,820 new patients diagnosed with invasive cervical cancer and about 4,360 deaths from the disease in 2024. 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, including one for high-risk early-stage disease, and five approved indications across certain types of 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 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. 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. 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 PD-1 or the 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. 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 treatment 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, and palmar-plantar erythrodysesthesia. 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 events 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 mUC. 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 mUC. 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 versus standard of care for diarrhea (53% vs 44%) and nausea (49% vs 44%). The most common adverse reactions (reported in ≥20%) of 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 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 discontinued due to adverse reactions in 15% of patients. The most common adverse reaction resulting in permanent discontinuation of KEYTRUDA (≥1%) were infections (1.8%) and diarrhea (1%). 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%). 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 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%). 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. 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. 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 Carcinoma 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. 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 carcinoma (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). 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. Endometrial Carcinoma KEYTRUDA, as a single agent, is indicated for the treatment of 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. Merck’s focus on cancer Our goal is to translate breakthrough science into innovative oncology medicines to help people with cancer worldwide. At Merck, the potential to bring new hope to people with cancer drives our purpose and supporting accessibility to our cancer medicines is our commitment. As part of our focus on cancer, Merck is committed to exploring the potential of immuno-oncology with one of the largest development programs in the industry across more than 30 tumor types. We also continue to strengthen our portfolio through strategic acquisitions and are prioritizing the development of several promising oncology candidates with the potential to improve the treatment of advanced cancers. For more information about our oncology clinical trials, visit . 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 and connect with us on X (formerly Twitter), Facebook, Instagram, YouTube and LinkedIn. 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 ( ). Please see Prescribing Information for KEYTRUDA (pembrolizumab) at and Medication Guide for KEYTRUDA at . View source version on businesswire.com: Contacts Media Contacts: Julie Cunningham (617) 519-6264 John Infanti (609) 500-4714 Investor Contacts: Peter Dannenbaum (732) 594-1579 Damini Chokshi (732) 594-1577 Source: Merck & Co., Inc. View this news release online at:

Record DANYELZA® net product revenues of $23.4 million and $84.3 million for Q4 and FY 2023 represents YoY growth of 42% and 71%, respectively Cash and cash equivalents of $78.6 million as of December 31, 2023; Reiterate anticipated cash runway into 2027 Management announces full year 2024 financial guidance The Company will host a conference call on Friday, March 1, 2024, at 8:00 a.m. ET NEW YORK, Feb. 29, 2024 (GLOBE NEWSWIRE) -- Y-mAbs Therapeutics Inc. (the “Company” or “Y-mAbs”) (Nasdaq: YMAB), a commercial-stage biopharmaceutical company focused on the development and commercialization of novel radioimmunotherapy and antibody-based therapeutic products for the treatment of cancer, today reported financial results for the quarter and full year ended December 31, 2023. “Y-mAbs has made significant progress across both the development and commercial fronts of our business resulting in a momentous 2023,” said Mike Rossi, President and Chief Executive Officer. “From a development standpoint, we demonstrated proof-of-concept of our Self-Assembly DisAssembly (“SADA”) Pretargeted Radioimmunotherapy (“PRIT”) platform, showing that GD2-SADA targets and binds to tumors in humans in a Phase 1 trial. We continue to expect to present mature data from Part A of our Phase 1 GD2-SADA clinical trial at a medical meeting in the second half of this year. In addition, we look forward to initiating our CD38-SADA Phase 1 trial this year. While we continue to advance our SADA PRIT platform and programs through clinical development, we are supported by the solid commercial performance of DANYELZA® (naxitamab-gqgk). We achieved record quarterly and annual net product revenues, and sales continue trending upward as more high-volume centers deploy DANYELZA for their patients. Our strong financial foundation and operational performance continue to fuel our mission of providing better and safe therapies for a variety of cancers and improve the lives of patients and their families.” Fourth Quarter 2023 and Recent Corporate Developments In December 2023, Y-mAbs announced that it was added to the NASDAQ Biotechnology Index (NASDAQ: NBI), effective December 18, 2023. On October 18, 2023, Y-mAbs announced that its Board of Directors appointed radiopharmaceutical industry veteran Mr. Rossi as President and Chief Executive Officer, effective November 6, 2023. Thomas Gad, who founded Y-mAbs in 2015 and has served as Interim Chief Executive Officer since 2022, transitioned to the role of Vice Chairman of the Board of Directors and Chief Business Officer. On October 17, 2023, the U.S. FDA cleared Y-mAbs’ IND for CD38-SADA, marking the second clinical development program utilizing the Company’s novel SADA PRIT technology platform. On October 16, 2023, Y-mAbs announced the publication of a study of naxitamab-based chemoimmunotherapy (“HITS”) study in patients with refractory high-risk neuroblastoma (“HR-NB”) in the journal Cancers. The study investigated the HITS combination in patients with HR-NB who did not respond well to induction or refractory therapy. Patients who received HITS immediately after induction had higher response rates (47% vs. 18%) and superior estimated three-year overall survival (85% vs. 29%), compared with those who received the same combination regimen later in the course of treatment. The publication is entitled, “Early Salvage Chemo-Immunotherapy with Irinotecan, Temozolomide and Naxitamab Plus GM-CSF (HITS) for Patients with Primary Refractory High-Risk Neuroblastoma Provide the Best Chance for Long-Term Outcomes.” On October 11, 2023, Y-mAbs showcased three poster presentations, in addition to an online publication, of DANYELZA at the 55th Congress of the International Society of Pediatric Oncology in Ottawa, Canada. Financial Results Revenues DANYELZA net product revenues were $23.4 million and $84.3 million for the quarter and year ended December 31, 2023, which represented increases of 42% and 71%, respectively, over $16.4 million and $49.3 million in the comparable periods of 2022. The DANYELZA net product revenues of $23.4 million in the fourth quarter of 2023, represented a favorable 17% increase compared to the third quarter of 2023, primarily driven by increased U.S. sales. As of December 31, 2023, Y-mAbs has delivered DANYELZA to 58 centers across the U.S. since initial launch, with ten new accounts added in 2023. The Company did not have license revenues in the quarter ended December 31, 2023 and had license revenues of $0.5 million for the year ended December 31, 2023. The Company reported license revenues of $15.0 million and $16.0 million for the quarter and year ended December 31, 2022. License revenues for the year ended December 31, 2023 arose from the September 2023 achievement of marketing authorization for DANYELZA in Mexico under the Company’s sublicense agreement with Adium. During the quarter and year ended December 31, 2022, the Company recognized a regulatory-based milestone of $15.0 million from SciClone Pharmaceuticals International Ltd. for the conditional approval of DANYELZA in China. Operating Costs and Expenses Cost of Goods Sold Cost of goods sold was $2.0 million for the quarters ended December 31, 2023 and 2022, respectively. The cost of goods sold was $11.4 million and $7.5 million for the years ended December 31, 2023, and 2022, respectively. The increase in cost of goods sold in both periods was primarily driven by increased product revenues. The Company experienced inventory write-downs of $0.8 million and $1.2 million in the years ended December 31, 2023, and December 31, 2022, respectively. The Company’s gross margin, excluding the 2023 and 2022 inventory write-downs, increased in the fourth quarter of 2023 to 91% due to the gross margin increase from higher U.S. revenues. The Company’s gross margin, excluding the 2023 and 2022 inventory write-downs, remained constant at 87% for the year ended December 31, 2023, compared to the year ended December 31, 2022, which was the net impact of the gross margin increase from higher U.S. revenues, offset by increased revenues from geographic areas outside the U.S., which were at a lower gross margin. The Company defines gross margin as net product revenues less cost of goods sold divided by net product revenues. Research and Development Research and development expenses were $13.4 million for the quarter ended December 31, 2023, a reduction of 32% compared to $19.8 million for the quarter ended December 31, 2022. The $6.4 million decrease was primarily due to decreased spending on deprioritized programs, which resulted in a $3.1 million decrease in outsourced manufacturing, a $2.0 million decrease in personnel-related costs, inclusive of stock-based compensation, and a $2.2 million decrease in outsourced research and supplies, partially offset by a $1.2 million increase in clinical trials expenses. For the year ended December 31, 2023, research and development expenses were $54.2 million, a reduction of 41% compared to $91.6 million for the year ended December 31, 2022. The $37.4 million decrease was primarily due to decreased spending on deprioritized programs, resulting in a $21.0 million decrease in outsourced manufacturing, a $9.0 million decrease in outsourced research and supplies, a $6.1 million decrease in personnel-related costs, inclusive of stock-based compensation, and a $2.0 million decrease in clinical trials, partially offset by a $3.8 million increase in milestones and license acquisition costs primarily related to a $4.1 million increase in milestones accrued under the Company’s SADA License Agreement, as the Company determined that achievement of certain time-based clinical milestones within the agreement are probable based on the availability of data and the assessment of clinical progress in the year of 2023. The $2.0 million and $6.1 million decreases in personnel-related costs during the quarter and year ended December 31, 2023, respectively, were driven by the headcount reduction as part of the Company’s restructuring plan announced in January 2023. The expense reduction in the year ended December 31, 2023 was partially offset by severance charges recognized in conjunction with the restructuring plan. Selling, General, and Administration Selling, general, and administrative expenses were $11.1 million for the quarter ended December 31, 2023, which was a slight increase compared to $10.8 million for the quarter ended December 31, 2022. For the year ended December 31, 2023, selling, general, and administrative expenses were $44.9 million, a reduction of 26% compared to $60.9 million for the year ended December 31, 2022. The $16.0 million decrease in selling, general and administrative expenses was primarily attributable to a $10.9 million charge in the year ended December 31, 2022 related to contractual severance-related benefits for the Company’s former Chief Executive Officer, and, to a lesser extent, a $3.4 million decrease in commercialization expenses, inclusive of costs of incurred in 2022 in anticipation of a potential omburtamab launch. Interest and Other Income/(Loss) Interest and other income/(loss) was relatively unchanged at $2.4 million as compared to $2.3 million during the quarters ended December 31, 2023 and 2022, respectively. Interest and other income/(loss) was $4.8 million of income as compared to $0.8 million of loss for the years ended December 31, 2023 and 2022, respectively. The $5.6 million favorable change in interest and other income/(loss), reflects increased interest income for the year ended December 31, 2023, and was driven by increased money market fund investment income. The Company recorded impairment charges totaling $1.4 million related to the write down of two Secured Promissory Notes during the year ended December 31, 2022. Net Loss Y-mAbs reported a net loss for the quarter ended December 31, 2023, of $1.0 million, or ($0.02) per basic and diluted share, compared to net income of $1.2 million, or $0.03 per basic and diluted share, for the quarter ended December 31, 2022. The net income for the quarter ended December 31, 2022, was after $15.0 million of license revenue recognized in the fourth quarter of 2022. For the year ended December 31, 2023, the Company reported a net loss of $21.4 million, or ($0.49) per basic and diluted share, compared to a net loss of $95.6 million, or ($2.19) per basic and diluted share, for the year ended December 31, 2022. The favorable decrease in net loss for the year ended December 31, 2023, was primarily driven by an increase in U.S. and international DANYELZA product revenues for the year ended December 31, 2023, as well as decreased research and development cost, and decreased selling, general and administration cost. Cash and Cash Equivalents As of December 31, 2023, Y-mAbs had approximately $78.6 million in cash and cash equivalents which, together with anticipated DANYELZA product revenues, is expected to support operations as currently planned into 2027. This estimate reflects the Company’s current business plan that is supported by assumptions that may prove to be inaccurate, such that Y-mAbs could use its available capital resources sooner than it currently expects. 2024 Financial Guidance Anticipated DANYELZA® net product revenues of between $95 million and $100 million; Anticipated operating expenses of between $115 million and $120 million; Anticipated total annual cash burn of between $15 million and $20 million; and Cash and cash equivalents anticipated to continue to support operations as currently planned into 2027. Webcast and Conference Call Y-mAbs will host a conference call on Friday, March 1, 2024, at 8:00 a.m. ET. To participate in the call, please use the following dial-in information. Investors (domestic): Investors (international): Conference ID: (877) 407-0792 (201) 689-8263 13744085 To access a live webcast of the update, please use this link. Prior to the call and webcast, a slide presentation pertaining to our quarterly earnings will be made available in the investor relations section of our website, shortly before the call begins. About Y-mAbs Y-mAbs is a commercial-stage biopharmaceutical company focused on the development and commercialization of novel, radioimmunotherapy and antibody-based therapeutic cancer products. The Company’s technologies include its investigational Self-Assembly DisAssembly (“SADA”) ​Pretargeted Radioimmunotherapy Platform (“PRIT”)​ and bispecific antibodies generated using the Y-BiClone platform. The Company’s broad and advanced product pipeline includes the anti-GD2 therapy DANYELZA® (naxitamab-gqgk), the first FDA-approved treatment for patients with relapsed or refractory high-risk neuroblastoma in the bone or bone marrow after a partial response, minor response, or stable disease to prior therapy. Forward-Looking Statements Statements in this press release about future expectations, plans and prospects, as well as any other statements regarding matters that are not historical facts, may constitute “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Such statements include, but are not limited to, statements about our business model, including financial outlook for 2024 and beyond, including estimated operating expenses, cash burn and DANYELZA product revenue and sufficiency of cash resources and related assumptions; implied and express statements regarding the future of the Company’s business, including with respect to expansion and its goals; the Company’s plans and strategies, development, commercialization and product distribution plans, including potential partnerships; expectations with respect to the Company’s products and product candidates, including otential territory and label expansion of DANYELZA and the potential market opportunity related thereto and potential benefits thereof, and the potential of the SADA Technology and potential benefits and applications thereof; statements with respect to DANYELZA as a growing commercial product and SADA as a differentiated radioimmunotherapy platform positioning the Company on a path to potentially transform the treatment paradigm for a variety of cancers and improve patients’ lives; expectations relating to key anticipated development milestones, including potential expansion of international commercialization efforts with respect to DANYELZA development efforts and the SADA Technology, including potential indications and applications, and the timing thereof; expectations with respect to current and future clinical and pre-clinical studies and the Company’s research and development programs, including with respect to timing and results; expectations related to the timing of the initiation and completion of regulatory submissions; additional product candidates and technologies; expectations regarding collaborations or strategic partnerships and the potential benefits thereof; expectations related to the use of cash and cash equivalents, and the need for, timing and amount of any future financing transaction; expectations with respect to the Company’s future financial performance; and other statements that are not historical facts. Words such as ‘‘anticipate,’’ ‘‘believe,’’ “contemplate,” ‘‘continue,’’ ‘‘could,’’ ‘‘estimate,’’ ‘‘expect,’’ “hope,” ‘‘intend,’’ ‘‘may,’’ ‘‘might,’’ ‘‘plan,’’ ‘‘potential,’’ ‘‘predict,’’ ‘‘project,’’ ‘‘should,’’ ‘‘target,’’ “will”, ‘‘would’’, “guidance,” and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Our product candidates and related technologies are novel approaches to cancer treatment that present significant challenges. Actual results may differ materially from those indicated by such forward-looking statements as a result of various factors, including but not limited to: risks associated with the Company’s financial condition and need for additional capital; the risks that actual results of the Company’s restructuring plan and revised business plan will not be as expected; risks associated with the Company’s development work; cost and success of the Company’s product development activities and clinical trials; the risks of delay in the timing of the Company’s regulatory submissions or failure to receive approval of its drug candidates; the risks related to commercializing any approved pharmaceutical product including the rate and degree of market acceptance of product candidates; development of sales and marketing capabilities and risks associated with failure to obtain sufficient reimbursement for products; the risks related to the Company’s dependence on third parties including for conduct of clinical testing and product manufacture; the Company’s inability to enter into partnerships; the risks related to government regulation; risks related to market approval, risks associated with protection of the Company’s intellectual property rights; risks related to employee matters and managing growth; risks related to the Company’s common stock, risks associated with macroeconomic conditions, including the conflict between Russia and Ukraine and sanctions related thereto, the state of war between Israel and Hamas and the related risk of a larger regional conflict, inflation, increased interest rates, uncertain global credit and capital markets and disruptions in banking systems; and other risks and uncertainties affecting the Company including those described in the "Risk Factors" section included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023, the Company’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2023 and future filings and reports by the Company. Any forward-looking statements contained in this press release speak only as of the date hereof, and the Company undertakes no obligation to update any forward-looking statement, whether as a result of new information, future events or otherwise. DANYELZA®, OMBLASTYS® and Y-mAbs® are registered trademarks of Y-mAbs Therapeutics, Inc. Investor Contact: Courtney Dugan VP, Head of Investor Relations cdu@ymabs.com Y-MABS THERAPEUTICS, INC. Consolidated Balance Sheets (unaudited) (in thousands, except share and per share data) As of December 31, December 31, 2023 2022 ASSETS CURRENT ASSETS Cash and cash equivalents $ 78,637 $ 105,762 Accounts receivable, net 22,454 12,531 Inventories 5,065 6,702 Other current assets 4,955 5,452 Total current assets 111,111 130,447 Property and equipment, net 224 604 Operating lease right-of-use assets 1,412 1,739 Intangible assets, net 2,631 2,986 Other assets 12,491 5,680 TOTAL ASSETS $ 127,869 $ 141,456 LIABILITIES AND STOCKHOLDERS’ EQUITY LIABILITIES Accounts payable $ 6,060 $ 14,175 Accrued liabilities 13,166 13,241 Operating lease liabilities, current portion 902 868 Total current liabilities 20,128 28,284 Accrued milestone payments 5,375 2,250 Operating lease liabilities, long-term portion 517 899 Other liabilities 864 802 TOTAL LIABILITIES 26,884 32,235 STOCKHOLDERS’ EQUITY Preferred stock, $0.0001 par value, 5,500,000 shares authorized and none issued at December 31, 2023 and December 31, 2022 - - Common stock, $0.0001 par value, 100,000,000 shares authorized at December 31, 2023 and December 31, 2022; 43,672,112 and 43,670,109 shares issued and outstanding at December 31, 2023 and December 31, 2022, respectively 4 4 Additional paid-in capital 558,002 543,929 Accumulated other comprehensive income 449 1,331 Accumulated deficit (457,470 ) (436,043 ) TOTAL STOCKHOLDERS’ EQUITY 100,985 109,221 TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY $ 127,869 $ 141,456 Y-MABS THERAPEUTICS, INC. Consolidated Statements of Net Loss and Comprehensive Loss (unaudited) (In thousands, except share and per share data) Three months ended December 31, Years ended December 31, 2023 2022 2023 2022 REVENUES Product revenue, net $ 23,363 $ 16,447 $ 84,319 $ 49,267 License revenue — 15,000 500 16,000 Total revenues 23,363 31,447 84,819 65,267 OPERATING COSTS AND EXPENSES Cost of goods sold 2,039 2,020 11,366 7,467 License royalties — — 50 100 Research and development 13,388 19,787 54,219 91,572 Selling, general, and administrative 11,135 10,793 44,856 60,939 Total operating costs and expenses 26,562 32,600 110,491 160,078 Loss from operations (3,199 ) (1,153 ) (25,672 ) (94,811 ) OTHER INCOME/(LOSS), NET Interest and other income/(loss) 2,406 2,310 4,806 (757 ) LOSS BEFORE INCOME TAXES (793 ) 1,157 (20,866 ) (95,568 ) Provision for income taxes 195 — 561 — NET INCOME/(LOSS) $ (988 ) $ 1,157 $ (21,427 ) $ (95,568 ) Other comprehensive loss Foreign currency translation (1,400 ) (3,371 ) (882 ) (40 ) COMPREHENSIVE LOSS $ (2,388 ) $ (2,214 ) $ (22,309 ) $ (95,608 ) Net income/(loss) per share attributable to common stockholders, basic $ (0.02 ) $ 0.03 $ (0.49 ) $ (2.19 ) Weighted average common shares outstanding, basic 43,627,270 43,668,690 43,645,388 43,703,663 Net income/(loss) per share attributable to common stockholders, diluted $ (0.02 ) $ 0.03 $ (0.49 ) $ (2.19 ) Weighted average common shares outstanding, diluted 43,627,270 44,692,485 43,645,388 43,703,663

Merck & Co. announced that the FDA broadened the cervical cancer label for its PD-1-targeting immunotherapy Keytruda (pembrolizumab), but stopped short of including the overall population represented in a pivotal Phase III study. This new indication – the third for Keytruda in cervical cancer – is for use in combination with chemoradiotherapy (CRT) as treatment for newly-diagnosed patients with FIGO 2014 Stage III-IVA disease.The decision was based on results from the KEYNOTE-A18 trial, which enrolled 1060 patients with high-risk, locally advanced cervical cancer who had not previously received any definitive surgery, radiation or systemic therapy for their disease. Subjects were roughly split between those with FIGO 2014 Stage III-IVA cervical cancer with either node-positive or node-negative disease, and those with FIGO 2014 Stage IB2-IIB cervical cancer with node-positive disease.PFS benefit driven by later-stage cohortResults demonstrated a significant improvement in progression-free survival (PFS) in the overall study population, although an exploratory analysis among the earlier-stage cohort suggested most of that benefit was derived from the 56% of trial participants who had Stage III-IVA disease. In this later-stage cohort, there was a PFS benefit of 41% with Keytruda versus placebo plus CRT, whereas the benefit was only 9% for the earlier-stage group. Merck noted that overall survival data were not mature at the time of the PFS analysis."Keytruda plus chemoradiotherapy is now the first anti-PD-1-based regimen approved in the US for the treatment of patients with FIGO 2014 Stage III-IVA cervical cancer regardless of PD-L1 expression," noted Gursel Aktan, vice president of global clinical development at Merck Research Laboratories.The drug was already approved in two other cervical cancer indications in the US. These included Keytruda plus chemotherapy, with or without bevacizumab, for patients with persistent, recurrent or metastatic cervical cancer whose tumours express PD-L1 (CPS ≥1). It is also approved as a single agent for patients with recurrent or metastatic cervical cancer with disease progression on or after chemotherapy whose tumours express PD-L1 (CPS ≥1).