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FDA Approves Merck’s KEYTRUDA® (Pembrolizumab) for First-Line Treatment of Patients with Unresectable or Metastatic MSI-H or dMMR Colorectal Cancer, First Single-Agent, Anti-PD-1 Therapy Approved for the First-Line Treatment of These Patients

On June 29, 2020, Merck (NYSE: MRK), known as MSD outside the United States and Canada, announced that the U.S. Food and Drug Administration (FDA) has approved KEYTRUDA (, Merck’s anti-PD-1 therapy, as monotherapy for the first-line treatment of patients with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) colorectal cancer. The approval is based on results from the Phase 3 KEYNOTE-177 trial, in which KEYTRUDA significantly reduced the risk of disease progression or death by 40% (HR=0.60 [95% CI, 0.45-0.80; p=0.0004]) compared with chemotherapy, the current standard of care. In the study, treatment with KEYTRUDA also more than doubled median progression-free survival (PFS) compared with chemotherapy (16.5 months [95% CI, 5.4-32.4] versus 8.2 months [95% CI, 6.1-10.2]). “Today’s approval has the potential to change the treatment paradigm for the first-line treatment of patients with MSI-H colorectal cancer, based on the important findings from KEYNOTE-177 that showed KEYTRUDA monotherapy demonstrated superior progression-free survival compared to standard of care chemotherapy,” said Dr. Roy Baynes, Senior Vice President and Head of Global Clinical Development, Chief Medical Officer, Merck Research Laboratories. “Our commitment to pursuing biomarker research continues to help us bring new treatments to patients, particularly for those who have few available options.” Immune-mediated adverse reactions, which may be severe or fatal, can occur with KEYTRUDA, and these include pneumonitis, colitis, hepatitis, endocrinopathies, nephritis and renal dysfunction, severe skin reactions, solid organ transplant rejection, and complications of allogeneic hematopoietic stem cell transplantation (HSCT). Based on the severity of the adverse reaction, KEYTRUDA should be withheld or discontinued and corticosteroids administered if appropriate. KEYTRUDA can also cause severe or life-threatening infusion-related reactions. Based on its mechanism of action, KEYTRUDA can cause fetal harm when administered to a pregnant woman. For more information, see “Selected Important Safety Information” below.
This approval was granted less than one month following the submission of a new supplemental Biologics License Application (sBLA), which was reviewed under the FDA’s Real-Time Oncology Review (RTOR) pilot program.

This review also was conducted under Project Orbis, an initiative of the FDA Oncology Center of Excellence that provides a framework for concurrent submission and review of oncology drugs among its international partners. For this application, a modified Project Orbis was undertaken, and the FDA is collaborating with the Australian Therapeutic Goods Administration, Health Canada, and Swissmedic on their ongoing review of the application.
“Patients with unresectable or metastatic MSI-H colorectal cancer have historically faced poor outcomes, and, until today, chemotherapy-containing regimens were the only FDA-approved first-line treatment options,” said Luis A. Diaz, MD, Head of the Division of Solid Tumor Oncology, Memorial Sloan Kettering Cancer Center.

“In patients who were treated with KEYTRUDA and responded (n=67) in the KEYNOTE-177 trial, 43% of patients experienced a duration of response lasting two years or longer. This approval helps address the unmet need to provide a new monotherapy treatment option for patients.”


The approval was based on data from KEYNOTE-177 (NCT02563002), a multi-center, randomized, open-label, active-controlled trial that enrolled 307 patients with previously untreated unresectable or metastatic MSI-H or dMMR colorectal cancer. Microsatellite instability (MSI) or mismatch repair (MMR) tumor status was determined locally using polymerase chain reaction (PCR) or immunohistochemistry, respectively. Patients with autoimmune disease or a medical condition that required immunosuppression were ineligible.

Patients were randomized 1:1 to receive KEYTRUDA 200 mg intravenously every three weeks or investigator’s choice of the following chemotherapy regimens given intravenously every two weeks:

--mFOLFOX6 (oxaliplatin, leucovorin, and fluorouracil) or mFOLFOX6 in combination with either bevacizumab or cetuximab: oxaliplatin 85 mg/m2, leucovorin 400 mg/m2 (or levoleucovorin 200 mg/m2), and fluorouracil 400 mg/m2 bolus on Day 1, then fluorouracil 2,400 mg/m2 over 46-48 hours; plus bevacizumab 5 mg/kg on Day 1 or cetuximab 400 mg/m2 on first infusion, then 250 mg/m2 weekly.

--FOLFIRI (irinotecan, leucovorin, and fluorouracil) or FOLFIRI in combination with either bevacizumab or cetuximab: irinotecan 180 mg/m2, leucovorin 400 mg/m2 (or levoleucovorin 200 mg/m2), and fluorouracil 400 mg/m2 bolus on Day 1, then fluorouracil 2,400 mg/m2 over 46-48 hours; plus bevacizumab 5 mg/kg on Day 1 or cetuximab 400 mg/m2 on first infusion, then 250 mg/m2 weekly.

Treatment with KEYTRUDA or chemotherapy continued until Response Evaluation Criteria in Solid Tumors (RECIST) v1.1-defined progression of disease as determined by the investigator or unacceptable toxicity. Patients treated with KEYTRUDA without disease progression could be treated for up to 24 months. Assessment of tumor status was performed every nine weeks. Patients randomized to chemotherapy were offered KEYTRUDA at the time of disease progression.
The main efficacy outcome measure was progression-free survival (PFS), as assessed by blinded independent central review (BICR) according to RECIST v1.1, modified to follow a maximum of 10 target lesions and a maximum of five target lesions per organ, and overall survival (OS). Additional efficacy outcome measures were objective response rate (ORR) and duration of response (DOR).

Patients were enrolled and randomized to KEYTRUDA (n=153) or chemotherapy (n=154). The baseline characteristics of these 307 patients were: median age of 63 years (range, 24 to 93), 47% age 65 or older; 50% male; 75% White and 16% Asian; 52% had an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0, and 48% had an ECOG PS of 1; and 27% received prior adjuvant or neoadjuvant chemotherapy.

Among the 154 patients randomized to receive chemotherapy, 143 received chemotherapy per the protocol. Of these 143 patients, 56% received mFOLFOX6, 44% received FOLFIRI, 70% received bevacizumab plus mFOLFOX6 or FOLFIRI, and 11% received cetuximab plus mFOLFOX6 or FOLFIRI. The median follow-up time was 27.6 months (range, 0.2 to 48.3 months).

In this study, KEYTRUDA monotherapy significantly reduced the risk of disease progression or death by 40% (HR=0.60 [95% CI, 0.45-0.80; p=0.0004]) and showed a median PFS of 16.5 months (95% CI, 5.4-32.4) compared with 8.2 months (95% CI, 6.1-10.2) for patients treated with chemotherapy. For PFS, in the KEYTRUDA arm, there were 82 patients (54%) with an event versus 113 patients (73%) in the chemotherapy arm. At the time of the PFS analysis, the OS data were not mature (66% of the required number of events for the OS final analysis).

For patients treated with KEYTRUDA, the ORR was 44% (95% CI, 35.8-52.0), with a complete response rate of 11% and a partial response rate of 33%, and for patients treated with chemotherapy, the ORR was 33% (95% CI, 25.8-41.1), with a complete response rate of 4% and a partial response rate of 29%. Median DOR was not reached (range, 2.3+ to 41.4+) with KEYTRUDA versus 10.6 months (range, 2.8 to 37.5+) with chemotherapy.

Based on 67 patients with a response in the KEYTRUDA arm and 51 patients with a response in the chemotherapy arm, 75% in the KEYTRUDA arm had a DOR greater than or equal to 12 months versus 37% in the chemotherapy arm, and 43% in the KEYTRUDA arm had a DOR greater than or equal to 24 months versus 18% in the chemotherapy arm.

Among the 153 patients with MSI-H or dMMR colorectal cancer treated with KEYTRUDA, the median duration of exposure to KEYTRUDA was 11.1 months (range, 1 day to 30.6 months). Adverse reactions occurring in patients with MSI-H or dMMR colorectal cancer were similar to those occurring in 2,799 patients with melanoma or non-small cell lung cancer treated with KEYTRUDA as a single agent.


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

Merck has the industry’s largest immuno-oncology clinical research program. There are currently more than 1,200 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.


For more than 125 years, Merck, known as MSD outside of the United States and Canada, has been inventing for life, bringing forward medicines and vaccines for many of the world’s most challenging diseases in pursuit of the company’s mission to save and improve lives. Merck demonstrates its commitment to patients and population health by increasing access to health care through far-reaching policies, programs, and partnerships. Today, Merck continues to be at the forefront of research to prevent and treat diseases that threaten people and animals--including cancer, infectious diseases such as HIV and Ebola, and emerging animal diseases – as the company aspires to be the premier research-intensive biopharmaceutical company in the world. For more information, visit

[Merck Press Release] [Merck] [KEYTRUDA (Pembrolizumab)]