KEYTRUDA® (pembrolizumab) Plus Chemotherapy Significantly Improved Overall Survival Versus Chemotherapy Alone as First-Line Treatment for Unresectable Advanced Pleural Mesothelioma

Merck (NYSE: MRK), known as MSD outside of the United States and Canada, and the Canadian Cancer Trials Group (CCTG) today announced results from the Phase 3 CCTG IND.227/KEYNOTE-483 trial evaluating KEYTRUDA, Merck’s anti-PD-1 therapy, plus chemotherapy as first-line treatment for patients with unresectable advanced pleural mesothelioma. At the final analysis of the study, KEYTRUDA plus chemotherapy significantly improved overall survival (OS), reducing the risk of death by 21% (HR=0.79 [95% CI, 0.64-0.98]; two-sided p value=0.0324), with a median OS of 17.3 months (95% CI, 14.4-21.3) versus 16.1 months (95% CI, 13.1-18.2) for chemotherapy alone. These late-breaking data are being presented today during an oral abstract session at the 2023 American Society of Clinical Oncology (ASCO) Annual Meeting (abstract #LBA8505) and are being discussed with regulatory authorities worldwide.

“Patients with pleural mesothelioma are usually diagnosed at an advanced stage, when the five year survival rate is only 12% and curative surgery is not an option,” said Dr. Lesley Seymour, Director of the Investigational New Drug program at CCTG, and Senior Investigator for IND.227. “The addition of pembrolizumab to platinum-pemetrexed in our study resulted in significantly improved overall survival, progression-free survival and objective response rates compared to platinum-pemetrexed alone, regardless of PD-L1 expression. This regimen represents a potential new treatment option for patients with advanced pleural mesothelioma.”

“These results support the potential of KEYTRUDA plus chemotherapy as a new first-line option for patients with advanced pleural mesothelioma, who currently have limited treatment options,” said Dr. Gregory Lubiniecki, Vice President, Global Clinical Development, Merck Research Laboratories. “These data demonstrate our commitment to improving outcomes for patients with different types of thoracic cancer through our expansive clinical development program and research evaluating KEYTRUDA in new, difficult-to-treat tumors.”

Study design and additional data from IND.227/KEYNOTE-483

IND.227/KEYNOTE-483 is a randomized, open-label Phase 2/3 trial (, NCT02784171) sponsored and conducted by CCTG in collaboration with National Cancer Institute of Naples (NCIN) and Intergroupe Francophone de Cancérologie Thoracique (IFCT). Merck provided KEYTRUDA and support for the trial. The trial evaluated KEYTRUDA plus chemotherapy versus chemotherapy alone for the treatment of patients with unresected advanced pleural mesothelioma. The primary endpoint of the study is OS, and secondary endpoints include progression-free survival (PFS) and objective response rate (ORR) as assessed by blinded independent central review (BICR) per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST v1.1) modified for mesothelioma, safety and quality of life. The Phase 3 part of the trial enrolled 440 patients who were randomized to receive:

  • KEYTRUDA (200 mg intravenously [IV] every three weeks [Q3W] for up to 35 cycles) plus pemetrexed (500 mg/m2 Q3W for six cycles) and cisplatin (75 mg/m2 Q3W for six cycles; carboplatin substitution [AUC 5-6 Q3W for six cycles] was permitted), or
  • Pemetrexed and cisplatin (carboplatin substitution was permitted) alone.

PFS was also significantly improved for KEYTRUDA plus chemotherapy compared to chemotherapy alone (HR=0.80 [95%CI, 0.65-0.99], two-sided p value = 0.0372; median PFS 7.13 months versus 7.16 months respectively). At 12 months, the estimated PFS rate was 26% for KEYTRUDA plus chemotherapy versus 17% for chemotherapy alone. The ORR was significantly higher for KEYTRUDA plus chemotherapy versus chemotherapy alone (62% versus 38%, p<0.0001).

The safety profile of KEYTRUDA plus chemotherapy in this study was consistent with previously reported studies. Adverse events related to study treatment of grade 3 or 4 occurred in 27% of patients in the KEYTRUDA plus chemotherapy arm, and 15% of patients on the chemotherapy-alone arm. The most common grade ≥3 adverse events in the KEYTRUDA arm were fatigue (7%), nausea (5%) and febrile neutropenia (5%); the corresponding values for the chemotherapy arm were 6%, 1% and 1%. KEYTRUDA-related adverse events resulting in discontinuation of KEYTRUDA occurred in 16% of patients receiving KEYTRUDA plus chemotherapy.

About mesothelioma

Mesothelioma is a type of cancer that starts in the linings of certain parts of the body, including the chest, abdomen, heart and testicles. Worldwide, it is estimated there were more than 30,000 new cases of mesothelioma diagnosed and more than 26,000 deaths from the disease in 2020. Pleural mesothelioma, which develops in the lining of the lungs, is the most common form of mesothelioma, accounting for about 75% of all cases. Pleural mesothelioma often progresses rapidly, and the five-year survival rate is only 12%. Although incidence of mesothelioma has gradually declined in the U.S., continued use of and exposure to asbestos around the world has resulted in increasing global rates of this aggressive disease.

About the Canadian Cancer Trials Group

The Canadian Cancer Trials Group (CCTG) is a cancer clinical trials research cooperative that develops, conducts and analyses phase I-III trials to test anti-cancer and supportive therapies at over 85 hospitals and cancer centres across Canada and internationally. From their operations centre at Queen’s University, CCTG has supported more than 600 trials enrolling 100,000 patients from 40 countries on 6 continents through a global network of 20,000 investigators and clinical trial staff. CCTG is a national program of the Canadian Cancer Society (CCS) and their aim is to improve survival and quality of life for all people with cancer. CCTG IND.227 was supported by a grant from CCS (707213).


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