Health Canada approves KEYTRUDA^® for the treatment of adult patients, in combination with paclitaxel, with or without bevacizumab, with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal carcinoma whose tumours express PD-L1 (CPS ≥1) as determined by a validated test, and who have received one or two prior systemic treatment regimens

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Kirkland, Quebec – Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced that Health Canada approved KEYTRUDA^® (pembrolizumab for injection), in combination with paclitaxel, with or without bevacizumab, for the treatment of adult patients with platinum-resistant epithelial ovarian, fallopian tube or primary peritoneal carcinoma whose tumors express PD-L1 with a Combined Positive Score (CPS) ≥1 as determined by a validated test, and who have received one or two prior systemic treatment regimens.

“At Merck Canada, our driving purpose is to deliver innovations that make a real difference for patients. This approval marks an important moment for women facing difficult-to-treat ovarian cancer, as it provides a new immunotherapy option for their treatment,” said André Galarneau, Executive Director of the Oncology Business Unit at Merck Canada.

For complete information, refer to the KEYTRUDA^® product monograph.

About Platinum-Resistant Ovarian Cancer

According to the latest available data from the Canadian Cancer Society, approximately 3,100 Canadian women were diagnosed with ovarian cancer in 2025, and approximately 2,000 died from the disease. Epithelial ovarian cancer is the most common type of ovarian cancer, making up approximately 85% – 95% of cases. It starts in the cells that cover the epithelium of the fallopian tube or the ovary.

Research indicates that approximately 85% of patients with epithelial ovarian cancer experienced recurrence and eventual treatment resistance following initial treatment with platinum-based chemotherapy. In one study, approximately 25% of patients developed platinum-resistance within six months of completing their first-line platinum-based chemotherapy treatment, a condition defined as platinum-resistant ovarian cancer. The 5-year survival for ovarian cancer is approximately 40-50 %.

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 about our operations in Canada, visit www.merck.ca and connect with us on LinkedIn @MerckCanada.

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. 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, 2025 and the company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site (www.sec.gov).

CA-NON-04695

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