Merck says trial of combination treatment for colon cancer failed to meet main goal

By Ciara Linnane

Combination did not demonstrate an improvement in overall survival

Merck & Co.'s stock was flat on Wednesday, after the drug company said a late-stage trial of its blockbuster cancer drug Keytruda in combination with favezelimab failed to meet the main goal of overall survival (OS) as a treatment for a type of colon cancer.

The fixed dose combination did not demonstrate an improvement in OS compared to standard of care in patients with previously treated PD-L1 positive microsatellite stable metastatic colorectal cancer, although the safety profile was consistent with previous studies.

Merck (MRK) is working on a full analysis of the data and will work with investigators to share the results with the wider scientific community.

"Metastatic colorectal cancer continues to be a challenging disease to treat, especially for the majority of patients who have microsatellite stable disease, which has had limited response to immunotherapies," said Dr. M. Catherine Pietanza, vice president, global clinical development, Merck Research Laboratories, in prepared remarks.

Keytruda is approved in the U.S. as a treatment for patients with unresectable or metastatic microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) colorectal cancer as determined by an FDA-approved test.

Between 5% and 15% of colon cancers fit into that category, according to the National Institutes of Health.

The combination of Keytruda and favezelimab is also currently being studied in certain hematologic malignancies and multiple solid tumor types, said Merck.

The Phase 3 colon cancer trial enrolled 441 patients, who received either the fixed-dose combination intravenously on day 1, and then every three weeks to cover 35 cycles; or they were given the standard of care.

Colon cancer, or rectal cancer depending on where the cancer starts, is the third most commonly diagnosed cancer and second most common cause of cancer deaths worldwide. In 2022, an estimated 1.9 million patients were diagnosed and more than 900,000 patients died from the disease.

The five-year relative survival rates in the U.S. for metastatic colon cancer and rectal cancer (stage IV) are estimated to be 13% and 18%, respectively, said the company.

Keytruda is approved for a range of indications globally and drummed up more than $25 billion in sales in 2023. In the company's most recent quarter, Keytruda sales rose 16% to $7.3 billion.

Merck's stock has gained 5.9% in the year to date, while the S&P 500 has gained 20.3%.

Read now: Merck wins first FDA approval for Keytruda as a treatment for mesothelioma

-Ciara Linnane

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09-25-24 0959ET

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