A combination of Merck & Co. and Eisai cancer medicines has failed two separate late-stage trials in a setback to the partners’ ambitions to expand use of the regimen.
In a statement Friday, the companies said a pairing of the Merck immunotherapy Keytruda and the Eisai drug Lenvima didn’t succeed in Phase 3 studies in skin and colorectal cancers.
Trial monitors stopped one study early after finding the Keytruda-Lenvima regimen wasn’t extending the lives of patients with newly diagnosed, metastatic melanoma compared to Keytruda alone.
The combination also didn’t improve survival of colorectal cancer patients whose tumors have a genetic abnormality — mismatch repair deficiency — in a separate Phase 3 trial. In that study, Merck and Eisai found a “trend toward improvement” in survival among those who had received their drugs instead of the cancer treatment Stivarga and a pair of other medicines. The results weren’t statistically significant, however.
Other positive trends in response rates and a slowing of tumor progression were also observed by investigators, but these weren’t tested for statistical significance, the companies said.
Merck and Eisai only provided summary results, not specific details. They plan to share the full results with the scientific community at a later date.
The two companies have been working together since 2018, when they struck a deal worth as much as $5.76 billion to co-develop Lenvima and split potential profits. For Merck, the deal represented one of many bets the company has made on Keytruda-based drug combinations.
Those combinations are meant to improve response rates to its immunotherapy and, in turn, help Merck grab an even greater share of the oncology market than it already has. They also represent chances for Merck to offset the loss of Keytruda’s patent protection later this decade.
Merck and Eisai have had some success so far. The partners won a pair of approvals in endometrial and kidney tumors for the combination in 2021, and Merck reported $876 million for its share of Lenvima sales last year.
They had reason for optimism in the skin cancer trial, too, as, upon an earlier analysis, Keytruda and Lenvima held tumors in check longer than Keytruda monotherapy, meeting the other goal of the Phase 3 study.
“While these results are different from our initial expectation, insights from both studies will help contribute to our understanding of Keytruda plus Lenvima,” said Corina Dutcus, Eisai’s senior vice president of clinical development in oncology, in the statement. The company “remain[s] confident” in the drug “as a pillar of Eisai’s oncology portfolio,” she added.
Merck and Eisai are still testing the combination in more than 10 other trials, including studies in lung, liver, and head and neck cancers.
Lenvima is what’s known as a kinase inhibitor, and its pairing with Keytruda is one bright spot in drugmakers’ efforts to combine immunotherapies with other medicines. Other attempts to partner immunotherapies together have fallen short after showing early promise in testing.
Editor’s note: This story has been update to clarify the enrollment criteria and protocol of the colorectal cancer study.