Phase III Failure for Keytruda in Endometrial Cancer

Merck's Keytruda faced a setback in endometrial cancer research for the second time within half a year. On Thursday, the pharmaceutical company disclosed that its prominent medication did not succeed in a Phase III trial involving high-risk patients.

Keytruda was tested as an adjuvant therapy in conjunction with chemotherapy, with or without radiotherapy, for newly diagnosed high-risk endometrial cancer patients. The treatment failed to achieve the primary endpoint of disease-free survival when compared to a placebo in an interim analysis.

Despite these results, Keytruda is already approved for two specific types of endometrial cancer. It is authorized in combination with Eisai’s Lenvima for advanced, inoperable endometrial carcinoma that has continued to progress after previous treatment and as a monotherapy in similarly diagnosed patients. Merck is also conducting an ongoing development program to test Keytruda both in combination with chemotherapy and as a standalone treatment in specific patient groups.

Earlier, in December 2023, the Keytruda-Lenvima combination did not succeed in extending survival rates in patients with advanced or recurrent endometrial carcinoma.

These results followed two previous failures of Keytruda in non-small cell lung cancer (NSCLC). In December, Merck announced that Keytruda, combined with their experimental anti-TIGIT antibody vibostolimab, did not improve progression-free survival in NSCLC patients. Additionally, on the same day, a trial combining Keytruda with AstraZeneca’s Lynparza failed to significantly enhance overall survival rates in metastatic squamous NSCLC patients. Again in March, Merck reported that the combination with Lynparza did not meet the primary endpoints in specific patients with metastatic non-squamous NSCLC.

Despite these letdowns, Keytruda remains a significant revenue generator for Merck. The immunotherapy has amassed over 30 approved indications since its initial approval in 2014 for treating advanced melanoma patients with a BRAF mutation.

In April, Merck revealed a 20% increase in Keytruda sales for the first quarter of 2024 compared to the same period in the previous year. This growth brought in $6.9 billion, representing nearly half of Merck’s total pharmaceutical sales of $14 billion for the period. Analysts predict that Keytruda's annual sales could surpass $30 billion by 2026 before experiencing a decline with the introduction of biosimilars as early as 2028.