Merck Discontinues Keytruda Combo Trial for Prostate Cancer

In an interim analysis, Keytruda/Lynparza did not improve overall survival in patients with metastatic castration-resistant prostate cancer who progressed after treatment with chemotherapy.

Merck is stopping the phase 3 KEYLYNK-010 trial investigating Keytruda (pembrolizumab), the company’s anti-PD-1 therapy, in combination with AstraZeneca’s Lynparza (olaparib), a PARP inhibitor, for the treatment of patients with metastatic castration-resistant prostate cancer (mCRPC) who progressed after treatment with chemotherapy and either abiraterone acetate or enzalutamide.

Merck is discontinuing the study following the recommendation of an independent data monitoring committee after a planned interim analysis showed that the combination did not demonstrate a benefit in overall survival, one of the study’s dual primary endpoints, compared with the control arm of either abiraterone acetate or enzalutamide.

The trial’s other primary endpoint, radiographic progression free survival, was evaluated at an earlier interim analysis and did not demonstrate improvement compared with the control arm.

Additionally, the combination was associated with a higher incidence of grade 3 to grade 5 adverse events and drug-related serious adverse events, compared with the control arm.

“Merck continues to evaluate the combination of Keytruda and Lynparza in a range of cancers, and to research other Keytruda-based combinations for patients with advanced prostate cancer,” Roy Baynes, Ph.D., senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories, said in a press release.

Prostate cancer is the second most common cancer in men and is associated with a significant mortality rate. In patients with mCRPC, their prostate cancer grows and spreads to other parts of the body even when therapy is used to block testosterone.

The American Cancer Society’s estimates there will be about 268,490 new cases of prostate cancer in the United States for 2022 and about 34,500 deaths from prostate cancer in 2022.

About 10% to 20% of patients with prostate cancer develop castration-resistant disease within five years. The prevalence of mCRPC is growing, according to one study of insured patients over an eight-year period.