Merck Breaks Off Keytruda Combo Trial with AstraZeneca, Begins Another with Imugene

Merck (known as MSD outside the United States and Canada) and partner AstraZeneca have ditched a Phase 3 combination trial of Keytruda and Lynparza in metastatic castration-resistant prostate cancer (mCRPC). The same day, Merck revealed a new clinical trial collaboration with Australia-based Imugene that would test a combination of Keytruda and Imugene’s HER-Vaxx against HER-2 positive gastric or gastroesophageal junction adenocarcinomas.   

Keytruda/Lynparza Did Not Improve Overall Survival Versus Control

Merck and AstraZeneca had jointly worked together to develop Lynparza (olaparib), a PARP inhibitor. By inhibiting PARP which is an essential enzyme in DNA repair, Lynparza had the potential to act against ovarian, breast and prostate cancer. The drug received its first FDA approval for BRCA-mutated HER2-negative breast cancer.

Merck’s Tuesday decision to stop the Phase 3 Keylink-010 Keytruda/ Lynparza trial for mCRPC followed a recommendation from an independent data monitoring committee (DMC). 

In an interim analysis reviewed by the DMC, Keytruda/ Lynparza failed to show benefit in overall survival compared to the control groups of abiraterone acetate or enzalutamide. 

An earlier interim readout showed that the study did not meet the other primary endpoint, radiographic progression-free survival (rPFS), after the combo did not demonstrate improvement compared to control. 

Related Article: Recent Advances in Breast Cancer Treatments: An Overview

Keytruda/HER-Vaxx for Gastric Cancer  

In a separate development, Merck and Imugene will begin a Phase 2 trial dubbed nextHERizon investigating Keytruda/ HER-Vaxx in patients with HER-2 positive gastric cancer that have failed trastuzumab. 

HER-Vaxx is a B-cell activating cancer vaccine, designed to train B-cells to recognize cancer cells that over express HER-2. It is constructed from several B epitopes, or antigens, derived from the extracellular domain of HER-2.  According to Imugene CEO Leslie Chong, the drug shows a tolerable safety profile and encouraging efficacy in patients with metastatic HER-2 positive gastric cancer, and will be tested in the relapsed/ refractory/ metastatic setting. 

Imugene will fund the study, while Keytruda will be provided by Merck during the trial, which is expected to last at least 24 months. 

Related Article:  Merck’s Keytruda Bags FDA Approval for Early Kidney Cancer in Adjuvant Setting

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Joy Lin

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