Genentech’s investigational cancer agent Omnitarg (pertuzumab) has failed to show a benefit as a single agent in ovarian, breast or prostate tumours, according to data from Phase II studies highlighted at the American Society of Clinical Oncology meeting. However, the company says it will continue to pursue Omnitarg’s development as a combination therapy in patients with advanced ovarian cancer.

The 65-patient Phase II study in ovarian cancer showed partial responses in 3% of the patients (2/60), and stable disease of greater than six months in an additional 12% of patients (7/60).

Omnitarg is a monoclonal antibody and the first in a new class of agents know as HER dimerization inhibitors (HDIs), which works by binding to the HER2 receptor and blocking its interaction with other HER family members, thus preventing activation of the HER signaling pathway, which may play a role in cancer proliferation. Unlike Roche and Genentech’s top-selling Herceptin (trastuzumab), Omnitarg is designed to target tumors that have normal, rather than overexpressed, levels of the HER2 protein.