Dako and Genentech are working on submitting to the US Food and Drug Administration two genetic tests — Dako's HercepTest and HER-2 FISH pharmDx test — as companion diagnostics for Herceptin in the treatment of gastric cancer, Dako said this week.
Both tests are already listed in labeling for Herceptin as companion diagnostics for the treatment of HER-2-positive breast cancer. The joint approval of Herceptin and HercepTest in 1998 was the first example of a drug/diagnostic combination product.
Under the terms of the agreement, Dako and Genentech will collaborate on regulatory submissions for the HercepTest and HER2 FISH pharmDx. The tests will be used to identify gastric cancer patients who will benefit with Herceptin treatment.
Based on data from a Phase III study presented at the American Society for Clinical Oncology's annual meeting this year, Genentech said it may seek FDA approval for Herceptin in stomach cancer [see PGx Reporter 06-03-2009]. Genentech is a subsidiary of Roche Group.
The abstract presented at ASCO's annual meeting by Van Cutsem et al. conducted a study, ToGa (for trastuzumab in gastric cancer), in which they randomized 594 patients with HER2-positive gastroesophageal and gastric adenocarcinoma to receive Herceptin plus chemotherapy (5-fluorouracil or capecitabine and cisplatin) or chemotherapy alone for six cycles.
The results showed that median overall survival "significantly improved" for patients on the trastuzumab/chemo combination versus those on just chemo. The objective response rate was 47 percent in the trastuzumab/chemo arm and 35 percent in the chemo arm.
The researchers concluded that "the overall survival benefit indicates that Herceptin is a new, effective, and well-tolerated treatment for HER2-positive gastric cancer."
Gastric cancer is hard to diagnose since most patients don't show symptoms in the early stages of the disease. According to Dako, approximately 22 percent of stomach tumors are HER-2 positive. The rate of HER-2-positive tumors is the same in Europe and in Asia, where there is a higher prevalence of stomach cancer.