Herceptin

Analyst Outlook

Herceptin (trastuzumab; Roche/Chugai) is a monoclonal antibody (MAb) currently approved for the

first-line treatment of advanced or metastatic gastric cancer expressing human epidermal growth

factor receptor 2 (HER2). Herceptin was the first targeted therapy approved for gastric cancer, and has

since risen to become the standard of care for HER2-positive patients. Branded sales of Herceptin are

expected to come under threat from biosimilars as key patents protecting the drug’s exclusivity have

expired in Japan and the EU, with US patent expiry expected in 2019. Roche and Chugai are currently

developing Perjeta (pertuzumab; Genentech/Roche/Chugai), a distinct but complementary HER2-

targeted MAb, for use in combination with Herceptin. Perjeta’s development will be used to offset

biosimilar competition, and allow Roche and Chugai to retain their dominance in the HER2-positive

gastric cancer market. In addition, several studies have suggested Herceptin’s potential efficacy

beyond the first-line setting, and may serve the basis for future label expansion. These developments

will be critical for Herceptin’s continued success as the HER2 gastric cancer therapy of choice.

Drug Overview

Herceptin is a humanized MAb targeting the HER2 receptor, a member of the human epidermal

growth factor receptor family. HER2 expression promotes cell proliferation and suppresses apoptosis.

Overexpression of HER2 can facilitate uncontrolled growth and tumorigenesis (Boku, 2014). Herceptin

mediates antibody-dependent cellular cytotoxicity and has been shown in vitro to be preferentially

exerted on HER2-overexpressing cancer cells (Herceptin prescribing information, 2015). In vivo models

have also shown Herceptin’s ability to inhibit the proliferation of human tumor cells that overexpress

HER2 (Gravalos and Jimeno, 2008).