Antibody Drug Conjugate is a smart way to improve chemotherapy. That is the strategy of Roche / Immunogen's drug Kadcyla®, which has just failed in Phase III clinical trial to extend its indications. Here are the facts...\r\n\r\nAntibody Drug Conjugate is at the boundary between chemical and biological drug. The principle is pretty simple; once the antibody fixes to its target, the cell-killing agent is released. Referring to our previous article, this brings an advantage compared to chemo because only tumors will be targeted and healthy cells are spared... Theoretically.\r\n\r\nIn this way, Roche's partner Immunogen has combined Genentech's well-known antibody trastuzumab and its proprietary cell-killing agent DM1 (aka mertansine). First, it was designed to be used as a single agent for the treatment of patients with HER2-positive metastatic breast cancer who previously received trastuzumab and a taxane. With good outcomes in the trial, it had been approved by the FDA in February 2013 followed by the EMA approval in November of the same year.\r\n\r\nSuch kind of drugs is expensive to develop and market. A good strategy of increasing return on investment is to extend indications.\r\n\r\nThat's why Roche had launched its GATSBY clinical trial (NCT01641939) to target HER2-positive gastric cancer (sounds great knowing that 8% to 38% of gastric cancer cases overexpress HER2).\r\n\r\n\r\n\r\nBut a clinical trial is never fully predictable. And this time, it failed in Phase III (which is the most expensive phase - over 300 M$). Details have not been released yet, but should be reported at a future medical conference.\r\n\r\nIn addition to the cost, failing at such a late stage damages the image of the company running the trial. Therefore, it's definitely a bad news for Roche and Immunogen.