DO NOT CONFUSE T-DM1 WITH HERCEPTIN 

The US Food and Drug Administration (FDA) today warned that clinicians may confuse a recently approved breast cancer drug called ado-trastuzumab emtansine (Kadcyla, Genentech) with a predecessor called trastuzumab (Herceptin, Genentech), possibly leading to patient harm.

The mix-up, said the agency, stems from some electronic health record systems, pharmacy software, compendia references, Internet sites, and other parties shortening ado-trastuzumab emtansine, the name approved by the FDA, to trastuzumab emtansine.

The FDA approved ado-trastuzumab emtansine, also known as T-DM1, on February 22 to treat patients with HER2-positive metastatic breast cancer who had previously received the anti-HER2 therapy trastuzumab and taxane-based chemotherapy. Since the newer drug's approval, the FDA has not received any reports of medication errors caused by a name mix-up.

However, such medication errors did occur during the clinical trials for ado-trastuzumab emtansine, according to the agency. Four patients received the new cancer drug at a dose of 6 mg/kg when the intended drug was trastuzumab; 6 mg/kg every 3 weeks is the recommended maintenance dose for trastuzumab but exceeds the recommended dose for ado-trastuzumab emtansine, which is 3.6 mg/kg administered as a single agent by intravenous infusion every 3 weeks.

The label of the new drug warns that clinicians should not substitute it for trastuzumab.

The original name of ado-trastuzumab emtansine had been trastuzumab emtansine, as established by the US Adopted Name Council. Anticipating a name mix-up, the FDA required the addition of the prefix "ado" followed by a hyphen.

The FDA advises all healthcare professionals to use both the approved generic name as well as the approved brand name, Kadcyla, when they prescribe ado-trastuzumab emtansine.

More information on today's announcement is available on the FDA Web site.