Trastuzumab emtansine (Kadcyla; Roche) is an antibody‑drug conjugate consisting of trastuzumab linked to maytansine, which is a cytotoxic agent. Because the antibody targets human epidermal growth factor receptor 2 (HER2), and HER2 is overexpressed in breast cancer cells, the conjugate delivers the toxin directly to the cancer cells.
Trastuzumab emtansine, as a single agent, has a UK marketing authorisation 'for the treatment of adult patients with HER2‑positive, unresectable locally advanced or metastatic breast cancer who previously received trastuzumab and a taxane, separately or in combination. Patients should have either:
received prior therapy for locally advanced or metastatic disease or
developed disease recurrence during or within 6 months of completing adjuvant therapy'.
The summary of product characteristics includes the following adverse reactions for trastuzumab emtansine: increase in serum transaminases, left ventricular dysfunction, infusion-related reactions, hypersensitivity reactions, decreased platelet counts, an immune response to trastuzumab emtansine, and reactions secondary to the accidental administration of trastuzumab emtansine around infusion sites. For full details of adverse reactions and contraindications, see the summary of product characteristics.
Trastuzumab emtansine is administered as an intravenous infusion. The recommended dose is 3.6 mg/kg bodyweight every 3 weeks (21‑day cycle). Patients should have treatment until the disease progresses or unacceptable toxicity occurs.
The list price for trastuzumab emtansine is £1,641.01 for a 100 mg vial and £2,625.62 for a 160 mg vial (excluding VAT, British national formulary online, accessed February 2017). The company estimates that the average cost of a course of treatment is £91,614, using the list price, and based on a 3‑weekly dose of 3.6 mg/kg, a patient weight of 70.1 kg and an average length of treatment of 14.5 months. The pricing arrangement considered during guidance development was one in which Roche had agreed a complex patient access scheme with the Department of Health. In October 2017 Roche agreed a simple discount patient access scheme with the Department of Health. The discount to the list price is applied at the point of purchase or invoice. The level of the discount is commercial in confidence. The Department of Health considered that this patient access scheme does not constitute an excessive administrative burden on the NHS.