Trastuzumab (Herceptin), a monoclonal antibody, was launched on September 8 for the treatment of metastatic breast cancer (see p429). The drug targets a specific growth factor receptor, blocking the action of the growth factor and suppressing tumour growth.
Trastuzumab is indicated for the treatment of patients with metastatic breast cancer whose tumours overexpress human epidermal growth factor 2 (HER2). The drug's manufacturer, Roche, says that this group accounts for between 20 and 30 per cent of patients with metastatic breast cancer and that it produces a particularly aggressive form of the disease. Dr Paul Ellis (consultant medical oncologist, Guy's King's and St Thomas's NHS Trust, London) said at the drug's launch that trastuzumab was "the first targeted cancer treatment with proven survival benefits" and provided a "new era in cancer care". Chemotherapy, the mainstay of treatment for metastatic breast cancer, worked in an indiscriminate way, killing not only tumour cells but also bystanders. On the other hand, trastuzumab would bind only to its target [the HER2 receptor] which would result in decreased toxicity, he said.
Trastuzumab is not associated with the cytotoxic effects of chemotherapy including hair loss and severe vomiting. However, it has been associated with cardiotoxicity, particularly in combination with or following anthracycline treatment. Other serious adverse reactions include infusion-related reactions, hypersensitivity and pulmonary events. In terms of adverse effects, the most common are fever and chills following infusion.
Trastuzumab is licensed as monotherapy for the treatment of patients who have received at least two chemotherapy regimens for metastatic disease and in combination with paclitaxel for the treatment of patients who have not received chemotherapy and for whom an anthracycline is not suitable. Roche says that when given in combination with paclitaxel, trastuzumab has been shown to improve overall survival by 39 per cent in patients who moderately to strongly overproduce HER2 compared with paclitaxel alone. It also prolonged time to disease progression. As monotherapy in patients who had failed to respond to chemotherapy, trastuzumab produced an 18 per cent response rate and increased duration of response by 75 per cent, Roche says.
Following a loading dose, the recommended dose of trastuzumab is 2mg/kg weekly by infusion. A single use vial of trastuzumab 150mg in 15ml costs £407.40. The National Institute for Clinical Excellence will be appraising trastuzumab. Dr Ellis said that the drug's application would be completed by the end of this year and a decision from the NICE was expected in 2001.