Amgen, the world’s largest biotechnology company, has sent a letter to doctors to alert them to the fact that higher doses of drugs similar to its anaemia offering, Aranesp (darbepoetin alfa), were linked with an increased risk of blood clots – and even death – in clinical trials.

In a letter dated January 11, but posted on the US Food and Drug Administration’s website late last week, Amgen said that the new warning came as a result of two studies including two other anaemia drugs – Johnson & Johnson’s Eprex (epoetin alfa), and Roche’s NeoRecormon (epoetin beta) – which aimed to boost cancer patients’ haemoglobin levels beyond what is currently recommended. As a result, J&J’s Ortho Biotech unit sent a similar letter to doctors last summer.

Last year an FDA advisory panel recommended that J&J and Amgen investigate a potential link between their two top-selling anaemia drugs – Aranesp and Procrit (epoetin alfa) respectively – and stimulation of tumour growth after two European studies reported tumour proliferation and negative survival outcomes [[05/05/04d]], [[22/03/04e]]. Amgen is now investigating the effects of its product in breast cancer, head and neck cancer, lymphoma and small cell lung cancer.