Amgen’s stock has slipped 4% following the release of data from a breast cancer study which revealed that the firm’s anaemia drug Aranesp had no significant effect in decreasing tumours.

The company said that it had received interim results from the independent investigator-sponsored Phase III study called PREPARE, which was looking at Aranesp (darbepoetin alfa) in 733 neoadjuvant breast cancer patients who were receiving preoperative chemotherapy compared to a standard chemotherapy regimen. However the study, which was begun in 2002 and was conducted and analysed by the German Gynaecological Oncology Study Group and the German Breast Group, showed that there was no significant difference in tumour shrinkage between the Aranesp and control arms.

What is more, the preliminary data show numerically more deaths (37/377 for control and 50/356 for Aranesp) and tumour progression events (70/377 for control and 88/356 for Aranesp) on the arm using Amgen’s drug compared to the standard chemotherapy regime group in the long-term follow up.

Commenting on the results, principal investigator Michael Untch said they show that the use of Aranesp “to support neo-adjuvant chemotherapy has no significant impact on tumour response to chemotherapy at the time of surgery”. Nevertheless, he noted that “no definitive conclusions should be drawn from the interim results of the long-term follow up until the final study report is completed". A formal statistical analysis of survival is anticipated in early 2009 and Prof Untch added that during the treatment period, “there were as expected, no deaths, and we continue to monitor long-term follow-up results”.

The study is one of five which make up part of Amgen’s ongoing pharmacovigilance programme, which was undertaken in agreement with the US Food and Drug Administration in May 2004 to determine if the use of Aranesp stimulates tumour growth. It does not represent good news for the firm particularly at a time when the class of drugs to which Aranesp belongs – erythropoiesis-stimulating agents – is again being scrutinised amid claims that these anaemia drugs increase the risk of heart attack and stroke, as well as compromise the safety of patients when used in cancer management.