Amgen Inc. on Friday announced it has discontinued development of its megakaryocyte growth and development factor (MGDF) after neutralizing antibodies were seen both in cancer patients and healthy platelet donors.

The failure of MGDF was not unexpected, due to past concerns over the protein's activity. But Genentech Inc. (GNE) is continuing development of its thrombopoietin (TPO), a slightly different formulation of the same growth factor that has not encountered the same problems.