The company initially planned to report first quarter earnings on April 19 but has postponed the announcement to incorporate results of the Aranesp study in small cell lung cancer patients receiving chemotherapy.
Concerns have been raised about drugs like Aranesp, that they may spur the growth of tumors in cancer patients.
Amgen also said its chief financial officer has resigned, sending the company's shares down. Amgen said Richard Nanula was leaving the company to pursue other opportunities and would be replaced by Robert Bradway as executive vice president and chief financial officer.