The number of blood tests drawn (about 3 teaspoons each) will depend on your clinical condition. These samples will be taken at least 2 times a week and as often as once a day during portions of the study. You will also have blood (about 1 teaspoon) collected for the evaluation of anti-AMG 531 antibody status before treatment starts, at the end of Cycles 2 and 4, and at the end of study.