<qa>  What is the dose of AMG 531?Three 3 weeks later, in Cycle 2, all participants will receive either AMG 531 or placebo following R-Ara-CMTX. The AMG 531placebo will be given as an injection under the skin on Days -5 and 5 Arm A or on Days 5 and 7 Arm B. After 2 cycles of treatment, based on response of the disease and tolerance to the treatment, all participants may be able to receive up to 4 more cycles of chemotherapy followed by AMG 531. For Cycles 3-6, you will follow the same schedule of therapy as in the first 2 cycles. The dose of AMG 531 may be increased at one time point during the study based on the response of the platelet counts. 