 This is an open label, multicenter, dose ranging study, sequentially enrolled by study dose, with a non-inferiority design to compare the effectiveness of HM10460A relative to a fixed dose of pegfilgrastim as a concurrent active control to each dose of HM10460A in patients with breast cancer. The study will include 4 arms: 3 dose levels of HM10460A versus pegfilgrastim. The start of study treatment is defined as the initiation of HM10460A or pegfilgrastim. The duration of treatment consists of a maximum of 4 cycles, which begin on Day 1 with chemotherapy administration and continue through Day 21. 