This is a phase 3, randomized, placebo-controlled, multicenter, international study for the treatment of CIT in adult subjects receiving chemotherapy for the treatment of NSCLC, ovarian cancer, or breast cancer. Subjects must have a platelet count ≤ 85 x 10^9/L on day 1 of the study. The study will consist of a screening period of up to 4 weeks, a treatment period long enough to allow for assessment of 3 planned cycles of chemotherapy, a follow-up visit, and long-term follow-up (LTFU). Given that subjects are required to have 3 remaining planned cycles of chemotherapy, the chemotherapy cycles may be 3 or 4 weeks in duration, and the investigational product dose adjustment guidelines allow for up to 12 weeks of dosing before a subject is declared a non-responder, the majority of study subjects will receive investigational product for a range of 10-24 weeks.