Study of KHK2375 in Subjects With Advanced or Recurrent Breast Cancer

Inclusion Criteria: * Postmenopausal women aged ≥ 20 and \< 75 years at the time of consent; * Estrogen receptor positive and/or progesterone receptors positive; * HER2-negative * Nonresectable advanced or recurrent breast cancer previously treated with nonsteroidal aromatase inhibitor (AI), and planning to be treated with exemestane Exclusion Criteria: * Radiation therapy or immuno therapy within 14 days before the first dose of investigational product; * Chemotherapy, biological medicines, other pharmacotherapy or major surgery within 21 days before the first dose of the investigational product; * Prior chemotherapies of ≥ 3 regimens for advanced or recurrent breast cancer; * Ongoing treatment with other investigational product