Study of Sotatercept for the Treatment of Chemotherapy Induced Anemia in Patients With Metastatic Breast Cancer (MK-7962-012)

Inclusion Criteria:

* Has a histologically confirmed diagnosis of breast cancer documented by cytology or biopsy.
* Has evidence of metastatic breast cancer with a minimum of one lesion per Response Evaluation Criteria in Solid Tumors v 1.1 (RECIST v 1.1) criteria.
* Is receiving a chemotherapy regimen including one of the following: anthracycline, taxane, gemcitabine, vinorelbine or capecitabine.
* Has planned treatment with the same chemotherapy regimen for a minimum of 9 weeks after Day 1 of study intervention administration.
* ≥ 30 days elapsed (from Day 1) since previous treatment with an erythropoiesis stimulating agent (ESA) (including treatment with intravenous (IV) iron) for chemotherapy induced anemia.
* ≥ 7 days elapsed (from Day 1) since the last red blood cell (RBC) transfusion and receipt of ≤ 2 units of blood in the past 30 days.
* Life expectancy of ≥ 6 months.

Exclusion Criteria:

* Has had prior radiation therapy to \> 20% of the whole skeleton.
* Has had \> 5 prior chemotherapy treatment regimens for metastatic breast cancer.
* Has a history of autoimmune or hereditary hemolysis or gastrointestinal bleeding.
* Has clinically significant pulmonary, endocrine, neurologic, gastrointestinal, hepatic or genitourinary disease unrelated to underlying hematologic disorder.
* Has heart failure as classified by the New York Heart Association (NYHA) classification of 3 or higher.
* Has a recent history of thrombosis, deep vein thrombosis (DVT), pulmonary emboli, or embolic stroke, occurring within the last 6 months.
* Has untreated central nervous system (CNS) metastases or CNS metastases treated with whole brain radiotherapy \< 6 months prior to Day 1.
* Has a diagnosis of a myeloid malignancy or known history of myelodysplasia.
* Has a history of second malignancy within 5 years (except excised and cured basal cell carcinoma, squamous cell carcinoma of the skin or cervical carcinoma in situ).
* Has had administration of IV antibiotics or febrile (temperature elevation \> 38 ° C) within 14 days of Day 1.
* Has uncontrolled hypertension.
* Has known history of hepatitis B surface antigen (HBsAg and HB core antibody (Ab)), human immunodeficiency virus (HIV) antibody or active hepatitis C.
* Has clinically significant iron (transferrin saturation \< 20%), vitamin B12, or folate deficiency.
* Has a history of anemia as a result of inherited hemoglobinopathy such as sickle cell anemia or thalassemia.
* Has a history of autoimmune or hereditary hemolysis; active gastrointestinal bleeding (within the last 6 months as compared to Day 1).
* Has received treatment with another investigational drug or device within 1 month prior to Day 1.
* Is pregnant or lactating.
* Has a history of severe allergic or anaphylactic reactions or hypersensitivity to recombinant proteins or excipients in the investigational product.
* Has had major surgery within 30 days prior to Day 1 (patients must have completely recovered from any previous surgery prior to Day 1).