Dose-finding Study of Empegfilgrastim for Neutropenia Prophylaxis in Patients With Breast Cancer

Inclusion Criteria: * Signed informed consent form; * Histologically verified diagnosis of stage IIb/III/IV breast cancer; * Age of 18-70 years inclusive; * If the patient had received the chemotherapy for breast cancer, it should be finished 30 days before the beginning of the study; * ECOG Performance Status of 0, 1 or 2, not increasing within during 2 weeks before randomization; * ANC level of 1500/μL and more at the beginning of the study * Platelet count of 100 000/μL and more at the beginning of the study * Hemoglobin level of 90 g/l and more * Creatinine level \<1.5 mg/dl * Total bilirubin level \<1.5 × the upper limit of normal (ULN) * ALT and/or AST levels \<2.5×ULN (5×ULN for patients with liver metastases); * Alkaline phosphatase \<5×ULN; * Left ventricular ejection fraction \>50% and more; * If the patient had received adjuvant and/or neoadjuvant therapy, the cumulative dose of anthracyclines should not exceed 500 mg/m2 for doxorubicin or 500 mg/m2 for epirubicin; * Ability of the participant to follow the protocol requirements, according to the Investigator's opinion; * Patients of childbearing potential must implement reliable contraceptive measures during the study treatment, starting 4 weeks prior randomization and for 6 months after the last administration of the study drug. Exclusion Criteria: * Patient has received two or more chemotherapy regimens for the metastatic breast cancer; * Documented hypersensitivity to filgrastim, pegfilgrastim, docetaxel, doxorubicin, dexamethasone and/or its excipients, PEGylated drugs, recombinant proteins. * Pregnancy or breastfeeding; * Systemic antibiotic therapy within 72 h prior empegfilgrastim/filgrastim administration; * Concomitant radiotherapy (except selective radiotherapy of bone metastases); * Surgery, radiotherapy (except selective radiotherapy of bone metastases), administration of any experimental drugs within 30 days prior randomization; * History of bone marrow/stem cell transplantation; * Conditions limiting the patient's ability to follow the protocol; * CTCAE grade 2/4 neuropathy * HIV, HCV, HBV, T.Pallidum infection(s); * Acute or active chronic infections.