Prolgolimab 250 mg Q3W in Patients With Unresectable or Metastatic Melanoma (FLAT)

Inclusion Criteria: Signed informed consent and the subject's ability to comply with the protocol requirements. Age ≥18 years at the time of informed consent. Histologically confirmed unresectable or metastatic melanoma (with available documented evidence of relevant examinations). Primarily detected advanced or metastatic melanoma, or the disease progression on or after previous systemic therapy. Measurable target tumor lesions (at least 1 lesion) according to RECIST 1.1 criteria, confirmed by an independent reviewer. ECOG score 0-1. Absence of severe organ and system disorders. Life expectancy of at least 12 weeks at screening. For patients of childbearing potential: willingness to use reliable methods of contraception throughout the study, from the time of informed consent and for up to 6 weeks after the last dose of the study drug. Available blocks for a histological examination and/or the patient's consent for collection of biopsy43 samples to obtain histological material to assess the PD-L1 status. Exclusion Criteria: Patients with severe concomitant disorders, life-threatening acute complications of the primary disease (including massive pleural, pericardial, or peritoneal effusions requiring intervention, pulmonary lymphangitis) at the time of informed consent. CNS metastases that are progressing or associated with clinical symptoms (e.g., cerebral edema, spinal compression) or requiring the use of glucocorticosteroids and/or anticonvulsants; Ongoing concomitant diseases at the time of screening increasing the risk of severe adverse events during the study treatment. The need for glucocorticoids or any other drugs with immunosuppressive effects. Hematologic abnormalities. Renal impairment. Hepatic impairment. Increased LDH >2 ULN. Prior treatment with anti-CTLA4 and/or anti-PD-1/PD-L1/PDL-2 drugs. Prior targeted therapy. A history of malignancies, except for radically treated diseases in remission for over 5 years prior to starting the study. Conditions limiting the patient's ability to comply with the protocol requirements (dementia, neurologic or mental disorders, drug or alcohol addiction, etc). Simultaneous participation in other clinical studies55 or participation in other clinical studies within 30 days prior to starting the study treatmen. Acute infections or activation of chronic infectious diseases within 28 days prior to the beginning of the study treatment. Active hepatitis B, active hepatitis C, HIV-infection, syphilis. Impossibility to administer the study drug intravenously. Impossibility to perform imaging examinations requiring administration of intravenous contrast media. Hypersensitivity to any of the components of BCD-100. A history of hypersensitivity to monoclonal antibody products. Pregnancy or breastfeeding.