Prolgolimab 250 mg Q3W in Patients With Unresectable or Metastatic Melanoma

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.