Clinical Study of the Efficacy and Safety of BCD-263 and Opdivo® As Monotherapy in Subjects with Advanced Melanoma of the Skin

Inclusion Criteria:

1. Signed informed consent and the subject's ability to comply with the protocolrequirements.

2. Age ≥18 years at the time of signing the informed consent form.

3. Histologically confirmed melanoma with the following prognostic characteristics:

• LDH <ULN of local laboratory (enrollment of subjects with LDH <2 x ULN of locallaboratory is allowed until the number of subjects with LDH >ULN is 30% of thetotal population of randomized subjects. The Sponsor will inform whenenrollment of subjects is limited by LDH level <ULN of the local laboratory).

• Absence, according to the Investigator, of clinically significant symptomsassociated with the tumor.

• Absence, according to the Investigator, of rapidly progressing metastaticmelanoma.

4. Newly diagnosed advanced unresectable (stage III) or metastatic disease (stage IV),or progressive disease during / relapsing after radical treatment.

5. Presence of a tumor sample (archived or new biopsy) that is suitable for evaluationfor PD L1 expression in the Investigator's opinion.

6. At least one measurable lesion as per RECIST 1.1 based on independent centralreview.

7. ECOG score 0-1.

8. Laboratory test results consistent with adequate functioning of systems and organs.

Exclusion Criteria:

1. Indications for radical treatment (surgery, radiation therapy).

2. Uveal or mucosal melanoma.

3. Previous systemic anticancer therapy for advanced unresectable or metastatic skinmelanoma.

4. Active CNS metastases and/or carcinomatous meningitis.

5. Previous invasive cancer, excluding diseases treated with potentially radicaltherapy with no evidence of recurrence for 2 years from the start of this therapy (subjects with radically resected basal cell carcinoma of the skin, superficialbladder cancer, squamous cell carcinoma of the skin, cervical carcinoma in situ ofthe uterus and other carcinomas in situ may be included).

6. Subjects with severe concomitant disorders, life-threatening acute complications ofthe primary disease (including massive pleural, pericardial, or peritoneal effusionsrequiring intervention, pulmonary lymphangitis, bleeding or organ perforation) atthe time of signing the informed consent and during the screening period.

7. Concomitant diseases and/or conditions that significantly increase the risk ofadverse events (AEs) during the study.

8. Active, known or suspected autoimmune disorders (subjects with type 1 diabetesmellitus or hypothyroidism requiring only hormone-replacement therapy and those withskin disorders [vitiligo, alopecia, or psoriasis] not requiring systemic therapy areeligible to participate).

9. The need for systemic corticosteroids (at doses equivalent to >10 mg/dayprednisolone) or any other immunosuppressive drugs within 14 days prior torandomization. The use of inhaled and topical corticosteroids is allowed.

10. History of (non-infectious) pneumonitis requiring corticosteroid therapy orpneumonitis at the time of screening.

11. Any anticancer therapy or major surgery within 28 days prior to randomization, orthe subject's AE (other than alopecia) caused by anticancer therapy has not yetrecovered to CTCAE grade 1 or has not completely resolved.

12. Concomitant use of drugs or medical devices studied in other clinical studies ortheir use within 28 days prior to randomization.

13. Infections requiring therapy or systemic antibiotics within 14 days prior torandomization.

14. Administration of a live and/or attenuated vaccine within 28 days prior torandomization.

15. Positive HIV-1 or HIV-2 test.

16. HBV/HCV infections (subjects with a negative PCR result for hepatitis C virus RNA,without significant abnormalities in blood chemistry tests, examined by aninfectious disease specialist and not requiring specific antiviral treatment at thetime of screening, may be included in the study. Subjects with a positive HbsAg testresult cannot be included in the study).

17. Impossibility to administer intravenous contrast agents (including due tohypersensitivity to contrast media).

18. Hypersensitivity or allergy to any of the nivolumab product components.Hypersensitivity or allergy to medicinal products obtained based on Chinese hamsterovary cells, or history of severe allergic, anaphylactic or other hypersensitivityreactions to chimeric or humanized antibodies or hybrid proteins.

19. Pregnancy or breastfeeding, as well as intention to become pregnant or father achild during the study period.