TQB2450 is a humanized monoclonal antibody targeting programmed death ligand-1 (PD-L1), which prevents PD-L1 from binding to PD-1 and B7.1 receptors on T cell surface, restores T cell activity, thus enhancing immune response and has potential to treat various types of tumors.

Inclusion Criteria:

1.18 and 75 years; Eastern Cooperative Oncology Group (ECOG) performance status score of 0 or 1; Life expectancy ≥ 3 months.

2. Histologically or cytologically confirmed advanced acral malignant melanoma. 3. At least one measurable lesion. 4. Providing tumor specimen obtained by biopsy or surgical sample within 2 years.

5. Has received at least first-line treatment but appeared disease progression or intolerance.

6. The main organs function are normally, the following criteria are met:

1. hemoglobin ≥ 90 g/L; neutrophils ≥ 1.5*10^9/L; platelets ≥ 100 x 10^9/ L;
2. total bilirubin ≤ 1.5 x upper limit of normal (ULN); aspartic transaminase (AST) and alanine transaminase (ALT) ≤ 2.5 x ULN ; serum creatinine ≤1╳ULN，creatinine clearance >50 umol/L ;
3. INR, aPTT, PT≤1.5 x ULN;
4. left ventricular ejection fraction (LVEF) ≥50%. 7. Male or female subjects should agree to use an adequate method of contraception starting with the first dose of study therapy through 6 months after the last dose of study (such as intrauterine devices , contraceptives or condoms) ；No pregnant or breastfeeding women, and a negative pregnancy test are received within 7 days before the randomization.

8.Understood and signed an informed consent form.

Exclusion Criteria:

1. Prior therapy with VEGFR-target TKI included anlotinib or an anti-programmed cell death (PD)-1, anti-PD-L1, anti-PD-L2, anti-tumor necrosis factor CD137, or anti-cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) antibody ,or any other antibody or drug specifically targeting T-cell co-stimulation or checkpoint pathways.
2. Hypersensitivity to recombinant humanized anti-PD-1 monoclonal Abm or its components.
3. Has diagnosed and/or treated additional malignancy within 5 years prior to randomization. Exceptions include cured basal cell carcinoma of skin and carcinoma in situ of cervix.
4. Has any active autoimmune disease or history of autoimmune disease.
5. Immunosuppressive therapy with immunosuppressive agents or systemic or absorbable local hormones (dosage > 10 mg/day prednisone or other therapeutic hormones) is required for the purpose of immunosuppression, and is still in use for 2 weeks after the first administration.
6. Has multiple factors affecting oral medication.
7. Has uncontrollable pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures.
8. Has any bleeding or bleeding events ≥ grade 3 or with unhealed wounds, ulcerative , or fractures within 4 weeks prior to the first administration.
9. Has uncontrollable symptoms of brain metastasis, spinal cord compression, cancerous meningitis during screening within 8 weeks before first dose.
10. Has received chemotherapy, surgery, radiotherapy, the last treatment from the first dose less than 4 weeks, or oral targeted drugs for less than 5 half-lives, or oral fluorouracil pyridine drugs for less than 14 days, mitomycin C and nitrosourea for less than 6 weeks.
11. Has any serious and / or uncontrolled disease.
12. Has vaccinated with vaccines or attenuated vaccines within 4 weeks prior to first dose.
13. Has received granulocyte colony stimulating factor(G -CSF)，or Granulocyte macrophage colony stimulating factor (GM-CSF) within 4 weeks prior to first dose.
14. According to the judgement of the researchers, there are other factors that may lead to the termination of the study. For example, other serious diseases including mental disorders need to be treated together, serious laboratory abnormalities, accompanied by family or social factors, which will affect the safety of the subjects, or the collection of data and samples.