This is a phase 1b/2, open label study to evaluate the safety, tolerability, pharmacokinetics and initial efficacy of KD6001 in combination with toripalimab in patients with advanced melanoma.

Main Inclusion Criteria:

1. Being voluntary to sign the informed consent form.
2. Male or female, aged ≥ 18 years.
3. Patients whose estimated survival time is more than 3 months.
4. Eastern Cooperative Oncology Group (ECOG) performance status score 0 or 1.
5. Histologically or cytologically confirmed advanced or metastatic melanoma, and the overall proportion of subjects with mucosal malignant melanoma will not exceed 22%.
6. At least one measurable lesion is used as the target lesion according to the Response Evaluation Criteria in Solid Tumors Version 1.1(RECIST V1.1).
7. The results of laboratory examination during the screening period suggest that the subjects have good organ function.
8. Male subjects with reproductive ability or female subjects with the possibility of pregnancy use effective contraceptive methods.
9. Good compliance and follow-up.

Main Exclusion Criteria:

1. Systematic treatment with antitumor drugs within 4 weeks prior to the start of this study.
2. Received immunotherapy (including PD-1/PD-L1 therapy and cell therapy) within 4 weeks prior to the start of this study.
3. Prior treatment with anti-CTLA-4 antibody.
4. Subjects with an active, known or suspected autoimmune disease.
5. Subjects with hepatitis (nonalcoholic steatohepatitis, alcoholic or drug-related, autoimmune hepatitis) and liver cirrhosis; active hepatitis B or hepatitis C.
6. Subjects with an active infection requiring systemic treatment.
7. Known history of testing positive for human immunodeficiency virus (HIV).
8. Subjects known to have active tuberculosis (TB).
9. Known to be allergic to KD6001 or Toripalimab and its components.