The goal of this clinical trial is provide new treatment for patients with advanced melanoma who have failed previous immunotherapy. The main questions it aims to answer are:

• Efficacy of PD1 monoclonal antibody combined with recombinant human adenovirus type 5 injection in patients with advanced malignant melanoma.
• Safety of PD1 monoclonal antibody combined with recombinant human adenovirus type 5 injection in patients with advanced malignant melanoma.

The study is divided into 5 phases: screening phase, washout phase, baseline phase, treatment phase and follow-up phase. Patients with advanced malignant melanoma who are eligible for screening and have failed previous anti-PD1 antibody therapy and who meet the inclusion exclusion criteria undergo elution with 1 PD1 monoclonal antibody injection, patients whose tumours progress after PD1 monoclonal antibody injection enter the treatment phase and are followed up every 1 month for at least 2 years in the follow-up phase.

Inclusion Criteria:

1. 18 years of age ≤ age ≤ 75 years of age, regardless of gender

2. have a pathological histological diagnosis of malignant melanoma

3. current physical condition and anticipated treatment plan judged by the investigator to be suitable for the treatment regimen of this trial;

4. a patient with malignant melanoma who has failed previous immunotherapy

5. at least one injectable lesion which must meet the RECIST 1.1 and iRECIST measurable target lesion requirements

6. the longest diameter of the injectable lesion must be ≥ 10 mm and ≤ 80 mm;

7. an Eastern Cooperative Oncology Group (ECOG) physical status score of 0-2;

8. laboratory tests must meet the following criteria:

   • A white blood cell count of ≥ 1.0 x 109/L;
   • Absolute neutrophil count ≥ 1.0 x 109/L;
   • Platelet count ≥ 80 x 109/L;
   • Haemoglobin ≥ 70 g/L;
   • INR ≤ 1.5 and APTT ≤ 1.5 x ULN;
   • Total bilirubin ≤ 1.5 x ULN;
   • ALT and AST ≤ 5 x ULN;
   • Blood creatinine ≤ 1.5 x ULN or creatinine clearance ≥ 50 ml/min.

9. have recovered from previous antineoplastic treatment to baseline or below grade 1 (CTCAE version 5.0) (except for alopecia and grade 2 anaemia) after an interval of ≥14 days between the date of first treatment and the date of the last previous antineoplastic treatment;

10. voluntarily signed informed consent with good expected compliance;

11. female patients of childbearing potential (including early menopause, menopause < 2 years and non-surgical sterilisation), male patients and partners of male patients must agree to use effective contraception during the study period: surgical sterilisation, oral contraceptive pills, intrauterine device, abstinence or barrier contraceptive method combined with spermicide; and contraception must be continued for 6 months after receiving the last, treatment.

Exclusion Criteria:

1. the injectable lesion has received other local treatment, such as ablation, intervention, or Hepatome, within the previous 6 months;
2. previous treatment with lysoviruses or similar drugs (e.g. T-VEC)
3. local lesions that do not meet the volume requirements for intratumoral injection or for which intratumoral injection is inappropriate
4. have received antiviral therapy, such as acyclovir, ganciclovir, vancomycin, adenosine, etc., within 4 weeks prior to the first dose of the trial treatment
5. known hypersensitivity to the study drug or its active ingredient, excipients or to anti-PD-1 monoclonal antibodies and their components
6. positive for hepatitis B surface antigen (HBsAg) and clinically judged to have active hepatitis B;
7. other active viral infections;
8. patients with any unstable systemic disease, including but not limited to: severe infection, uncontrolled diabetes mellitus, unstable angina pectoris, cerebrovascular accident or transient cerebral ischaemia, myocardial infarction, congestive heart failure, severe arrhythmia requiring pharmacological treatment, liver, renal or metabolic disease;
9. the presence of an autoimmune disease
10. the patient has a concomitant disease (e.g. mental illness, etc.) or condition (e.g. alcohol or drug abuse, etc.) that would increase the patient's risk of receiving the trial drug or would affect the patient's ability to comply with the requirements of the trial, or would have the potential to confound the results of the study
11. the patient has been treated with any other experimental drug or participated in another interventional clinical trial within 14 days prior to treatment in this study
12. women who are pregnant or breastfeeding or who are planning to become pregnant or breastfeeding during the study period; men or women who do not wish to use effective contraception
13. evidence of central nervous system metastases at baseline
14. other circumstances which, in the judgment of the investigator, make the patient unsuitable for participation in the clinical trial.