The phase 1 clinical trial of anti-PD-1 (pucotenlimab) plus intrahepatic injection of oncolytic virus (OH2) combined with radiotherapy of liver metastasis in stage IV melanoma

e21545 Background: Melanoma pts with liver metastasis has poor prognosis and reduced response to systemic immunotherapy. Oncolytic herpes simplex virus 2 (OH2) is an oncolytic virus derived from herpes simplex virus type 2. PD-1 antibody combined with intrahepatic oncolytic virus intralesional injection had shown preliminary efficacy in previous clinical trial. The radiation of liver metastasis might exert action on its tumor microenvironment and get benefit from immunotherapy combination. So we perform this phase I study to assess the safety and efficacy of OH2 and pucotenlimab (a humanized immunoglobulin G4 monoclonal antibody) combine with liver metastasis radiation in melanoma pts. Methods: Eligible pts included those over 18 with injectable liver metastasis confirmed by biopsy with or without extra-hepatic metastasis; the ocular melanoma and brain metastasis were excluded. Pts received intravenous Pucotenlimab Q3W combined with ultrasound guided intrahepatic injection (metatstasis lesion) of OH2 Q2W (10 7 CCID50/mL, 8ml per injection) after stereotactic body radiotherapy (24-30Gy/3Fx) of liver metastasis. Liver biopsy performed at baseline and first tumor evaluation (8-12weeks). The primary endpoint was ORR; secondary:toxicity, DCR, PFS and OS. Results: From Dec 2021 to Jan 2023, 10 pts were eligible and enrolled. Baseline characteristics: 70% got previous treatment; LDH＞ULN 50.0%; 90% got extra-hepatic metastasis; median size of ed lesions: 36mm(19-120mm); median number of liver metastasis: 5.5. Among these pts, 5 pts could be evaluated for efficacy (follow-up 10.0 m). The global ORR by investigator was 40.0% (2/5), DCR 80% (4/5). Biopsies of 4 pts for injected lesions at 8 to 12 weeks after first injection were examined to determine the situation of tumor regression and TIL infiltration. Among them, 2 pts ( 1 PR and 1 SD) had no tumor cells residual by immunohistochemistry in biopsies with impressive TIL infiltration, both of them showed PFS more than12.0 months. Most adverse events (AE) were grade 1-2. Only one pts had grade 3-4 thrombocytopenia, with treatment modified. No treatment-related deaths occurred. The median PFS was not reached and now in follow up. Conclusions: Systemic anti-PD-1 plus intralesional injection of Oncolytic virus combined with radiotherapy has shown remarkable ORR and pathological response in melanoma pts with liver metastases with manageable toxicity. Clinical trial information: NCT05068453 . [Table: see text]