Five-Year Follow-Up of POLARIS-01 Phase II Trial: Toripalimab as Salvage Monotherapy in Chinese Patients With Advanced Melanoma.

Background: To investigate the efficacy and toxicity after long-term follow-up of anti-PD-1 antibody in advanced melanoma with predominantly acral and mucosal subtypes.

Methods And Patients: In the POLARIS-01 phase II trial, 128 Chinese patients with advanced melanoma refractory to standard therapy received toripalimab until disease progression or unacceptable toxicity for ≤2 years. For those who progressed after discontinuation due to 2-year treatment completion, rechallenge was allowed. The primary objectives were safety and overall response rate (ORR).

Results: As of February 8, 2021, ORR was 17.3% (95% CI: 11.2-25.0) evaluated by the independent radiologic review committee. The median overall survival (OS) for patients with known melanoma subtypes was 16.3 m for acral, 41.5 m for nonacral cutaneous, and 10.3 m for mucosal melanoma. Thereafter, the evaluation was continued by investigators. As of November 4, 2022, 5 years after the last enrollment, median duration of response was 15.6 months (range, 3.7-64.5+), median progression-free survival (PFS) was 3.5 months (95% CI, 2.2-5.3), and 60-month OS rate was 28.5% (95% CI: 20.2-37.2). Thirteen patients completed a 2-year treatment of toripalimab, with the subtypes of acral (2/13), non-acral cutaneous (4/13), mucosal (3/13) and unknown primary (4/13). Five patients were rechallenged. Four of them, all of whom were non-mucosal, completed the rechallenge course of 2 years with PFS ≥ 24 months.

Conclusions: This is the largest prospective anti-PD-1 trial with mature data in advanced melanoma in China. Toripalimab demonstrated a manageable safety profile and durable clinical response in Chinese patients with metastatic melanoma who had failed in standard therapy. Immunotherapy seems less efficacious for long-term responders with mucosal primaries as rechallenge therapy.