Toripalimab (anti-PD-1) plus recombinant human endostatin as adjuvant therapy in patients with resected stage III melanoma: Interim analysis of an open-label phase II trial.

e21557 Background: Patients with completely resected stage III melanoma are under high risk of disease recurrence. Recurrence-free survival (RFS) remains unsatisfactory despite there is adjuvant anti-PD-1 monotherapy following surgery, with the 1-year RFS about 70% and 2-year RFS about 49% in our country. It's urgent to explore combined regimens with anti-PD-1 to further improve the RFS. Here we report the interim efficacy and safety results of toripalimab (a PD-1 inhibitor) plus recombinant human endostatin (an angiogenesis inhibitor) as combined adjuvant therapy for patients with resected stage III melanoma. Methods: This prospective single-center, single-arm, open-label phase II trial screened adult patients with stage III melanoma who had undergone complete tumor resection within the previous 13 weeks for eligibility. Toripalimab was administrated in intravenous drip to patients at 3 mg/kg every 2 weeks in a 4-week cycle (day 1 and day 15 of each cycle), for up to 13 cycles or until disease recurrence, unacceptable toxicity or decease. Recombinant human endostatin was administrated in a continuous intravenous infusion at a dose of 210 mg from day 1 to day 3 for each 4-week cycle, for up to 6 cycles or until disease recurrence, unacceptable toxicity or decease. The primary endpoints were the 1-year and 2-year RFS. Results: By the data cut-off on Jan 25, 2024, 43 eligible patients with resected stage III melanoma between October 2021 and December 2023 were enrolled. In ITT population (n = 43), patients' median age was 56 (IQR 52~69) years. There were 25 (58%) male and 18 (42%) female; 27 (63%) with acral melanoma and 16 (37%) with cutaneous melanoma. With a median follow-up of 14 months, the 1-year and 2-year RFS rates were 83% and 71%, respectively. For security, 33 (77%) patients experienced at least one adverse event (AE), including 27 grade 1-2 AEs and 6 grade 3~4 AEs. One patient discontinued the combined therapy due to immunotherapy-associated myocarditis. Conclusions: Toripalimab in combination with recombinant human endostatin as adjuvant therapy could further improve disease-free survival in Chinese patients with completely resected stage III melanoma, with a manageable toxicity profile. Clinical trial information: 05907512 .