Adjuvant recombinant human endostatin combined with toripalimab (anti-PD-1) in locally advanced melanoma: an exploratory phase 2 clinical trial incorporating single-cell RNA/TCR/BCR sequencing.

PURPOSE: In East Asia, melanoma mainly presents as the acral lentiginous subtype, followed by the cutaneous subtype. Patients with completely resected stage III or IV melanoma in East Asia are at a high risk of disease recurrence. The adjuvant efficacy of PD-1 inhibitors as monotherapy remains limited in this patient population, underscoring the need for combination strategies. PATIENTS AND METHODS: This prospective, single-arm, phase II trial (NCT05907512) aimed to investigate adjuvant recombinant human endostatin (rh-endostatin, an angiogenesis inhibitor) combined with toripalimab (a PD-1 inhibitor) in Chinese patients with resectable stage III to oligometastatic stage IV melanoma. The primary endpoint was 1-year relapse-free survival (RFS). Paired peripheral blood samples before and after the combined adjuvant therapy were collected for single-cell RNA sequencing, TCR/BCR sequencing, and biomarker identification. Two independent real-world cohorts of patients with locally advanced melanoma were assessed to validate the biomarkers. RESULTS: Forty-three eligible patients with resected stage III melanoma were prospectively enrolled. No patients with resected oligometastatic stage IV disease were enrolled. The 1-year RFS of the patients was 74.4%, with a median RFS of 27 months (95% confidence interval: 19, not reached). Anemia (12/43, 27.9%), elevated liver enzymes (11/43, 25.6%), and thyroid dysfunction (9/43, 20.9%) were the three most common treatment-related adverse events. The combined adjuvant therapy expanded the patients’ peripheral total T and NK cells, increased circulating CD8+ Tem and Teff cells and their TCR clonal diversities, improved the antigen-presenting capacity of B cells, elevated BCR clonal diversity, and raised the number of non-classical monocytes and their antigen-presenting capacity. The neutrophil-to-lymphocyte ratio and circulating CD8+ Tem cells were supported as candidate biomarkers associated with outcomes in the independent real-world cohorts. CONCLUSIONS: Adjuvant rh-endostatin combined with toripalimab shows encouraging clinical activity and may be associated with a potential survival benefit in Chinese patients with resected locally advanced melanoma. Adverse reactions were manageable. The increased quantities and functional changes of peripheral T cells, NK cells, B cells, and monocyte subsets provide mechanistic insights for the optimization of immunotherapy.