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

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. 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. 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. 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.