Ifosfamide alleviates autoimmune toxicity and enhances antitumor efficacy in melanoma immunotherapy

Autoimmune toxicity affects up to 60 % of patients receiving immune checkpoint inhibitor (ICI) therapy for cancer, presenting a notable clinical obstacle that constrains its wider application. Hence, there is an imperative demand to develop novel strategies to manage immune-related adverse events (irAEs). Ifosfamide (IFO) shares structural and functional resemblances with cyclophosphamide (CPA). Despite the acknowledged dual anti-tumor and immunomodulatory effects of CPA, the specific effect of IFO on autoimmune conditions remains elusive. Here, we evaluated the efficacy of IFO on experimental autoimmune uveitis (EAU) mouse models and explored the cell-specific effects of IFO under autoimmune conditions using single-cell RNA sequencing. Our data indicated that IFO effectively alleviated inflammatory infiltration and reversed pathological alterations of EAU. Subsequent single-cell data analysis and in vivo experiments suggested IFO exerted broad suppressive effects on autoimmune responses, concurrently restoring the balance between Th17 and Treg populations. In addition, we observed that IFO enhanced CD8⁺ T cell activation and its cytotoxic immune responses, highlighting the cell-type-specific immunomodulatory effects of IFO. Moreover, we constructed EAU models on tumor-bearing mice under ICI treatment, and found that ICI exacerbated EAU symptoms. IFO not only possessed anti-tumor effects as monotherapy, but also augmented ICI efficacy by promoting CD8⁺ T cell-mediated immunity. Furthermore, we found that IFO alleviated EAU symptoms exacerbated by ICI treatment and effectively restored Th17/Treg balance. Our results elucidated the immunomodulatory effects of IFO treatment, providing evidence for the application of IFO in managing autoimmune conditions and irAEs.