Successful 15-step desensitization protocol for nivolumab and ipilimumab after a skin-test confirmed anaphylaxis to polysorbate 80: case report.

Checkpoint inhibitors (CPIs) are essential in advanced melanoma but may cause rare, potentially life-threatening hypersensitivity reactions. We report a 53-year-old man who developed grade III anaphylaxis during his first nivolumab infusion. Allergy testing identified immediate hypersensitivity to polysorbate 80 (PS80), an excipient shared by several CPIs, while testing for polysorbate 20 was also positive, limiting alternative treatment options. Following melanoma progression requiring combined immunotherapy, a one-bag, 15-step desensitization protocol was developed for sequential administration of nivolumab and ipilimumab. Both desensitizations were successfully completed without anaphylaxis, allowing subsequent administration of standard doses. This case demonstrates the feasibility of desensitization to both nivolumab and ipilimumab in a patient with confirmed PS80 hypersensitivity and provides a practical therapeutic option when no suitable excipient-free CPI is available.