SIRPA and melanoma: SIRPα-targeting antibodies, hAB21, a humanized IgG1 mAb, with an inactive Fc domain, and 1H9, a humanized IgG1 mAb, have shown, in a variety of mouse models, to be an effective adjuvant to immunotherapies against highly immunogenic tumors, including melanoma.94,95 Although not yet in clinical trials for melanoma, two anti-SIRPα mAbs are currently in phase 1/2 clinical trials for solid tumors: BI 754091, a humanized IgG4 is being trialed in colorectal and endometrial cancer (NCT03990233) and BI 765063, a humanized IgG4, is being tested in head and neck and liver cancer (NCT05249426).