Used in targeted cancer therapy, particularly for melanoma and breast cancer. Binds specifically to GPNMB (glycoprotein non-melanoma associated protein), a protein overexpressed in tumor cells. This binding enables selective delivery of cytotoxic agents when conjugated to drugs, as in antibody-drug conjugates like glembatumumab vedotin. Facilitates tumor cell killing while minimizing damage to normal cells. Also used in diagnostic imaging to detect GPNMB-positive tumors. Supports research in immunotherapy and biomarker development for cancer progression.