Placental alkaline phosphatase (ALPP) is a membrane-bound enzyme normally restricted to placental tissue. However, it is aberrantly overexpressed in various solid tumors, including ovarian, testicular, and cervical cancers, making it a highly specific tumor biomarker. High-affinity anti-ALPP antibodies are essential for early clinical cancer diagnostics (IHC/serum screening) and the development of targeted therapies like antibody-drug conjugates (ADCs) and CAR-T cells.