A method of treating a human having a condition or disease related to a bone defect characterized by at least one of: increased level of an alkaline phosphatase ligand, particularly PPi, PLP, or PEA； and decreased alkaline phosphatase activity, compared to a human without said condition or disease, comprising administering to the human a therapeutically effective amount of a polypeptide comprising the amino acid sequence of SEQ ID NO: 1, wherein the polypeptide is administered through at least one subcutaneous injection to the human in a frequency of fewer than three times each week.
