The invention relates to a pharmaceutical composition comprising a bone delivery conjugate having the structure Z-sALP-Y-Dn-X, wherein X is absent or is an amino acid sequence of at least one amino acid; Y is absent or is an amino acid sequence of at least one amino acid; Z is absent or is an amino acid sequence of at least one amino acid; Dn is a poly aspartate, wherein n=10 to 16; and sALP is a soluble alkaline phosphatase and uses thereof.