Compositions and methods for increasing bone mineralization

Abstract

A novel class or family of TGF-β binding proteins is disclosed. Also disclosed are assays for selecting molecules for increasing bone mineralization and methods for utilizing such molecules. In particular, compositions and methods relating to antibodies that specifically bind to TGF-beta binding proteins are provided. These methods and compositions relate to altering bone mineral density by interfering with the interaction between a TGF-beta binding protein sclerostin and a TGF-beta superfamily member, particularly a bone morphogenic protein. Increasing bone mineral density has uses in diseases and conditions in which low bone mineral density typifies the condition, such as osteopenia, osteoporosis, and bone fractures.

We claim the following:  
     
         1 . An antibody, or an antigen-binding fragment thereof, that binds specifically to a sclerostin polypeptide, said sclerostin polypeptide comprising an amino acid sequence set forth in SEQ ID NOS: 2, 6, 8, 14, 46, or 65, wherein the antibody competitively inhibits binding of the sclerostin polypeptide to at least one of (i) a bone morphogenic protein (BMP) Type I Receptor binding site and (ii) a BMP Type II Receptor binding site, wherein the BMP Type I Receptor binding site is capable of binding to a BMP Type I Receptor polypeptide comprising an amino acid sequence set forth in a sequence selected from the group consisting of GenBank Acc. Nos. NM — 004329 (SEQ ID NO: 102); D89675 (SEQ ID NO: 103); NM — 001203 (SEQ ID NO: 104); S75359 (SEQ ID NO: 105); NM — 030849 (SEQ ID NO: 106); D38082 (SEQ ID NO: 107); NP — 001194 (SEQ ID NO: 108); BAA19765 (SEQ ID NO: 109); and AAB33865 (SEQ ID NO: 110) and wherein the BMP Type II Receptor binding site is capable of binding to a BMP Type II Receptor polypeptide comprising the amino acid sequence set forth in a sequence selected from the group consisting of GenBank Ace. NOs. U25 110 (SEQ ID NO: 111); NM — 033346 (SEQ ID NO: 112); Z48923 (SEQ ID NO: 114); CAA88759 (SEQ ID NO: 115); and NM — 001204 (SEQ ID NO: 113).  
     
     
         2 . An antibody, or an antigen-binding fragment thereof, that binds specifically to a sclerostin polypeptide and that impairs formation of a sclerostin homodimer, wherein the sclerostin polypeptide comprises an amino acid sequence set forth in SEQ ID NOS: 2, 6, 8, 14, 46, or 65.  
     
     
         3 . The antibody of either  claim 1  or  claim 2 , wherein the antibody is a polyclonal antibody.  
     
     
         4 . The antibody of either  claim 1  or  claim 2 , wherein the antibody is a monoclonal antibody.  
     
     
         5 . The antibody of  claim 4  wherein the monoclonal antibody is selected from the group consisting of a mouse monoclonal antibody, a human monoclonal antibody, a rat monoclonal antibody, and a hamster monoclonal antibody.  
     
     
         6 . A hybridoma cell producing the antibody of  claim 4 .  
     
     
         7 . A host cell that is capable of expressing the antibody of  claim 4 .  
     
     
         8 . The antibody of either  claim 1  or  claim 2 , wherein the antibody is a humanized antibody or a chimeric antibody.  
     
     
         9 . A host cell that is capable of expressing the antibody of  claim 8 .  
     
     
         10 . The antibody of either  claim 1  or  claim 2 , wherein the antigen-binding fragment is selected from the group consisting of F(ab′) 2 , Fab′, Fab, Fd, and Fv.  
     
     
         11 . The antibody of either  claim 1  or  claim 2  that comprises a single chain antibody.  
     
     
         12 . A host cell that is capable of expressing the antibody of  claim 11 .  
     
     
         13 . A composition comprising an antibody, or antigen-binding fragment thereof, according to either  claim 1  or  claim 2  and a physiologically acceptable carrier.  
     
     
         14 . An immunogen comprising a peptide comprising at least 21 consecutive amino acids and no more than 50 consecutive amino acids of a SOST polypeptide, said SOST polypeptide comprising an amino acid sequence set forth in SEQ ID NOS: 2, 6, 8, 14, 46, or 65, wherein the peptide is capable of eliciting in a non-human animal an antibody that binds specifically to the SOST polypeptide and that competitively inhibits binding of the SOST polypeptide to at least one of (i) a bone morphogenic protein (BMP) Type I Receptor binding site and (ii) a BMP Type II Receptor binding site, wherein the BMP Type I Receptor binding site is capable of binding to a BMP Type I Receptor polypeptide comprising an amino acid sequence set forth in a sequence selected from the group consisting of GenBank Acc. Nos. NM — 004329 (SEQ ID NO: 102); D89675 (SEQ ID NO: 103); NM 001203 (SEQ ID NO: 104); S75359 (SEQ ID NO: 105); NM — 030849 (SEQ ID NO: 106); D38082 (SEQ ID NO: 107); NP — 001194 (SEQ ID NO: 108); BAA19765 (SEQ ID NO: 109); and AAB33865 (SEQ ID NO: 110) and wherein the BMP Type II Receptor binding site is capable of binding to a BMP Type II Receptor polypeptide comprising the amino acid sequence set forth in a sequence selected from the group consisting of GenBank Acc. NOs. U25110 (SEQ ID NO: 111); NM — 033346 (SEQ ID NO: 112); Z48923 (SEQ ID NO: 114); CAA88759 (SEQ ID NO: 115); and NM — 001204 (SEQ ID NO: 113).  
     
     
         15 . An immunogen comprising a peptide that comprises at least 21 consecutive amino acids and no more than 50 consecutive amino acids of a SOST polypeptide, said SOST polypeptide comprising an amino acid sequence set forth in SEQ ID NOS: 2, 6, 8, 14, 46, or 65, wherein the peptide is capable of eliciting in a non-human animal an antibody that binds specifically to the SOST polypeptide and that impairs formation of a SOST homodimer.  
     
     
         16 . The immunogen of either  claim 14  or  claim 15  wherein the peptide is associated with a carrier molecule.  
     
     
         17 . The immunogen of  claim 16  wherein the carrier molecule is carrier polypeptide.  
     
     
         18 . The immunogen of  claim 17  wherein the carrier polypeptide is keyhole limpet hemocyanin.  
     
     
         19 . A method for producing an antibody that specifically binds to a SOST polypeptide, comprising immunizing a non-human animal with an immunogen according to  claim 14 , wherein (a) the SOST polypeptide comprises an amino acid sequence set forth in SEQ ID NOS: 2, 6, 8, 14, 46, or 65; (b) the antibody competitively inhibits binding of the SOST polypeptide to at least one of (i) a bone morphogenic protein (BMP) Type I Receptor binding site and (ii) a BMP Type II Receptor binding site; (c) the BMP Type I Receptor binding site is capable of binding to a BMP Type I Receptor polypeptide comprising the amino acid sequence set forth in a sequence selected from the group consisting of GenBank Acc. Nos. NM — 004329 (SEQ ID NO: 102); D89675 (SEQ ID NO: 103); NM — 001203 (SEQ ID NO: 104); S75359 (SEQ ID NO: 105); NM — 030849 (SEQ ID NO: 106); D38082 (SEQ ID NO: 107); NP — 001194 (SEQ ID NO: 108); BAA19765 (SEQ ID NO: 109); and AAB33865 (SEQ ID NO: 110); and (d) the BMP Type II Receptor binding site is capable of binding to a BMP Type II Receptor polypeptide comprising the amino acid sequence set forth in a sequence selected from the group consisting of GenBank Acc. NOs. U25110 (SEQ ID NO: 111); NM — 033346 (SEQ ID NO: 112); Z48923 (SEQ ID NO: 114); CAA88759 (SEQ ID NO: 115); and NM — 001204 (SEQ ID NO: 113).  
     
     
         20 . A method for producing an antibody that specifically binds to a SOST polypeptide, said SOST polypeptide comprising an amino acid sequence set forth in SEQ ID NOS: 2, 6, 8, 14, 46, or 65, comprising immunizing a non-human animal with an immunogen according to  claim 15 , wherein the antibody impairs formation of a SOST homodimer.