Polypeptide variants

Abstract

A variant of a polypeptide comprising a human IgG Fc region is described, which variant comprises an amino acid substitution at amino acid position 329, or at two or all of amino acid positions 329, 331 and 322 of the human IgG Fc region. Such variants display altered effector function. For example, Clq binding and/or complement dependent cytotoxicity (CDC) activity may be reduced or abolished in the variant polypeptide. The application also describes an immune complex and an assay for determining binding of an analyte, such as an Fc region-containing polypeptide, to a receptor.

1 . A variant of a polypeptide comprising a human IgG Fc region, which variant comprises an amino acid substitution at amino acid position 329, or at two or all of amino acid positions 329, 331 and 322 of the human IgG Fc region, where the numbering of the residues in the IgG Fc region is that of the EU index as in Kabat.  
     
     
         2 . The variant of  claim 1  having Pro329 of the human IgG Fc region substituted with another amino acid.  
     
     
         3 . The variant of  claim 1  wherein the polypeptide comprises an antibody.  
     
     
         4 . The variant of  claim 1  wherein the polypeptide comprises a human IgG1 Fc region.  
     
     
         5 . The variant of  claim 1  which does not activate complement.  
     
     
         6 . The variant of  claim 5  which binds an FcR.  
     
     
         7 . The variant of  claim 6  which binds FcγRI, FcγRII, FcγRIII and FcRn.  
     
     
         8 . A variant of a polypeptide comprising a human IgG Fc region, which variant binds FcγRI, FcγRII, FcγRIII and FcRn but does not activate complement and comprises an amino acid substitution at amino acid position 322 or amino acid position 329, or both amino acid positions of the human IgG Fc region, where the numbering of the residues in the IgG Fc region is that of the EU index as in Kabat.  
     
     
         9 . A composition comprising the variant of  claim 1  and a physiologically acceptable carrier.  
     
     
         10 . A method for modifying a polypeptide comprising a human IgG Fc region comprising substituting an amino acid residue at amino acid position 329, or at two or all of amino acid positions 329, 331 and 322 of the human IgG Fc region, where the numbering of the residues in the IgG Fc region is that of the EU index as in Kabat.  
     
     
         11 . Isolated nucleic acid encoding the variant of  claim 1 .  
     
     
         12 . A vector comprising the nucleic acid of  claim 11 .  
     
     
         13 . A host cell comprising the vector of  claim 12 .  
     
     
         14 . A process of producing an polypeptide variant comprising culturing the host cell of  claim 13  so that the nucleic acid is expressed.  
     
     
         15 . The process of  claim 14  further comprising recovering the polypeptide variant from the host cell culture.  
     
     
         16 . A method of treating a mammal suffering from a disorder comprising administering to the mammal a therapeutically effective amount of a variant of a polypeptide comprising a human IgG Fc region, which variant binds FcγRI, FcγRII, FcγRIII and FcRn but does not activate complement and comprises an amino acid substitution at amino acid position 329, 331 or 322 of the human IgG Fc region, where the numbering of the residues in the IgG Fc region is that of the EU index as in Kabat.  
     
     
         17 . An immune complex comprising: 
 (a) an Fc region-containing polypeptide;    (b) a first target molecule which comprises at least two binding sites for the Fc region-containing polypeptide; and    (c) a second target molecule which comprises at least two binding sites for the first target molecule.    
     
     
         18 . A method for determining binding of an analyte to a receptor comprising the following steps performed sequentially: 
 (a) forming a molecular complex between the analyte and a first target molecule, wherein the first target molecule comprises at least two binding sites for the analyte; and    (b) determining binding of the molecular complex of step (a) to the receptor.    
     
     
         19 . The method of  claim 18  wherein the analyte is an Fc region-containing polypeptide.  
     
     
         20 . The method of  claim 18  wherein the receptor is a low affinity receptor.  
     
     
         21 . The method of  claim 18  wherein the receptor is an FcR.  
     
     
         22 . The method of  claim 18  wherein the molecular complex of step (a) further comprises a second target molecule which comprises at least two binding sites for the first target molecule.  
     
     
         23 . A kit useful for determining binding of an analyte to a receptor comprising: 
 (a) a first target molecule which comprises at least two binding sites for the analyte; and    (b) a second target molecule which comprises at least two binding sites for the first target molecule.