definiens: shall mean ( i ) an immunoglobulin protein or similar immune - derived, antigen - binding protein, ( ii ) a fragment of suchimmunoglobulin protein or similar immune - derived, antigen - binding protein ( e.g., Fab fusion proteins ), or ( iii ) an immune - derived antigen - binding fusion protein ( e.g., Fc fusion protein ) or other modified protein construct, which in each case has an antigen - binding region that hasspecific binding affinity for the antigen to which the same is directed . For clarity, the antigen - binding region of any such protein may beobtained by ( A ) conventional immunization of animals with the particular antigen of interest and/or one or more other antigens able to crossreact with such particular antigen, ( B ) lymphocyte cultures with the particular antigen of interest and/or one or more other antigens able tocross react with such particular antigen, ( C ) affinity selection from libraries of variable or hypervariable domains with the particular antigen ofinterest and/or one or more other antigens able to cross react with such particular antigen, or ( D ) genetic engineering of such proteins derivedpursuant to ( A ), ( B ) or ( C )