Patent ID: 7098006

Claim:
A process for the preparation of an antibody chain having a variable domain comprising three complementarity determining region(s) (CDRs), designated CDR1, CDR2 and CDR3, and a framework, wherein the CDRs are those of a first mammalian species and the framework and any constant domain present are those of a second different mammalian species, which process comprises: (i) mutating one or more individual bases within the framework-encoding regions of DNA encoding a variable domain of an antibody chain of the said first mammalian species such that the resulting framework-encoding regions encode the said framework of the said second mammalian species; and (ii) expressing the said antibody chain utilising the DNA resulting from step (i); step (i) being such that an antibody incorporating the antibody chain expressed in step (ii) retains the antigen binding capability of the antibody of the first mammalian species, wherein the variable domain framework of said second mammalian species is selected from variable domain sequences of the second mammalian species that have the most overall homology to that of said variable domain sequence of the first mammalian species, homology being determined on the basis of the respective variable domains including at least CDR1 and CDR2.