In their ongoing race to develop human antibodies, Cell Genesys Inc. (CEGE) and GenPharm International reported simultaneously that they have produced human monoclonals in mice.

CEGE reported in Nature Genetics that it used gene targeting to inactivate the mice genes for generating murine antibodies. Yeast artificial chromosomes (YACs) were then used to insert large fragments of human antibody genes for heavy and K light chain loci into mouse embryo cells. The engineered mice were then bred to create animals that generate human monoclonals after immunization with a protein of interest.