Optimization of existing domain or traditional antibodies is aimed at improving desired biological properties such as binding affinity, expressibility, or developability. We use several complementary techniques in combination to introduce targeted diversity into the antibody sequence. Our techniques include in vivo antibody evolution via inducible hypermutation in CDR regions. For optimization of human IgG antibody, we also use heavy chain or light chain shuffling using pre-made human heavy chain or light chain libraries, respectively. Yeast clones expressing antibodies with desired attributes are isolated by FACS followed by individual clone validation.