Described herein is an antibody format, which is amenable to bispecific antibody creation. This format is referred to herein as “Domain Insertion Immunoglobulin G” or “(Di-IgG)”. The Di-IgG molecules are capable of specifically binding two different antigens simultaneously, show high level recombinant expression, and are sufficiently aggregation-free to be amenable to commercial production. Further described herein are, Di-IgG-encoding nucleic acids and vectors, host cells for making Di-IgGs, Di-IgG pharmaceutical compositions, and methods of treatment.
