HUMANIZATION OF A MOUSE ANTI-HUMAN INTERLEUKIN-6 RECEPTOR ANTIBODY COMPARING 2 METHODS FOR SELECTING HUMAN FRAMEWORK REGIONS

Mouse monoclonal antibody AUK12-20 binds to human IL-6 receptor and in hibits IL-6 functions. It has been humanized by CDR-grafting for thera peutic use. In the design of reshaped human AUK12-20 V(L) region, the human framework regions (FRs) from.the human Bence-Jones protein REI w ere used. The reshaped human AUK12-20 light chain, in combination with chimeric AUK12-20 heavy chain, bound to antigen as well as chimeric A UK12-20 antibody. In the design of reshaped human AUK12-20 V(H) region , two sets of the human FRs were chosen and compared. One set was from the consensus amino acid sequence for human V(H) regions subgroup (HS G)-I and the other set was from human antibody HAX, the most similar h uman V(H) region found in a database of human immunoglobulin sequences . The HSG-I-based and the HAX-based reshaped human AUK12-20 heavy chai ns in combination with the reshaped human AUK12-20 light chain, showed approximately 90 and 100% antigen-binding and competition-binding act ivities as compared to the chimeric or mouse AUK12-20 heavy chains. Mo st importantly, these humanized antibodies inhibited the IL-6-dependen t tumor cell growth as well as the original mouse antibody suggesting that these humanized antibodies could be efficacious in human patients . Our results show that both approaches for the design of reshaped hum an antibodies can be used for successful humanization. The approach ba sed on FRs from the most similar individual human antibody, however, s eemed to be best for designing a reshaped human antibody that mimicked as closely as possible the original mouse antibody.