Humanization of a mouse monoclonal antibody directed against a cell surface-exposed epitope of membrane-associated heat shock protein 70 (Hsp70).

The translocation of heat shock protein 70 (mHsp70) into the plasma membrane has been found to be associated with various cancers including breast cancer, head-and-neck cancer, and acute myeloid leukemia. Parts of the C-terminal substrate-binding domain (SBD) of mHsp70 are accessible to binding by monoclonal antibodies (mAb). One of these mAbs, cmHsp70.1, has been extensively studied and showed promising results as diagnostic and therapeutic antibody. Here, we describe cloning and humanization of cmHsp70.1 by complementarity determining region grafting resulting in an antibody (humex) possessing a similar affinity (3 nM) as the parental antibody and an improved production and thermal stability. Epitope mapping confirmed that the parental, chimeric, and humanized antibodies recognize the same region including amino acids 473-504 of the SBD. Hence, this humanized antibody provides a basis for further development of an anti-mHsp70 antibody therapy.