We generated humanized knock-in mice to evaluate the in vivo efficacy of human IO antibodies. For example, human OX40 knock-in (B-hOX40) mice were generated with a chimeric OX40 receptor, which is recognizable by stimulatory human OX40 antibodies. Additionally, more knock-in mice targeting stimulatory immune checkpoint molecules were developed and validated, such as B-hCD137, B-hGITR, B-hCD27, B-hCD40, B-hCD28, B-hCD3 et al,.
CD47 is a transmembrane protein found on the surface of many cells in the body. Its expression is often up-regulated in many cancer cells. The receptor of CD47 was identified as SIRPa, which is expressed on phagocytic cells. Engagement of SIRPa by CD47 serves as “do not eat me” signal, thus inhibiting the phagocytic activity of macrophages.
CTLA4 (cytotoxic T-lymphocyte-associated protein 4), is a member of the immunoglobulin superfamily. It is expressed in T cells upon activation and transmits an inhibitor signal to T cells. Also, it is constitutively expressed in regulatory T cells (Tregs) which is associated with their immunosuppressive phenotype. CTLA4 is homologous to the co-stimulatory protein CD28, and both receptor binds to CD80 and CD86.
We developed a cohort of OX40 specific antibodies using the classic hybridoma technology. In order to screen their efficacy to stimulate anti-tumor activity in live animals, we managed to rank these antibodies using Biocytogen’s humanized mouse platform of immune checkpoints. Specifically, we utilized humanized OX40 mice (h-OX40) and implanted syngeneic tumors subcutaneously, followed by treating mice with purified testing antibodies.
Having an access to Biocytogen’s antibody discovery and in vivo efficacy screening platform for immune checkpoints, we asked whether we could find suitable anti-CD40 reagents which can successfully combat developed tumors in preclinical settings. We designed a powerful screening strategy using Biocytogen’s humanized CD40 mouse (B-hCD40).
We generated humanized double knock-in mouse to evaluate the in vivo efficacy of combination therapy. For example, humanized double Knock-in B-hPD-1/hOX40 mice pairing with mouse cancer cells, demonstrated a synergistic effect of using hPD-1 and hOX40 antibodies.