Over the past years, monoclonal antibodies have been successfully utilized in clinical trials to block or activate key mediators of immune checkpoint pathways, including CTLA-4, PD-1, PD-L1 and OX40 et.al. Although significant benefits including complete regression and long-term survival were reported among the majority of participants, not all patients respond. In order to optimize the efficacy and minimize toxicities of anticancer immunotherapies, immune checkpoint antibodies are being tested in combination with other conventional therapeutics and newer immunotherapies. However, along the IO drug development process, in vivo efficacy models have always been a rate-limiting step, especially for the combination therapy of two IO antibodies.
Here, we generated human PD-1 knock-in (B-hPD-1) mice with a chimeric PD-1 receptor, which is recognizable by human PD-1 antibodies, and can be used to test human PD-1 antibody. Mouse colon cancer MC38 were genetically modified with over-expression of hPD-L1 and knock-out of mPD-L1 (MC38-hPD-L1) and used to evaluate the in vivo efficacy of human PD-L1 antibodies. RNA and protein expression of human PD-1 were evaluated by RT-PCR and flow cytometry. We utilized this humanized PD-1 mice and implanted MC38-hPD-L1 subcutaneously, followed by treating mice with Keytruda/Tecentriq and/or Cisplatin. In this way, we also generated double humanized PD-1/OX40 mouse (B-hPD-1/hOX40) to evaluate the in vivo efficacy of combination therapy. The synergistic effect of Keytruda and human OX40 Ab were evaluated by using humanized double Knock-in B-hPD-1/hOX40 mice pairing with three syngeneic tumor models respectively.
Both the FDA approved human PD-1 antibody Keytruda and human PD-L1 antibody Tecentriq showed a synergistic effect with chemotherapy Cisplatine in B-hPD-1 mice inoculated with MC38-hPD-L1 cells. Keytruda and anti-human OX40 mAb shown clear combination effect in B-hPD-1/OX40 mouse with not only hot tumor MC38, but also moderate tumor EL4 and cold tumor B16F10.
B-hPD-1 mouse and B-hPD-1/hOX40 mouse, represent useful in vivo efficacy models for evaluation of the combination effects of IO/Chemotherapy drugs and IO/IO.
Beijing Biocytogen Co., Ltd.
Beijing Biocytogen Co., Ltd.
All authors have declared no conflicts of interest.