Abstract:
Background:
Immune checkpoint blockade (ICB) therapy, represented by PD-1/PD-L1 inhibitors, has revolutionized cancer treatment by reactivating immune responses within the tumor microenvironment (TME). However, resistance to ICB therapy often occurs due to the highly immunosuppressive nature of the TME. Interleukin-12 (IL12), a key immunoregulatory cytokine, can enhance cytotoxic T and NK cell activity, inhibit angiogenesis, promote lymphocyte trafficking, and reverse tumor-induced immunosuppression. Despite its potent antitumor effects, systemic administration of recombinant IL12 has shown limited clinical application due to a narrow therapeutic window and severe side effects. Recent studies have demonstrated that combining IL12 with PD-1 blockade may offer synergistic antitumor efficacy, making it a promising strategy for overcoming resistance to ICB therapy.
Methods:
To enable preclinical evaluation of anti-human PD-1 and IL12-based therapies, Biocytogen developed a novel triple humanized mouse model (B-hPD-1 plus/hIL12RB1/hIL12RB2) expressing human PD-1, IL12 receptor β1, and IL12 receptor β2. Flow cytometry was used to confirm the expression of human PD-1 on T cells from spleens of these mice. Functional validation of the humanized IL12 receptor complex was conducted by stimulating isolated CD4+ T cells from these mice with human IL12 and measuring IFN-γ secretion. A bispecific antibody targeting human PD-1 and IL12 (provided by a client) was tested in vivo using the MC38 colon cancer model established in the triple humanized mice.
Results:
Human PD-1 expression was confirmed on splenic T cells of B-hPD-1 plus/hIL12RB1/hIL12RB2 mice. In vitro stimulation with mouse IL12 induced IFN-γ secretion from CD4+ T cells of C57BL/6 mice, while human IL12 induced IFN-γ secretion from CD4+ T cells of the humanized mice, confirming the functionality of the human IL12 receptor complex. In vivo, treatment with the anti-human PD-1/IL12 bispecific antibody significantly inhibited MC38 tumor growth in B-hPD-1 plus/hIL12RB1/hIL12RB2 mice.
Conclusion
The B-hPD-1 plus/hIL12RB1/hIL12RB2 humanized mouse model provides a valuable platform for evaluating combination immunotherapies targeting PD-1 and IL12 pathways. Functional validation of human IL12 receptor signaling and the demonstrated antitumor efficacy of the PD-1/IL12 bispecific antibody in this model support its potential for preclinical and translational cancer immunotherapy research.
