A novel bispecific antibody targeting CD3 and prolactin receptor (PRLR) against PRLR-expression breast cancer

摘要

PRLR is one kind of type I cytokine receptors highly expressed in breast cancer cells [ ]. It is only slightly expressed in normal breast tissues while highly expressed in tumor breast tissues [ – ]. Engineered monoclonal antibodies (mAbs) are important therapeutic proteins [ ]. Jason has reported that humanized anti-PRLR antibody could inhibit the dimerization of PRL and its receptor PRLR, which subsequently could inhibit the tumor cell proliferation that mediated by its downstream signaling effectively [ ]. The blocking PRLR antibody has shown a very good safety profile in phase I clinical trials [ ]. In addition, an anti-PRLR antibody-drug conjugate (ADC) had significant PRLR-specific antitumor activity against breast cancer [ ], and bispecific antibody-ADCs bridging HER2 and PRLR improved efficacy of HER2 ADCs [ ]. Therefore, PRLR is considered to be a tumor associated antigen (TAA) with a high potential in clinical applications. However, the PRLR antibody is showed to be lack of efficacy in clinical trials despite of its favorable pre-clinical data [ ]. Tumor immunotherapies including immune checkpoints [ , ], CAR-T [ ], oncolytic virus [ ] and bispecific antibodies [ ] are proved to be effective anti-tumor treatments. The PD-1/PD-L1 checkpoint blockade has significant progress in melanoma, lung cancer, and lymphoma [ , ], and a number of clinical trials in breast cancer and glioma are also being efficiently carried out worldwide [ , ]. Bispecific antibodies targeting the CD3 antigen, which could recruit T cells to tumor cells to enhance cytotoxicity, are demonstrated to have both good pre-clinical and clinical potency. Currently there are two CD3-bispecific antibodies approved for treatment, one is BiTE-based CD3/CD19 (Blinatumomab) [ ] for the treatment of B cell acute lymphoblastic leukemia and the other is Triomab-based CD3/EpCAM (Catumaxomab) [ ] indicated for malignant ascites caused by EpCAzM+ cancer cells. Moreover there are many other clinical trials with bispecific antibodies for the treatment of solid tumors and hematological tumors based on other tumor antigens such as CEA [ ], HER2 [ ], EGFRvIII [ ], EGFR [ ] and CD20 [ ]. It is reported more than 60 structures have been developed for the bispecific antibodies, including symmetric and asymmetric structures based on IgG fragments and types used [ ]. Recently our lab has developed a novel universal platform for generating IgG type bispecific antibodies (BAPTS). The platform is based on split intein, which could solve the mismatch between light and heavy chains with high efficiency through its trans-splicing function. The CD3/HER2 bispecific antibody generated with this method showed a good affinity for its targets and a favorable pharmacokinetic profile, as well as a significant anti-tumor activity [ ]. In this research we generated a bispecific antibody PRLR-DbsAb targeting both PRLR and T cell surface antigen CD3 by BAPTS platform. In vitro PRLR-DbsAb efficiently inhibited the growth of breast cancer cells with high PRLR expression, accompanied with T cell activation and cytokines release. In vivo it promoted the infiltration of immune cells that subsequently inhibited the tumor development and extended the survival time of mice. As a result, PRLR-DbsAb could be a new treatment for breast cancer.