Triple negative breast cancer (TNBC) comprises 10-20% of all breast cancers and is characterized by rapid growth, metastasis, and recurrence. Furthermore, human TNBC often regrows after primary treatment, leading to poor prognosis in patients with TNBC. The standard cytotoxic chemotherapies for TNBC have the poor clinical benefit and severe side effects. Targeted therapies, such as monoclonal antibodies (mAbs), antibody-drug conjugates (ADCs), chimeric antigen receptor engineered T cells and small molecule inhibitors, have been developed to treat solid tumors while minimizing the side effects on normal cells, but none of these therapies has been applied to treat TNBC. Thus, targeted therapy remains an unmet medical need to effectively treat TNBC. Our preliminary studies identified the targeting surface receptors (such as CD276 and CD47) in TNBC, developed novel tumor-specific mAbs that target TNBC but not to normal cells, tested multiple small molecules showing high toxicity, established the construction and evaluation procedures of anti-CD276/CD47 ADCs, and evaluated the potential safety and anticancer efficacy of our ADCs in vitro and in vivo. Our central hypothesis is that the ADCs-based therapy can effectively eliminate TNBC with a limited side effect via integrated anti-cancer mechanisms. In this study, we propose to develop targeted therapies for curative treatment of TNBC. In Aim 1, we aim to build an effective platform of ADC therapies to treat CD276+ TNBC, and identify the most efficient treatment strategy by investigating the targeting specificity, ADC payloads-mediated anti-TNBC efficacy, and anti-CD276 mAb-induced immune cell activation and suppression of tumor angiogenesis. In Aim 2, we will develop anti-CD47 ADC-based targeted therapies to eliminate CD47+ TNBC, especially chemotherapy-induced CD47+ TNBC, and prevent tumor recurrence and metastasis. We will investigate the anti-tumor efficacy using multiple TNBC cell lines and xenograft tumors, and delineate the anti-TNBC mechanisms, including ADC- mediated drug cytotoxicity, anti-CD47 mAb-dependent cellular cytotoxicity, and synergistic action of ADC drug and anti-CD47 mAb. In Aim 3, we plan to use our established protocols of maximal tolerated dose, pharmacokinetics, biodistribution and anti-tumor efficacy to evaluate the therapeutic values of our combined dual CD276 and CD47 targeting ADCs in our metastatic syngeneic TNBC xenograft models after surgery and/or chemotherapy. If the anti-cancer efficacy is confirmed in the preclinical models, this will be the first combined ADCs-based targeted therapy for TNBC treatment, which may overcome drug resistance, enhance cytotoxicity to tumor cells with low dose, limit systemic toxicities, and prevent antigen-loss relapse. Importantly, our designs will model clinical therapies for potential translational application, which would improve life quality and the survival rate of TNBC patients in combination with surgery and/or chemotherapy.

The triple negative breast cancer (TNBC), which is characterized by rapid growth, metastasis and recurrence, comprises about 15% of all breast cancers, and often regrows after primary treatment, leading to poor prognosis in TNBC patients. It is highly desired to develop an effective therapy for elimination of TNBC. Therefore, the combined antibody-drug conjugates (ADCs) that integrate the advantages of specific targeting and antibody- dependent cellular cytotoxicity of a novel tumor-specific monoclonal antibody and the direct cytotoxicity of the antibody-delivered payloads will be developed and characterized for TNBC treatment.