Abstract 5958: CD276/CD47-targeted antibody-drug conjugates to treat triple-negative breast cancers

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Abstract Triple-negative breast cancers (TNBCs) are highly aggressive, heterologous and frequently recurrent. The standard radiotherapy and chemotherapy have limited clinical benefits while the combined therapies or antibody-drug conjugates (ADCs) are promising to treat TNBC. The objective of this study was to develop a combined therapy, CD276/CD47-targeted ADCs, for TNBC treatment. Specifically, the CD276 and CD47 surface receptors were identified with immunohistochemistry staining of drug-sensitive and resistant patient tissues and confirmed in other assays. Two innovative monoclonal antibodies (mAbs), i.e. anti-CD276 mAb and anti-CD47 mAb that target the N-glycosylated extracellular domains (Leu29-Pro245 and Gln19-Glu141) of surface receptors, were developed using hybridoma technology. The top mAb clones with high surface binding, drug delivery and affinity were screened, produced in fed-batch culture, purified using liquid chromatography, and conjugated with payload mertansine (DM1). Flow cytometry, confocal microscopy, and in vivo imaging system (IVIS) showed that the CD276/CD47 ADCs effectively target human and mouse TNBC cells and xenograft models. The in vitro anti-cancer cytotoxicity was confirmed in multiple cell lines (MDA-MB-468, MDA-MB-231, 4T1), and in vivo evaluations using TNBC cell line-derived xenograft models and patient-derived xenograft (PDX) models demonstrated high anti-tumor efficacy and tumoral immunity of the dually targeted ADCs. In addition, whole blood analysis indicated that neither CD276 mAb nor CD47 mAb showed general immune toxicity in immunocompetent model. The maximal tolerated dose (MTD), pharmacokinetics (PK) and biodistribution will be further investigated. This study indicated that the ADCs dually targeting CD276 and CD47 have great potential to treat TNBCs. Citation Format: Yingnan Si, Kai Chen, Seulhee Kim, Zhuoxin Zhou, Lufang Zhou, X. Margaret Liu. CD276/CD47-targeted antibody-drug conjugates to treat triple-negative breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5958.