Preclinical Proof of Concept for the Single‐Protein Anticancer Molecule Targeting Both a Tumor Surface Antigen and an Intracellular Oncoprotein

ABSTRACT Although antibody‐drug conjugates (ADCs) are a widely used platform for developing various anticancer immunotherapeutics, the use of cancer non‐selective chemicals is recognized as a drawback of ADC development. To address the issues regarding the safety and manufacturing complexity of ADCs, this study conceptualizes a single‐protein platform, named dual‐targeting anticancer therapeutics (DTAT), that links a cancer cell‐selective cytotoxic peptide to an antibody via a linker peptide cleavable on cancer cells. As a model molecule for preclinical proof of the concept, an anti‐Her2 single‐chain variable fragment (scFv)‐based DTAT protein named DTAT‐D311 is established, which contains a recently developed anticancer peptide, herein named CPTin, as its cell‐penetrating payload. This recombinant single protein efficiently induces the apoptotic death of cancer cells, which is characterized by a very early onset. In terms of in vivo efficacy in suppressing tumor growth, DTAT‐D311 outperforms the anti‐Her2 therapeutic antibody, trastuzumab (Herceptin). By targeting an intracellularly addictive oncoprotein, CP2c, CPTin exhibits broad‐spectrum anticancer activity. In conclusion, this study demonstrates that DTAT provides an innovative pharmaceutical modality to target both a tumor surface antigen and an intracellular oncoprotein. In addition, DTAT‐D311 is suggested to be a promising biopharmaceutical agent for targeted immunotherapy against Her2‐positive cancers, exhibiting favorable safety profile.