AC480 (BMS-599626) is a potent small-molecule inhibitor primarily investigated for its antitumor activity. It functions by selectively inhibiting members of the ErbB family of receptor tyrosine kinases, particularly EGFR (ErbB1) and HER2 (ErbB2), which are often overexpressed or dysregulated in various cancers. Due to this mechanism, it has been studied extensively in oncology for the treatment of solid tumors, including non-small cell lung cancer, breast cancer, and head and neck cancers. Its ability to block downstream signaling pathways such as PI3K/AKT and MAPK/ERK makes it effective in reducing cancer cell proliferation, survival, and migration. AC480 has shown activity against both wild-type and certain mutant forms of EGFR, making it a candidate for use in tumors resistant to other EGFR inhibitors. In preclinical studies, AC480 demonstrated enhanced efficacy when used in combination with chemotherapy or other targeted agents, suggesting a role in combination therapy regimens. Although clinical development has been limited, its pharmacological profile supports continued interest in its potential as a targeted cancer therapeutic, especially in tumors driven by ErbB receptor signaling.