Novel treatment strategies for patients with HER2‑positive breast cancer who do not benefit from current targeted therapy drugs (Review)

Human epidermal growth factor receptor-2 positive breast cancer (HER2⁺ BC) is characterized by a high rate of metastasis and drug resistance. The advent of targeted therapy drugs greatly improves the prognosis of HER2⁺ BC patients. However, drug resistance or severe side effects have limited the application of targeted therapy drugs. To achieve more effective treatment, considerable research has concentrated on strategies to overcome drug resistance. Abemaciclib (CDK4/6 inhibitor), a new antibody-drug conjugate (ADC), src homology 2 (SH2) containing tyrosine phosphatase-1 (SHP-1) and fatty acid synthase (FASN) have been demonstrated to improve drug resistance. In addition, using an effective vector to accurately deliver drugs to tumors has shown good application prospects. Many studies have also found that natural anti-cancer substances produced effective results during <i>in vitro</i> and <i>in vivo</i> anti-HER2⁺ BC research. This review aimed to summarize the current status of potential clinical drugs that may benefit HER2⁺ BC patients in the future.