Abstract
Breast cancer encompasses a diverse array of conditions classified as hormone receptor-positive, human epidermal growth factor receptor 2-positive, and triple-negative breast cancer subtypes, dictating treatment approaches. The therapeutic strategies commonly involve addressing estrogen receptors (ER) and HER2, which have exhibited efficacy in managing cancer. Nevertheless, the prevalence of resistance to these therapies, whether inherent or acquired, persists despite the introduction of novel treatment modalities. Progress in comprehending the biology of tumors has facilitated the identification of fresh targets, such as inhibitors targeting different pathways like phosphoinositide 3-kinase/mammalian target of rapamycin (PI3K/mTOR), cell-cycle regulation, heat shock protein, and epigenetic pathways, demonstrating encouraging outcomes in clinical experiments. For example, the mTOR inhibitor everolimus has been sanctioned for ER+ breast cancer and resistance to aromatase inhibitors in the advanced or metastatic phase. Triple-negative breast cancer, characterized by the absence of estrogen receptors, progesterone receptors, and HER2, currently lacks established targeted therapies. While poly (ADP-ribose) polymerase inhibitors exhibit effectiveness in BRCA-related cancers, their efficiency in addressing triple-negative breast cancer residues is uncertain. This paper furnishes a comprehensive outline of the principal targeted therapies presently employed or under exploration for breast cancer treatment within the three clinical subsets.