Used in the treatment of hormone receptor-positive, HER2-negative advanced or metastatic breast cancer, particularly in patients with a PIK3CA mutation. It works by inhibiting the PI3K alpha isoform, a key component in the PI3K/AKT/mTOR signaling pathway, which is often dysregulated in cancer cells. By blocking this pathway, alpelisib helps reduce tumor growth and cell proliferation. It is typically administered in combination with fulvestrant, an estrogen receptor antagonist, to enhance therapeutic efficacy. Alpelisib is especially beneficial for postmenopausal women and men with breast cancer who have progressed on prior endocrine therapy. Its targeted action makes it a valuable option in precision oncology, allowing treatment to be tailored based on genetic profiling of the tumor.