Capivasertib as a Therapeutic Agent for Breast Cancer: Targeting AKT to Overcome Endocrine Resistance

Background/Objectives: Capivasertib is a selective pan-AKT inhibitor recently approved in combination with fulvestrant for the treatment of hormone receptor-positive (HR+)/HER2- breast cancer with alterations in the PI3K/AKT pathway. The PI3K/AKT/mTOR signaling cascade represents a critical indication of endocrine resistance and tumor progression in this subtype of breast cancer. The present review summarizes current clinical data regarding the efficacy of capivasertib, either as monotherapy or in combination with other therapeutic agents and discusses emerging biomarkers and mechanisms of resistance. Methods: A literature search of the PubMed database was conducted to identify clinical trials evaluating capivasertib in breast cancer. Studies on capivasertib as monotherapy or in combination with fulvestrant, paclitaxel, or olaparib were included. Results: Findings from phase I–III clinical trials indicate that capivasertib in combination with fulvestrant significantly prolongs progression-free survival in patients with HR+/HER2- advanced breast cancer, particularly in tumors containing PIK3CA, AKT1, or PTEN alterations. Drug combination approaches with paclitaxel or olaparib have demonstrated additive or synergistic effects in triple-negative and DNA repair-deficient contexts, respectively. Monotherapy studies confirm effective pathway inhibition with modest clinical benefit, primarily in AKT1-mutant tumors. Translational analyses suggest that persistent mTORC1-mediated protein synthesis and compensatory signaling activation contribute to acquired resistance. Conclusions: Capivasertib constitutes a clinically validated therapeutic approach for the inhibition of AKT signaling in breast cancer. Its efficacy is most evident when combined with endocrine therapy; however, optimization of patient selection and rational combination strategies remains necessary to overcome resistance associated with mTORC1 activation and signaling redundancy.