Oleanolic acid and its derivatives in breast cancer therapy: mechanistic insights, structural modifications, and novel delivery strategies.

Oleanolic acid is a natural pentacyclic triterpenoid widely found in dietary plants and has attracted translational interest in breast cancer research. This review addresses how oleanolic acid and its derivatives exert anticancer effects in breast cancer models, and how structural modification and delivery strategies may mitigate key barriers that currently limit clinical translation. Drawing primarily on studies and preclinical animal evidence, we summarize major mechanistic themes, including induction of apoptosis and cell-cycle arrest, and regulation of autophagy, ferroptosis, oxidative stress, cancer metabolism, and tumor microenvironment-associated processes. We further highlight representative medicinal-chemistry advances showing that selected derivatives, such as SZC014 and HIMOXOL, can exhibit improved physicochemical properties and enhanced anticancer activity in specific breast cancer models. In parallel, we review formulation and delivery approaches aimed at improving exposure and tumor delivery, including nanoparticle-based systems and emerging co-delivery or self-assembly strategies developed to address poor solubility and limited bioavailability. Importantly, we critically discuss why pharmacokinetic limitations remain a central obstacle, including poor aqueous solubility, variable absorption, extensive first-pass metabolism, uncertain tumor exposure, and limited PK/PD linkage. We also note that derivatization and nanocarriers may introduce new uncertainties related to metabolic fate, drug-drug interactions, off-target accumulation, manufacturability, and long-term safety. Across the field, conclusions are additionally constrained by model heterogeneity, incomplete subtype coverage, limited normal-cell controls, and insufficient mechanistic causality testing. Overall, oleanolic acid and its derivatives should be viewed as preclinical leads with potential relevance to breast cancer, and future progress will require standardized multi-model validation, rigorous PK and biodistribution profiling with PK/PD integration, systematic toxicology, and rational combination strategies before clinical utility can be concluded.