Advances in Polymer Micelles for Cancer Therapy: From Conventional to Smart Delivery Systems

Polymeric micelles have become a versatile and clinically significant class of nanocarriers for cancer therapy. They effectively solubilize poorly water-soluble anticancer drugs, extend their circulation in the bloodstream, and promote accumulation in tumors. Early studies focused on conventional PEG-based polymeric micelles that utilize passive targeting based on the enhanced permeability and retention (EPR) effect, with several of these advancing to clinical trials. Active targeting strategies using modified polymer micelles with various targeting ligands have been introduced to enhance cellular uptake and improve tumor specificity. Recently, the field has shifted toward smart polymer micelles that can respond to both internal (endogenous) and external (exogenous) stimuli. These stimuli-responsive systems enable controlled drug release, enhance delivery inside cells, and improve therapeutic effectiveness, all while reducing systemic toxicity. This review summarizes recent advancements in polymer design, drug-loading techniques, preparation methods, and targeting strategies for polymeric micelles, highlighting both preclinical progress and systems that have reached clinical stages. The transition from conventional to smart polymer micelles is a significant advancement toward achieving more precise, effective, and personalized cancer nanomedicine.