Anticancer peptides (ACPs) have emerged as a transformative class of next-generation therapeutics that bridge molecular precision with multifunctional tunability. Unlike many conventional small molecule chemotherapeutics, ACPs offer intrinsic selectivity toward malignant cells through preferential membrane targeting, immunomodulation, and disruption of oncogenic signalling pathways. Advances in peptide engineering, including sequence optimization, incorporation of non-natural amino acids, cyclization, stapling, PEGylation, and structure-activity relationship-guided refinement, have substantially improved their stability, potency, and pharmacokinetic performance. Parallel progress in nanotechnology has further expanded the translational potential of ACPs by enabling controlled release, cancer cell specific targeting, and multimodal theranostic integration. Lipid nanoparticles, solid lipid nanoparticles, polymeric systems, dendrimers, mesoporous silica nanoparticles, and stimuli-responsive platforms now provide multiple and combinatorial strategies to overcome biological barriers, enhance intracellular delivery, and minimize systemic toxicity. Emerging concepts such as enzyme-activated nanocarriers, ligand-directed precision delivery, and light- or pH-responsive systems are redefining and energizing the spatial and temporal control of peptide therapeutics research fields. Despite encouraging preclinical and early clinical progress, including FDA-approved peptide-based agents and peptide receptor radionuclide therapies, challenges related to stability, immunogenicity, manufacturing scalability, and regulatory harmonization remain significant. This review highlights current advances in ACP discovery, molecular engineering, and nanotheranostic integration, and outlines a roadmap for advancing peptide-based precision oncology. Collectively, next-generation ACP platforms hold promise to reshape cancer therapy by integrating targeted cytotoxicity, immune activation, and real-time imaging within a single modular framework.
