An anticancer agent is a pharmacologically active substance intended to selectively inhibit, control, or eliminate malignant cells or to interfere with biological processes that are necessary for tumor maintenance and progression. The term encompasses conventional cytotoxic drugs, molecularly targeted agents, endocrine agents, immunotherapeutics, and other therapeutic substances whose primary pharmacological purpose is the treatment of cancer. Anticancer agents may act by damaging DNA, disrupting cell division, inhibiting oncogenic signaling, altering hormone-dependent growth, activating antitumor immunity, or affecting the tumor microenvironment ^[1][2][3][4]. Their defining feature is a demonstrable antineoplastic mechanism or therapeutic objective, rather than merely the ability to produce nonspecific cellular toxicity. Thus, an anticancer agent is distinct from a supportive-care medicine, which manages symptoms or treatment-related complications without directly exerting an antineoplastic effect, and from a preventive or diagnostic substance, which does not primarily treat established malignant disease.