Certain chemotherapeutic agents (cell cycle–specific drugs) destroy cells actively reproducing by means of the cell cycle. Many of these agents are specific to certain phases of the cell cycle. Most affect cells in the S phase by interfering with DNA and RNA synthesis. Others, such as the vinca or plant alkaloids, are specific to the M phase, where they halt mitotic spindle formation.
Chemotherapeutic agents that act independently of the cell cycle phases are termed cell cycle–nonspecific agents. These agents usually have a prolonged effect on cells, leading to cellular damage or death. Many treatment plans combine cell cycle–specific and cell cycle–nonspecific agents to increase the number of vulnerable tumor cells killed during a treatment period.
Chemotherapeutic agents are also classified according to various chemical groups, each with a different mechanism of action. These include the alkylating agents, nitrosureas, antimetabolites, antitumor antibiotics, plant alkaloids, hormonal agents, and miscellaneous agents. The classification, mechanism of action, common
drugs, cell cycle specificity, and common side effects of antineoplastic agents.
Chemotherapeutic agents from each category may be used to enhance the tumor cell kill during therapy by creating multiple cellular lesions. Combined medication therapy relies on medications of differing toxicities and with synergistic actions. Using combination drug therapy also prevents development of drugresistant
mechanisms.
Combining older medications with other agents, such as levamisole, leucovorin, hormones, or interferons (IFN), has shown some benefit in combating resistance of cells to chemotherapeutic agents. Newer investigational agents are being studied for effectiveness in resistant tumor lines. For more information about
investigative drugs,
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