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Many different types of chemotherapy drugs are used to treat cancer. The different types of chemotherapy drugs can be grouped or classified into a variety of categories. These classifications can change as new drugs are developed.
Chemotherapy drugs are usually classified based on their chemical structure and how they act on cancer cells.
The cell cycle describes the steps, or phases, that normal and cancer cells go through when they make new cells. The cell cycle is important in chemotherapy because some drugs work best when the cells are active or quickly dividing, while other drugs work better with cells that are in a certain phase in the cycle. Many drugs also seem to have some effect on cells that are at rest (not in cycle).
Although most drugs fit into more than one category, the following classifications can be helpful in understanding the action of the drug.
Cell cycle–specific drugs (also called phase-non-specific drugs) are effective on cells that are actively growing and dividing, but they do not need the cell to be in a particular phase of the cell cycle. Some drugs in this group are more effective on cells that are in a specific phase of the cell cycle, although not to the degree of cell cycle phase–specific drugs.
Cell cycle phase–specific drugs are most active against cells that are in a particular phase of the cell cycle, for example during a growth phase.
Cell cycle–non-specific drugs appear to be effective on cancer cells on any phase of the cell cycle.
Chemotherapy drugs are usually divided into several classes. Different types of drugs in each class are grouped based on their action, structure or source. Some drugs seem to fit into more than one class. Others don’t fit into any class.
The category name indicates the drug’s action. Alkylating drugs affect cells so the DNA isn’t copied, or replicated, properly. Cancer cells are more sensitive to DNA damage because they reproduce quickly, which means they don’t have time to repair the damaged DNA.
Most alkylating drugs are cell cycle–specific drugs, but not phase-specific drugs. Some are cell cycle–non-specific.
The category name indicates the drug’s action. Antimetabolites act as a substitute for the metabolites that are used in normal metabolism. Antimetabolites affect cancer cells more than normal cells because cancer cells divide more quickly.
Antimetabolites are cell cycle–specific. Many are also phase-specific.
The category name reflects the source of the drug.
Most antibiotics, or anthracyclines, are made from bacteria. They don’t act in the same way as antibiotics used to treat infection. Some antibiotics are covered in a fatty coating and they are called liposomal therapy.
Mitotic inhibitors are another type of natural product. They interfere with mitosis, or cell division. Some mitotic inhibitors are developed from the periwinkle plant.
Taxanes also interfere with mitosis. They are developed from certain types of yew trees.
Topoisomerase inhibitors are made from a Chinese tree or the mayapple plant. These drugs interfere with certain enzymesenzymesA protein that speeds up certain chemical reactions in the body., which affects the growth of cancer cells or makes them die.
The drugs in this category are grouped together because they don’t fit easily into other categories.
The following table lists examples of common chemotherapy drugs by their classification and type.
topoisomerase I inhibitors
topoisomerase II inhibitors
Details on specific drugs change quite regularly. Find out more about sources of drug information and where to get details on specific drugs.