Types of Cytotoxic Drugs
or
Types of Antineoplastic Drugs
or
Types of Anti cancerous Drugs
The majority of chemotherapeutic drugs can be divided in to alkylating agents, antimetabolites, anthracyclines, plant alkaloids, topoisomerase inhibitors, and other antitumour agents.[8] All of these drugs affect cell division or DNA synthesis and function in some way.
Some newer agents do not directly interfere with DNA. These include monoclonal antibodies and the new tyrosine kinase inhibitors e.g. imatinib mesylate (Gleevec or Glivec), which directly targets a molecular abnormality in certain types of cancer (chronic myelogenous leukemia, gastrointestinal stromal tumors). These are examples of targeted therapies.
In addition, some drugs that modulate tumor cell behaviour without directly attacking those cells may be used. Hormone treatments fall into this category.
Where available, Anatomical Therapeutic Chemical Classification System codes are provided for the major categories.
[edit] Alkylating agents (L01A)
Main article: Alkylating antineoplastic agent
Alkylating agents are so named because of their ability to alkylate many nucleophilic functional groups under conditions present in cells. Cisplatin and carboplatin, as well as oxaliplatin, are alkylating agents. They impair cell function by forming covalent bonds with the amino, carboxyl, sulfhydryl, and phosphate groups in biologically important molecules.[8]
Other agents are mechlorethamine, cyclophosphamide, chlorambucil, ifosfamide.[8] They work by chemically modifying a cell's DNA.
[edit] Anti-metabolites (L01B)
Main article: Antimetabolite
Anti-metabolites masquerade as purines ((azathioprine, mercaptopurine)) or pyrimidines—which become the building blocks of DNA. They prevent these substances from becoming incorporated in to DNA during the "S" phase (of the cell cycle), stopping normal development and division. They also affect RNA synthesis. Due to their efficiency, these drugs are the most widely used cytostatics.
Plant alkaloids and terpenoids (L01C)
These alkaloids are derived from plants and block cell division by preventing microtubule function. Microtubules are vital for cell division, and, without them, cell division cannot occur. The main examples are vinca alkaloids and taxanes.
Vinca alkaloids (L01CA)
Vinca alkaloids bind to specific sites on tubulin, inhibiting the assembly of tubulin into microtubules (M phase of the cell cycle). They are derived from the Madagascar periwinkle, Catharanthus roseus (formerly known as Vinca rosea). The vinca alkaloids include:
Vincristine
Vinblastine
Vinorelbine
Vindesine
Podophyllotoxin (L01CB)
Podophyllotoxin is a plant-derived compound which is said to help with digestion as well as used to produce two other cytostatic drugs, etoposide and teniposide. They prevent the cell from entering the G1 phase (the start of DNA replication) and the replication of DNA (the S phase). The exact mechanism of its action is not yet known.
The substance has been primarily obtained from the American Mayapple (Podophyllum peltatum). Recently it has been discovered that a rare Himalayan Mayapple (Podophyllum hexandrum) contains it in a much greater quantity, but, as the plant is endangered, its supply is limited. Studies have been conducted to isolate the genes involved in the substance's production, so that it could be obtained recombinantly.
Taxanes (L01CD)
The prototype taxane is the natural product paclitaxel, originally known as Taxol and first derived from the bark of the Pacific Yew tree. Docetaxel is a semi-synthetic analogue of paclitaxel. Taxanes enhance stability of microtubules, preventing the separation of chromosomes during anaphase.
Topoisomerase inhibitors (L01CB and L01XX)
Topoisomerases are essential enzymes that maintain the topology of DNA. Inhibition of type I or type II topoisomerases interferes with both transcription and replication of DNA by upsetting proper DNA supercoiling.
Some type I topoisomerase inhibitors include camptothecins: irinotecan and topotecan.
Examples of type II inhibitors include amsacrine, etoposide, etoposide phosphate, and teniposide. These are semisynthetic derivatives of epipodophyllotoxins, alkaloids naturally occurring in the root of American Mayapple (Podophyllum peltatum).
Cytotoxic antibiotics (L01D)
These include:
actinomycin (L01DA01).
anthracyclines
doxorubicin (L01DB01)
daunorubicin (L01DB02)
valrubicin
idarubicin
epirubicin (L01DB03), which also inhibit topoisomerase II)
other cytotoxic antibiotics
bleomycin (L01DC01). Bleomycin acts in unique way through oxidation of a DNA-bleomycin-Fe(II) complex and forming free radicals, which induce damage and chromosomal aberrations.
plicamycin (L01DC02)
mitomycin (L01DC03)
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