Chemotherapy Agents

There is a large  number of  chemotherapeutic drugs and they are generally divided or classified into different categories, namely alkylating agents, antimetabolites, anti-tumour agents, anthracyclines, topoisomerase inhibitors, plant alkaloids.Chemotherapy AgentsThese chemotherapy agents or drugs affect the cell division or DNA function and synthesis in some way or the other.There are some newer agents which do not interfere directly with the DNA. They include the antibodies which are monoclonal and there are the kinase inhibitors which cause abnormality in some types of cancer like gastrointestinal cancer or in myelogenous leukemia. Some chemotherapy drugs can be used for modulating the cell behavior without attacking the cells directly.

The most important chemotherapy agents are the Alkylating agents. They are named so because they can add alkyl groups to the many electronegative groups under conditions which are present in some cells. Oxaliplatin along with Carboplatin and Cisplatin are alkylating agents. Chlorambucil, cyclophosphamide, mechlorethamine are the other agents. They modify a cell’s DNA chemically.

The Anti-metabolites are another form of agents. These agents are the purine (mercaptopurine, azathioprine) or pyrimidine which are the DNA building blocks. They prevent substances from getting into the DNA and also by stopping the normal division and development. The RNA synthesis is also affected.

Some other agents are Terpenoids and Plant alkaloids. These alkaloids come from the plants and they block the division of cells by preventing the microtubule function. These are very important for cell division and the main examples of these are the taxanes and vinca alkaloids.

The Vinca Alkaloids are derived from the Madagascar periwinkle and the Catharanthus roseus. The Vinca Alkaloids include Vinblastine, Vindesine, Vincristine and Vinorelbine.

Podophyllotoxin is a compound derived from the plant and it produces the two cytostatic drugs – teniposide and etoposide. They prevent the cells from getting into the G1 phase and the S phase. The Himalayan May Apple has it in a large quantity. The supply is limited as the plant is an endangered species.

The taxanes is derived from the natural product called paclitaxel, which is sold under the brand name Taxol and it is derived from the Yew tree bark. This prevents the separation of chromosomes and enhances the strength of microtubules.

The Topoisomerase inhibitors are the essential enzymes which interfere with the replication of the DNA.

Then there are the Anti tumor antibiotics. This is the most important immunosuppressant. Dactinomycin is one of them and it is used in the transplantation of kidneys.

The other agents are the monoclonal antibodies which work by targeting the tumor with the help of specific antigens. This enhances the response to the tumor cells. The examples of these types of agents are cetuximab, trastuzumab (Herceptin), rituximab (Rituxan or Mab Thera). Bevacizumab (Avastin) does not directly harm the tumor cells but blocks the creation of the new tumors. This is a monoclonal antibody.

Chemotherapy agents affect the growth and division of cells. The myelogenous leukemia, the lymphomas and the Hodgkin’s disease are very much sensitive to chemo therapy. The malignancies that grow at a slower rate respond to cancer chemotherapy more modestly. There are agents in the drugs that affect the tumors and tumor cells are lost, and they become much less responsive to the chemotherapeutic agents. These problems can be dealt with the different types of therapies in combination with chemotherapy.