Substances used in chemotherapy

General information

There are numerous different cytostatic drugs that have their point of attack at different points in a tumour cell. The cytostatic drugs are divided into groups according to their respective mechanisms of action. The most important cytostatic drug groups are listed below.

However, in view of the abundance of terms, brand names and possible combinations (so-called schemes), it is not possible to go into each of these details. The following examples of the substances are given with their active ingredient names. The tyrosine kinase inhibitors also belong to the chemotherapeutic agents.

In contrast to the classical chemotherapeutic drugs, however, the tyrosine kinase inhibitors act specifically and thus cause fewer side effects. These chemotherapeutic drugs interfere with tumour cell production at the DNA level. They cross-link the molecules of the DNA (through alkylation) in a way that leads to the normal reading processes for the production of proteins being disturbed.

Since a tumour cell is dependent on the proteins, this leads to the death of the tumour cell. In addition, the alkylating agents prevent the new formation of DNA, which thus also causes the tumour cell to die. This group is further divided into subgroups, all of which follow the above-mentioned mechanism of action:

  • Bendamustine, Cyclophosphamide, Chlorambucil, Melphalan, Ifosfamide, Trofosfamide
  • Alkyl sulfonates: busulfan, treosulfan
  • Nirosoureas: Carmustine, Lomustine, Nimustine
  • Platinum-containing compounds: Carboplatin, cisplatin, oxaliplatin (this group of substances is very effective and is often used in combination with other cytostatic drugs)

Such cytostatic drugs are incorporated into the newly produced DNA as “false” building blocks.

This stops the new formation of DNA (the so-called DNA polymerase is inhibited). Since the DNA only doubles during cell division, the antimetabolites have a very specific effect on tumour cells. Here too, 3 subgroups can be distinguished, which differ in their nature as ” wrong building blocks”.

  • Folic acid analogues: methotrexate (has been around for a long time, but is still one of the most important substances), pemetrexed
  • Purine Analogues: Mercaptopurine, Nelarabine, Cladribine, Fudarabine,
  • Pyrimidine analogues: fluoruracil (5-FU), capecitabine, gemcitabine

Originally this substance comes from the evergreen plant (Vinca). During cell division, as already mentioned, the entire chromosome set (the DNA) is doubled. In order to distribute this equally over 2 cells, the cell needs an “apparatus”, the so-called mitotic (from mitosis = cell division) spindle, which is made up of subunits, the so called.

microtubules. Without the mitotic spindle a cell cannot divide regularly. The vinca alkaloids disturb the structure of this spindle and thus the ability of tumour cells to divide.

Examples: Vinblastine, vincristine… These also have the so-called microtubules as their target structure. In contrast to the vinca alkaloids, however, they do not interfere with the structure of the microtubules, on the contrary, they stabilize them.

It is important to know that the mitotic spindle is subject to constant build-up and breakdown. If one inhibits the degradation, which is just as important for the correct division of a cell, the tumor cells are again disturbed in their growth. Examples: Docetaxel, Paclitaxel.

Just as bacteria are normally killed by antibiotics, some antibiotics can even kill tumor cells. In principle, they do the same thing as they do with bacteria; some bacteria, like humans, have DNA in the form of a double helix, a double strand of DNA wound around each other. In order to unravel these coils, we need a protein (an enzyme), the so-called topoisomerase.

Only in the unravelled state can the information be read from the DNA. The antibiotic, which in this case has a cytotoxic, i.e. cell-damaging, effect, sits between the DNA strands in such a way that the topoisomerase is blocked. Examples: anthracyclines such as doxorubicin, mitoxantrone