Pyrimidine analogues

Pyrimidine analogues belong to the large group of non-selective cytotoxic chemotherapeutic agents (cytostatics). These are substances from different drug classes that have an antineoplastic effect. In a narrower sense, the term "cytostatic agents" refers to the conventional non-selective cytostatic agents which use a broad spectrum of non-selective substances to inhibit the growth of proliferating cells, i.e. of tumour cells, but also of healthy cells with a high proliferation rate (see side effects, see also antineoplastic tumour therapeutics).

Pyrimidine analogues belong to the group of antimetabolites (like folic acid analogues and purine analogues), which have a structural relationship with the respective amino acids: cytosine, uracil, thymine. They act as false building blocks and are incorporated into the RNA or DNA after appropriate metabolism or they prevent the correct incorporation of the physiological building blocks. In this way, they interfere with cell division in phases (mainly in the S phase) and thus with the proliferation of the cells.

Pyrimidinaloga includes:

• Azacitidine
• 5-Fluorouracil (5-FU - inhibits the thymidilate synthase, the metabolites 5FU-triphosphate and 5-FU-fluorodesoxyuridine triphosphate are built into the RNA or DNA as false building blocks)
• Capecitabine (prodrug of 5-fluorouracil, inhibits thymidilate synthase)
• Tegafur (prodrug of 5-fluorouracil, inhibits the thymidilate synthase)
• Gemcitabine (deoxycytitide analogue, is incorporated into the DNA as a false base)
• Cytarabin (isomer of the nucloside cytidine, is incorporated into the DNA as the wrong building block (cytarabinoside triphophate), further inhibits DNA repair mechanisms)