Most antineoplastic agents are classified according to their structure or cell cycle activity - either cell cycle phase specific or cell cycle phase non-specific:9
- Cell cycle phase specific agents act on the cells in a specific phase. They are most effective against tumours that have a large proportion of cells actively moving through the cell cycle and cycling at a fast rate. Rapid cycling ensures that the cell passes through the phase in which it is vulnerable to the drugs' effects.
- Cell cycle phase non-specific agents are not dependant on the cell being in a particular phase of the cell cycle for them to work - they affect cells in all phases of the cell cycle. Resting cells (phase G0) are as vulnerable as dividing cells to the cytotoxic effects of these agents. As a result, phase non-specific agents have been found to be some of the most effective drugs against slow-growing tumours.
The following figure highlights the action of common agents at each point of the cell cycle.10
Antineoplastic agents are also traditionally divided by their origin or mechanism of action. The main groups include:1, 7, 11
- Alkylating and alkylating-like agents
- Antitumour antibiotics
- Plant alkaloids
- Miscellaneous agents
- Hormonal agents.