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An introduction to preclinical research

Before a potential drug is tested in a clinical trial setting, it is extensively tested in model systems. This can take years and only a few compounds make it to clinical trials. Most of these compounds fail to show effectiveness in model systems or turn out to be unsafe, and their development is discontinued.

It is very important that compounds are tested thoroughly before initiating a clinical trial. This is done firstly to assess whether the proposed mechanism works (proof-of-concept). If it does, additional tests are needed to ensure optimal trials can be designed.

Development stages

There are several steps in therapy development. After discovery, candidate compounds are first tested in cell models, thereafter in animal models and in the end in humans in clinical trials. Cell and animal models are very important to show proof-of-concept (i.e. does it work in a model system?). It should be stressed that success early on is no guarantee for success in subsequent steps.

The next steps is always more complicated. So the fact that ‘it works’ in a two dimensional layer of cultured patient cells, does not mean that the approach will also be effective and safe in an animal model. Likewise, the fact that something is safe and effective in an animal model, does not mean it will lead to clinical benefit in patients.