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What happens during preclinical testing of a potential new drug?
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Docking of the anticancer drug Gleevec (imatinib) in the abl domain of the bcr-abl tyrosine kinase. Abnormalities in bcr-abl stimulate the continuous proliferation of bone marrow stem cells, causing an increase in myelogenous cells (granulocytes and macrophages) in the body and leading to chronic myelogenous leukemia (CML).
Preclinical testing is a critical phase in drug development that occurs after a potentially useful chemical compound is identified in the laboratory but before it is administered to humans. The primary goal of this stage is to evaluate the safety and suitability of the lead chemical and its dosage form.12
Key activities during preclinical testing include:
- Animal Toxicity Studies: Researchers conduct extensive tests on animals, typically using two mammalian species, to observe effects on various organs and tissues. These include acute toxicity (single large doses), subacute and chronic toxicity (repeated daily administration), and assessments for carcinogenicity, mutagenicity, and reproductive or developmental toxicity.132
- Pharmacokinetic Investigation: Scientists study the rates and extent of drug absorption, distribution, metabolism, and excretion. This helps determine how often a drug should be taken and identifies potential interactions with other substances.4
- Biopharmaceutical Evaluation: The chemical makeup and stability of the drug are analyzed to ensure the dosage form can release the medication appropriately.4
These rigorous, often multi-year studies are essential for predicting potential human toxicity and determining a safe starting dose for clinical trials. Only compounds that demonstrate satisfactory safety profiles proceed to human testing.135