Toxicity refers to the degree to which a substance can be harmful to an organism. In drug development, toxicity refers to the potential harmful or toxic effects of a new active substance. The assessment of toxicity is a critical part of safety testing and begins long before the first application in humans.
In the preclinical phase, extensive toxicological studies are conducted in animals to investigate organ toxicity, carcinogenic effects (carcinogenicity), effects on reproduction (reproductive toxicity), and other harmful effects. These data help establish a safe starting dose for the first clinical trial in humans (Phase I). Throughout clinical development, toxicity in humans is continuously assessed through careful monitoring of adverse events (AEs), laboratory values, and vital signs.