What is the primary purpose of drug testing on human cells and tissues in Stage 1?

The primary purpose of drug testing on human cells and tissues in Stage 1 is to assess the safety and preliminary effectiveness of the drug at a cellular level. During this initial stage of drug development, researchers aim to gather data on how the drug interacts with human cells, which helps determine whether the drug shows potential for beneficial effects before it is tested on whole organisms. This includes assessing factors such as cell response and biological activity.

While evaluating a drug's effectiveness against the whole body system is crucial in later stages, Stage 1 focuses specifically on understanding the effects at a smaller, more controlled scale, which is essential for informing further testing protocols. Therefore, it sets the foundation for subsequent stages by ensuring that the drug demonstrates potential before wider-ranging investigations take place.