Preclinical development is the stage in drug development that occurs before clinical trials in humans. It involves laboratory and animal studies to assess the safety, efficacy, and pharmacokinetics of a new drug candidate. This phase helps researchers understand how the drug behaves in a biological system and identifies any potential side effects. During preclinical development, various tests are conducted, including toxicity studies and dosage optimization. The results are crucial for determining whether a drug is suitable for testing in humans. Successful completion of this phase is necessary to obtain regulatory approval to move forward to clinical trials.