The phases of pharmaceutical development describe the different stages involved in taking a potential medicine from an early idea to an approved product and continued safety monitoring. The process generally begins with drug discovery, where researchers identify and study promising compounds that may help treat a particular disease. This is followed by preclinical development, where laboratory and nonclinical studies are performed to understand the candidate’s safety, pharmacology, toxicity, and other important properties before human testing. The next major stage is clinical development of drug candidates, which includes Phase I, Phase II, and Phase III clinical trials. These studies gradually evaluate safety, dosage, tolerability, effectiveness, and the overall benefit-risk profile in people. After successful clinical studies, the available evidence is submitted for regulatory review and approval. Once the medicine is approved, post-marketing monitoring continues to identify potential safety concerns and evaluate its performance in real-world use. Together, these phases of drug development form an important part of the new drug development process, covering the major stages of drug discovery and development from initial research through clinical research, approval, and ongoing safety assessment.