Final answer:
Thalidomide is now used to treat cancer, leprosy, rheumatoid arthritis, and other autoimmune diseases, due to its anti-inflammatory and anti-angiogenic properties. Initially introduced as a sedative, its teratogenic effects led to severe birth defects, prompting tighter drug regulations.
Step-by-step explanation:
Besides being used for morning sickness in the past, thalidomide is now utilized for treating various medical conditions including cancer, leprosy, rheumatoid arthritis, and other autoimmune diseases. Its effectiveness in these treatments is largely attributed to its anti-inflammatory properties and its ability to inhibit angiogenesis, the process of new blood vessel formation which is crucial for tumor growth. While it was initially introduced as a sedative for conditions such as anxiety and insomnia, the thalidomide tragedy exposed its teratogenic effects, leading to severe birth defects. This contributed to significant changes in drug regulation and monitoring. Today, its enantiomeric structure is understood to play a crucial role in its effects, with the 'S' isomer being particularly teratogenic. It's a poignant reminder of the importance of thorough drug testing before approval.