Thalidomide is a pharmaceutical sedative that was developed in the late 1950s as a seemingly safer alternative to barbituates. However, in pregnant women, thalidomide turned out to have a very large risk of birth defects, generally foreshortened arms and legs. Thousands of infants were born with these defects before thalidomide was identified as the culprit and taken off the marketplace in the early 1960s.
Thalidomide is so dangerous to pregnant woman that they cannot even handle the tablets without risk to the developing fetus. However, the drug still has limited use, primarily in the treatment of leprosy. Another use of Thalidomide is in cancer patients, as the drug prevents the tumor from being able to grow arteries to it, vital for the growth of the tumor. It doesn't actually fight the cancer, it merely stops it from worsening.