In the United States, the last new drug that the Food and Drug Administration - USFDA approved is only 20% of the total number of new drugs originally applied for clinical trials.
Occasionally, during clinical trials, a drug found to be effective in treating malignant diseases and will have to discontinue in clinical trials and becomes usable directly to treat patients. For example, the first clinical trial of ATZ, a new drug for treatment of AIDS, was found to significantly increase the patients' survival after only 106 days. Then US Food and Drug Administration (USFDA) suspended the clinical trial and approved it immediately. It was allowed for its use to treat more than 4,000 AIDS patients before it went to the markets.