There are high risks for clinical trials, as the different steps often take considerable time: often more than seven years in clinical testing. The patents generally last 20 years after filing (may be extended by up to 5 years in US and EU on case by case basis). After patent expiry generics often arrive and capture most of the sales. With all the regulations, personal costs and control, there are huge costs involved, with up to 10,000 euros per human participant. The costs are usually over $100 million.

 https://www.risklick.ch/blogs/Risk-management-in-clinical-trials