Question: @Mark what does phase 3 involve?

Mark Collins answered on 15 Nov 2015:

Hi Chloe, When a drug is developed in the laboratory, we cannot just make and sell as we please and so we have to satisfy regulations, so that things are safe for patients. This testing is what we call clinical trials and they are incredibly detailed and can take a very long time, typically 12-15 years. Initially the drug may be tested in cell cultures in the lab an then on to animals. We have phase I and phase II trials where it will be tested on a very small number of patients. If the drug is successful and it is better than what is already on the market then it will be go on to phase III and the country may have many thousands of patients trialling it across many countries or continents to ensure it is effective in what it is supposed to do. If it passes phase III it can then undergo one final trial then it is ready of registration and release to patients across the world. At any point the drug can fail its trial and the company that has developed it to that point will lose a lot of money. We also have the situation where a lot of small companies will produce a drug and then sell it to a major pharmaceutical company as it is extremely expensive to go through clinical trials, especially phase III.