The following provides details of the various phases, but I'm not sure how a Phase IIb differs from a Phase II.
A new drug is tested on people only if extensive laboratory work and animal studies show promising results. If a treatment does go on to trial stage, the trials themselves have to progress through a set sequence of ‘phases’ – one to four – to ensure that the information obtained is reliable and everyone taking part is protected. Phase one must be completed successfully, before moving to phase two and so on for the remaining phases. Trials stop if there is any cause for concern.
Phase I trials are small, with between ten and 50 people – and everybody gets the new treatment. Phase I studies reveal how best to give a drug and how much can be given safely. Side effects are unpredictable so people are watched very closely. If the risks are high, for example, a treatment might only be offered to people who can’t be helped any other
Phase II trials find out whether a new treatment is of real benefit to people. They set the optimum dose and continue to monitor side effects. Usually 100 to 300 people are recruited for a relatively short time, around
six months to two years.
Phase III trials are huge studies with anything up to 1,000 to 3,000 participants, often from many different countries. They look at the benefits and side effects of a new drug in the long term – over two to four years –
and nowadays often assess people’s perceptions of their ‘quality of life’ on a new treatment.
Phase III trials need to be large to make sure they can detect small differences between treatments. In the case of a treatment for relapsing remitting MS, for example, even larger numbers may be required to distinguish real effects of the drug from spontaneous recovery.
Recruiting such large numbers of people can take years. As a result, it can be five to ten years before a trial reaches its conclusion. Because each person has to be followed for the same amount of time (two to four years), the last people to be recruited may only be just starting their treatment when the first people are finishing.
Phase IV: Success in phases I to III usually means that the drug will be given a European license, which 3 gives the manufacturers permission to market the drug. Once it is marketed, if it’s then prescribed, monitoring continues for any new side effects that might emerge.