In the drug discovery pipeline, Phase I trials are first used to evaluate if a new drug is safe, then Phase II trials are done to assess the drug’s efficacy, and finally Phase III trials are performed to monitor side effects and compare the drug to similar compounds already on the market. Each consecutive phase includes more people to refine the results obtained in the previous phase. A recent analysis by the Centre for Medicines Research in the UK has concluded that since 2008, the failure rate for drugs in Phase II and III clinical trials has been rising [1-2]. Phase II success rates are currently at 18%, lower than at any other phase of drug development.

The first analysis evaluated 108 reported Phase II failures from 2008 to 2010 for new drugs and major new indications of existing drugs [1]. Sixty-eight percent of the failures fell into only five therapeutic areas:

1,alimentary/metabolism (including diabetes) (23%)
2,cancer (20%)
3,neurological disorders (16%)
4,cardiovascular diseases (11%)
5,other (32%)

Diabetes is a fairly well-served market; since there are a number of effective drugs currently in use, it is tougher for new drugs to demonstrate their superiority to extant treatments. This demonstration is a requirement for gaining approval. Treating cancer and neurological disorders entail a high degree of risk, explaining the high failure rate. But drugs treating cardiovascular diseases have traditionally enjoyed a relatively high success rate in clinical trials. It is possible that, like diabetes, its market has been saturated with effective drugs.

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