Drug Lifecycle

2nd July 2011
Saturday 08:47 PM
Banaras

Hello, friends many of my students asked how a drug reach in the market. Today I would like to share with you how a drug from scratch goes to the market through various stages. It is a very interesting phenomenon. I hope that you like this post.

Various Stages of Drug Lifecycle

The diagram above shows the typical length of time that it takes for a new drug to go through the various stages of its life cycle.

It is possible in the diagram to distinguish between components of the production process that can be considered 'international' (namely can be located anywhere in the world for supply to any given country) and those that are 'national' (that is need to be located in the country in question). As the diagram moves from left to right and becomes lighter, so the activities become increasingly 'national' in scope.

More formally, the term 'international' is used to denote those stages of a drug's lifecycle for which

       

               • The activity can be located anywhere in the world where a suitable environment exists

            • Once the costs of that activity have been incurred somewhere in the world, they do not have to be incurred again in order to make the product available in other countries.

R & D is an 'international' activity in this sense of the term, as it can be located wherever a suitable research environment exists, and once a drug has been developed the R & D cost does not need to be incurred again to make the drug available in other countries. In addition, some of the costs of global manufacturing facilities may also represent an 'international' cost element.

The different stages shown in the chart above normally follow the patent application and are described in the next few paragraphs. Even before patent application a considerable amount of time and money may have been spent on basic research to identify suitable entities for investigation, although much basic research is carried out in universities and publicly-funded institutes.

Pre-clinical trials precede any testing on humans, and involve rigorous testing of selected NCEs in laboratories and animals. There are very high attrition rates8 at this stage of development: less than one per cent of compounds successfully make the transition from pre-clinical trials to clinical studies in humans.

Clinical trials are carried out in humans. Three stages are carried out before drugs receive marketing authorisation, namely:

         • Phase I: trials in 20-100 healthy adults to test the drug's safety. 70 per cent of investigational new         drugs (INDs) proceed successfully through Phase I.

                 • Phase II: trials in 100-300 patient volunteers to determine the safety and efficacy of the drug. A third of INDs make it through both Phase I and II, and

                • Phase III: trials on larger groups of patients (typically 1,000–3,000), to gain further data on safety and efficacy. Around 25 per cent of INDs progress through all three phases to a regulatory review.

Marketing authorization must then be obtained before drugs can be launched onto the market. Even after the preclinical stage, with its high attrition rate, only a small proportion of drugs proceed successfully to marketing approval.

After the drug reaches the market, Phase IV pharmacovigilance trials begin. These seek to identify any adverse drug reactions and continue throughout the lifetime of the drug.

As discussed earlier, generic manufacturers are able to enter the market and sell generic copies of the drug after a drug's patent (and any supplementary protection certificate) has expired.

In general it is clear that only a small fraction of drug entities will on average achieve a stage where commercialisation is valuable. For each new successful drug, there are many which prove unsuccessful.