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International Clinical Trials

Not Just a Phase

Stuart J Mair at Charles River Laboratories Clincial Services puts forward the case that better planning and design in early drug development may increase the value of information and reduce risk in later phases

Successful drug development will always depend on two criteria – efficacy and safety – and underlying these is the ability to make a profit. Efficacy is obvious, but the importance of safety is often undervalued. Drug safety and issues involving drug companies are always emotive subjects within wider society. The issues regarding the side effects of drugs have made headline news recently – just think of Merck’s Vioxx and the surrounding lawsuits (1), GSK’s Seroxat and its links to suicidal behaviour (2) and the fallout following the TGN1412 trial in London last year, where six young men nearly died after participating in a Phase I study (3,4).

Adverse drug reactions place a considerable economic burden on health resources and society in general; they resulted in over a quarter of a million UK hospital admissions in 2004, giving a prevalence of 6.5 per cent and incurring an estimated cost of around £466 million ($870 million) a year (5,6). Similar findings have been reported in other European countries. In the Netherlands, for example, a national study in 2006 reported that problems related to the incorrect use of drugs or adverse drug reactions were responsible for twice as many hospital admissions as road traffic accidents, accounting for 5.6 per cent of acute admissions (7). The importance of drug safety cannot be overstated and there is a requirement to produce better, safer drugs. This represents a significant challenge to the pharmaceutical industry, and to companies involved in early drug development in particular.


The first goal in clinical drug development is to establish safety. Almost all new drugs are studied first in healthy volunteers – usually young males. The notable exception to this is cytotoxic anti-cancer drugs, which are studied first in cancer patients as the risk/benefit ratio makes it unethical to study these drugs in healthy people. Clinical drug development begins in Phase I, which is defined as a non-efficacy clinical pharmacology study in humans.

There are two reasons why Phase I studies are conducted in healthy volunteers rather than patients. The first is scientific: it is easier to study a new drug’s safety in a young, fit individual, with no confounding disease or concomitant medication factors to consider, than it would be in a patient where these factors apply. The second is practical: it is more economic and time efficient, both in terms of availability and cost, to study safety in healthy volunteers than it is in patients.

There are, of course, limitations to studying new drugs in healthy volunteers, as they are a young, fit, homogeneous group who are likely to be better able to tolerate the drugs than the patients who the drugs are intended for (who are likely to be an older, more diverse population). A compromise may be to include a cohort of healthy elderly volunteers within the sample population, which may provide a direct comparison between young and old subjects.

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Dr Stuart J Mair is a Medical Advisor at Charles River Laboratories, Edinburgh. He has worked as a Physician in a specialist Phase I clinical pharmacology unit for 11 years. Stuart has extensive experience in all aspects of early drug development from the preclinical to clinical interface through to proof-of-principle, mainly as a Principal Investigator. In 1999, he gained a diploma in Clinical Pharmacology from the Society of Apothecaries, London. He graduated in Medicine from Aberdeen University in 1990 and during his early career gained experience in several different medical specialities, before completing training as a General Practitioner in 1995.
Dr Stuart J Mair
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