The drug development process – Part 3 of 3
All trials must undergo the same rigorous process as outlined in our previous post, but are quite distinctly different and influenced by a number of other factors.
Phase I trials are carried out on healthy volunteers and are primarily focused on exploring the drugs potential toxicity and tolerability in humans. Alongside that are extensive PK and PD studies (more detail in part 1). These trials normally consist of a small number (20-100) of healthy volunteers and usually include studies on ways of administering the substance, dose ranging, or dose escalation, where the different amounts of the drug are administered to help ascertain the optimum balance of effectiveness versus adverse events (side effects).
If the drug is proved safe and well tolerated in phase I, the drug will progress to phase II trials, where the focus is on the substances ‘activity’. This phase traditionally consists of 100-1000 patients and has a maximum trial length of two years.
Phase II trials involve assessing the activity of the drug on patients suffering from a specific disease or disorder (indication) where the clinical trial may lead to scientific evidence, be effective in preventing, treating or curing the condition. During this phase adverse events are monitored and optimal dosages are assessed.
This phase is often the point at which drugs fail, as they prove to be ineffective on the chosen indication, or the treatment is discovered to be not practical or efficient.
If a drug shows that it is effective in treating an indication, it will progress to phase III. This phase aims to provide a definitive study of the treatment, and if there is an existing treatment for the indication, to prove that the new treatment is its equal, or better. The primary focus is on the drugs efficacy and the gathering of statistical proof of efficacy. These trials can involve between 1000 and 5000 patients and run for several years.
Upon completion of the 3 Phases, the results and findings of the entire development process are compiled into a dossier for submission to the relevant regulatory body, hopefully to receive a Marketing Authorisation Approval (MAA). It is estimated that the entire process costs an average of $500 million and for every five drugs that reach Ph III trials, just one will be approved for market.
And it doesn’t end there. Following the granting of MAA and the drug becoming available, it is then necessary to run phase IV trials, which monitor long term and widespread use of the drug for several years.
This is post 3 of 3 on the drug development process.