How are new medicines developed?

Simon MacKay compressed for webBy Simon MacKay, Professor of Medicinal Chemistry, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde.

Every day we see stories in the media about new drug discoveries.  Medicines have revolutionised the treatment of disease, reduced the need for hospitalisation and surgery, and improved the quality of life of patients. Pharmacists and pharmaceutical scientists are central to the discovery of new drugs and the development of new medicines for the treatment of many conditions. But how do new medicines get discovered in the first place?

Identifying an unmet medical need is the first stage in the development of a new medicine. The need is matched with a disease and a potential drug is tested to assess whether it produces the required result. The next step is to improve the characteristics of the drug so that it can be used as a medicine. Frequently hundreds, or even thousands, of possible drugs are made and tested until the best compound is identified.

Once identified, the compound is tested to find out about how it might behave in the body. In the preclinical phase, particular attention is given to how well it works and if it’s predicted to cause harm, as these are the main reasons for failure of a new medicine.

If the compound emerges successfully from these tests, the clinical development of a new drug can start with exploratory ‘Phase 1’ studies. These help determine if the drug is safe in a small number of healthy people. The only exceptions to this are anti-cancer drugs, which are only studied in people who have cancer. If Phase 1 studies show promise, the process moves onto Phase 2 clinical trials.

Phase 2 trials investigate how well the medicine works and the safety of the medicine in a small number of patients, typically 100-300 people. It has been estimated that more than 50% of failures at Phase 2 stage are because they are not as effective at treating the condition as previously thought. Phase 3 studies take place across the world and involve many thousands of patients. About 2-5% of drugs fail at this stage, leaving the company with considerable, unrecoverable expense.

The results from all these studies are submitted to the Medicines and Healthcare Products Regulatory Agency. They regulate medicines and can grant a ‘marketing authorisation,’ which is a licence allowing the medicine to become available to the public. Before granting a licence, they need to know whether the medicine works well with minimal harm for most people who’ll take it and that it’s acceptably safe.

The medicine must be continuously monitored after its release to ensure that it is safe and any side effects are recorded. Findings from research into the use, safety and efficacy of medicines in patients feed back into the medicines development process to inform the creation of new medicines. This creates a circular drug discovery process where the safety and effectiveness of new medicines can be improved.