What Are The Five Phases of Drug Development?
Every new medicine goes on a long journey before it ends up on a pharmacy shelf. It can take more than a decade and cost hundreds of millions of dollars to make this happen. However, it’s a necessary journey to ensure that each new drug is effective and safe.
During the drug development process, there are five main phases: discovery, preclinical research, clinical research, regulatory review and post-market monitoring. In this post, we’ll take a walk through these five phases.
- Discovery
Every new drug is developed in the hope of treating some kind of health problem whether it’s stopping a virus, lowering cholesterol or even shrinking tumours.
After studying the biology of a health problem, researchers will then identify a ‘target’ to focus on. This target is a molecule of some kind (e.g. a protein, a gene or a metabolite) that plays a crucial role in the development of that disease.
Many modern labs now use advanced tools like AI-driven screening and high-throughput assays. Third-party services with specialist protein analysis capabilities may be chosen for detailed characterization.
When a compound is found that has successful effects, it is known as a ‘hit’. This hit is further tweaked for potency, stability and safety until a solution can be chosen that is worthy of being called the ‘candidate drug’.
- Preclinical research
Once a candidate drug has been chosen, the preclinical research phase begins. This is when the drug is first tested on organic matter.
First comes in vitro tests. These are experiments on cells and tissues within petri dishes or in test tubes. Studies are made to determine how the drug behaves in different concentrations.
Next, comes in vivo tests. This involves testing drugs on animals to study the potential effects. This phase is designed to help find a safe starting dose for humans.
- Clinical research
Clinical trials involve testing drugs on human participants. This phase is divided into three sub-phases:
- Phase 1: The drug is tested on around 20 to 100 healthy volunteers. If there are no serious side effects, the drug moves onto the next phase.
- Phase 2: The drug is then tested on around 100 to 300 patients who have the disease or condition it is trying to treat. This is a proof of concept phase to determine whether the drug actually works.
- Phase 3: The drug is then tested on 1000 or more patients across multiple sites and countries. Such trials are typically randomised with neither doctor or patient knowing whether a patient has been given the drug or placebo. This phase minimises bias and confirms effectiveness in a large, diverse population.
- Regulatory review
For a drug to be marketed and sold in a country, it must pass that country’s regulatory agency review. Examples of regulatory agencies around the world include the FDA (USA), MHRA (UK), EUA (EU) and NMPA (China).
A detailed application is filed containing all preclinical and clinical data. Information on the drug formulation and labeling instructions are also provided. The regulatory agency then evaluates the drug, weighing up its effectiveness with any side effects discovered during testing.
The review process has to be thorough. At the end of the process, it is either approved or rejected. Some drugs may be approved, but with conditions (such as specific label warnings).
- Post-market monitoring
Sometimes known as ‘phase 4 clinical trials’, post-market monitoring involves continuing to study side effects in patients after the drug has been approved. Regulatory bodies continue to carry out reviews and will withdraw a drug if dangerous long-term effects are discovered.
If new laws are brought in or new side effects are identified, a drug may need to be recalled and reformulated or simply relabelled.
In other words, drug development never truly stops – even after a drug has hit the shelves.
