How are new drugs developed and tested?

How are new drugs developed and tested?

Many thousands of new drugs are developed every year. Before these can be administered by doctors and hospitals,  they must undergo a thorough development and testing process.

Drug development is a lengthy process, involving several important steps to ensure the drug is effective, safe and beneficial. It takes several years to develop and test new drugs, and can cost millions, sometimes billions to complete.

Whilst the drug development process is long and costly, it is essential that new drugs undergo rigorous testing to ensure they are safe and do not pose serious risks.

Find out more about reducing drug development cost and increasing efficency.

The drug development process

New drugs are typically developed and tested through the following process:

  1. Discovery and development
  2. Preclinical research
  3. Clinical trials
  4. FDA review
  5. Post marketing safety monitoring

New drugs are firstly developed in a laboratory setting where researchers test on human cells and animals to ascertain basic safety. Drugs are then tested on human subjects in clinical trials to determine safety and efficacy. The drug then undergoes FDA approval and post-market safety monitoring.

1. Drug discovery

Initial stages of drug development begin with discovery. In this first stage, researchers have usually identified a chemical compound that can potentially be used to treat particular diseases. 

There are many ways that scientists may discover promising new compounds. From systematically testing molecule compounds, to developing drugs based on new disease insights.

Testing molecule compounds

Drug discovery is a systematic process, whereby scientists test a number of molecule compounds to uncover potential beneficial effects against diseases. There are usually thousands of compounds that are tested during this stage to determine which show the most potential as medical treatments.

The compounds that show the most promising effects then undergo further research and development into new medical drugs. 

Those that don’t show promising effects, or those that show potential high risks are not carried through into further drug development research. 

Applying new disease insights

As well as testing compounds for potential benefits, scientists apply findings and insights from the latest disease research in order to design appropriate new drug treatments.

The aim of this is to develop new drugs that target diseases in ways that have not previously been possible or available.  

For example, a new drug may be necessary to treat previously underreported effects of a disease. Similarly, existing treatments may begin to cause unanticipated side effects, requiring a new drug development that minimises the adverse effects.

Advancements in technology

In recent years, technological advances have allowed researchers to gain deeper and more targeted insights into medicine and diseases. 

As medical technology continues to develop at rapid rates, scientists can investigate drugs and diseases in ways that were not always possible. And in doing so, gain a richer understanding of how to develop new drugs appropriately.

Advancements in technology also have implications on drug testing. For instance, online systems allow for patients and researchers to report drug side effects in real-time, in a centralised database that is accessible to the contract research organisation (CRO), sponsors, and approval boards.

2. Preclinical research

Once scientists have identified compounds with potential for further development, researchers will investigate the drug in more detail through a number of preclinical research tests. 

These tests are carried out to understand basic information about the drug:

  • How the drug should be administered
  • Potential interactions with other drugs
  • The drug’s benefits
  • How effective the drug is in comparison to other drugs for the same disease
  • Safe dosage levels

Information from preclinical research is used to determine the best way to develop new drugs. For instance, these findings help researchers understand how to administer the development drug safely to volunteer and patient groups in clinical trials.

This research also prevents any potentially harmful compounds from reaching human clinical trials. If molecule compounds react negatively with preclinical test cells, or show no promising reactions, then the drug will not undergo further clinical development.

Preclinical research is an important step in the drug testing process, since this identifies which compounds are worth further investigation. 

Additionally, this identifies and discounts any molecule compounds that present themselves as toxic to humans.

3. Clinical trials

Researchers engage with patients to develop the drugs. Following successful preclinical findings, researchers investigate how the new drug presents itself and behaves in the human body – this is done through phased clinical trial research. 

In clinical trials, the development drug is tested in human subjects for the first time, often referred to as a first in human (FIH) study. Throughout clinical trial stages, the drug is tested for safety and efficacy, determining how beneficial the drug is in relation to its possible risks.

As clinical research is conducted using human participants, this is a vital step in the drug development process. A new development medicine or drug must undergo clinical trial research in order to be approved for market use.

The drug development process continues across three main phases in the clinical trial.

Phase 1

  • Researchers investigate the safety and pharmacology of the development drug. Find out more: what is clinical pharmacology?
  • Small doses of the development drug are administered to around 20 to 100 healthy volunteers (those that do not have the disease or condition). 

View our phase 1 CRO services.

Phase 2

  • Researchers investigate the efficacy of the development drug, continually monitoring its safety profile and risks.
  • The drug is administered to volunteer patients who suffer from the target condition.
  • The drug is usually tested on around 100 to 500 patient volunteers.

Phase 3

  • Phase 3 clinical trials are similar to phase 2 trials, although there are several key differences
  • Researchers compare the development drug’s benefits and risks against existing drugs used to treat the target condition.
  • The development drug is tested on a larger group of patients, usually around 1,000 to 5,000. This can be more challenging in rare disease clinical trials.

4. FDA review

Once a new drug’s safety and efficacy has been evidenced through clinical testing, it will undergo FDA review for market use. FDA approval is required for any drug before it enters the medical market. 

Approval is usually granted when clinical and preclinical research findings prove that the drug is safe for human use, with no significant risks posed to patients. As well, FDA approval requires evidence that the drug is effective in treating the target condition.

If a drug is approved by the FDA, it can be manufactured for market use and can be administered by doctors and hospitals. 

5. Post marketing safety monitoring

The drug development and testing process continues even after clinical trial research and FDA approval. When the drug has been approved for market use, it is continuously monitored by researchers to highlight any potential safety risks that weren’t present throughout clinical research.

At this point in the drug testing process, research will have evidenced that the drug is generally safe for public use. 

Although in some cases, side effects may only emerge after much longer periods of time. For instance, rare side effects may only present themselves in 1 out of 10,000 patients.

Post market safety monitoring can help identify rare side effects, acting as a vital stage in the drug testing process.


New drugs are developed under a rigorous and systematic process. This ensures that patients can take the drug safely, and that it provides beneficial effects for the disease.

The main phases of development and testing take place throughout clinical trials, which can last several years and involve a large number of volunteers. 

Although from initial drug discovery through to post market safety monitoring, new drugs are heavily tested from the offset and throughout.