Introduction to the Drug Discovery Process

The drug discovery process is anything but easy. Several stages, trials and adaptions are needed until a drug finally appears on the market. Typically, it takes up to 12 years of research until a drug is ready to be launched. The screening of promising compounds and clinical trials require long-running and accurate studies. In this article, we uncover the stages involved in a drug discovery process and why the work isn't finished after the launch.

Stage 1: Discovery and Development (3-6 years)

Researchers discover new drugs in many ways. The first stage identifies a target for a drug to act on. This implies that there is a disease that needs to be treated, and it is important to understand the cause of the disease. Next, up to 10,000 promising compounds are screened in laboratory tests to check their ability to affect the target. During those experiments, potential benefits and mechanisms of actions are identified, as well as how the drug interacts with other drugs and what the best dosage is. The effectiveness of the compounds are then compared with similar drugs.

Stage 2: Preclinical studies (1 year)

Preclinical research is important to test whether a drug has the potential to cause serious harm. The 10,000 tested compounds from the first stage are reduced to around 250 compounds in stage two. There are two types of research here: in vitro and in vivo. While in vitro studies include laboratory experiments on cells or molecules outside of their usual biological surroundings, in vivo studies include animal testing like toxicology and efficacy tests. It is necessary for drugs to be tested on at least two mammals when testing for toxicity. Passing the animal tests successfully means that the drugs are allowed to proceed to clinical trials, which involve human participants.

Stage 3: Clinical trials (4-7 years)

To learn about safety and efficacy, drugs are tested on volunteers. The clinical trials stage consists of four phases. In phase one around 20 to 100 people are tested to study safety and dosage of the drug. The volunteers split into two groups: healthy volunteers and people with the disease/conditions. Approximately 70% of drugs move to phase two. In this phase up to several hundred people who suffer from the disease/condition are tested to determine efficacy and side effects. After this trial, only 33% of drugs will move to the third phase. Phase three covers the efficacy and monitoring of adverse reactions. Around 300 to 3,000 volunteers who have the disease/condition participate in this phase, which can take up to four years. In the final phase safety and efficacy are tested on several thousand volunteers who have the disease/condition.

Stage 4: Review and approval (1 – 2 years)

In most cases only one out of 5,000 drugs make it to this stage. The approval process takes around one to two years and during this time a regulating body like the FDA examines all submitted data on the drug to decide whether the drug should be approved or not. For this stage, it is necessary that a New Drug Application (NDA) is filed by the company to market the drug. The NDA tells the full development story of a drug as well as information about:

  • Proposed labeling
  • Safety updates
  • Drug abuse information
  • Patent information
  • Directions for use.

Once the review team of the regulatory body receives the NDA, the team needs to decide whether it is complete and if yes, a decision has to be made on whether the drug can be approved.

Stage 5: Post-release monitoring

It is nearly impossible to know everything about the safety of a drug once it is approved. Therefore post-market drug safety monitoring is a necessary step to ensure safety and pharma quality. The process may take months or even years and the regulatory body is required to add cautions to the dosage or usage information when needed.


FDA: The Drug Development Process: (
An Overview of the Drug Discovery Process: (
Compoundchem: Understanding the Drug Discovery Process: (