Stages of Drug Development

Drug development takes place in multiple stages.


The process of drug discovery – usually where the drug molecule is being discovered and optimized. Usually a majority of this is being done on computer, less in a lab. Testing comes later! 

Intermediate Phases

Usually when the drug is being tested in cells, for the effect on living beings. Labs here we come! It is also tested in small batches of humans for side effects. But cells first! Scientists have to be careful to introduce the drug to TINY batches because they are still in the process of testing the effects of drugs… 

The rest, we’ll hand it off to Merck AGAIN! What can I say? They have a good article here. 

“These studies occur in several phases and only in volunteers who have given their full consent.

  • Phase 1 evaluates the drug’s safety and toxicity in people. Different amounts of the drug are given to a small number of healthy, young, usually male people to determine the dose at which toxicity first appears.
  • Phase 2 evaluates what effect the drug has on the target disorder and what the right dose might be. Different amounts of the drug are given to up to about 100 people who have the target disorder to see whether there is any benefit. Just because a drug is effective in animals in early development does not mean it is effective in people.
  • Phase 3 tests the drug in a much larger (often hundreds to thousands) group of people who have the target disorder. These people are selected to be as similar as possible to the people who might use the drug in the real world. The drug’s effectiveness is studied further, and any new side effects are noted. Phase III tests usually compare the new drug against an established drug, a placebo, or both.

In addition to determining a drug’s effectiveness, studies in people focus on the type and frequency of side effects and on factors that make people susceptible to these effects (such as age, sex, other disorders, and the use of other drugs).

If the drug passes all 3 phases, then yay! It then seeks approval to the FDA (food and drug administration) to commercially sell the drug. The average drug takes 10 years and BILLIONS of dollars. 

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