What is the usual process for developing a new medical treatment?

This process is also known as clinical translation.

The process starts with very general research into how a tissue or cell usually works and what goes  wrong in a particular disease or injury. This information is used to design and develop ways to diagnose, stop or fix what goes wrong.

To test whether and how a new intervention might work for a particular disease or injury, studies are done first in vitro (in a dish), and then wherever possible in animals with a disease or injury like ours. These are referred to as preclinical studies; preclinical studies should be reviewed by other experts, published and repeated before moving to research  in patients.

After demonstrating a reasonable expectation that the treatment will work and be safe, permission is sought to conduct a clinical trials in humans, starting with a very small number of individuals. In some cases, new experimental treatments might be tried on a very small number of people before a clinical trial is started.

As the safety and side effects are better understood and methods to get the treatment to the correct part of the body are improved, the number of patients is gradually increased and the new intervention is compared against existing treatments.

Once safety and effectiveness is demonstrated through this formal process, a national or regional regulatory agency, for example, the US Food and Drug Administration (FDA) or the European Medicines Agency (EMEA), will approve the use of the treatment for particular diseases or conditions.