Drug Discovery
The first part of drug development is the discovery (or chemical synthesis) of a novel biologically active molecule. These molecules can either be found in nature (by testing to see if different molecules can have medicinal purposes) or by making new molecules (via chemistry). These molecules may be similar to other drugs, or they may be completely new in structure. Usually, these drugs will be tested for medicinal purposes by introducing them to cultures of cells. These types of experiments rely on carefully grown cell populations to see what effects the drug has and if it is toxic to the cells.
Animal Models
The next step in the drug development process is testing the medication in animals. These animals are typically genetically modified so that they develop certain diseases (that the medication is designed to treat). Animal testing is critical for the drug development process because whole animals may respond completely differently than cell cultures, but human tests are expensive and potentially dangerous to the test subjects. Most animal models are designed to test both the effectiveness and the toxicity of the drug in a fully living organism. These tests are more expensive than the cell culture tests but are necessary before drug development can proceed to human testing.
Human Testing
Once a drug has gone through (and passed) the animal model tests, the final test involves using the drug on humans. Typically, the first step is to identify the maximum dose that humans can tolerate without severe side effects, which is determined by giving volunteers increasing amounts of the medication. The next step is to prove that the drug can effectively treat some condition, which can be shown by dividing a population of diseased patients into two groups (one that receives the drug and one that doesn't) and comparing the two groups. This step is the most expensive and complicated due to government regulations, but if a drug passes this step it can usually be marketed to the public.
Phase III
Phase III trials are generally the final step in the drug development process. These trials are designed to determine if the new drug is more effective than other already existing medications. As a result, it uses a large pool of patients who either receive the new drug or the current standard treatment. Sometimes patients are recruited to try out a new drug by doctors who are participating in the trial, which gives patients the opportunity to try out a new and potentially better drug. The new drug will be approved if it is either more effective than existing treatments (even if only for a small percentage of the population) or if it is similarly effective but causes fewer side effects. If the new drug passes phase III, it will probably be provisionally accepted, pending further safety testing.
