For any patient or caregiver who is new to the world of drug development, the different clinical trials can be difficult to comprehend at first. Below are brief summaries of the most common clinical trials conducted in the drug development process.

Phase 1 study

This is a clinical trial that will first test the treatment in a human subject – either a healthy volunteer or a person with the disease the treatment is designed for. The main purpose of the study is to see if the treatment is safe at a variety of doses and to see if it has a biological effect on the subject.

Phase 2 study

This is a clinical trial, often the first one involving patients with a specific disease, designed to test the safety and efficacy of the treatment at a fixed dose (or fixed ranges of doses). These studies, may be divided into phase 2a and 2b studies and may also be combined with a phase 3 study (phase 2/3 study). A formal definition of these latter studies has not been established.

Phase 3 study

This is usually the clinical trial that is used by regulatory agencies to approve a treatment. It is a large, properly powered study designed to determine if a specific treatment is better than another treatment in patients with a well-defined condition. Most of these studies are randomized, double-blind, placebo-controlled studies that are largely funded by the pharmaceutical industry and involve numerous research centres. They are large, expensive, and often must limit the patient population to those that do not have a lot of comorbidities to better insure the drug is effective for a specific condition. The phase 3 clinical trial will have a ‘primary outcome measure’ which is usually a measurement that best defines if the treatment is working on that patient. If the trial fails to meet this primary outcome measure, it usually means that from a statistical point of view, the new treatment is not any better than the treatment it is being compared to (either a placebo or another approved treatment). If the trial is said to meet its primary outcome, that usually means the treatment is effective and odds are in favour of it getting approval.

Note. There are numerous variations of the above studies and in small disease populations, many of the guidelines that try to govern a well-designed clinical trial need to be adjusted. With that said, the further away a trial design is from the more traditional trial design, the more likely that clinical trial will be criticized by regulatory agencies when reviewing the treatment.

Below is a video from YourekaScience explaining the clinical trials.

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