Clinical trials are an essential part of therapeutic development. At each step, researchers take great care to ensure the treatments they are testing are both safe and effective. You may have noticed that when people talk about new therapies, they often refer to what ‘phase’ of a clinical trial it is currently in. Each phase reflects a distinct stage of testing, which serves a specific purpose:

Preclinical Studies

Almost all therapies are first tested in cell and animal models. This early work helps researchers determine whether a treatment is worth pursuing and whether there are any safety concerns.

IND Applications

When preclinical results are promising, researchers submit an Investigational New Drug (IND) application to FDA. Most countries outside of the US follow a similar process, typically called a Clinical Trial Application (CTA). If regulators determine the results are convincing, the therapy moves into clinical trials where it is tested in people.

Phase 1

The first step in clinical trials focuses on safety. In Phase 1, the therapy is administered to a small group of healthy participants to assess its effects on the body and identify any adverse effects. If it is found to be safe, it moves forward. In some cases, particularly for rare diseases, Phase 1 studies may enroll affected people in addition to healthy volunteers.

Phase 2

The therapy is then tested in a larger group of people, this time including those with the studied disorder, to determine how well it improves the targeted symptoms. Safety and dosing continue to be closely monitored, with researchers carefully weighing risks against potential benefits. If results are positive, the therapy moves on.

Phase 3

This is the largest and longest phase of clinical trials. Here, the therapy is studied in a much larger population than previously. The goal of this phase is to confirm that the therapy maintains its beneficial effect while remaining safe to use. These participants are often divided into random groups to receive different doses and combinations of treatments.

FDA Approval

After collecting all the data, a final application is submitted to the FDA for review. If approved, the therapy becomes available to people who meet the criteria for the condition it was tested in (called an indication).

Off-Label Use

The process of developing a new therapy often requires significant time and resources, which is why alternative approaches, such as off-label use, can be helpful. These avenues are especially useful for rare-disease populations who are often overlooked in clinical trials because they don’t meet eligibility criteria. Even though clinical trials for our indication haven’t started yet, seeing existing drugs show promise in related conditions is encouraging (see our Biohaven post). Doctors can prescribe FDA-approved therapies off-label when they think it may help, so progress in related conditions is always good news.