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Clinical Trials and Studies

Clinical trials are a key component of clinical research and are at the heart of all medical advances in mitochondrial disease. A clinical trial or study adds to medical knowledge by seeking to answer a scientific or medical question about the safety or potential benefit of an intervention, such as a medication, device, teaching concept, or behavioral change.

Many clinical trials are conducted to assess the safety and efficacy of new or investigational drugs, devices, or procedures. Typically, researchers first test new therapies or procedures in the laboratory and in animals. The treatments that prove to be safe and show promise are moved into clinical trials, often requiring multiple phases (Phases I – III) to move the drug or therapy toward approval by the Food and Drug Administration (FDA).

A volunteer’s participation in a clinical trial helps researchers to ultimately uncover better ways to treat, prevent, diagnose, and understand human disease. This participation is critical to the advancement of clinical trials and, ultimately, therapy development.

Commonly Used Terms


This list was developed to provide easy-to-understand definitions of commonly used terms in clinical trials.

Randomized — The arm of the study (active treatment arm or placebo arm) that the patient will follow is determined by a flip of a coin (or like randomizing procedure).

Double-blind — Neither the patient, the treating physician, nor any other staff knows when or if the patient is receiving active treatment or placebo.

Placebo-controlled
— Some patients exclusively receive the study drug or treatment and some patients exclusively receive a placebo, a harmless substance that has no effect and is used as a control.

Placebo crossover — Study includes a point whereby participants change study arms, although the timing of that change and whether drug or placebo is received remains blind to all. Some may take placebo for 4 weeks, have a 2-week wash-out with no drug or placebo, and then switch to taking taking the study for 4 weeks, for example. Others in the same study would begin with study drug for 4 weeks, 2-week wash-out and then cross over to take the placebo for 4 weeks.

Safeguards and Ombudsmen — Many checks and balances are in place to ensure safety.

Types of Clinical Trials

Test new treatments or devices, new combination of drugs, or new approaches to surgery or radiation therapy. Treatment trials are often categorized by phases I through III.

Provide information about how health and disease progress over time.

Evaluate the effectiveness of ways to reduce the risk of developing a disease or preventing a disease from returning.

Develop better tests or procedures to identify/diagnose a particular disease or condition.

Assess new ways of detecting disease earlier in healthy people.

Evaluate measures to improve comfort of and quality of life for people with chronic illnesses through better therapies or psychosocial interventions.

Orphan Designation

Trials involving orphan or rare diseases may be awarded a special status that grants permission to run trials with much lower numbers of participants. Orphan designations include:

  • Rare disease is defined as fewer than 200,000 people in the United States having the disease, with some diseases considered to be “ultra orphan.”
  • Awarded by FDA to drugs developed explicitly for serious and life-threatening rare diseases, for which there is no treatment.
  • Awarded to drugs that have shown promise of being effective to treat these diseases.
  • Incentives awarded to help get the drug through the FDA approval process.
  • Additional incentives gained once drug has FDA approval, again to encourage companies to help develop drugs for rare diseases.

Clinical Trial Phases

Each clinical trial phase has a different purpose and helps answer different questions.

Researchers test an experimental drug or treatment in a small group of people (20–80) for the first time, often using healthy volunteers to test drug metabolism, safety, and dose ranges.

The purpose is to evaluate its safety and identify side effects.

The experimental drug or treatment is administered to a larger group of people (100–300) to determine its effectiveness, optimal therapeutic dose, and to further evaluate its safety. This phase may be blinded (unknown if patient receives the study drug) or open label studies (known if patient receives study drug) in the target population.

The target population encompasses the group for which the drug is ultimately intended. Any drug metabolism, safety, or dosing difference between the Phase I healthy individuals and the Phase II target population is also evaluated.

Hints of efficacy may be obtained as well.

The experimental drug or treatment is administered to large groups of people (1,000–3,000*) to confirm its effectiveness, monitor side effects, compare it with standard or equivalent treatments, and collect information that will allow the experimental drug or treatment to be used safely.

Phase II studies are randomized, double-blind, placebo-controlled in target population for hard data on safety and efficacy.

Phase II studies are needed to ensure that bias does not affect study results.

After a drug is approved by the FDA and made available to the public, researchers track its safety, seeking more information about a drug or side effects.




Current Clinical Trials