The Types of Clinical Trials


    Before a new drug, surgical procedure, or therapy becomes available to the
    public, it must go through a rigorous testing process and be evaluated by the US
    Food and Drug Administration (FDA). This testing process consists of a series of
    clinical trials that are designed to test the safety and usefulness of the new
    drug compared to the current standard treatment.

    The clinical trials that make headlines are usually what are called phase III
    trials. These are large-scale tests with hundreds or thousands of patients. They
    are the culmination of earlier phase I and phase II trials that include many
    fewer people and still earlier preclinical experiments with animals. They are
    also the final tests in humans before the FDA is asked to authorize sale of new
    medicines.

    Why Are Large-Scale Trials
    Needed?

    Clinical trials are designed to test whether a drug is safe for humans, and
    whether the drug is effective in treating human diseases or conditions. Although
    the drug has generally gone through extensive animal testing before the trial
    begins, animal trials cannot always predict how new medicines will affect
    humans. Even the most painstaking tests with animals give only approximate
    indications of how people will respond to drugs. At some point, after thorough
    study in animals (and when the FDA is convinced human experimentation will
    probably be safe), tests with humans become necessary.

    Not only is it necessary to test new drugs in humans, but they need to be
    tested in a large number of humans in order for the results of the trial to be
    clear. The reason so many volunteers are required is that people are highly
    variable in how they respond to drugs. It is not unusual, for example, for a
    drug be somewhat effective in only 30 percent of those who take it. For medical
    researchers to prove such a slight benefit requires testing the drug in as many
    as several thousand patients.

    This extensive testing is part of what drives up the cost of new drugs – the
    average development time is over 10 years and costs from 500 to 700 million
    dollars.

     
    What Goes on Prior to a Large-Scale
    Phase III Trial?

    An enormous amount of testing has gone on by the time a drug is ready for
    phase III. In general, a new drug or treatment goes through preclinical testing
    in animals, then small phase I and phase II trials in humans before being ready
    for large-scale testing.

    Preclinical testing

    When a drug is discovered that seems to have medical potential, a drug
    company will test it exhaustively in animals, looking for signs it may be
    poisonous, cause cancer, or cause birth defects. Animal studies will also be
    used to estimate the initial drug doses to be tested in humans.

    When animal experiments are finished, the company asks the FDA for permission
    to begin clinical trials. The FDA only grants approval once they are satisfied
    that the animal experiments are sound and that clinical trials are likely to be
    safe.

    Phase I

    The first test of the drug in humans is known as phase I. It is designed to
    find out if the drug is safe rather than whether the drug is effective. Phase I
    is also used to learn what drug doses to use in later trials, how the drug is
    broken down in the body and excreted, and study short-term side effects.

    A phase I trial rarely has more than 100 participants. Often healthy people
    are enrolled in phase I trials rather than patients on the assumption that if
    the drug has unexpected side effects, healthy people have the best chance of
    escaping permanent harm. But on other occasions, as with a drug treating a
    serious disease like cancer, phase I subjects may be patients who have failed
    standard treatments.

    Phase II

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