Trial Phases for Investigating Drugs and Treatments
A Phase I clinical trial tests for safety in humans,
with typically less than 100 healthy volunteers.
Investigators observe how the human body
responds to the medication to determine safe
doses and related side effects. Phase I trials are
referred to as "open label" and "unblinded,"
because everyone - the patient, medical staff,
and investigators - knows the drug and dose
that each participant is receiving. Phase I trials
can take several months to one year to
Phase II clinical trials, which look at safety
and efficacy (effectiveness), typically run for
several months to two years. In this phase,
approximately 100 to 300 people with the
disorder (in this case, MS) are given either the
active drug or a "placebo" (a medication that
looks the same as the drug being tested, but
has no active ingredients). Phase II studies are
often "double-blinded," meaning that the
participants, medical staff, and investigators are
not told who is receiving the drug and who is
receiving the placebo. These studies are also
"randomized," so that participants are assigned
to treatment groups (or "treatment arms")
based on chance.
Roughly one-third of experimental medications
for MS reach the Phase III clinical trial level. These
trials can take several years to complete and
involve 1,000 to 3,000 participants at many
different medical locations. These studies are
randomized, placebo-controlled, and doubleblinded.
They are designed to provide more
information on a drug's safety and efficacy, as well
as additional benefits, side effects, and adverse
reactions. Upon completion, a data analysis is
performed. If the results are favorable, an
application for approval is submitted to the Food
and Drug Administration (FDA), whose panel
reviews the results and recommends approval if it
finds the treatment to be beneficial and safe.
Phase IV clinical trials are conducted after a
drug has been approved. Participants are
enrolled to further monitor safety and side
effects, while evaluating long-term efficacy.