Etanercept
A Patient Education Monograph prepared for the American Uveitis Society January 2003
by Justine R. Smith, MBBS, PhD ***INSERT
DEGREES***
Assistant Professor
, Casey
Eye Institute
, Oregon
Health & Sciences University***INSERT TITLES,
DEPARTMENT, AND
INSTITUTION***
NOTE: The opinions expressed in this monograph are those of the author(s) and not necessarily those of the membership of the American Uveitis Society, its leadership, or the Editorial Board of UveitisSociety.org. All medical decisions should be made in consultation with one's personal physician.
Introduction
Etanercept (e-tan-er-SEPT) is the generic name of the drug Enbrel® and is marketed by the pharmacetical company Amgen for the treatment of several forms of inflammatory arthritis. At present, there is little published information available regarding the use of etanercept in the treatment of eye inflammations.
Chemistry
Etanercept is a human protein which has been engineered in the laboratory, rather than being isolated from the blood or tissues of another person, ensuring that the drug preparation is not contaminated by microorganisms such as hepatitis virus or human immunodeficiency virus (HIV).
How it Works
Many forms of
uveitis are presumed to be autoimmune in origin, that is, caused by a patient's
own white blood cells, which move into the eye to cause inflammation, in the
absence of the usual triggers such as an infection. These cells cause
inflammation in part by producing small molecules called cytokines. One such signal
molecule
is termed named tumor
necrosis factor alpha or
TNF-a.
Etanercept
consists of two identical TNF-a "receptors" linked together.
Each of Etanercept's "receptors" is able to recognize and bind to one TNF-a
molecule, thereby preventing the interaction between the TNF-a
molecule,
as well as another molecule that is closely related to TNF-a, and its the
naturally occurring receptor. I
HAVE ALTERED THE WORDING AS STRICTLY SPEAKING ETANERCEPT IS NOT A
TNF-"A" BLOCKER ALONE. MY APOLOGIES AS THIS WAS MY ERROR. In this way etanercept inhibits the
effects of TNF-a .PLEASE
INSERT FULL STOP AND
DELETE DASH. Consequently, this
drug has the potential to reduce inflammation.
History of Usage
Non-Eye Disease
In early large
clinical studies, it was established that etanercept was beneficial for at
least 2 forms of inflammatory joint disease;,:
rheumatoid arthritis in adults,
and juvenile idiopathic arthritis (also known as juvenile rheumatoid arthritis)
in children. More recently, new studies suggest it is likely that this drug will
be useful in the treatment of other inflammatory diseases, such as psoriatic
arthritis and ankylosing spondylitis.
Eye Disease
Several small studies have tested the use of etanercept in patients with different forms of uveitis. In one study involving 10 children with uveitis-most with juvenile idiopathic arthritis-the authors reported that etanercept was an effective treatment for some of the children. In a second study involving four academic institutions in the United States, patients with either uveitis or scleritis were included. Researchers found that only 2 of the 8 patients with uveitis and 2 of the 6 patients with scleritis appeared to benefit from etanercept therapy.
How it is Given
Etanercept is
given by an injection under the skin using a very fine needle (subcutaneous
injection, similar to how the way that insulin
shots are given). The drug is supplied from the pharmacist as a powder, but
with
athe package containings
everything necessary to prepare it as a solution liquid ready
for injection. The final volume is very small, generally 1 ml or less (less
than 1/5 of a teaspoon). Injections are usually performed twice a week. Most Generally, patients
or someone in their family are able to administer the injections without
difficulty.
Possible Side Effects and Drug Interactions
The most common
side effect of etanercept, which may occur in over one-third of persons taking
the drug, is the development of some redness, itching, pain, or swelling at the
injection site. Generally this reaction is not severe enough to require
stopping the drug. Etanercept increases a person's susceptibility to infection.
It can increase the risk of both common infections and unusual infections such
as tuberculosis and fungal infections. Etanercept may lead to the development
of proteins in the blood that can be associated with the development of an
autoimmune lupus-like disease. There is theoretical concern that blocking the
action of TNF-a could promote the development of cancer.
However, in clinical trials to date, there is no evidence that patients treated
with etanercept have a higher rate of cancer. This issue continues to receive
careful monitoring. Some data suggest that etanercept may worsen multiple
sclerosis, which is also considered to be an autoimmune disease. There have
been cases of eye inflammation occurring in patients treated with etanercept or
another TNF-a PLEASE DELETE
DASH blocker called
infliximab. In other words, this drug might be detrimental rather than
beneficial for some patients with uveitis. There is no information regarding
the safety of etanercept for very young children (less that 4 years old),
although the drug appears to be well-tolerated by older children. It should be
used only if clearly necessary in pregnant women. Its, as
safety
for the unborn child during
pregnancy is not established. Specific drug interaction studies
have not been undertaken for this drug.
Monitoring
A skin test for
tuberculosis exposure should be performed prior to the first treatment with
etanercept. It is also DELETE GAPusual
for a physician to order routine blood tests periodically for patients managed
with etanercept. While undergoing treatment with etanercept, it is important
that patients immediately report any symptoms of an infection, such as a fever
or productive cough, to the treating physician. A form of uveitis called pars
planitis is sometimes associated with multiple sclerosis. If a person is
diagnosed with pars planitis, it may be advisable to undergo an MRI imaging
study of the brain, checking for evidence of multiple sclerosis, before
beginning etanercept therapy.
Conclusions
Studies are
presently being conducted at United States centers on the use of etanercept in some forms of uveitis., such that Consequently,
over the next few years, we should learn whether or not the
etanercept is useful for the treatment of these conditions.
Copyright © 2003 The American Uveitis Society. All rights reserved.