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Medical Areas: Endocrinology | Musculoskeletal
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The following drug information is obtained from various newswires, published
medical journal articles, and medical conference presentations.
Company: Pharmacia & Upjohn
Approval Status: Approved March 2003
Treatment Area: Acromegaly
Somavert is the first in a new class of medicines called growth
hormone receptor antagonists and the only medicine designed to
specifically block the effects of excess growth hormone in
Somavert (pegvisomant), an analog of human growth hormone, is an
injectable medication that has been structurally altered to act as
a growth hormone (GH) receptor antagonist. Over production of
growth hormone leads to abnormally high insulin-like growth factors
(IGF-I), which then cause acromegaly like symptoms.
Somavert is indicated for the treatment of acromegaly in
patients who have had an inadequate response to surgery and/or
radiation therapy and/or other medical therapies, or for whom these
therapies are not appropriate. The goal of treatment is to
normalize serum IGF-I levels.
Somavert is available in single-dose, sterile glass vials in 10,
15, or 20 mg strengths.
FDA approval of Somavert was based on the data from a 12-week,
randomized, double blind, placebo-controlled study enrolling 112
subjects with acromegaly previously treated with therapy. Results
showed that after 12 weeks of treatment, serum IGF-I levels were
normalized in 39%, 75%, and 82% of subjects treated with 10, 15, or
20 mg/day of Somavert, respectively, versus 10% of subjects treated
with placebo. The three Somavert groups also showed dose-dependent
reductions in serum levels of IGF-I and IGF binding proteins
compared with placebo at all post-baseline visits.
Following withdrawal from previous medical therapy, the 80
patients randomized to treatment with Somavert received a
subcutaneous (SC) loading dose, followed by 10, 15, or 20 mg/day
SC. Each individual score (for soft-tissue swelling, arthralgia,
headache, perspiration and fatigue) was based on a nine-point
ordinal rating scale (0 = absent and 8 = severe and
incapacitating), and the total score was derived from the sum of
the individual scores.
In addition, subject's ring size at week 12 was smaller in
the groups treated with Somavert (15 or 20 mg) of, compared with
placebo. The mean total score for signs and symptoms at week 12 was
lower in each of the groups treated with Somavert, compared with
the group treated with placebo.
Adverse events associated with the use of Somavert may include
(but are not limited to) the following:
- Back pain
- Flu syndrome
- Chest pain
- Peripheral edema
Mechanism of Action
Pegvisomant is a recombinant DNA protein containing 191 amino
acid residues to which several polyethylene glycol (PEG) polymers
are covalently bonded. It is synthesized by a specific strain of
Escherichia coli bacteria that has been genetically modified by the
addition of a plasmid that carries a gene for GH receptor
antagonist. Pegvisomant selectively binds to growth hormone (GH)
receptors on cell surfaces, where it blocks the binding of
endogenous GH, and thus interferes with GH signal transduction.
This inhibition of signal results in the decrease of insulin-like
growth factor (IGF-I) and IGF binding proteins. High IGF-I levels
lead to the numerous health complications associated with
van der Lely AJ, Hutson RK, Trainer P, et al.
Long-term treatment of acromegaly with pegvisomant, a growth
hormone receptor antagonist. The Lancet 2001 ; 358:
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Bates AS,Van't Hoff W, Jones JM, et al. An
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