Omeros Elucidates Mechanism of its PDE7 Inhibitors in Addiction

       Omeros Elucidates Mechanism of its PDE7 Inhibitors in Addiction

-- Clinical Entry Planned for Second Half of 2013 --

PR Newswire

SEATTLE, March 19, 2013

SEATTLE, March 19, 2013 /PRNewswire/ -- Omeros Corporation (NASDAQ: OMER)
today announced that it has elucidated the mechanism of action of its
phosphodiesterase 7 (PDE7) inhibitors in the neural network shown to be
responsible for addiction in humans. Omeros believes that it is the first to
discover the link between PDE7 and any addiction or compulsive disorder, and
the Company is establishing a broad intellectual property position around this
discovery. Omeros expects to submit an Investigational New Drug application or
the European equivalent for its lead PDE7 inhibitor (OMS527) to permit the
initiation of human clinical trials later this year.

Most, if not all, addictions and compulsions are directly tied to increased
release of dopamine in the brain. Through an extensive battery of behavioral,
electrophysiological and neurotransmitter studies in animals, Omeros
identified the mechanism by which its proprietary PDE7 inhibitors reduce the
heightened dopamine release caused by drugs of abuse. These studies generated
consistent data demonstrating that Omeros' PDE7 inhibitors are effective in
nicotine, cocaine, opioid and alcohol addiction as well as in binge eating and
uncovered the activities of these compounds at specific sites within the
neural network that controls addiction. These same neural pathways have been
shown to be responsible for addictions and compulsive behaviors in humans.

"The mechanism by which our PDE7 inhibitors work in addiction cuts across
multiple drugs of abuse," stated Gregory A. Demopulos, M.D., chairman and
chief executive officer of Omeros. "With almost 1.5 billion nicotine addicts,
140 million alcoholics, 15 million cocaine addicts and 6 million opioid
addicts worldwide, the addiction problem – and the pharmaceutical industry's
interest in treating that problem – is growing. We look forward to evaluating
OMS527 in humans, and we are advancing through toxicology studies in
preparation for clinical trials later this year."

About Omeros' PDE7 Programs
Omeros' phosphodiesterase 7 (PDE7) program is based on its discoveries of
previously unknown links between PDE7 and any addiction or compulsive disorder
and between PDE7 and any movement disorders, such as Parkinson's disease. PDE7
appears to modulate the dopaminergic system, which plays a significant role in
regulating both addiction and movement. Omeros believes that PDE7 inhibitors
could be effective therapeutics for the treatment of addiction and compulsive
disorders as well as movement disorders. Data generated in preclinical studies
support both of these potential indications. Omeros also believes that it
controls the worldwide rights to any PDE7 inhibitor for the treatment of any
movement disorder, including Parkinson's disease, restless leg syndrome and
Huntington's disease. Omeros has licensed its PDE7 inhibitors from Daiichi
Sankyo Co., Ltd. for worldwide exclusivity in the fields of movement
disorders, addictions and compulsive disorders.

About Addiction
Addiction is a significant medical problem with major socioeconomic impact. In
the United States alone, the total socioeconomic cost of addiction is
estimated at $484 billion per year, which is more than 60% greater than that
for cancer and diabetes combined. Sales of current addiction medications
exceed $4.4 billion worldwide, though they are either largely ineffective or
have significant side-effects.

About Omeros Corporation
Omeros is a clinical-stage biopharmaceutical company committed to discovering,
developing and commercializing products targeting inflammation, coagulopathies
and disorders of the central nervous system. The Company's most clinically
advanced product candidates, OMS302 for lens replacement surgery and OMS103HP
for arthroscopy, are derived from its proprietary PharmacoSurgery™ platform
designed to improve clinical outcomes of patients undergoing a wide range of
surgical and medical procedures. Omeros has five clinical development
programs. Omeros may also have the near-term capability, through its GPCR
program, to add a large number of new drug targets and their corresponding
compounds to the market. Behind its clinical candidates and GPCR platform,
Omeros is building a diverse pipeline of protein and small-molecule
preclinical programs targeting inflammation, coagulopathies and central
nervous system disorders.

Forward-Looking Statements
This press release contains forward-looking statements as defined within the
Private Securities Litigation Reform Act of 1995, which are subject to the
"safe harbor" created by those sections. These statements include, but are not
limited to, Omeros' expectations regarding that it will begin clinical trials
evaluating OMS527 this year, the potential indications that OMS527 could
treat, and that Omeros may have capability, through its GPCR program, to add a
large number of new drug targets and their corresponding compounds to the
market. Forward-looking statements are based on management's beliefs and
assumptions and on information available to management only as of the date of
this press release. Omeros' actual results could differ materially from those
anticipated in these forward-looking statements for many reasons, including,
without limitation, the risks, uncertainties and other factors described under
the heading "Risk Factors" in the Company's Annual Report on Form 10-K filed
with the Securities and Exchange Commission on March 19, 2013. Given these
risks, uncertainties and other factors, you should not place undue reliance on
these forward-looking statements, and the Company assumes no obligation to
update these forward-looking statements publicly, even if new information
becomes available in the future.

SOURCE Omeros Corporation

Contact: Jennifer Cook Williams, Investor and Media Relations, Cook Williams
Communications, Inc., +1-360-668-3701,
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