Omeros Reports Additional Positive Results from OMS824 Program

        Omeros Reports Additional Positive Results from OMS824 Program

-- Phase 1 Trial Data Predict Substantially Greater Target Engagement with
Better Tolerability Than Seen with Other PDE10 Inhibitors --

PR Newswire

SEATTLE, Sept. 12, 2013

SEATTLE, Sept. 12, 2013 /PRNewswire/ -- Omeros Corporation (NASDAQ: OMER)
today announced positive data from the Company's Phase 1 clinical trial
evaluating the pharmacokinetics of OMS824, the lead compound in Omeros'
phosphodiesterase 10 (PDE10) program, further supporting that OMS824 can
achieve superior target engagement with lesser side effects compared to other
PDE10 inhibitors in development. With these data and the previously announced
encouraging results from the OMS824 positron emission tomography (PET)
clinical trial, Omeros is advancing OMS824 into Phase 2 clinical programs.
OMS824 selectively inhibits PDE10, an enzyme expressed in areas of the brain
linked to a wide range of diseases that affect cognition, including
Huntington's disease and schizophrenia.

The OMS824 Phase 1 clinical trial included single- and multiple-dose
escalation studies that enrolled 100 healthy male subjects: 60 subjects
received a single dose of OMS824, 24 subjects received multiple doses for
seven to 10 days, and 16 subjects received placebo. The data announced today
are at the highest multiple-dose level administered and, at this dose, OMS824
was well tolerated and the only apparent drug-related adverse events were
mild. Almost all adverse events were self-limiting, resolving during the
10-day dosing period. In May of this year, Omeros reported that a lower dose
evaluated in an ongoing PET clinical trial demonstrated target engagement
greater than had previously been reported for any PDE10 inhibitor (an average
of approximately 50-percent and a maximum of approximately 70-percent
engagement) without the dose-limiting side effects seen with other PDE10
inhibitors. Pharmacokinetic data at the high dose announced today showed an
approximately two-fold increase in plasma concentration over that of the dose
used in the earlier-reported PET trial. This same high dose level is scheduled
to be evaluated in the ongoing PET trial and is expected to demonstrate
substantially higher target engagement. The Phase 1 clinical trial results
predict that OMS824, at well-tolerated doses, will effectively inhibit PDE10
and support continuing development for the treatment of Huntington's disease,
schizophrenia and other central nervous system disorders.

"These findings are unprecedented based on our knowledge of the work to date
in the area of PDE10 inhibition and could result in a significant competitive
advantage across a range of CNS indications," stated Gregory A. Demopulos,
M.D., chairman and chief executive officer of Omeros. "With this further
confirmation of the unique pharmacology of our PDE10 inhibitor, Omeros is well
positioned to initiate Phase 2 programs in schizophrenia and Huntington's
disease before year-end."

About Omeros' PDE10 Program
PDE10 is an enzyme that is expressed in areas of the brain linked to diseases
that affect cognition and psychomotor functions, including Huntington's
disease and schizophrenia. Huntington's disease is a hereditary
neurodegenerative disorder that leads to movement, cognition, and behavioral
abnormalities and premature death. Schizophrenia is a group of severe brain
disorders characterized by an abnormal interpretation of reality, which can
manifest as delusions, hallucinations, and/or disordered thinking and
behavior. Cognitive dysfunction is responsible for substantial disability in
both of these diseases and is not meaningfully improved by current
medications. Omeros' proprietary compound OMS824 inhibits PDE10 and is being
developed for the treatment of cognitive disorders. In addition to potential
benefits on cognition, OMS824 could also improve the motor and psychiatric
abnormalities in Huntington's disease as well as the positive (e.g.,
hallucinations) and negative (e.g., flat affect) symptoms of schizophrenia.

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 six 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 pharmaceutical industry. 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 within the meaning of
Section 27A of the Securities Act of 1933 and Section 21E of the Securities
Exchange Act of 1934, which are subject to the "safe harbor" created by those
sections for such statements. These statements include, but are not limited
to, Omeros' expectations regarding the potential competitive advantages of
OMS824, including its therapeutic benefits; that it will advance OMS824 into
Phase 2 clinical programs for Huntington's disease and schizophrenia before
year end; regarding the potential qualities of OMS824; regarding demonstration
of target engagement in the PET trial; and that it may have capability,
through its GPCR program, to add a large number of new drug targets and their
corresponding compounds to the pharmaceutical industry. 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 Quarterly Report on Form 10-Q filed with the
Securities and Exchange Commission on August 9, 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, Cook Williams Communications, Inc., Investor
and Media Relations, 360.668.3701, jennifer@cwcomm.org