Omeros Reports Additional Positive Clinical Data for its Drug Candidate to Treat Cognitive Disorders

  Omeros Reports Additional Positive Clinical Data for its Drug Candidate to
                          Treat Cognitive Disorders

-- PDE10 Target Engagement Continues to Increase with Well-Tolerated Doses -

PR Newswire

SEATTLE, Oct. 17, 2013

SEATTLE, Oct. 17, 2013 /PRNewswire/ --Omeros Corporation (NASDAQ: OMER) today
announced additional positive data from its Phase 1 program for OMS824, the
lead compound in Omeros' phosphodiesterase 10 (PDE10) program. This latest
clinical trial evaluated the extent to which OMS824, at a dose higher than
previously reported, binds to PDE10, an enzyme expressed in the region of the
brain that has been linked to a wide range of diseases that affect cognition.
OMS824 achieved an average of 63-percent engagement at PDE10 and did not
trigger the dose-limiting side effects seen with other PDE10 inhibitors. These
data further support advancing OMS824 through clinical trials in patients with
cognitive disorders. Last month, Omeros started a Phase 2 trial evaluating the
drug in patients with schizophrenia and plans to start a Phase 2 trial in
Huntington's disease later this year.

The results reported today were in healthy male subjects receiving OMS824 once
daily for seven days at a dose higher than those previously evaluated in the
target-engagement clinical trial. Positron emission tomography (PET) scans
were used to measure the binding activity of OMS824 to PDE10 in the brain. An
average of 63-percent occupancy at PDE10 was seen in the basal ganglia, the
region of the brain that plays a critical role in cognition. The drug was well
tolerated with mild somnolence as the only apparent side effect.

While the level of target engagement seen in this PET trial is significantly
higher with lesser side effects than has been reported for any other PDE10
inhibitor in development, a recently completed Phase 1 clinical
pharmacokinetic trial with 10 days of OMS824 dosing achieved approximately 50
percent higher plasma concentrations than in the PET trial, and all side
effects were mild and well-tolerated, and most were self-limiting. PET data
were not obtained in this pharmacokinetic trial but, based on modeling of all
data obtained in the OMS824 Phase 1 program, it is estimated that the drug
engaged the PDE10 enzyme at levels substantially greater than 63 percent.
Omeros is now planning to evaluate a higher dose of OMS824 in the PET trial to
confirm this estimate.

Effective inhibition of PDE10 is considered a novel and promising mechanism to
treat Huntington's disease, schizophrenia and other central nervous system
disorders. Omeros was recently awarded Orphan Drug Designation by the US Food
and Drug Administration to evaluate OMS824 in Huntington's disease and a Fast
Track application to the FDA is currently under review. The company plans to
begin enrollment in a Phase 2 clinical trial in Huntington's disease before
year-end, and a Phase 2 clinical trial is already underway in schizophrenia.

"We are encouraged by the continued stream of positive data from our PDE10
program," stated Gregory A. Demopulos, M.D., chairman and chief executive
officer of Omeros. "PDE10 is an exciting target for the treatment of cognitive
disorders, and OMS824 is being recognized for attributes that appear to be
superior to those of other PDE10 inhibitors in development. We look forward to
reviewing the series of data from our ongoing programs in patients suffering
from Huntington's disease and schizophrenia."

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, currently in Phase 2
clinical programs, 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. Omeros was recently awarded Orphan
Drug Designation by the US FDA to evaluate OMS824 in Huntington's disease and
a Fast Track application to the FDA is currently under review.

About Omeros Corporation
Omeros is a clinical-stage biopharmaceutical company committed to discovering,
developing and commercializing small-molecule and protein therapeutics
targeting inflammation, coagulopathies and disorders of the central nervous
system. Derived from its proprietary PharmacoSurgery® platform, the Company's
lead drug product, OMS302 for lens replacement surgery, is currently under
review for marketing approval by both the US Food and Drug Administration and
the European Medicines Agency with commercial launch planned for 2014. Omeros'
five other clinical programs are focused on schizophrenia, Huntington's
disease and cognitive impairment; addictive and compulsive disorders;
complement-related diseases; and preventing problems associated with surgical
procedures. Omeros also has a proprietary GPCR platform, which is making
available an unprecedented number of new GPCR drug targets and corresponding
compounds to the pharmaceutical industry for drug development.

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 a Phase 2 clinical trial in Huntington's
disease later this year; drug engagement levels in clinical trials; the
potential therapeutic benefits and qualities of OMS824; and the
commercialization of OMS302. 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,
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