Omeros Announces Successful Completion of PDE10 Phase 1 Multiple Ascending Dose Trial

  Omeros Announces Successful Completion of PDE10 Phase 1 Multiple Ascending
                                  Dose Trial

-- Data Predict OMS824 has Greater Brain Activity without Movement
Side-Effects Seen with other PDE10 Inhibitors --

PR Newswire

SEATTLE, March 26, 2013

SEATTLE, March 26, 2013 /PRNewswire/ -- Omeros Corporation (NASDAQ: OMER)
today announced positive data from the multiple-ascending-dose (MAD) portion
of the Company's Phase 1 clinical trial evaluating OMS824, the lead compound
in Omeros' phosphodiesterase 10 (PDE10) program. With these data and the
previously announced successful single-ascending-dose portion of this clinical
trial, Omeros is advancing OMS824 toward a Phase 2 clinical program. 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 was a randomized, double-blind,
placebo-controlled, single- and multiple-dose escalation study. The trial
enrolled 64 healthy male subjects; 40 subjects received a single dose and 24
subjects received daily dosing for 7 to 10 days. OMS824 was well tolerated by
all subjects, and the only apparent drug-related adverse event was mild
somnolence at the highest dose evaluated. No subject had extrapyramidal
symptoms (e.g., involuntary muscle movements), which are associated with
marketed antipsychotic medications and have been seen with other companies'
PDE10 inhibitors at levels of approximately 50-percent engagement of the PDE10
enzyme in the brain. A radiotracer imaging study is underway to confirm the
target engagement of OMS824 in human brains.

The study results showed that the pharmacokinetic parameters (C[max] and AUC)
increased linearly with the dose and that OMS824 had a long half-life that is
consistent with once daily dosing. OMS824 was detected in the cerebrospinal
fluid at the expected concentration relative to that in the blood. The drug
concentration in the cerebrospinal fluid is predicted to achieve near-complete
inhibition of the PDE10 target in the brain. These results show that OMS824,
at well-tolerated doses, achieves concentrations that are anticipated to
effectively inhibit PDE10 and support continuing development for the treatment
of Huntington's disease, schizophrenia and other central nervous system

"These results are exciting – it appears that OMS824 is able to achieve
significantly higher concentrations at the target enzyme in the brain than
other PDE10 inhibitors being developed across the industry without incurring
the movement abnormalities seen with those other compounds," stated Gregory A.
Demopulos, M.D., chairman and chief executive officer of Omeros. "While
wrapping up the Phase 1 program, we are aggressively advancing OMS824 into
Phase 2 trials. Our initial focus will be Huntington's disease, for which we
will be requesting orphan drug as well as Fast Track designations from the
FDA, and a Phase 2a trial in patients with schizophrenia is expected to follow
shortly thereafter. In addition to our progress in the OMS824 program, we plan
to submit the NDA next quarter and the MAA mid-year for OMS302, our ophthalmic
drug product, and we remain on track to advance our MASP-2 and PDE7 programs
into the clinic in the coming months."

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. Cognitive dysfunction is responsible for
substantial disability in these diseases and is not 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 psychiatric manifestations,
such 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 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 the potential qualities of OMS824;
that it will request orphan drug and Fast Track designations for OMS824; that
it will advance OMS824 into a Phase 2 clinical program; that it will submit an
NDA and MAA for OMS302 this year; that it will advance its MASP-2 and PDE7
programs into the clinic in the coming months; 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., 360.668.3701,
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