Omeros Obtains Regulatory Approval to Initiate Phase 1 Clinical Trial for Lead Antibody in MASP-2 Program

Omeros Obtains Regulatory Approval to Initiate Phase 1 Clinical Trial for Lead
                          Antibody in MASP-2 Program

-- Enrollment Expected to Begin Next Month --

PR Newswire

SEATTLE, June 13, 2013

SEATTLE, June 13, 2013 /PRNewswire/ -- Omeros Corporation (NASDAQ: OMER) today
announced that it has obtained regulatory clearance to start the Phase 1
clinical trial evaluating OMS721, the Company's lead human monoclonal antibody
from its mannan-binding lectin-associated serine protease-2 (MASP-2) program.
The first clinical trial with OMS721 will be conducted in Europe and will
evaluate the safety, tolerability, pharmacodynamics and pharmacokinetics of
OMS721 administered subcutaneously in healthy subjects. Omeros plans to follow
this study with a clinical trial evaluating OMS721 in patients with atypical
hemolytic uremic syndrome (aHUS), a rare but life-threatening form of
thrombotic microangiopathy (TMA). Enrollment in the initial clinical trial is
scheduled to begin next month.

Omeros has filed for orphan drug designation in the United States for the use
of OMS721 to treat aHUS and will request orphan drug designation in Europe as
well. Omeros controls the worldwide rights to MASP-2 and all therapeutics
targeting MASP-2.

OMS721 selectively inhibits MASP-2, a novel pro-inflammatory protein involved
in activation of the complement system, which is an important component of the
immune system and plays a role in the inflammatory response to tissue damage
or microbial infection. By selectively inhibiting MASP-2, OMS721 blocks the
lectin pathway of the complement system while leaving intact the classical
pathway, which represents the acquired immune response to infection.

Omeros' previously reported preclinical findings indicate that blockade of
MASP-2 by OMS721 may have a preventive or therapeutic effect in the treatment
of aHUS and other life-threatening TMAs, such as hemolytic uremic syndrome and
thrombotic thrombocytopenic purpura, as well as a wide range of additional
disorders, including age-related macular degeneration, ischemia-reperfusion
injury and transplant-related complications.

"We are pleased that the European regulatory authorities have cleared the way
for us to evaluate the potential of OMS721 in humans," stated Gregory A.
Demopulos, M.D., chairman and chief executive officer of Omeros. "The lectin
pathway appears to play an important role across a wide range of serious
disorders. The preclinical data for OMS721 are strong, and we continue to
drive the clinical development of the antibody."

About Omeros' MASP-2 Program

Omeros controls the worldwide rights to MASP-2 and all therapeutics targeting
MASP-2, a novel pro-inflammatory protein target involved in activation of the
complement system, which is an important component of the immune system. The
complement system plays a role in the inflammatory response and becomes
activated as a result of tissue damage or microbial infection. MASP-2 appears
to be unique to, and required for the function of, one of the principal
complement activation pathways, known as the lectin pathway. Importantly,
inhibition of MASP-2 does not appear to interfere with the antibody-dependent
classical complement activation pathway, which is a critical component of the
acquired immune response to infection, and its abnormal function is associated
with a wide range of autoimmune disorders. MASP-2 is generated by the liver
and is then released into the circulation. Adult humans who are genetically
deficient in one of the proteins that activate MASP-2 do not appear to be
detrimentally affected by the deficiency. Therefore, Omeros believes that it
may be possible to deliver MASP-2 antibodies systemically and OMS721, its lead
MASP-2 antibody, is designed to be self-administered by subcutaneous
injection.

Omeros also believes that it has identified the proteins that activate the
complement system's alternative pathway in humans, which is linked to a wide
range of immune-related disorders. In addition to its lectin pathway
inhibitors, the Company is advancing the development of antibodies that would
block activation of the alternative pathway alone or in combination with the
lectin pathway.

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‚ĄĘ 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 when it will commence clinical
trials evaluating OMS721; Omeros' plans to request orphan drug designation in
Europe; the potential indications that OMS721 may treat; the potential
advantages of OMS721 over current treatments; 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 Quarterly Report on Form 10-Q filed with the
Securities and Exchange Commission on May 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