Arrowhead RNAi Candidate ARC-520 Induces Greater than 90% Reduction in Circulating HBV DNA in Chimpanzee with Chronic Hepatitis

  Arrowhead RNAi Candidate ARC-520 Induces Greater than 90% Reduction in
  Circulating HBV DNA in Chimpanzee with Chronic Hepatitis B

  *Single injection at low end of the projected therapeutic dose range
  *Well tolerated based on clinical chemistry markers and clinical
  *Additional data to be discussed at analyst event on March 25

Business Wire

PASADENA, Calif. -- March 14, 2013

Arrowhead Research Corporation (NASDAQ: ARWR), a targeted therapeutics
company, today announced that a study of its RNAi-based candidate ARC-520 in a
chimpanzee chronically infected with the human hepatitis B virus (HBV)
supports findings from rodent models indicating that it can knock down HBV DNA
and key viral antigens. Dr. Robert Lanford and his team at the Texas
Biomedical Research Institute are conducting the study. The chimpanzee being
treated has had chronic HBV for over 30 years, has high viral-titer and
antigenemia, and nearly 100% of hepatocytes stain positive for HBV. Studies
are ongoing and additional data will be discussed when the company hosts an
analyst and investor event on March 25, and at upcoming scientific

“It’s encouraging to see data from our preclinical rodent models confirmed in
a true primate disease setting,” said Bruce Given, MD, Arrowhead’s COO and
Head of R&D. “There are very few high primates that develop chronic HBV. We
understand these studies to be useful predictors of the response we might
expect in human patients as we approach clinical trials later this year.”

Investors and analysts may access the live presentation on March 25 on the
Arrowhead Research website at or by calling
1.888.771.4371 (US toll free) or 1.847.585.4405 (US toll) and using the
confirmation number: 34474854. The webcast will also be available for 90 days
following the event.

About Arrowhead Research Corporation

Arrowhead Research Corporation is a clinical stage targeted therapeutics
company with development programs in oncology, obesity, and chronic hepatitis
B virus infection. The company is leveraging its platform technologies to
design and develop peptide-drug conjugates (PDCs) that specifically home to
cell types of interest while sparing off-target tissues, create targeted drugs
based on the gene silencing RNA interference (RNAi) mechanism, and work with
partners to create improved versions of traditional small molecule drugs.

For more information please visit, or follow
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news directly, please send an email to

Safe Harbor Statement under the Private Securities Litigation Reform Act:

This news release contains forward-looking statements within the meaning of
the "safe harbor" provisions of the Private Securities Litigation Reform Act
of 1995. These statements are based upon our current expectations and speak
only as of the date hereof. Our actual results may differ materially and
adversely from those expressed in any forward-looking statements as a result
of various factors and uncertainties, including our ability to finance our
operations, the future success of our scientific studies, our ability to
successfully develop drug candidates, the timing for starting and completing
clinical trials, rapid technological change in our markets, and the
enforcement of our intellectual property rights. Arrowhead Research
Corporation's most recent Annual Report on Form 10-K and subsequent Quarterly
Reports on Form 10-Q discuss some of the important risk factors that may
affect our business, results of operations and financial condition. We assume
no obligation to update or revise forward-looking statements to reflect new
events or circumstances.


Arrowhead Research Corporation
Vince Anzalone, CFA
The Trout Group
Lauren Glaser, 646-378-2972
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