Arrowhead Data Demonstrates RNAi Candidate ARC-520 Silences Hepatitis B Virus

  Arrowhead Data Demonstrates RNAi Candidate ARC-520 Silences Hepatitis B
  Virus

  *Single injection induces multi-log repression of viral RNA, proteins, and
                                    viral DNA
                 *Long duration of effect lasting over 30 days
  *Regulatory submissions planned for Q2 2013

Business Wire

PASADENA, Calif. -- February 26, 2013

Arrowhead Research Corporation (NASDAQ: ARWR), a targeted therapeutics
company, today announced the publication of data demonstrating multi-log
reductions in hepatitis B viral DNA and proteins lasting over 30 days after a
single injection in animal models. This suggests that Arrowhead’s RNAi-based
candidate ARC-520 has the potential to treat chronic hepatitis B virus
infection in a fundamentally different manner, with the goal of achieving a
functional cure. The paper, entitled “Hepatocyte-targeted RNAi therapeutics
for the treatment of chronic hepatitis B virus infection,” by Wooddell et al,
was published online ahead of print in the journal Molecular Therapy
(doi:10.1038/mt.2013.31).

In the publication, Arrowhead scientists describe the use of a novel Dynamic
PolyConjugate (DPC) technology to deliver small interfering RNAs (siRNAs)
designed against the hepatitis B virus (HBV). This DPC technology incorporates
a biodegradable peptide composed of naturally occurring amino acids and a
liver-targeted molecule that is co-injected with a cholesterol-conjugated
siRNA (chol-siRNA). In proof-of-concept studies, utilization of this DPC to
deliver chol-siRNA targeting Factor 7 to non-human primates results in >99%
knockdown of target gene expression and >80% knockdown for over one month
after a single injection. Multi-dose studies in mice showed no diminution of
knockdown activity or toxicity upon repeated injection at therapeutic doses.
In transient and transgenic mouse models of HBV infection, a single
co-injection of DPC with chol-siRNA targeting HBV sequences resulted in
multi-log knockdown of HBV RNA, proteins and viral DNA with long duration of
effect.

"This publication is important because it speaks to a specific product and a
broader platform,” said Dr. Christopher Anzalone, President and Chief
Executive Officer. “These data suggest that ARC-520 could be a powerful
therapy for chronic HBV infection, a disease with 350 million infected people
worldwide and no cure. We are on schedule to file with regulatory authorities
next quarter to begin first-in-human studies. During phase 1 we will be able
to measure the drug’s ability to knock down production of new infectious virus
as well as viral proteins, including s-antigen, e-antigen, and the core
protein that forms the capsid. The ability to substantially knock down these
viral proteins is what is unique about ARC-520 and what many in the field
believe will be necessary to revive the host immune response and potentially
provide a functional cure, which no other current therapy can reliably do.
More broadly, this paper reports on a delivery system capable of extremely
efficient gene silencing that can be used for a variety disease targets.”

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 http://www.arrowheadresearch.com, or follow
us on Twitter @ArrowRes. To be added to the Company's email list to receive
news directly, please send an email to ir@arrowres.com

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.

Contact:

Arrowhead Research Corporation
Vince Anzalone, CFA
626-304-3400
or
The Trout Group
Lauren Glaser
646-378-2972
ir@arrowres.com
 
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