Arrowhead Submits Application to Begin Phase 2a Trial of ARC-520 for the Treatment of Chronic Hepatitis B Infection

  Arrowhead Submits Application to Begin Phase 2a Trial of ARC-520 for the
  Treatment of Chronic Hepatitis B Infection

Business Wire

PASADENA, Calif. -- November 25, 2013

Arrowhead Research Corporation (NASDAQ:ARWR), a biopharmaceutical company
developing targeted RNAi therapeutics, today announced that it recently filed
an application for approval to begin a phase 2a clinical trial of its
RNAi-based therapeutic candidate, ARC-520, for the potential treatment of
chronic hepatitis B virus infection. Pending approval, Arrowhead intends to
proceed with a multicenter, randomized, double-blind, placebo-controlled,
dose-escalation study. The study is being conducted to determine the depth and
duration of hepatitis B surface antigen (HBsAg) reduction after a single
intravenous dose of ARC-520 in combination with entecavir in patients with
chronic HBV infection. Additional details on study design and anticipated
timelines will be provided when patient enrollment begins.

An application for a Certificate for Clinical Trial was submitted to the Hong
Kong Department of Health, and the study protocol, investigator brochure, and
informed consent were submitted to the ethics committees at two sites in Hong
Kong. Hong Kong was chosen as the location for the study based on the high
prevalence of chronic HBV infection and for the advanced healthcare and
regulatory system, which has a history of successful participation in clinical
trials for antiviral agents.

Principal investigators Professor Man-Fung Yuen, Chief of Gastroenterology and
Hepatology at The University of Hong Kong, Queen Mary Hospital, and Professor
Henry LY Chan, Head of Gastroenterology and Hepatology at The Chinese
University of Hong Kong, Prince of Wales Hospital, will conduct the study.
These investigators and sites were selected based on their large pool of
patients currently under care, their international standing as HBV
researchers, and track record of high accrual rates for clinical trials
involving viral hepatitis.

About ARC-520

Approximately 350 million people worldwide are chronically infected with the
hepatitis B virus. Chronic HBV infection can lead to cirrhosis of the liver
and is responsible for 80% of primary liver cancers globally. Arrowhead’s
RNAi-based candidate ARC-520 is designed to treat chronic HBV infection by
reducing the expression and release of new viral particles and key viral
proteins. The goal is to achieve a functional cure, which is an immune
clearant state characterized by hepatitis B s-antigen negative serum with or
without sero-conversion. The siRNAs in ARC-520 intervene at the mRNA level,
upstream of where nucleotide and nucleoside analogues act. In transient and
transgenic mouse models of HBV infection, a single co-injection of Arrowhead’s
DPC delivery vehicle with cholesterol-conjugated siRNA targeting HBV sequences
resulted in multi-log knockdown of HBV RNA, proteins and viral DNA with long
duration of effect. In a chimpanzee chronically infected with HBV and high
viremia and antigenemia, ARC-520 induced rapid reductions of 90-95% in HBV
DNA, e-antigen, and s-antigen, which did not return to baseline until study
day 43, 43, and 71, respectively. Data also suggested that a therapeutic
immunological flare occurred, which is thought to be part of a cascade that
under chronic therapy may lead to HBsAg seroconversion and functional cure.
Arrowhead has completed enrollment in a phase 1 single ascending dose study in
normal volunteers, which the company expects to follow with a phase 2a study
in chronic HBV patients.

About Arrowhead Research Corporation

Arrowhead Research Corporation is a biopharmaceutical company developing
targeted RNAi therapeutics. The company is leveraging its proprietary drug
delivery technologies to develop targeted drugs based on the RNA interference
mechanism that efficiently silence disease-causing genes. Arrowhead
technologies also enable partners to create peptide-drug conjugates that
specifically home to cell types of interest while sparing off-target tissues.
Arrowhead’s pipeline includes clinical programs in chronic hepatitis B virus
and obesity and partner-based programs in oncology.

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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
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