Arrowhead Issues a Statement on Intellectual Property Protection for ARC-520

PASADENA, Calif.–(BUSINESS WIRE)–

Arrowhead Research Corporation (NASDAQ:ARWR), a biopharmaceutical

company developing targeted RNAi therapeutics, today reaffirmed its

belief that it has broad access to intellectual property required to

develop ARC-520, its clinical candidate against chronic hepatitis B

infection. The Company has licenses to relevant patents and patent

applications enabling the development and commercialization of ARC-520

in key pharmaceutical markets globally. Arrowhead does not believe there

are additional unlicensed patents directed to RNAi therapeutics

targeting the hepatitis B virus that affect its freedom to operate.

The company signed a license agreement with Alnylam Pharmaceuticals in

January 2012, giving it access to intellectual property that enables the

discovery, development, and commercialization of an RNAi therapeutic

targeting the hepatitis B virus. Moreover, Arrowhead holds multiple

levels of patent protection on ARC-520 including U.S. Patent Nos.

8,313,772 and 8,501,930 covering the Dynamic Polyconjugate (DPC)

delivery system, and U.S. Patent Application number 13/535,454 covering

ARC-520’s siRNA component, which was recently allowed by the U.S. Patent

and Trademark Office.

Arrowhead and its legal advisors continually review the patent landscape

to ensure freedom to operate and the Company believes that development

and commercialization of ARC-520 would not infringe patents governing

RNAi therapeutics targeting the hepatitis B virus, including U.S. Patent

No. 8,618,277 in the McSwiggen patent estate.

“We are moving ARC-520 as quickly as possible to market and do not

believe anything limits our ability to do so,” said Christopher

Anzalone, Ph.D., Arrowhead’s President and Chief Executive Officer. “The

roughly 400 million people world-wide with chronic hepatitis B infection

currently have limited options, and we remain committed to them.”

About ARC-520

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. Arrowhead has completed enrollment in a Phase 1

single ascending dose study in normal volunteers. The company is

conducting a single dose Phase 2a study in chronic HBV patients, which

it expects to follow with a multi dose, multi national Phase 2b study.

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.

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 silences 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 partner-based programs in

obesity and oncology.

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.

Arrowhead Research Corporation
Vince Anzalone, CFA,

626-304-3400
ir@arrowres.com
or
Investor

Relations:
The Trout Group
Lauren Glaser, 646-378-2972
ir@arrowres.com
or
Media:
Russo

Partners
Martina Schwarzkopf, Ph.D., 212-845-4292
martina.schwarzkopf@russopartnersllc.com

Source: Arrowhead Research Corporation

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