Press Release Details

Arrowhead to Present at Series of Upcoming Scientific Conferences PASADENA, California, May 3, 2012 — Arrowhead Research Corporation (NASDAQ:ARWR) today announced that senior management will present data for its Dynamic PolyConjugate^TM (DPC) delivery platform for siRNA delivery including its RNAi therapeutic candidate for the treatment of hepatitis B virus (HBV) at several upcoming scientific conferences.

"Arrowhead's DPC delivery system and the associated HBV program have been under development for several years at our Madison site, first as Mirus Bio and then as a subsidiary of Roche. It's been several years since data regarding the programs have been presented to the scientific community at large. We are looking forward to unveiling advanced and exciting results in these forums and to related publications later this year," said Dr. Christopher Anzalone, Arrowhead's CEO & President.

Scheduled conference presentations are as follows:

European Foundation for Clinical Nanomedicine (CLINAM)
Basel, Switzerland
An oral presentation titled, "DPC Technology for Safe and Effective siRNA Delivery," will be presented by Dr. David Lewis, Vice President, Biology and Site Head on May 9, 2012 at 8:35 AM CEST

TIDES: Oligonucleotide & Peptide® Research, Technology & Product Development
Las Vegas, NV, May 20-23
A poster titled, "Liver-targeted and reversibly masked-polycation co-delivery improves cholesterol-conjugated siRNA efficacy" will be presented by Dr. Darren Wakefield, Senior Scientist

RNA Society Annual Meeting
Ann Arbor, MI
A poster titled, "Effective RNAi Therapeutic to Treat Chronic Hepatitis B Virus Infection." will be presented by Dr. Christine Wooddell, Senior Scientist

RNAi Research & Therapeutics Conference
Boston, MA, May 29-June 3
An oral presentation titled, "The Development of Dynamic Poly Conjugates" will be presented by Dr. David Rozema, Vice President, Chemistry, on May 30, 2012 at 10:30 AM ET

RNAi & Nanotechnology Conference
London, UK
An oral presentation titled, "DPC Technology for siRNA Delivery: from rodents to primates" will be presented by Dr. David Lewis on June 11, 2012 11:40 AM GMT

International Congress on Infectious Diseases
Bangkok, Thailand
An oral presentation in the session New Developments in Viral Diseases: "RNAi therapeutics for the treatment of chronic hepatitis B virus infection" will be presented by Dr. David Lewis on Friday, June 15, 2012, 3:45 PMICT

Arrowhead published a white paper providing an overview of its proprietary DPC technology for safe and effective delivery of siRNA. This white paper can be found on the Arrowhead website at http://www.arrowheadresearch.com/pdf/Arrowhead-Research-Corporation_-_DPC-Technology-White-Paper-November2011.pdf

Arrowhead has also released a white paper describing the health problem posed by the hepatitis B virus (HBV), the substantial unmet need for chronic HBV infected patients, and how Arrowhead's Dynamic Polyconjugate (DPC) enabled RNAi therapeutic in development could potentially address deficiencies of current treatment options. This white paper can be found on the Arrowhead website at http://www.arrowheadresearch.com/pdf/whitepaper-hbv-3-7-12.pdf

About Arrowhead Research Corporation
Arrowhead Research Corporation is a clinical stage nanomedicine company developing innovative therapies at the interface of biology and nanoengineering. Arrowhead's world-class capabilities and intellectual property covering nucleic acid delivery, siRNA chemistry, and tissue targeting allow it to design and develop therapeutic agents for a wide range of diseases. The company's lead products include CALAA-01, an oncology drug candidate based on the gene silencing RNA interference (RNAi) mechanism, and AdipotideTM, an anti-obesity peptide that targets and kills the blood vessels that feed white adipose tissue. Arrowhead is leveraging its proprietary Dynamic PolyConjugate (DPC), Liposomal Nanoparticle (LNP), and RONDELTM delivery platforms to support its own pipeline of preclinical and clinical candidates and to secure external partnerships and collaborations with biotech and pharmaceutical companies.

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