Press Release Details

Arrowhead Releases White Paper on Hepatitis B Virus and Potential RNAi TreatmentPASADENA, Calif. — March 7, 2012 — Arrowhead Research Corporation (NASDAQ: ARWR), a nanomedicine company with development programs in RNA therapeutics and obesity, announced today that it has 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.

"Hepatitis B is a global health problem without effective treatment for a vast number of patients with chronic disease.  The World Health Organization estimates that 360 million people, or 5% of the world's population, suffer from chronic hepatitis B," said Christopher Anzalone, Ph.D., President and CEO of Arrowhead.  "Advances in hepatitis C treatment have drawn considerable attention over the last year, and we see HBV as a similarly high value target.  Extensive data from our development programs across multiple in vitro and animal models suggest that we can leverage RNAi and our DPCs to produce a powerful and highly specific candidate to fight HBV."

HBV infection occurs primarily in hepatocytes and long-term infection causes hepatic inflammation that leads to acute and chronic hepatic dysfunction including acute hepatic failure, cirrhosis, and hepatocellular carcinoma.  The DPC delivery platform is being employed for the HBV product candidate, which is supported by multiple studies including demonstration in non-human primates of safe and effective delivery of siRNA to hepatocytes and promising data generated through mouse models of HBV using a DPC formulation.

"The development of a DPC-enabled HBV candidate began under Roche and we are very pleased with the progress that our scientists have made," said David Lewis, Ph.D., Vice President of Biology and the site head at Arrowhead's research and development facility in Madison, WI.  "We are excited to provide more detail on the DPC platform and the HBV program during upcoming scientific conferences and through future publication in peer-reviewed journals."

The white paper is available on Arrowhead's home page:  www.arrowheadresearch.com.

About Arrowhead Research Corporation

Arrowhead Research Corporation is a clinical stage targeted therapeutics company with development programs in oncology, obesity, and infectious disease. The company leverages its platform technologies to design and develop peptide-drug conjugates (PDCs) which specifically home to cell types of interest while sparing off-target tissues, creates targeted drugs based on the gene silencing RNA interference (RNAi) mechanism, and works 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.