Press Release Details

PASADENA, Calif. — January 4, 2012 — Arrowhead Research Corporation (NASDAQ: ARWR), a nanomedicine company with development programs in oncology and obesity, today announced that the Investigational New Drug Application (IND) for its first obesity drug candidate, AdipotideTM, was accepted by the U.S. Food and Drug Administration allowing the initiation of a clinical trial to test the safety of the compound. AdipotideTM specifically targets and kills blood vessels supplying white fat tissue. The Phase I clinical trial will be conducted by The University of Texas MD Anderson Cancer Center, which will bear the costs of the planned clinical trial.

"This is a significant milestone for our rapidly moving obesity program," said Dr. Christopher Anzalone, President and Chief Executive Officer. "Less than two months ago, data demonstrating substantial weight loss in obese rhesus monkeys using AdipotideTM was published in the prominent peer-reviewed journal, Science Translational Medicine. We are very excited to take this next step and that MD Anderson plans to start treating patients shortly. We believe we have a powerful suite of drug candidates that not only may help to combat obesity, but also may help to reverse symptoms associated with Type II Diabetes."

About Adipotide™

Adipotide™, or Prohibitin-Targeting Peptide 1 (Prohibitin-TP01), is an anti-obesity peptide which specifically targets and kills blood vessels supplying white fat tissue. Data demonstrating substantial weight loss, reduction in body mass index and abdominal circumference, and marked improvements in insulin resistance in obese rhesus monkeys was published in the peer-reviewed journal Science Translational Medicine in November 2011. This program is partnered with MD Anderson Cancer Center in Houston Texas, which is bearing the costs of the preclinical studies, drug candidate manufacturing, and the Phase I clinical trial. MD Anderson plans to initiate a Phase I study shortly in obese prostate cancer patients.

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 Adipotide™, 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 RONDEL™ 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 www.arrowheadresearch.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 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.

Contacts:
Michael Levitan
The Trout Group, LLC
646-378-2920
ir@arrowres.com