Arrowhead Research Corporation (NASDAQ: ARWR), a targeted therapeutics company, today announced that it has received a Notice of Allowance from the U.S. Patent and Trademark Office for U.S. Patent Application Number 13/336,028 entitled, “In Vivo Polynucleotide Delivery Conjugates Having Enzyme Sensitive Linkages.” This new IP expands the Dynamic Polyconjugate (DPC) platform, broadly protecting Arrowhead's next generation DPC polymer masking technology. Using this masking technology, DPCs can be engineered for long circulation times and improved tissue-targeting characteristics. In addition, hepatocyte-targeted DPCs formulated using this new masking technology have shown to be highly potent upon subcutaneous administration. The company has previously reported target gene knockdown of 99% in monkeys after a single subcutaneous injection of 1 mg/kg, with >80% knockdown for 3 months. Additional data will be reported at upcoming scientific conferences and through peer-reviewed publications. “This patent protects a new masking chemistry that broadens the reach of DPC-enabled RNAi therapeutics. It enables efficient subcutaneous delivery of siRNA and opens up new therapeutic area targets including oncology,” said Dr. Chris Anzalone, President and CEO of Arrowhead. “Arrowhead scientists continue to discover innovative solutions for siRNA delivery and we look forward to providing updates on how these technologies are being deployed to create new drug candidates.” About Arrowhead Research Corporation Arrowhead Research Corporation is a clinical stage targeted therapeutics company with development programs in oncology, obesity, and chronic hepatitis B virus infection. The company is leveraging its platform technologies to design and develop peptide-drug conjugates (PDCs) that specifically home to cell types of interest while sparing off-target tissues, create targeted drugs based on the gene silencing RNA interference (RNAi) mechanism, and work 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 firstname.lastname@example.org. 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.