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nanotechnology arrowhead pasadena california nasdaq arwr nanotechnology arrowhead pasadena california nasdaq arwr nanotechnology arrowhead pasadena california nasdaq arwr compound semiconductor materials nano particles laboratory
PRESS RELEASE
September 24, 2007

Arrowhead Subsidiary, Insert Therapeutics, Awarded Patent for Cyclosert™ Camptothecin, the Company's Lead Oncology Candidate

PASADENA, California – September 24, 2007 – Insert Therapeutics, Inc., a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today the issuance of a patent covering its lead oncology product, IT-101. IT-101 is a conjugate of Insert’s proprietary drug delivery molecule, Cyclosert™, and the potent anti-cancer compound camptothecin. The newly-issued United States Patent No. 7,270,808 entitled “Cyclodextrin-based polymers for therapeutic delivery” covers Cyclosert-linked prodrugs, including camptothecin and camptothecin derivatives.

IT-101 is a nanoparticle therapeutic and has been in Phase I clinical trials since July 2006. In June 2007, interim Phase I data was published in the 2007 American Society for Clinical Oncology (ASCO) Proceedings (Abstract ID 32638), and reported stable disease in several patients who completed the six-cycle treatment regimen.

“The granting of this patent, that covers conjugates of the Cyclosert™ delivery polymers with camptothecin as well as a large number of other therapeutics, is an important milestone in our path to becoming a multi-product therapeutics company,” said John Petrovich, President and Chief Executive Officer of Insert. “It enables us to continue our plan to build a portfolio of novel nanoparticle therapeutics that will benefit patients with cancer and a wide range of other diseases and conditions.”

The full text of the Cyclosert-camptothecin patent may be found by conducting a patent number search utilizing the U.S. Patent Office’s web site at www.uspto.gov/patft/.

About Arrowhead Research Corporation

Arrowhead Research Corporation (www.arrowheadresearch.com) is a publicly-traded nanotechnology company commercializing new technologies in the areas of life sciences, electronics, and energy. Arrowhead is building value for shareholders through the progress of majority owned subsidiaries founded on nanotechnologies originally developed at universities. The company works closely with universities to source early stage deals and to generate rights to intellectual property covering promising new nanotechnologies. Currently, Arrowhead has four subsidiaries commercializing nanotech products and applications, including anti-cancer drugs, RNAi therapeutics, carbon-based electronics and compound semiconductor materials.

About Insert Therapeutics, Inc.

Insert Therapeutics, Inc. (www.insertt.com), a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ:ARWR), is using its proprietary, nano-engineered, polymeric delivery system, Cyclosert™, to design, develop and commercialize drug-delivery-enhanced small-molecule therapeutics and nucleic acids. Cyclosert uses cyclodextrins as building blocks to create an entirely new class of biocompatible materials - linear cyclodextrin-containing polymers that are non-toxic and non-immunogenic at therapeutic doses. Insert’s affiliate company, Calando Pharmaceuticals, is using a related system for the systemic delivery of siRNA. The companies are pursuing this goal through internal research and development, and also through collaborations and partnerships with pharmaceutical and biotechnology companies.

Safe Harbor Statement under the Private Securities Litigation Reform Act of 1995:

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 recent economic slowdown affecting technology companies, the future success of our scientific studies, our ability to successfully develop products, rapid technological change in our markets, changes in demand for our future products, legislative, regulatory and competitive developments and general economic conditions. Our Annual Report on Form 10-K and 10-K/A, recent and forthcoming Quarterly Reports on Form 10-Q and 10-Q/A, recent Current Reports on Forms 8-K and 8-K/A, our Registration Statement on Form S-3, and other SEC filings discuss some of the important risk factors that may affect our business, results of operations and financial condition. We undertake no obligation to revise or update publicly any forward-looking statements for any reason.

Contacts

Virginia Dadey; Vice President, Investor Relations
Telephone: 212.541.3707
Email: vdadey@arrowres.com

John G. Petrovich
Telephone: 626.683.7200
Email: jpetrovich@insertt.com