Insert Therapeutics Files Investigational New Drug Application for Lead Anti-Cancer Compound IT-101

PASADENA, California – (BUSINESS WIRE) – Feb. 9, 2006 – Insert Therapeutics, Inc., a majority-owned subsidiary of Arrowhead Research Corporation (Nasdaq:ARWR), announced today that it has submitted an investigational new drug application (IND) to the U.S. Food and Drug Administration (FDA) to initiate a Phase I clinical trial using its lead anti-cancer compound, IT-101, a combination of its patented polymer technology, Cyclosert(TM), and the anti-cancer compound camptothecin, to treat patients with unresectable or metastatic solid tumors. The objectives of the Phase I clinical protocol submitted with the IND are to evaluate the safety, pharmacokinetics and tolerability of IT-101 in humans.

The clinical trials will be held at The City of Hope Cancer Center (COH) in Duarte, Calif., where Yun Yen, M.D., Ph.D., will lead the study. Patient enrollment can begin once the clinical protocol has been accepted by the FDA and COH. If the IND becomes effective with the FDA without delay or the need for additional studies, Insert expects to begin treating patients in the second quarter of 2006.

"We hope IT-101 will become a potent new therapy for patients suffering from various forms of cancer," said John Petrovich, President of Insert. "This IND filing is an important step in expanding the potential of Cyclosert," he continued, noting that in addition to preclinical test data on IT-101, the IND contains data that demonstrate the safety in animals of Cyclosert alone, potentially allowing Insert to accelerate Cyclosert's use in the clinic with other existing therapeutics.

Thomas Schluep, Insert's Chief Scientific Officer who led the development effort for IT-101, added, "While advancing the clinical development of IT-101 is Insert's highest priority, IT-101 is only the first in a series of therapeutics under development at Insert that will seek to take advantage of Cyclosert's unique properties."

Insert's proprietary Cyclosert delivery system is based on small cyclic repeating molecules of glucose called cyclodextrins. Using modified cyclodextrins as building blocks, Insert has developed an entirely new proprietary class of materials called linear cyclodextrin-containing polymers. To the company's knowledge, Cyclosert is the first nanoparticle drug delivery platform to be designed de novo and synthesized specifically to overcome limitations in existing delivery technologies used for the systemic delivery of therapeutics. The polymers were invented at Caltech in the lab of Dr. Mark Davis, a professor in Chemical Engineering and founder of Insert, and licensed exclusively to Insert.

Cyclosert polymers have been synthesized over a broad range of molecular weights providing tunable properties for systemic drug delivery that improve localization of active drug at the target tissue. This feature of the Cyclosert technology provides great flexibility for overcoming multiple hurdles encountered in formulation and delivery.

Discovered in the 1960s, camptothecin is a naturally occurring, water-insoluble alkaloid that has established potent activity against a broad spectrum of cancer types. Although analogues of camptothecin (e.g., irinotecan and topotecan) continue to realize nearly $1 billion in worldwide sales annually, camptothecin itself has not been commercialized due to its poor solubility and unfavorable pharmacokinetics. In numerous animal studies conducted by Insert, treatments with IT-101 result in protracted anti-tumor activities that are substantially more effective at significantly lower doses than all other treatment groups, including irinotecan.

About Insert Therapeutics, Inc.

Insert Therapeutics, Inc., a majority-owned subsidiary of Arrowhead Research Corporation, is using its proprietary, nano-engineered, polymeric delivery system, Cyclosert, to design, develop and commercialize drug-delivery-enhanced small-molecule therapeutics. Cyclosert uses cyclodextrins as building blocks to create an entirely new class of biocompatible materials -- linear cyclodextrin-containing polymers that are nontoxic and nonimmunogenic at therapeutic doses. The company is pursuing this goal through its internal research and development, and also through collaborations and partnerships with pharmaceutical and biotechnology companies. For more information, visit www.insertt.com.

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.

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

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