Arrowhead Research Corporation Acquires Early Nanosensor Patent Portfolio.

PASADENA, Calif. -- Arrowhead Research Corporation (NASDAQ:ARWR)(NASDAQ:ARWRW) announced today that it has acquired a suite of patent and patent applications covering nanosensor technology developed by Dr. Hermann Gaub, a Professor of Biophysics at the Center for Nanoscience at Ludwig-Maximilians University in Munich. Arrowhead and its subsidiaries now own or have licenses to over 250 U.S. and international patents and patent applications.

"Nanosensors are expected to radically change the way we diagnose disease. Now, we go to the doctor's office to have large samples of blood taken and then wait for days to get the results from a remote laboratory," said R. Bruce Stewart, President of Arrowhead. "With a nanosensor-enabled device, tests could be performed with a single drop of blood - and the results obtained within minutes."

The portfolio covers techniques for measuring biomolecular interactions by single-molecule force spectroscopy. As reported in "Science" in 2003, the devices are sensitive enough to detect single-base pair mismatches of DNA and have demonstrated significant improvement over state-of-the-art instrumentation. The patent applications also cover construction of parallel assays for placing millions of sensors on a chip. These patent and patent applications were acquired for a di minimus cash payment and are complementary to other patents to which Arrowhead already has rights.

About Arrowhead Research Corporation

Arrowhead Research is a nanotechnology company structured to bring together a diverse and innovative mix of technologies, rights to a broad suite of intellectual property, and some of the most respected minds in this dynamic field. There are three strategic components to Arrowhead's business model:

--Forming or acquiring majority-owned subsidiaries engaged in the development and commercialization of nanoscale materials, devices, and systems.

--Funding of prototype development at universities in exchange for the exclusive right to commercialize resulting intellectual property.

--Acquisition, license and sublicense of intellectual property in the field of nanotechnology.

Arrowhead Research operates four majority-owned subsidiary companies:

--Aonex Technologies, Inc. is developing and commercializing proprietary semiconductor nanomaterial technology.

--Insert Therapeutics, Inc. is developing and commercializing proprietary nanometer-sized therapeutics.

--Nanotechnica, Inc. is developing capabilities for mass-production of a variety of different, proprietary nanoscale devices and systems.

--Calando, Inc. is developing nanostructures for delivery of RNA interference.

Arrowhead is also funding three research efforts in nanotechnology at Caltech in the areas of nanomaterials, nanoelectronics, and nanobiomolecular tools.

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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, without limitation, our developmental stage and limited operating history, our ability to successfully develop products, rapid technological change in our markets, demand for our future products, legislative, regulatory and competitive developments and general economic conditions. Our Annual Report on Form 10-K, recent and forthcoming Quarterly Reports on Form 10-Q, Registration Statements on Form S-3, recent Current Reports on Forms 8-K and 8-K/A, 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.