Majority Investment Made in New Nanotech Subsidiary by Arrowhead Research Corporation

Insert Therapeutics, Inc. to Further the Development and Commercialization of

Small Molecule, Drug Delivery Systems

Apr 22, 2004, 01:00 ET from Arrowhead Research Corporation

    PASADENA, Calif., April 22 /PRNewswire-FirstCall/ -- Arrowhead Research
 Corporation (OTC Bulletin Board:   ARWR), an emerging company in the field of
 nanotechnology, announced today that it has agreed to take a majority position
 in Insert Therapeutics, Inc., a Pasadena-based company focused on designing,
 developing and commercializing delivery-enhanced therapeutics using its
 patented class of polymers.
     With research being led by Dr. Mark Davis, a professor of chemical
 engineering at the California Institute of Technology, Insert Therapeutics is
 currently expanding and leveraging its platform technology, Cyclosert(TM),
 through an internal small-molecule drug development program, a gene-therapy
 collaboration with San Diego-based Canji, Inc., a subsidiary of
     The founder of Insert Therapeutics, Dr. Davis is a Member of the National
 Academy of Engineering and a recipient of numerous awards including the
 prestigious Alan T. Waterman Award, given by the National Science Foundation
 annually to only one scientist in the United States across all disciplines.
 Dr. Davis was the first engineer to win this award for his work in rationally
 designed materials. Dr. Davis earned his B.S., M.S. and Ph.D. degrees in
 Chemical Engineering, holds over 30 patents, has published more than 300
 papers and has presented over 450 seminars throughout the world.
     Insert has designed a novel class of "intelligent" polymers that
 incorporate properties for the intracellular, systemic delivery of a broad
 range of therapeutics. The polymer-therapeutic composites form nanoparticles
 that have designable size and functions. These "smart" nanoparticles can
 deliver therapeutics ranging from small molecules to genes and their
 combinations.  Unlike passive drug carriers, Cyclosert polymers respond to
 biological mechanisms and micro-environmental conditions enabling the active
 release of their therapeutic payload into tumor cells or other selected
 tissues, that can be targeted with the attachment of various cell surface
 receptor ligands.
     Cyclosert's linear cyclodextrin-containing polymers can be designed to be
 neutral, positively charged or negatively charged. This feature is unique to
 Cyclosert technology and provides great flexibility for formulation and
 delivery. Cyclosert has been synthesized at molecular weights high enough to
 provide for to slowed renal clearance, enhanced circulation time and improved
 accumulation of active drug at the target tissue.  Using Cyclosert, Insert has
 significantly improved the solubility, stability, toxicity, efficacy and
 pharmacokinetic characteristics of anticancer drugs.
     About Arrowhead Research Corporation
     Arrowhead Research Corporation funds research at universities in
 pioneering scientific areas, primarily nanotechnology, in return for exclusive
 rights to commercialize technologies and associated intellectual property and
 patents developed as a result of this research. The Company has already
 entered into agreements with the California Institute of Technology and three
 of its faculty, and is actively pursuing other potential partners at Caltech
 and other leading research institutions and universities.
     Commercial applications that arise from Company-sponsored research
 projects will be developed and marketed by Arrowhead Research through a series
 of diversified subsidiaries representing each product or application, or
 through third-party licensing.  The first majority-owned subsidiary, Aonexx
 Technologies, was formed to commercialize an ultrathin crystal film (nanofilm)
 technology that was developed at Caltech.
     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, 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, recent and forthcoming
 Quarterly Reports on Form 10-Q, 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.

SOURCE Arrowhead Research Corporation