Nanotechnology Now - Press Release: Arrowhead subsidiaries Insert & Calando present data on Cyclosert(TM) drug delivery system at AACR meeting

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Novel Systems May Provide Cancer Patients With Improved Potential to Battle Their Disease

Arrowhead subsidiaries Insert & Calando present data on Cyclosert(TM) drug delivery system at AACR meeting

PASADENA, CA | Posted on April 16th, 2007

Arrowhead Research Corporation
(NASDAQ:ARWR) announced today that two of its majority-owned
subsidiaries, Insert Therapeutics Inc. and Calando Pharmaceuticals
Inc., are presenting data at the 2007 American Association for Cancer
Research (AACR) Annual Meeting. The presentations summarize the
latest research findings on two anticancer therapies currently under
development. Both therapies employ a novel delivery system called
Cyclosert(TM), developed at the California Institute of Technology
and exclusively licensed to Insert Therapeutics and, through Insert,
to Calando.

"We are pleased that our companies have outstanding data to present
at this prestigious conference," said R. Bruce Stewart, Chairman and
Chief Executive Officer of Arrowhead. "We see great promise going
forward for the treatment of cancer using our delivery system."

Cyclosert is the first nanoparticle drug transport platform to be
designed de novo and synthesized specifically to overcome limitations
in existing technologies used for the systemic transport of
therapeutics to targeted sites within the body. Based on small cyclic
repeating molecules of glucose called cyclodextrins, Cyclosert
promotes the ability of cytotoxic drugs to inhibit the growth of
human cancer cells while reducing toxicity and remaining
non-immunogenic at therapeutic doses. In particular, the system is
designed to reduce the toxicity of the drugs until they actually
reach the targeted tumor cells where the active drug is released in a
controlled fashion.

Insert's Chief Scientific Officer, Thomas Schluep, Sc.D., will
present data from in vitro and animal studies using the Cyclosert
system to deliver tubulysin A, a potent, but highly toxic, (antitumor
agent. In vitro studies have shown the tubulysin-Cyclosert conjugate
to be effective against multiple human cancer cell lines. The
conjugate was found to be stable and 100 times more water soluble
than the free drug.

Calando's Chief Scientific Officer, Jeremy Heidel, Ph.D, will present
data from animal studies using the Cyclosert system augmented by
Calando's own proprietary technology. Calando is developing a type of
ribonucleic acid (RNA) called small interfering RNA, or siRNA, for
anticancer use. In the tests, this siRNA-containing formulation,
using Cyclosert as a delivery system, showed significant antitumor
activity and was well-tolerated.

Testing and development is ongoing for both drugs.

####

About Arrowhead Research Corporation
Arrowhead Research Corporation ( http://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) is using its proprietary,
nano-engineered, polymeric delivery system, Cyclosert(TM), 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. The company is
pursuing this goal through its internal research and development, and
also through collaborations and partnerships with pharmaceutical and
biotechnology companies.

About Calando Pharmaceuticals Inc.

Calando Pharmaceuticals Inc. (www.calandopharma.com ) is using its
proprietary technologies in targeted polymeric delivery systems and
siRNA design to design and create new, targeted siRNA therapeutics.
Small interfering RNAs (siRNA) use RNA interference, or RNAi, a
naturally occurring mechanism within cells to selectively silence and
regulate specific genes. The ability to silence genes selectively
through RNAi could provide a new way to treat a wide range of human
diseases. The company is pursuing this goal through its 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 ofthe "safe harbor" provisions of the Private Securities
Litigation Reform Actof 1995. These statements are based upon our
current expectations and speak onlyas 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 factorsand
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 filingsdiscuss 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.