Arrowhead Reports Fourth Quarter and Full Year 2008 Financial Results

Calando Pharmaceuticals Publishes New Results of siRNA Delivery
Using Its RONDEL(TM) Technology in Sepsis

Calando's RONDEL(TM) technology involves the use of cyclodextrin-containing polymers that form the foundation for its two-part siRNA delivery system. The first component is a linear, cyclodextrin-containing polycation that, when mixed with small interfering RNA (siRNA), binds to the anionic "backbone" of the siRNA. The polymer and siRNA self-assemble into nanoparticles smaller than 100 nm in diameter that fully protect the siRNA from nuclease degradation in serum. The siRNA delivery system has been designed to allow for intravenous injection. Upon delivery to the target cell, the targeting ligand binds to membrane receptors on the cell surface and the RNA-containing nanoparticle is taken into the cell by endocytosis. There chemistry built into the polymer functions to unpackage the siRNA from the delivery vehicle. Based upon this breakthrough in siRNA delivery enabled by the RONDEL(TM) system, the promise of using siRNA in new systemic therapies may finally be realized.

Arrowhead Raises $5.4 Million into Two Subsidiaries; Initiatives Strengthen Balance Sheet for 2009

PASADENA, Calif. — Arrowhead Research Corporation (NASDAQ: ARWR) (Arrowhead) announced today recent moves as part of its initiative to conserve capital while maintaining commercialization progress at its subsidiaries. It has raised a total $2.7 million into majority-owned subsidiary, Unidym, Inc. from existing strategic investor, Tokyo Electron Ventures and from the sale of certain non-core assets; it raised $2.7 million into majority-owned subsidiary, Calando Pharmaceuticals, Inc.; it redirected $1.7 million from wholly-owned subsidiary, Tego Biosciences Inc. back into Arrowhead. Calando and Unidym are Arrowhead’s most mature subsidiaries and, consequently, its greatest consumers of capital. Raising $5.4 million directly into these companies while bringing $1.7 million from Tego back to Arrowhead strengthens the company’s cash position for fiscal 2009.

TEL VENTURE CAPITAL, INC. Invests Additional Capital into UNIDYM,
Plans Collaboration in LCD and Solar Industries

PASADENA, Calif. — Unidym, a majority owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today that TEL Venture Capital, Inc., the U.S. investment arm of Tokyo Electron, has invested additional capital into the company. Concurrent with the investment, Unidym and Tokyo Electron intend to enter into a program to develop equipment for use in the production and integration of Unidym’s films. The two companies also agreed to share information to advance Unidym's progress in printed electronics, a disruptive approach to electronics manufacturing that leverages inexpensive wet coating processes rather than the more expensive processes currently employed in the electronics industry.

Arrowhead CEO Provides Update on Tego Biosciences Corporation

PASADENA, Calif. — Arrowhead Research Corporation’s (NASDAQ: ARWR) Chief Executive Officer announces an update to stockholders on its wholly owned subsidiary, Tego Biosciences Corporation. Dear Arrowhead Stockholders; Since Arrowhead’s inception in 2003, we have followed the development of a relatively new class of molecules, known as fullerenes, with great interest. These are highly ordered clusters of carbon atoms with unique properties that may be leveraged across multiple fields, from industrial uses to medical imaging and therapeutics. In November 2007, we formed Tego Bioscience, Inc. to address these opportunities. Tego, a wholly owned subsidiary of Arrowhead, was created around the acquisition of C Sixty, Inc., a company that had been developing fullerene-based products since 1999. We saw this as a powerful platform because C Sixty was widely recognized as a leader in the new field and the Chairman of its Scientific Advisory Board was Dr. Richard Smalley, who won the 1996 Nobel Prize in Chemistry for his role in discovering fullerenes.

Arrowhead Research Corporation Retains The Piacente Group, Inc.
as Strategic Investor Relations Consulting Firm

PASADENA, Calif. - November 17, 2008 - Arrowhead Research Corporation (NASDAQ: ARWR) (“Arrowhead”), a leading nanotechnology company, who, through its majority-owned subsidiaries, commercializes new technologies in the areas of life sciences, electronics and energy, today announced that it has retained The Piacente Group, Inc. (“TPG”), a full service investor relations consulting firm based in New York City. TPG will assist Arrowhead in implementing investor communications and Wall Street outreach programs aimed at making new connections in the financial community for the Company.

Arrowhead CEO Provides Update on Nanotope, Inc.

PASADENA, Calif.— Arrowhead Research Corporation’s (NASDAQ: ARWR) Chief Executive Officer announces an update to stockholders on its minority investment, Nanotope, Inc.. Dear Stockholders: In 2005, Dr. Samuel Stupp, Director of Northwestern University’s Institute for Bionanotechnology in Medicine, and I co-founded Nanotope Inc., a regenerative medicine company. I strongly believed that medicine would be forever transformed if we could move beyond simply replacing failed body parts and shift the industry toward a less invasive method of regenerating damaged tissues. This would represent no less than a paradigm shift in healthcare, but, of course, identifying an opportunity is simple; the difficult challenge is to develop and scale an appropriate technology platform. Dr. Stupp had been working toward this vision and his work was well positioned to be the technology basis of a new regenerative medicine company.

Arrowhead CEO Provides Update on Majority Owned Subsidiary Unidym, Inc.

PASADENA, Calif.—Arrowhead Research Corporation’s (NASDAQ: ARWR) Chief Executive Officer announces an update to stockholders on its majority owned subsidiary, Unidym: Dear Stockholders: Unidym is Arrowhead’s most developed nanomaterials company and a premier example of our model for building new technology companies. As with Calando, we believe Unidym is a demonstration of our ability to build potentially transformational companies that have near-term market entry points. Unidym is a platform company positioned to address sizeable long-term product opportunities in the electronics industry and, more importantly in the current market environment, significant short-term opportunities in the high growth touch panel and display industries.

Calando Pharmaceuticals to Present at 19th Annual
Oppenheimer Healthcare Conference on November 4, 2008

Pasadena, Calif., - Calando Pharmaceuticals, Inc., a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today that its CEO, Dr. James Hamilton, will present at the 19th Annual Oppenheimer Healthcare Conference on Tuesday, November 4, 2008 at 11:00am ET. The conference is being held at the Waldorf Astoria Hotel in New York City. Dr. Hamilton's presentation will discuss Calando's proprietary delivery systems for siRNA and small molecule drugs and Calando's clinical program for its two lead compounds, CALAA-01 and IT-101.

Arrowhead Research Corporation to Present at
AeA Classic Financial Conference November 4 and 5, 2008

Pasadena, Calif., - October 31, 2008 - Arrowhead Research Corporation (NASDAQ: ARWR) will present at the Annual AeA Classic Financial Conference at the Manchester Grand Hyatt Hotel in San Diego, CA. Chris Anzalone, CEO and President of Arrowhead, and Art Swift, CEO and President of Arrowhead subsidiary, Unidym, Inc., will host four presentations on Tuesday November 4 starting at 2:00 p.m. PT and five presentations on Wednesday November 5, starting at 8:00 a.m. PT.

Arrowhead CEO Provides Update on Wholly Owned Subsidiary Agonn Systems, Inc.

PASADENA, Calif. — Arrowhead Research Corporation’s (NASDAQ: ARWR) Chief Executive Officer announces an update to stockholders on its wholly owned subsidiary, Agonn Systems Corporation: Dear Arrowhead Stockholders, Agonn Systems Corporation, Arrowhead’s newest subsidiary, seeks to leverage Arrowhead’s expertise in carbon nanotechnology to improve energy storage products. Consistent with our conservative strategy in the current market environment, Agonn is currently pursuing a capital efficient R&D model based on outsourced prototyping and testing in partnership with its key technical consultants at Georgia Tech, MIT, University of Pittsburgh, and University of Dayton.

Calando Pharmaceuticals Announces Completion of IT-101 Phase 1 Clinical Study

Calando Pharmaceuticals, a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ:ARWR), announced today completion of the IT-101 Phase I clinical study conducted at City of Hope in Duarte, California. The company expects the entire study data to be published in early 2009. IT-101 is an experimental, nanoparticle therapeutic that consists of the drug camptothecin (CPT) conjugated to a cyclodextrin polymer. IT-101, the first drug candidate in Calando's proprietary Cyclosert(TM) pipeline, has now successfully completed a Phase I trial designed to evaluate its safety, tolerability, and pharmacokinetics in patients with inoperable or metastatic tumors.

Arrowhead CEO Provides Update on Majority Owned Subsidiary Calando Pharmaceuticals Inc.

PASADENA, Calif.—Arrowhead Research Corporation (NASDAQ: ARWR) announced today that the Company's CEO has provided an update letter to stockholders on its majority owned subsidiary, Calando Pharmaceuticals: Dear Arrowhead Stockholders, Calando Pharmaceuticals is Arrowhead’s most mature biopharmaceutical subsidiary. Based on technology developed at the California Institute of Technology, Calando’s proprietary linear cyclodextrin nanoparticle technology has been optimized to deliver small molecule drugs using Calando’s CyclosertTM system and RNAi therapeutics using the RONDELTM system. Using these platform systems, Calando has developed two anti-cancer drug candidates that are currently undergoing human clinical trials.

Unidym Announces a Demonstration by Samsung Electronics of
the First Color Carbon Nanotube-Based Electrophoretic Display

Menlo Park, CA –October 16, 2008 - Unidym, Inc, a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ:ARWR), announced today that Samsung Electronics is demonstrating the world’s first carbon nanotube-based color active matrix electrophoretic display (EPD) e-paper at the International Meeting on Information Display (iMiD) at KINTEX, Ilsan, Korea from October 13th through October 17th. The new color e-paper device is a 14.3” format display and is the result of an ongoing joint development program between Samsung Electronics Co., Ltd. and Unidym. The e-paper device uses a carbon nanotube (CNT) transparent electrode developed by Unidym.

Arrowhead CEO Updates Stockholders

Pasadena, California — Arrowhead Research Corporation (NASDAQ: ARWR) announced today that the Company's CEO has provided an update letter to stockholders: Dear Arrowhead Stockholders, In order to provide an update on Arrowhead’s operational and strategic initiatives, I plan to release seven weekly newsletters. This first edition focuses on Arrowhead’s overall strategy and provides a broad overview of its subsidiaries. Every week over the next six weeks, Arrowhead will release a focused newsletter on each of its four majority-owned subsidiaries: Unidym Inc., Calando Pharmaceuticals Inc., Agonn Systems Corporation and Tego Biosciences Corporation. This and future newsletters will also review developments at Nanotope Inc. and Leonardo Biosystems, Inc., both entities in which Arrowhead currently holds a minority interest. We intend to increase our equity position in these two companies over time to achieve majority ownership.

Calando Patent Issued for Active Ingredient of Lead siRNA Drug Candidate, CALAA-01

PASADENA, Calif. - October 7, 2008 - Calando Pharmaceuticals, Inc. ("Calando"), a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today the issuance of U.S. Patent No. 7,427,605, entitled, "Inhibitors of ribonucleotide reductase subunit 2 and uses thereof." The patent contains claims directed to inhibitory nucleic acid sequences targeting the Ribonucleotide Reductase Subunit 2 ("R2") gene, as well as pharmaceutical compositions and methods for inhibiting tumor growth utilizing the sequences. R2 is the gene targeted by Calando's lead siRNA-containing nanoparticle therapeutic, CALAA-01, which is currently in a Phase I clinical trial for patients with non-resectable or metastatic solid tumors. CALAA-01 is the only RNAi therapeutic for cancer to have reached the clinic.

Unidym Licenses Technology for Semiconductor Applications

MENLO PARK, Calif.— Unidym, Inc., a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today that it has completed a non-exclusive license for certain intellectual property in its portfolio to one of the world's leaders in advanced semiconductor materials for high performance integrated circuits.

Calando Pharmaceuticals Announces Next siRNA Therapeutic Candidate for Oncology

PASADENA, Calif. - September 15, 2008 - Calando Pharmaceuticals, a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today that pre-clinical development of a second siRNA oncology therapeutic, CALAA-02, is underway. The intracellular target for CALAA-02 is HIF-2alpha, or Hypoxia Inducible Factor-2 alpha. HIF-2alpha is overexpressed in a number of solid tumors and is critical for many aspects of tumorigenesis, such as metastasis, angiogenesis, tumor cell proliferation, and tumor response to radiation. HIF-2alpha has been difficult to target using traditional drugs but is effectively targeted by the proprietary siRNA in CALAA-02.

CALANDO PHARMACEUTICALS PHASE II CLINICAL STUDY OPENS TO PATIENT ENROLLMENT

Pasadena, CA - September 11, 2008 - Calando Pharmaceuticals, Inc., a majority owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today that it has initiated a Phase II clinical trial in the United States evaluating the safety and efficacy of its drug candidate, IT-101 in patients with platinum-sensitive ovarian cancer. The study is open for enrollment.

ARROWHEAD COMPLETES PREVIOUSLY ANNOUNCED REGISTERED DIRECT OFFERING RAISES A TOTAL OF $6.9 MILLION TO FUND OPERATIONS

Pasadena, CA - Arrowhead Research Corporation (NASDAQ:ARWR) announced today that it has completed its previously announced registered direct offering, increasing total gross proceeds to approximately $6.9 million and net proceeds to approximately $6.4 million. The final closing raised an additional $2.5 million over the $4.4 million previously announced last month. A total of 3.9 million units consisting of common stock and common stock warrants were sold to investors, the large majority of whom are either long-standing shareholders or members of Arrowhead’s senior management team.

UNIDYM ENTERS INTO SECOND JOINT DEVELOPMENT AGREEMENT WITH SAMSUNG ELECTRONICS TO INTEGRATE CARBON NANOTUBES INTO DISPLAY DEVICES

Menlo Park, CA - August 12, 2008 - Unidym, Inc, a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), announced today that it has entered into a second joint development agreement with Samsung Electronics Co., Ltd. to extend their collaboration into a second year. The companies have been working jointly to integrate carbon nanotube materials as the transparent conductive layer in display devices. One achievement from the first year of this collaboration was the world’s first public demonstration of a working prototype of a carbon nanotube-based active matrix electrophoretic display (EPD) e-paper at the Society for Information Display (SID) International Symposium in May of 2008.

ALNYLAM GRANTS NEW INTERFERX(TM) INTELLECTUAL PROPERTY LICENCE TO CALANDO FOR DEVELOPMENT AND COMMERCIALIZATION OF RNAi THEARPEUTICS

CAMBRIDGE, Mass. & PASADENA, Calif. - July 21, 2008 - Alnylam Pharmaceuticals, Inc. (Nasdaq: ALNY), a leading RNAi therapeutics company, today announced that it has granted Calando Pharmaceuticals Inc., a majority-owned subsidiary of Arrowhead Research Corporation (NASDAQ: ARWR), a new target-specific InterfeRx(TM) license to discover, develop, and commercialize a synthetic siRNA directed toward an undisclosed cancer gene target. The new non-exclusive, gene-specific license agreement includes an Alnylam right of first negotiation to opt-in for co-development and co-commercialization of the RNAi therapeutic product in the U.S. market. Detailed financial terms were not disclosed, but include upfront, and milestone payments, and royalties on sales of any products covered by the licensing agreement.

ARROWHEAD FORMS NEW SUBSIDIARY TO COMMERCIALIZE ENERGY STORAGE DEVICES

Pasadena, CA - July 9, 2008 - Arrowhead Research Corporation (NASDAQ: ARWR) announced today that it has formed Agonn Systems Corporation to explore, develop and commercialize nanotechnology-based energy storage devices for electric vehicles and other large format applications. Agonn has initiated a strategy to acquire energy storage technologies based on nanoscale engineering from research institutions and expects to begin prototyping ultracapacitors based on carbon nanotubes and other advanced materials this year. The formation of Agonn Systems is part of a strategy at Arrowhead to leverage nanotechnology for clean energy applications.

ARROWHEAD SUBSIDIARY, UNIDYM, RECEIVES STRATEGIC INVESTMENT FROM ENTEGRIS

Pasadena, CA - June 17 -2008 - Arrowhead Research Corporation (NASDAQ: ARWR) announced today that Unidym, Inc., its majority-owned subsidiary, has received a $2.0 million strategic investment from Entegris, Inc. (NASDAQ: ENTG), a leading provider of products for purifying, protecting and transporting critical materials used in processing and manufacturing in semiconductor and other high-tech industries. Arrowhead made a $2.0 million matching investment.