Arrowhead Research to Report Fiscal Third Quarter 2009 Financial Results and Host Conference Call on Monday, August 10, 2009

PASADENA, Calif. — August 4, 2009 — Arrowhead Research Corporation (NASDAQ: ARWR) today announced that it will report its financial results for the third quarter of fiscal 2009 ended June 30, 2009, on Monday, August 10, 2009 at 4:30 p.m. ET (1:30 p.m. PT). To participate in the conference call, please dial 888-846-5003 or 480-629-9856. Investors may also access a live audio webcast of this conference call on the Company's website at  www.arrowheadresearch.com.

A replay of the webcast will be available approximately two hours after the conclusion of the call. The webcast replay will remain available for 90 days. An audio replay will also be available approximately two hours after the conclusion of the call and will be made available until Monday, August 17, 2009. The audio replay can be accessed by dialing 800-406-7325 or 303-590-3030 and entering passcode 4134570#.

About Arrowhead Research Corporation

Arrowhead Research Corporation ( www.arrowheadresearch.com ) (NASDAQ: ARWR) is a nanotechnology company commercializing new technologies in the areas of life sciences, electronics, and energy. Arrowhead is seeking to build value for shareholders through the progress of majority owned subsidiaries. Currently, Arrowhead has four subsidiaries commercializing nanotech products and applications and minority investments in two privately held nanobiotech companies.