Arrowhead to Report Fiscal 2012 Third Quarter Financial Results

PASADENA, California, August 7, 2012 — Arrowhead Research Corporation (NASDAQ:ARWR) today announced that it will report its financial results for the fiscal 2012 third quarter ended June 30, 2012, on Monday, August 13, 2012 at 4:30 p.m. Eastern time (1:30 p.m. Pacific time). To participate in the conference call, please dial 1-877-317-6789 (toll free from the US), 1-866-605-3852 (toll free from Canada), or 1-412-317-6789 (for international callers). Investors may also access a live 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 archive will remain available until 8/13/2013. An audio replay will also be available approximately one hour after the conclusion of the call and will be made available until Thursday, September 13, 2012. The audio replay can be accessed by dialing 1-877-344-7529 (toll free from the US and Canada), or 1-412-317-0088 (for international callers) and entering Event ID 10017170.

About Arrowhead Research Corporation

Arrowhead Research Corporation is a clinical stage targeted therapeutics company with development programs in oncology, obesity, and infectious disease. The company leverages its platform technologies to design and develop peptide-drug conjugates (PDCs) which specifically home to cell types of interest while sparing off-target tissues, creates targeted drugs based on the gene silencing RNA interference (RNAi) mechanism, and works with partners to create improved versions of traditional small molecule drugs.

For more information please visit http://www.arrowheadresearch.com, or follow us on Twitter @ArrowRes. To be added to the Company’s email list to receive news directly, please send an email to ir@arrowres.com