Arrowhead to Report Fiscal 2013 Second Quarter Financial Results

PASADENA, Calif. — May 2, 2013 — Arrowhead Research Corporation (NASDAQ: ARWR), a targeted therapeutics company, today announced that it will report its financial results for the fiscal 2013 second quarter ended March 31, 2013, on Thursday, May 9, 2013, at 4:30 p.m. Eastern time (1:30 p.m. Pacific time). To participate in the conference call, please dial 877-317-6789 (toll free from the US), 866-605-3852 (toll free from Canada), or 412-317-6789 (for international callers). 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 and will remain available for 90 days. An audio replay will also be available approximately one hour after the conclusion of the call and will be available for 30 days. The audio replay can be accessed by dialing 877-870-5176 (toll free from the US and Canada), or 858-384-5517 (for international callers) and entering Event ID 10028640.

About Arrowhead Research Corporation

Arrowhead Research Corporation is a clinical stage targeted therapeutics company with development programs in oncology, obesity, and chronic hepatitis B virus infection. The company is leveraging its platform technologies to design and develop peptide-drug conjugates (PDCs) that specifically home to cell types of interest while sparing off-target tissues, create targeted drugs based on the gene silencing RNA interference (RNAi) mechanism, and work 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