Arrowhead to Report Fiscal 2013 Third Quarter Financial Results

PASADENA, Calif. — July 31, 2013 — Arrowhead Research Corporation (NASDAQ: ARWR), a biopharmaceutical company developing targeted RNAi therapeutics, today announced that it will report its financial results for the fiscal 2013 third quarter ended June 30, 2013, on Wednesday, August 7, 2013, at 4:30 p.m. Eastern time (1:30 p.m. Pacific time). To participate in the conference call, please dial 877-300-8521 (toll free from the US), 855-669-9657 (toll free from Canada), or 412-317-6026 (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 105557.

About Arrowhead Research Corporation

Arrowhead Research Corporation is a biopharmaceutical company developing targeted RNAi therapeutics. The company is leveraging its proprietary drug delivery technologies to develop targeted drugs based on the RNA interference (RNAi) mechanism that efficiently and specifically silence target genes. Arrowhead technologies also enable partners to create peptide-drug conjugates (PDCs) that specifically home to cell types of interest while sparing off-target tissues. Arrowhead’s pipeline includes programs in chronic hepatitis B virus, obesity, and cancer.

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