Arrowhead Research Corporation (NASDAQ: ARWR), a biopharmaceutical company developing targeted RNAi therapeutics, is set to join the broad-market Russell 3000 Index when Russell Investments reconstitutes its comprehensive set of U.S. and global equity indexes on June 27, according to a preliminary list of additions posted June 13 on www.russell.com/indexes.

Annual reconstitution of Russell’s U.S. indexes captures the 4,000 largest U.S. stocks as of the end of May, ranking them by total market capitalization. Membership in the Russell 3000, which remains in place for one year, means automatic inclusion in the large-cap Russell 1000 Index or small-cap Russell 2000 Index as well as the appropriate growth and value style indexes. Russell determines membership for its equity indexes primarily by objective, market-capitalization rankings and style attributes. The Russell 3000 also serves as the U.S. component to the Russell Global Index, which Russell launched in 2007.

Russell indexes are widely used by investment managers and institutional investors for index funds and as benchmarks for active investment strategies. Approximately $5.2 trillion in assets are benchmarked to the Russell Indexes. Russell calculates more than 700,000 benchmarks daily covering approximately 98 percent of the investable market globally, more than 80 countries and 10,000 securities.

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 mechanism that efficiently silences disease-causing genes. Arrowhead technologies also enable partners to create peptide-drug conjugates that specifically home to cell types of interest while sparing off-target tissues. Arrowhead’s pipeline includes clinical programs in chronic hepatitis B virus and partner-based programs in obesity and oncology.

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.

Safe Harbor Statement under the Private Securities Litigation Reform Act:

This news release contains forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. These statements are based upon our current expectations and speak only as of the date hereof. Our actual results may differ materially and adversely from those expressed in any forward-looking statements as a result of various factors and uncertainties, including our ability to finance our operations, the future success of our scientific studies, our ability to successfully develop drug candidates, the timing for starting and completing clinical trials, rapid technological change in our markets, and the enforcement of our intellectual property rights. Arrowhead Research Corporation's most recent Annual Report on Form 10-K and subsequent Quarterly Reports on Form 10-Q discuss some of the important risk factors that may affect our business, results of operations and financial condition. We assume no obligation to update or revise forward-looking statements to reflect new events or circumstances.

Copyright Business Wire 2010