Pasadena, CA — June 17 -2008 — Arrowhead Research Corporation (NASDAQ: ARWR) announced today that Unidym, Inc., its majority-owned subsidiary, has received a $2.0 million strategic investment from Entegris, Inc. (NASDAQ: ENTG), a leading provider of products for purifying, protecting and transporting critical materials used in processing and manufacturing in semiconductor and other high-tech industries. Arrowhead made a $2.0 million matching investment.

"We are delighted to add Entegris to our expanding roster of customers and partners who are also strategic investors in Unidym," said Art Swift, Unidym's president and CEO. “We view this investment as an endorsement of our products, technology and overall strategic vision on the commercialization of our carbon nanotubes in the market.”

John Goodman, chief technology officer of Entegris, said: “We are pleased to expand our partnership with Unidym as it continues to be an industry leader in delivering high quality CNTs and CNT-enhanced products to the market. We are using Unidym's CNTs to develop a number of new materials that will enable us to augment our portfolio of highly differentiated, high performance products to the semiconductor industry. Our work with Unidym will also help us as we use our materials sciences core competencies to serve our customers in other high technology markets.”

Unidym is pursuing a cross-industry partnership strategy to capture value from the wide ranging uses of CNTs outside its core focus of carbon nanotube electronics. Unidym's licensing program, technical expertise and manufacturing facilities can enable partners to rapidly develop CNT solutions for their specific applications.

"We are impressed with Unidym's rapid progress and are happy to provide continued support," said Arrowhead CEO Chris Anzalone. "Unidym has had great success attracting powerful customers, partners and strategic investors. Entegris is yet another market leader to see real value in Unidym's platform and talented team."

The $4M of additional capital represents follow on investments in Unidym's Series C financing. Battelle, Tokyo Electron Ventures and several financial institutions also participated in the Series C round.