Arrowhead Research Corp. on Monday said it has expanded its genetic medicine business by acquiring the U.S.-based “gene-silencing” unit of Swiss drugmaker Roche.

The Pasadena nanotech healthcare holding company said the deal gives it three drug-delivery technologies and all of Roche’s RNA interference operations and facilities in Madison, Wis., which employ about 40 people. The RNAi approach to fighting disease targets and shuts off certain genes associated with cancer and other conditions.

“This acquisition is transformational for us and important to the broader RNAi field,” said Chief Executive Christopher Anzalone in a statement. “The combination of these assets and Arrowhead’s existing RNAi technologies results in what we believe to be the broadest RNAi therapeutics company in the world.”

As part of the deal, Roche took a stake in Arrowhead and also has the right to negotiate products, milestone payments and royalties on sales. Other financial terms were not disclosed. Roche acquired the RNAi business in its 2008 purchase of Mirus Bio Corp.

Separately, Arrowhead said it closed on $4 million of financing, which adds to more than $5.5 in a private placement announced earlier this month. The company also signed an agreement with Lincoln Park Capital to provide up to $15 million to support the new operations.

Shares of Arrowhead shares closed up 4 cents, or 7.6 percent, to 50 cents on the Nasdaq.