Arrowhead Research Corp. on Tuesday announced plans to sell an undisclosed number of common shares to raise money for clinical drug trials.

After the markets closed, the Pasadena biotech, which is developing drugs designed to block the action of genes linked to certain diseases, said Jefferies, Barclays Capital Inc. and Deutsche Bank Securities Inc. would be joint book-runners for the offering.

The company’s lead drug candidate targets chronic hepatitis B infections. It has a market cap of about $754 million, with nearly 39 million shares outstanding.

Shares earlier closed down 4 cents, or less than 1 percent, to $18.95 on the Nasdaq, and fell 2 percent in after-hours trading.