Pasadena biopharmaceutical firm Arrowhead Research Corp. announced Monday that the company will be added to the Nasdaq Biotechnology Index, a collection of biotech and pharmaceutical companies.

The move is part of an annual re-ranking that will go into effect before the market opens on Monday, Dec. 21.

“At Arrowhead, we are trying to change medicine with our suite of RNAi drugs that target a diverse set of diseases,” Arrowhead’s Vice President of Investor Relations Vincent Anzalone said. “We are excited to be selected as a constituent company of the Nasdaq Biotechnology Index that is full of innovative biotechnology and pharmaceutical companies.”

Arrowhead shares were up 1 percent on Monday, closing at $5.69.