Simulations Plus Inc. has named Shawn O’Connor as its new chief executive officer.

The Lancaster technology firm, which makes software that models the way medications impact the body, announced the appointment on Tuesday. O’Connor has worked for 30 years with software firms that serve the pharmaceutical industry, most recently as chief executive of Entelos, the assets of which Simulations Plus acquired in 2009. He also has served as chief executive of Pharsight Corp. and chief financial officer of Diasonics Inc.

O’Connor succeeds Walt Woltosz, who is retiring after leading the company for 22 years. Woltosz will remain with Simulations Plus during O’Connor’s transition and as an outside director thereafter, a company statement said.

“I am confident in Shawn’s unique qualifications to lead the company toward further growth and profitability,” Woltosz said in the statement.

Shares of Simulations Plus (SLP) rose 25 cents, or around 1 percent, on Tuesday to close at $23.75 on the Nasdaq.