Valeant Pharmaceuticals is adding three directors to its board, including an executive from activist investor Bill Ackman's hedge fund Pershing Square Capital Management.

The Canadian drugmaker says Pershing Vice Chairman Stephen Fraidin is joining its board, along with pharmaceutical executive Dr. Fred Eshelman and former University of North Carolina president Thomas W. Ross. Dr. Anders Lonner also is leaving. These moves will bump the board's size to 14 members.

Pershing Square holds a 6.3 percent stake in Valeant, as one of the embattled company's biggest shareholders.

Valeant Pharmaceuticals International Inc. is facing a Securities and Exchange Commission investigation and, separately, scrutiny from Congress over its drug pricing. CEO Michael Pearson also recently returned to work after missing several weeks due to health issues.

Valeant shares are up 1 percent in premarket trading.