Allergan Inc said on Tuesday that it has scheduled a special shareholders meeting for Dec. 18, when activist investor Bill Ackman, who supports a hostile bid for the company by Valeant Pharmaceuticals Inc, will attempt to oust most of its board.

Although Allergan set a date for the meeting, it said in a Delaware court filing that it will review the validity of the shareholder requests for the meeting on Sept. 4.

The company said later in the evening, that it had asked the U.S. District Court for the Central District of California to set an expedited schedule for an injunction that will bar Valeant, Ackman and his hedge fund firm from exercising rights associated with any shares that were acquired unlawfully.

"Such an order would prevent Valeant, Pershing Square, and Mr. Ackman from voting their shares in any special meeting," Allergan said in a statement.

Valeant and Pershing Square were not immediately available for comment outside regular business hours.

California-based Allergan, the maker of Botox anti-wrinkle skin injections, is trying to fend off a $49 billion hostile takeover by Canada's Valeant. Ackman's Pershing Square Capital Management, Allergan's biggest shareholder, hopes to see a revamped Allergan board that would be willing to negotiate with Valeant.

Ackman said on Friday that investors holding 31 percent of Allergan shares had asked for the meeting. Pershing Square said it also filed a lawsuit in Delaware to require Allergan to schedule the meeting, anticipating that the company would likely fight doing so.

At least 25 percent of shareholder support is necessary under Allergan's bylaws to call the meeting.