BOSTON, July 1 (Reuters) - Activist investor William Ackman has hired Credit Suisse in his fight to have Valeant Pharmaceuticals acquire Botox maker Allergan Inc. , a person familiar with the matter said on Tuesday.
Ackman's Pershing Square Capital Management owns 9.7 percent of Allergan and has been working with Canada's Valeant for months on an acquisition of Allergan in what would be, based on current value, the biggest deal of the year.
"Pershing Square has hired Credit Suisse for advice," said the source, who was not permitted to discuss the move publicly.
The move is the latest twist in a heated battle between the two pharmaceutical companies and Ackman, one of the hedge fund industry's most closely watched investors.
Allergan has steadfastly rebuffed Valeant's overtures, refusing to sell itself for $53 billion, while Ackman is working to call a special meeting of Allergan shareholders in order to elect new directors to the company's board.
Credit Suisse traditionally has helped defend companies against activist investors like Ackman who often acquire a big stake in a company and then agitate for change.
The corporate battle has already been playing out in unusual ways.
Pershing Square and Valeant received a boost last week when influential hedge fund manager John Paulson's Paulson & Co bought more than 6 million shares of Allergan and threw its weight behind the proposed takeover. (Reporting by Svea Herbst-Bayliss; Editing by Paul Simao)