The Canadian firm has offered to pay $72 in cash and 0.83 share of its stock for each Allergan share. Based on Friday's closing price, that would amount to $173.20 per share – about 5% higher than Allergan's Friday closing price.
Allergan's board has rejected two previous offers from Valeant, and it urged shareholders to do the same.
"The board strongly recommends that Allergan stockholders reject Valeant's exchange offer," Pyott said, "and prevent Valeant from taking control of Allergan at a price that does not appropriately reflect the underlying value of Allergan's assets, operations and prospects, including our industry-leading position and projected growth opportunities."
Valeant chief J. Michael Pearson said the merger would be best for both companies, and generate significant value for Allergan shareholders.