On a buying spree in the past four years, the Canadian company first made an unsolicited cash-and-stock buyout offer on April 22, valuing Allergan at $45.6 billion.
Valeant then raised the offer to about $50 billion on May 28, and, after that was rejected, increased it again to $53.5 billion on May 30.
Irving, California-based Allergan charged that "Valeant's unsustainable business model relies on serial acquisitions and cost reductions, as opposed to top-line revenue growth and operational excellence."
On Wall Street, Allergan shares opened 0.5% higher at $165. Valeant shares gained 0.1% to $126.75.
Copyright Agence France-Presse, 2014