The announcement Monday comes a week after AstraZeneca’s board rejected a proposed $119-billion buyout offer from Pfizer, the world’s second-biggest drugmaker by revenue.
Pfizer Chairman and CEO Ian Read says the company’s final proposal represented full value for AstraZeneca.
Pfizer, the maker of Lipitor and Viagra, has been courting No. 8 AstraZeneca since January, saying their businesses would be stronger together.
Pfizer had been waiting for AstraZeneca to engage in merger talks by a Monday deadline.
Pfizer has previously said it would not make a hostile takeover bid directly to AstraZeneca’s stockholders.