Billionaire investor Carl Icahn has said he's picked up a "large position" in Botox-maker Allergan, though would not disclose the size of the stake.
Icahn praised chief executive Brent Saunders, saying he is very supportive of Saunder's strategy, and confident he would enhance value to shareholders.
News of Icahn's purchase pushed shares in Allergan up by 2.6 per cent to $242 in early trading in New York as investors piled in after him.
A statement published on the activist investor's website read:
We were instrumental in bringing Brent on board as the new CEO of Forest Labs a few years ago and worked cooperatively and constructively with him to help increase value for all Forest shareholders.
Less than a year later Forest was acquired by Actavis (which subsequently merged with Allergan) resulting in massive gains for Forest shareholders. While we at that time disposed of our position in Forest, we still have always maintained great respect for Brent.
Shares have since fallen back somewhat and are now trading around 1.2 per cent higher.
Allergan sought to reassure investors that Icahn didn't take a stake in order to influence management of the company.
Icahn publicly came out against the now abandoned merger between Pfizer and Allergan that would have resulted in the combined company being headquartered in Ireland.
Icahn went as far as to launch a $150m political action committee advocating tax reform to eliminate inversions.
The Obama administration effectively blocked the Pfizer-Allergan deal by changing tax rules to make it unattractive, causing the companies to scrap the plans.