Activist investor Carl Icahn bought a small stake in Allergan PLC, Reuters reported, citing people familiar with the matter.
Icahn believes the Dublin-based drugmaker's stock is undervalued, the sources said.
A spokeswoman for Allergan said the company welcomes all investments.
The investment comes as investors have urged the company to restructure its board and focus on existing businesses instead of acquisitions.
Icahn, who previously invested in Allergan, has been a longtime supporter of its CEO, Brent Saunders, according to the report.
