CVS, the nation’s largest pharmacy chain, faces a class action securities litigation in Manhattan federal court over representations made about its 2015 merger with pharmacy services provider Omnicare.

The lawsuit, filed in the U.S. District Court for the Southern District of New York on Monday, claims that CVS hid the negative financial impact of the Omincare acquisition in the years that followed. On Feb. 20, CVS acknowledged to investors the impact the poor business performance of Omnicare was having on the company, including a $2.2 billion impairment charge.