Perrigo, Allegan County’s largest employer, is selling its generic prescription drug business to Altaris Capital Partners for $1.55 billion.

Perrigo, which employs more than 400 people, is based in Allegan and manufactures generic and house brand prescription drugs and over the counter pharmaceutical products.

Altaris has agreed to more than $50 million in payments for potential research and development milestones and buyer obligations with third-party prescription partners. Altaris, based in New York, manages 14 health care companies.

Perrigo Chief Executive Officer Murray Kessler said  the company now will be able to focus on self-care products and the move will result in more financial predictability and flexibility. He said the company will have more than $2 billion in cash available to invest in “growing trends towards self-managed health and wellness.”

Plans call for the sale to be finalized by next fall.