BOSTON, Dec 17 (Reuters) - Biogen Inc has agreed to pay $22 million to resolve U.S. allegations that it illegally used two charities that help cover Medicare patients' out-of-pocket drug costs as a means to pay them kickbacks to use its multiple sclerosis drugs.

The deal, announced by the U.S. Justice Department on Thursday, was the latest to result from an industry-wide probe of drugmakers' financial support of patient assistance charities that has resulted in more than $1 billion in settlements. (Reporting by Nate Raymond in Boston)