According to an Amgen Inc. (Amgen) executive, the pharma company plans to dispute a US$3.6b¹ tax deficiency assessed by the Internal Revenue Service (IRS) for tax years 2010, 2011 and 2012.² Amgen manufactures and markets the autoimmune disorder drug Enbrel, as well as the osteoporosis treatment sold as Prolia and Xgeva.

Amgen disclosed in its Form 10-Q that the IRS issued a notice of def…