ALLEGAN, Mich. (AP) — Generic drug developer Perrigo Co. said Wednesday it is being sued by Galderma and Dermalogix over plans to make a version of the plaque psoriasis treatment, Clobex spray. Perrigo has asked the Food and Drug Administration to approve a generic version of the topical spray. That prompted Galderma and Dermalogix to file the lawsuit in U.S. District Court for the Northern District of Texas, citing patent infringement. Perrigo said Clobex spray is worth about $55 million in annual sales. Shares of Allegan, Mich.-based Perrigo fell 5 cents to $39.45 in after-hours trading after falling 9 cents to close at $39.50 during the regular trading session.