A Delaware patent infringement case has erupted into an antitrust dispute, after an India-based generic drugmaker accused Mylan Pharmaceuticals of using its lawsuit to stifle competition for its topical foam acne treatment.

Glenmark Pharmaceuticals on Monday urged a federal judge in Wilmington to greenlight its counterclaims that Mylan had filed “sham litigation” in order to delay approval of a generic version of Evoclin, which is used to treat acne in teenagers and adults.