Glenmark Pharmaceuticals Ltd. and Glenmark Pharmaceuticals Inc., USA (“Glenmark”), the filers of an Abbreviated New Drug Application (“ANDA”) for a topical skin treatment, appealed a final judgement from the District of Delaware that found all claims of the patent-in-suit not invalid and infringed under the doctrine of equivalents. The Federal Circuit found no clear error in the district court’s application of the function prong of the function-way-result test for infringement under the doctrine of equivalents. More particularly, the Federal Circuit stated that a patent need not spell out a claim element’s function, way, and result in order for the doctrine of equivalents to apply. Instead, intrinsic and extrinsic evidence may be relied on in determining a claim element’s function. In this regard, Glenmark’s statements in its ANDA filing were sufficient to show that the function prong of the test was satisfied. The Federal Circuit was unpersuaded by Glenmark’s arguments that the ANDA statements were a “guess” and technically “wrong,” as those arguments were not made in Glenmark’s briefing. The Federal Circuit was also unconvinced that prosecution-history estoppel precluded application of the doctrine of equivalents, concluding that the amendments were made to clarify the dependent claims, not narrow them. Lastly, the Federal Circuit agreed that the claims of the patent-in-suit were not obvious over the cited art, finding no clear error in the district court’s determination that a skilled artisan would not have been motivated to combine the prior art.