Amneal Pharmaceuticals challenged Almirall, LLC’s acne treatment patent in an inter partes review (IPR) proceeding at the U.S. Patent and Trademark Office (USPTO). The U.S. Patent Trial and Appeal Board (PTAB) found the patent obvious, and the Federal Circuit has now affirmed.

The patent claimed a topical acne treatment that “does not comprise adapalene,” a compound sometimes used for treating dermatological conditions. The primary prior art reference relied on by Amneal did not indicate that any of its formulations include adapalene.

Almirall argued that more is needed for a disclosure of a negative claim limitation than silence and that, given the use of adapalene in the industry, the reference’s silence implied its use.

The Federal Circuit disagreed, noting its precedent that “a reference need not state a feature’s absence in order to disclose a negative limitation,” and upholding that, in the context of the reference, “a skilled artisan would recognize that the reference discloses a complete formulation—excluding the possibility of an additional active ingredient.”

The Federal Circuit also held that substantial evidence supported the PTAB’s motivation to combine and reasonable expectation of success analysis concerning Amneal’s combinations.