The U.S. Patent and Trademark Office’s Patent Trial and Appeal Board (PTAB) has instituted postgrant reviews of three patents owned by the Chicago Board Options Exchange Inc. that are at the center of a $525 million suit it filed against the International Securities Exchange LLC. The move could result in the invalidation of the patents.

Winston & Strawn partner Michael Murray, who represents the ISE, petitioned the PTAB to review the patents under the “covered business method” review procedure established under the America Invents Act. The review allows an accused infringer to challenge patents in a minitrial before the PTO’s board, which must decide the question of validity within a year. Before agreeing to institute a full review, the PTAB analyzes arguments presented by both sides and decides to hear a case only if it concludes that the asserted patents are “more likely than not” invalid.