Shares of Concert Pharmaceuticals Inc. took a sharp afternoon dive Monday, after the biopharmaceutical company said the patent trial and appeal board found that the claims of the patent on its alopecia areata treatment CTP-543 were "not patentable." The stock, which was little changed in afternoon trade just prior to the announcement, plunged 17% toward a 2-year low after the announcement. The company said the decision was appealable to the U.S. court of appeals. "While we're disappointed in this outcome, we believe we have strong arguments supporting the validity of our patent and intend to appeal the decision as we work to create additional intellectual property protecting CTP-543," said Chief Executive Roger Tung. In April 2017, Incyte Corp. had filed a petition challenging the validity of the patent on CTP-543. Incyte's stock slipped 0.1%. Over the past 12 months, Concert's stock has tumbled 43%, Incyte shares have rallied 29%, the iShares Nasdaq Biotechnology ETF has climbed 13% and the S&P 500 has gained 11%.