Law360, New York (August 27, 2014, 7:37 AM EDT) -- The validity of claims to classes of biologic and chemical compounds defined by their function, instead of structure, has been tested for decades under the written description requirement of Section 112 of the Patent Act.[1] This statutory requirement mandates that the patent specification have sufficient disclosure to "convey with reasonable clarity to those skilled in the art" that the applicant in fact "was in possession" of the claimed invention. The breadth of the claims determines the extent of the required disclosure and in a series of decisions in the biopharma context — most authored by Judge Alan Lourie — the Federal Circuit has relied on the written description requirement to guard against applicants claiming what they did not invent and thereby seeking to "preempt the future before it has arrived."[2] Genus claims that define covered compounds by function, rather than structure, have received particular attention from the Federal Circuit....