The Federal Circuit has clarified what the Patent Trial and Appeal Board (PTAB) may treat as prior art in inter partes reviews (IPRs). On February 1, the court ruled in a new precedential decision that the Board applied the wrong standard in invalidating claims based on the asserted combination of a prior art patent and statements in the specification of the challenged patent, the latter known as applicant-admitted prior art (AAPA). While the PTAB concluded that AAPA is itself “prior art”, the Federal Circuit held that this was legally erroneous—explaining that AAPA cannot serve as the statutory “basis” for an IPR decision, though it can be cited in support of an invalidity argument in some circumstances.