The Appeals Review Panel’s In Re Xencor Decision: The USPTO Provides Its Position on Written Description and Means-Plus-Function Claims


On May 17, 2024, an Appeals Review Panel (ARP) of the United States Patent and Trademark Office (“USPTO”) released its decision in Ex parte Chamberlain (referred to in Federal Circuit proceedings as In re Xencor; “Chamberlain”). The Chamberlain decision provides some clarity on the USPTO’s position on written description requirements for Jepson and means-plus-function claims in the life sciences space. Importantly, it suggests that carefully drafted means-plus-function claims are a potential path for Applicants to claim antibodies broadly by use of functional language (i.e., by their targets) once again.

The two claims considered in Chamberlain are functional claims to an antibody styled as (a) a Jepson claim (claim 8) and (b) a means-plus-function claim (claim 9). In the Chamberlain decision, officially dated May 21, 2024, the ARP maintains the Patent Trial and Appeal Board’s (“PTAB”) rejection of both claims for lack of written description, reverses the rejection of claim 9 for indefiniteness, and reverses the Examiner’s obviousness-type double patenting rejections of claims 8 and 9 (not addressed in this publication).

Read the full alert here.