by Dennis Crouch

I previously wrote about Allergan USA, Inc. v. MSN Laboratories Private Ltd. (Sun Pharma), No. 24-1061 (Fed. Cir. Aug. 13, 2024), focusing on Federal Circuit's about-face on obviousness-type double patenting.  My original post skipped over an important aspect of the opinion: the court's 2-1 decision favoring the patentee on the written description requirement of 35 U.S.C. § 112(a).  This portion of the case focuses once again on when an element is "essential" to the invention and therefore required in the claims.

Four key takeaways:

1. We presume that no element is "essential."
2. Courts should look for indications in the patent documents that the feature is critical, essential, etc.
3. The court here relied upon broad claims in the priority filing that were later deleted in order to show the inventor possessed embodiments that did not require the element.
4. The key focus for written description is comparing the specification with the claims.  Although expert testimony may be relevant, it must be directly tied to the intrinsic record.

All of these elements point to the idea that it is the job of the patent drafter and prosecutor to ensure the written description is sufficient, and to avoid pitfalls that might indicate otherwise.