A recent decision by the United States Court of Appeals for the Federal Circuit, which is the second-highest-ranking court that decides patent cases in the U.S., indicates that patent applicants must take extra care when claiming ranges in their patent applications. See Indivior UK Ltd. v. Dr. Reddy's Laboratories S.A., Appeal Nos. 2020-2073, 2020-2142 (Fed. Cir. November 24, 2021). The decision concerned a patent directed to orally dissolvable films that contain therapeutic agents.

The patent included claims that recited a range of about 40 wt. % to about 60 wt. % of a water-soluble polymeric matrix. However, the examples that were listed in the patent specification included 48.2 wt. % and 58.6 wt. % of the water-soluble polymeric matrix.

The party that was challenging the patent contended that the claimed range was not supported by the written description of the invention that was set forth in the patent specification. Every patent specification must include a written description of the claimed invention or the claims can be invalidated. However, the written description does not have to use the exact language as the claims.

The court concluded that the claimed range was not supported by the specification. The reasoning can be summed up as follows:

[a] written description sufficient to  satisfy the requirement of the law requires a statement of an invention, not an invitation to go on a hunting expedition to patch together after the fact a synthetic definition of an invention. “[A] patent is not a hunting license. It is not a reward for the search, but compensation for its successful conclusion.” Brenner v. Manson, 383 U.S. 519, 536 (1966).

The court further noted that “written description cases are intensively fact-oriented, and the cases vary, just as ranges vary.” Indivior, slip op. at 10 (citing In re Wertheim, 541 F.2d 257, 263-65 (CCPA 1976)).

Finally, the court indicated that earlier-issued decisions concerning patent ranges were not intended to be the basis for a mechanical rule about ranges in patent claims.

Court decisions on this issue are very unusual in the U.S., so that the potential outcome of a case involving this type of issue is unpredictable. Accordingly, patent applicants should take extra care in drafting patents that include ranges to make sure that the range is disclosed with sufficient specificity in the specification.