“[A]bsent more limiting language in the intrinsic record” the doctrine of equivalents can be applied to find infringement where the accused value is insubstantially different from the claimed value, even for fuzzy qualitative terms like “substantially all” that correspond to underlying quantitative ranges in the description. Importing a specific range from the description into such qualitative terms does not foreclose further equivalency protection.
Background / Facts: Pozen developed a method for treating migraines by combining two drugs, sumatriptan and naproxen, in a single tablet. Claim 1 of the patent requires that “substantially all of said triptan is in the first layer of said tablet and substantially all of said naproxen is in a second, separate layer.” The district court construed the “substantially all” phrases to mean “at least 90%, and preferably greater than 95%, of the total triptan present in the tablet is included within one distinct layer and at least 90%, and preferably greater than 95%, of the naproxen present in the tablet is included within a second distinct layer.” It was undisputed that even under this expansive construction there was no literal infringement because the first layer of Par’s tablet “contains 100% of the tablet’s sumatriptan, along with 15% of the tablet’s naproxen, with the remaining 85% of the naproxen in the second layer.” The district court nevertheless went on to find infringement under the doctrine of equivalents.
Issue(s): Whether the claim term “substantially all” is entitled to the doctrine of equivalents when its construction already imports a quantitative range into the claims.
Holding(s): Yes. It is true that where “a patentee has brought what would otherwise be equivalents of a limitation into the literal scope of the claim, the doctrine of equivalents is unavailable to further broaden the scope of the claim.” However, although the claim language itself is a qualitative measure, the claim construction pulls directly from the specification to give the term “substantially all” a quantitative definition, specifically, “at least 90%, and preferably greater than 95%,” and the doctrine of equivalents is not foreclosed with respect to claimed ranges. Pozen never stated that “at least 90%, and preferably greater than 95%” should be an absolute floor. The court found that under the doctrine of equivalents, a tablet layer with 85% of the agent can be fairly characterized as an insubstantial change from a tablet layer with 90% of the agent.