Case History: In an attempt to protect Lipitor" from generic competition, Pfizer sued Ranbaxy in district court asserting, in part, that Ranbaxy infringed upon dependent Claim 6 of U.S. Patent No. 5,273,995 ('995).
Pfizer won at the district court level, but lost on appeal at the Federal Circuit, in part because Claim 6 was not written in proper form . This case presents an excellent example of the "reach through" effect; how small actions early on in the patent process can have large consequences in litigation.
Analysis: The active ingredient in Lipitor is atorvastatin calcium. Pfizer lost because of a deficiency in the way dependent Claim 6 related to Claims 1 and 2. The following chart is presented to help understand how this happened:
Salts of Atorvastatin Acid or Lactone
Claim im 2:
Claim 1 is an independent claim containing three different categories of molecules shown as boxes in the diagram. Claim 2 is a dependent claim and therefore by law must refer back to independent Claim 1, while also narrowing the scope of Claim 1 [12,13]. Claim 2 met both of these requirements by referring to Claim 1 (indicated by the arrow linking Claims 1 and 2), and by narrowing Claim 1 by excluding the subject matter of Box 2 (atorvastatin lactone) and Box 3 (salts of atorvastatin acid and atorvastatin lactone), leaving only Box 1 (atorvastatin acid). Since Claim 6 is a dependent claim depending from Claim 2, it must reference and narrow Claim 2. Claim 6 however failed to properly narrow Claim 2 because it reintroduced a salt after Claim 2 eliminated a salt from Claim 1. Put differently, the subject matter of Claims 2 and 6 do not overlap because Claim 2 is drawn to an acid and Claim 6 is drawn to a salt. The Federal Circuit invalidated Claim 6 because of this legal glitch. Thus, a small error in claim drafting, missed during the process of obtaining the patent, "reached through" to create the large consequence of defeating the patent in court. (Pfizer had agreed not to sue under independent Claim 1) .
Suggested Best Practices for Chemists: 1. Claims in a patent application tend to begin broadly and then narrow down to important individual compounds. Scrutinize application claims to make sure the most important compounds (e.g., clinical candidates and backups) are individually claimed. One important compound = one claim.
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