Pfizer Inc v Ranbaxy Laboratories Ltd atorvastatin calcium

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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 [11]. 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:

Claim 1:

Atorvastatin Acid

Atorvastatin Lactone

Salts of Atorvastatin Acid or Lactone

Claim im 2:

Atorvastatin Acid

Claim 6

Atorvastatin Salt

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) [14].

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.

  1. To avoid legal glitches when claiming compounds, claim important compounds individually in independent claims. It costs more up front, but helps avoid expensive and potentially catastrophic patent defeating legal glitches later. If you do use dependent claims, make them all dependent on a broad, independent Claim 1.
  2. The "natural" language of medicinal chemists is chemical structure. When claiming important individual compounds, claim the compounds by chemical structure instead of, for example, International Union of Pure and applied Chemistry (IUPAC) chemical names. This minimizes the possibility that an error in a chemical structure will be missed.
  3. Scrutinize all claim interrelationships to ensure, where appropriate, overlapping subject matter. For example, if a dependent claim is drawn to a salt, make sure the claim from which it depends includes a salt.

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