Eli Lilly and Company v. Hospira, Inc.
933 F.3d 1320 (2019)
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Rule of Law:
A patentee who narrows a claim during prosecution to distinguish the invention from prior art is not barred by prosecution history estoppel from asserting infringement under the doctrine of equivalents if the rationale for the amendment bears no more than a tangential relation to the equivalent in question.
Facts:
- Eli Lilly & Company ('Lilly') marketed the cancer drug Alimta®, which used the compound pemetrexed in the form of a disodium salt.
- Lilly discovered that administering pemetrexed disodium with folic acid and vitamin B12 reduced the drug's toxic side effects without sacrificing efficacy.
- Lilly obtained U.S. Patent 7,772,209 ('209 patent) for this improved method, with claims requiring the 'administration of pemetrexed disodium.'
- During the patent prosecution process, Lilly had originally claimed a method for 'an antifolate' but narrowed the claim to 'pemetrexed disodium' to overcome a patent office rejection based on prior art disclosing a different antifolate, methotrexate.
- Hospira Inc. and Dr. Reddy's Laboratories ('DRL') sought FDA approval to market generic versions of the cancer treatment.
- The proposed generic products used a different salt of the same active ingredient, 'pemetrexed ditromethamine,' instead of the 'pemetrexed disodium' specified in Lilly's patent.
Procedural Posture:
- Eli Lilly & Co. filed separate patent infringement lawsuits against Hospira Inc. and Dr. Reddy's Laboratories (DRL) in the U.S. District Court for the Southern District of Indiana.
- In the DRL case, the district court denied DRL's motion for summary judgment of noninfringement.
- After a bench trial, the district court in the DRL case entered a final judgment finding that DRL's product infringed the '209 patent under the doctrine of equivalents.
- In the Hospira case, the district court granted Lilly's motion for summary judgment, finding that Hospira's product infringed both literally and under the doctrine of equivalents.
- Hospira and DRL, as appellants, appealed the judgments to the U.S. Court of Appeals for the Federal Circuit, with Lilly as the appellee.
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Issue:
Does a patentee's narrowing amendment from a general class of chemical compounds ('an antifolate') to a specific salt ('pemetrexed disodium') to overcome prior art disclosing a different compound in that class trigger prosecution history estoppel to bar a claim of equivalence against another functionally identical salt of the claimed compound ('pemetrexed ditromethamine')?
Opinions:
Majority - Lourie, Circuit Judge.
No, the patentee's narrowing amendment does not trigger prosecution history estoppel in this case because the reason for the amendment was merely tangential to the accused equivalent. The court found that Lilly’s amendment narrowing the claim from 'an antifolate' to 'pemetrexed disodium' was made to distinguish its invention from prior art that disclosed methotrexate, a completely different antifolate. The amendment was not made to surrender other salts of pemetrexed. Therefore, the choice between the 'disodium' salt and the 'ditromethamine' salt was only tenuously related to the reason for the amendment, and the tangentiality exception to prosecution history estoppel applies, allowing Lilly's claim under the doctrine of equivalents to proceed. The court also held there was no literal infringement because administering pemetrexed ditromethamine dissolved in saline is not the 'administration of pemetrexed disodium.' Finally, the court rejected the disclosure-dedication rule defense, finding that the patent's generic reference to another patent (Akimoto) did not constitute a specific disclosure of pemetrexed ditromethamine that would dedicate it to the public.
Analysis:
This decision clarifies and reinforces the flexibility of the 'tangential relation' exception to prosecution history estoppel, rejecting a rigid, formulaic application. It establishes that courts must conduct a case-specific inquiry into the prosecution record to determine the patentee's actual reason for an amendment. The ruling is significant for pharmaceutical and chemical patents, where competitors often attempt to design around a patent by making minor modifications, such as changing a salt form. By allowing patentees to pursue infringement claims against such functionally identical equivalents—when the original amendment was made for unrelated reasons—the court preserves the value of the doctrine of equivalents and protects inventors from overly harsh applications of estoppel.
