Background
Schering Corporation held U.S. Patent 4,282,233 covering the antihistamine loratadine — the active ingredient in Claritin, one of the best-selling allergy drugs of the 1990s. Claritin generated billions of dollars in annual sales before generic competition began. In addition to the loratadine patent, Schering obtained a later patent (the ‘716 patent) covering descarboethoxyloratadine (DCL) — the primary active metabolite formed in the human body when a patient takes a dose of loratadine. Schering argued that DCL was itself a separately patentable compound and used the ‘716 patent to attempt to extend its market exclusivity beyond the expiration of the loratadine patent.
Geneva Pharmaceuticals challenged the ‘716 patent in the context of Hatch-Waxman ANDA litigation. Geneva argued that the ‘716 patent was anticipated by the earlier loratadine patent: anyone who practiced the loratadine patent (by making or administering loratadine) would necessarily and unavoidably produce DCL in the patient’s body. If DCL is an inevitable result of practicing the loratadine patent, then the loratadine patent “inherently” discloses DCL even though DCL is never mentioned explicitly in that earlier patent.
The district court agreed with Geneva and held the ‘716 patent invalid. Schering appealed, arguing that inherent anticipation required recognition in the prior art — i.e., that the prior art disclosure must have actually recognized and described the inherent property for it to count as anticipation.
The Court’s Holding
The Federal Circuit affirmed the invalidity of the ‘716 patent. The court held that a prior art reference inherently anticipates a later patent claim if the claimed invention necessarily and unavoidably results from practicing the prior art, even if the inherent property was not recognized or appreciated at the time the prior art was created or disclosed. Recognition in the prior art is not required for inherent anticipation.
Applying this standard, the court found that anyone who practiced the ‘233 loratadine patent — by administering loratadine to a patient — would necessarily produce DCL through the natural metabolic processes of the human body. DCL does not appear by chance or under special conditions; it is an inevitable, unavoidable result of loratadine administration. Therefore, the ‘233 patent inherently anticipated DCL, and the ‘716 patent was invalid as anticipated by prior art.
The decision rejected Schering’s attempt to extend patent exclusivity through what critics called “evergreening” — obtaining follow-on patents on metabolites, reformulations, and minor variations of established drugs to prolong market exclusivity beyond the original patent term.
Key Takeaways
- A prior art reference inherently anticipates a patent claim if the claimed subject matter necessarily results from practicing the prior art, even without explicit disclosure or recognition.
- A metabolite of a patented drug compound that is inevitably formed upon administration of the drug cannot be separately patented — the drug patent inherently anticipates it.
- Inherent anticipation does not require that the person skilled in the art recognized or appreciated the inherent property at the time the prior art was made.
- Patent “evergreening” through metabolite patents faces significant inherent anticipation challenges.
- Pharmaceutical companies seeking to patent metabolites must demonstrate that the metabolite is not an inevitable consequence of using the previously patented parent compound.
Why It Matters
Schering v. Geneva is one of the most important pharmaceutical patent cases of the early 2000s. It directly addressed the pharmaceutical industry practice of “evergreening” — seeking new patents on metabolites, active isomers, polymorphs, and other derivatives of established drugs to extend market exclusivity beyond the original patent expiration. By holding that inevitable metabolites are inherently anticipated by the parent compound’s patent, the Federal Circuit created a significant barrier to this strategy.
The decision had immediate commercial consequences: without the ‘716 patent, Schering could not delay generic Claritin competition on the basis of the metabolite patent. The ruling encouraged generic pharmaceutical manufacturers to challenge metabolite patents as inherently anticipated, which they did with increasing frequency in ANDA litigation throughout the 2000s. Schering v. Geneva remains a landmark case in the law of inherent anticipation and a foundational precedent for challenges to pharmaceutical evergreening strategies.