Generic Claritin Does Not Infringe Schering Patent - Appeals Court

The Aug. 1 decision by a Washington D.C. federal appeals court finding certain loratadine patent claims invalid "does not preclude patent protection for metabolites of known drugs," the judges write.

"With proper claiming, patent protection is available for metabolites of known drugs," Circuit Judges William Bryson, Randall Rader and Jay Plager state.

The court upheld a Newark, N.J. federal court's decision that Schering-Plough's patent for loratadine ( Claritin ) inherently anticipated and thus invalidated two claims in the desloratadine ( Clarinex ) patent (¹ (Also see "Desloratadine Patent Claims No Bar To Generic Claritin, Judge Says" - Pink Sheet, 12 Aug, 2002.), p. 3).

The court rejects S-P's contention that firms marketing generic Claritin products infringed its Clarinex patent. Schering filed suit against a list of firms including Geneva Pharmaceuticals, Andrx, and Wyeth Consumer Healthcare, among others, arguing that the firms violated the patent because loratadine would metabolize into desloratadine, or DCL, after ingestion.

The appellate judges' comments regarding protection for metabolites reflect concerns raised by Schering during oral arguments in April (² (Also see "Desloratadine Production Not Anticipated In Loratadine Patent – Schering" - Pink Sheet, 14 Apr, 2003.), p. 12).

Schering maintained that denying patent protection to "new, unrecognized" metabolites such as DCL would impede new drug research into metabolites of other drugs. Furthermore, they maintained, firms might develop pro-drugs that would metabolize into existing drugs in order to thwart patent claims

"Those metabolites may not receive protection via compound claims" the decision states. Schering's claims "broadly encompass compounds defined by structure only. Such bare compound claims include within their scope the recited compounds as chemical species in any surroundings, including within the human body as metabolites of a drug."

The creation of DCL is inherent to the original Claritin patent, the judges find. "These broad compound claims are inherently anticipated by a prior art disclosure of a drug that metabolizes into the claimed compound."

Schering had argued that DCL could not have been anticipated in the prior art because it was not publicly known or described in the Claritin patent.

"This court rejects the contention that inherent anticipation requires recognition in the prior art," the decision states.

"A prior art reference may anticipate without disclosing a feature of the claimed invention if that missing characteristic is necessarily present, or inherent in the single anticipating reference."

DCL is a "necessary consequence of administering loratadine to patents," the judges conclude. "The record shows that a patient ingesting loratadine would necessarily metabolize that compound to DCL."

The case is somewhat unusual, the judges allow, "because the prior art supplies no express description of any part of the claimed subject matter.'

"In...prior cases," they note, "inherency was only necessary to supply a single missing limitation that was not expressly disclosed in the prior art. This case...asks this court to find anticipation when the entire structure of the claimed subject matter is inherent in the prior art."

"Thus, inherency operates to anticipate entire inventions as well as single limitations within an invention." The court maintains, however, that metabolites can still be afforded protection under its interpretation of the patent law.

"A skilled patent drafter...might fashion a claim to cover the metabolite in a way that avoids anticipation," they write. "For example, the metabolite may be claimed in its pure and isolated form...or as a pharmaceutical composition (e.g., with a pharmaceutically acceptable carrier)."

The patent drafter also could claim a method of administering the metabolite or the corresponding pharmaceutical composition."

Other claims in the Clarinex patent were unchallenged, and the decision is unlikely to affect that product. The decision notes that the remaining claims "were not found anticipated" by the earlier patent.