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31 October 2019Big PharmaSaman Javed

Fed Circuit sides with Gilead over hep C patent

The US Court of Appeals for the Federal Circuit has delivered a blow for Merck in a patent infringement dispute against Gilead, upholding one of its patents as invalid.

The decision, published yesterday, October 30, not only found the patent in dispute to be invalid on the stated grounds of lack of enablement, it further said the patent is invalid for lack of written description.

The patent in dispute (US patent number 7,608,597) claims a method of treating hep C by administering nucleoside compounds that have a specific chemical and stereochemical structure.

In 2013, it was the subject of a patent infringement suit against Gilead by pharmaceutical company Idenix. Idenix was later acquired by Merck in 2014.

At the time of the suit, both Idenix and Gilead were researching and developing drugs for the treatment of hepatitis C, a leading cause of chronic liver disease

Idenix alleged that the Food and Drug Administration’s approval and the subsequent launch of Gilead’s hep C treatment sofosbuvir would infringe the ‘597 patent.

Following years of litigation, a jury trial was held in 2016. While Gilead stipulated to infringement, it argued that the ‘597 patent was invalid for failure to meet the written description and enablement requirements under US patent law.

While the court initially sided with Idenix, it later held the ‘597 patent as invalid for not meeting enablement requirements.

Idenix argued that the key to its invention, and to treatment of hep C, is the use of 2'-methyl-up nucleosides which have a methyl substitution (‘CH3’) at the 2' ‘up’ position of the molecule’s sugar ring.

But, Gilead said this characterisation is “overly broad” because the ‘597 patent “provides no guidance in determining which of the billions of potential 2'-methyl-up nucleosides are effective in treating hep C”.

According to Gilead, the ’597 patent cannot enable the full scope of effective 2'-methyl-up nucleosides at least because its accused embodiment, 2'-methyl-up 2'-fluoro- down, is not disclosed in or enabled by the patent’s specification.

In its judgment, the Federal Circuit said it agreed with the district court that the quantity of experiment required to determine which 2'-methyl-up nucleosides meet claim 1 of the patent is very high, which favors a finding of non-enablement.

“The evidence presented to the jury could not support any other finding,” the Federal Circuit said.

At trial, Gilead presented expert testimony that because the claim allows for nearly any substituent to be attached at any position (other than 2'-up), a person of ordinary skill in the art would understand that “billions and billions” of compounds literally meet the structural limitations of the claim.

Idenix’s counsel conceded that in its “best case”, the structural limitations still encompass “some number of thousands” of compounds.

Additionally, the Federal Circuit agreed with Gilead that the ‘597 patent is invalid for lack of written description because fails to direct a person of ordinary skill in the art to the specific subset of 2'- methyl-up nucleosides that are effective in treating hep C.

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