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Federal Circuit Ruling Could Put Certain Drug Patents At Risk

Dec. 31, 2019, 4:59 PM

A recent Federal Circuit decision involving an opioid pain medication could leave certain pharmaceutical patents vulnerable to challenges by generic drug makers, attorneys say.

Claims in two Zohydro ER patents were obvious, and a district court correctly found that characteristics of those claims not explicitly disclosed in earlier documents would inevitably be present, or inherent, the appeals court said.

The Dec. 27 ruling could make it more difficult for companies to enforce certain types of patent claims that can be a fallback when protections for a drug’s active ingredient expire, attorneys say. Generic drug makers can use inherent obviousness as an avenue to challenge such claims, which can otherwise be difficult to bring down.

“Inherent obviousness is something that a lot of folks, especially in the biotech community, watch closely, and this is certainly a very important data point going forward,” said Pauline Pelletier, a Sterne Kessler Goldstein & Fox PLLC attorney whose clients include companies in the electronics, biotechnology, and software industries.

Courts have long used the so-called inherency doctrine when deciding whether a patent claim was anticipated by a prior invention. But applying the doctrine to decide whether a patent claim is obvious is less settled, attorneys say.

Patent Parameters

Alvogen Malta Operations Ltd. was sued for infringing U.S. Patent Nos. 9,265,760 and 9,339,499 covering a method of using extended-release hydrocodone to treat pain in patients with impaired livers. Alvogen allegedly infringed by applying to create a generic version of Zohydro ER.

Certain claims in the Persion Pharmaceuticals LLC patents describe measurable factors, known as pharmacokinetic parameters, for specific concentrations of the drug in the blood.

An earlier patent document described Zohydro ER’s formulation but not its pharmacokinetic parameters. The U.S. District Court for the District of Delaware said the parameters were inherent because they were “necessarily present” in the formulation.

The U.S. Court of Appeals for the Federal Circuit said the district court “did not err by finding that the pharmacokinetic limitations of the asserted claims were inherent and added no patentable weight to the pharmacokinetic claims.”

Pharmacokinetic parameter claims can be difficult for generic companies to avoid when copying a drug. Arguing the claims are obvious can also be challenging because pharmacokinetic parameters are rarely explicitly mentioned in prior art.

“Inherency is what saves the day, so to speak,” Jeffrey Hovden, a Robins Kaplan LLP attorney who focuses on pharmaceutical patent cases, said.

‘Trouble and Confusion’

Unlike the law on inherent obviousness, attorneys say the law on inherent anticipation is generally well understood.

If a past invention, published document, or other prior reference teaches each element of a patent’s claim, then the prior art anticipated the claim. Inherency can fill gaps in what the references explicitly teach.

Inherent obviousness, by comparison, has been less clear. Attorneys attribute this, in part, to tensions between inherency and the concept of obviousness.

Aydin Harston, a patent attorney at Rothwell Figg Ernst & Manbeck PC, said deciding what’s obvious to someone at the time of the invention can be subjective, while determining the prior art’s inherent teachings is objective.

“When you try to conflate those two, you run into trouble and confusion,” Harston, whose work includes pharmaceuticals and chemicals, said.

The Federal Circuit has emphasized that inherency must be carefully limited in the context of obviousness, writing in the 2017 ruling in Honeywell International Inc. v. Mexichem Amanco Holding SA, “‘that which may be inherent is not necessarily known’ and that which is unknown cannot be obvious.’”

Pelletier said the Federal Circuit’s ruling in the Persion Pharmaceuticals case is among the first to squarely apply inherent obviousness to pharmacokinetic parameters, and casts doubt on the validity of pharmacokinetic parameter claims when the drug itself is already known.

“If you have a drug in the prior art that will inherently produce these PK parameters, you can imagine that a patent like this would be harder to get and almost definitely harder to enforce,” she said.

The case is: Persion Pharmaceuticals LLC v. Alvogen Malta Operations Ltd., Fed. Cir., No. 2018-2361, 12/27/19

To contact the reporter on this story: Matthew Bultman at

To contact the editors responsible for this story: Rebecca Baker at; Keith Perine at