By Audrey A. Millemann

Enablement is one of the requirements a patent application must satisfy in order for the patent to be granted. Enablement means that the specification (the written text and drawings) teaches a person skilled in the art how to make and use the invention. 35 U.S.C. §112, ¶1. The enablement requirement is satisfied if a person, after reading the specification, could make and use the invention without undue experimentation. 

In Cephalon, Inc. v. Watson Pharmaceuticals, Inc., 707 F.3d 1330, 2013 U.S.App. LEXIS 3203 (Fed. Cir., February 14, 2013), the Federal Circuit Court of Appeals held that experimentation is not “undue” even if it is “complicated and difficult.” 

Cephalon owned two patents covering a method of drug delivery, which used effervescent agents to increase the absorption of the drug. Cephalon sold the brand-name drug Fentora to treat breakthrough cancer pain, which utilized the patented method.

Watson filed an Abbreviated New Drug Application (ANDA), seeking approval from the FDA for a generic version of Fentora. Watson also challenged Cephalon’s patents under the Hatch-Waxman Act, which permits a manufacturer who wants to make a generic version of a patented drug to challenge the patent before beginning to sell the generic. 

Cephalon then sued Watson for patent infringement in the district court for the District of Delaware. The case was tried to the court. The court held that Cephalon’s two patents were invalid for failure to meet the enablement requirement. The court also found that Watson had not infringed the patents. 

Cephalon appealed the court’s judgment on two grounds: (1) that Watson had not proved by clear and convincing evidence that Cephalon’s patents were invalid for lack of enablement; and (2) that Watson had literally infringed the patents.

The Court of Appeals for the Federal Circuit reversed the finding of invalidity and affirmed the finding of non-infringement.

The appellate court held that Watson had not proved by clear and convincing evidence that undue experimentation was necessary to practice the invention. The court explained that the existence of undue experimentation is determined by considering a number of factors, including the amount of experimentation needed, the guidance given, working examples, the nature of the invention, the prior art, the skill level of those in the art, the predictability of the field, and the breadth of the claims. (2013 U.S. App. LEXIS at *12, citing In re Wands,  858 F. 2d 731 (Fed. Cir. 1988).) These factors are not required, but are to be considered if they are relevant to the specific situation. The court stated that “[A] reasonable amount of routine experimentation required to practice a claimed invention does not violate the enablement requirement.” Id. at *12.

Cephalon argued that its expert testified that it would have been easy for a skilled person to calculate the amounts of the compounds needed to practice the claimed invention, which the district court had construed to require two dosage forms. Watson relied on its expert, who testified that it “would be very difficult…and complicated” to calculate the two dosage forms.

The district court had held that Watson had shown a prima facie case of lack of enablement, shifting the burden to Cephalon to rebut that evidence. The district court had then found that Cephalon had not rebutted Watson’s case, and held the patents invalid. In reviewing the district court’s holding, the appellate court emphasized that there is no burden shifting; the burden of proof is on the plaintiff challenging the patent to prove invalidity by clear and convincing evidence. 

The court found that Watson’s case was primarily based on its expert’s testimony and that the expert’s unsupported comments that the experimentation would be “difficult and complicated” did not constitute clear and convincing evidence. 

            “The question of undue experimentation is a matter of degree, and what is required is that the amount of experimentation not be ‘unduly extensive.’  In addition, extensive experimentation does not necessarily render the experiments unduly extensive where the experiments involve repetition of known or commonly used techniques.”

Id. at *19.

The court reviewed several prior cases and then summarized its holding, stating at *20:

“Likewise, we have held that the amount of experimentation would be undue where: (1) the specification lacks guidance by teaching away from the subject matter that was eventually claimed; and (2) there is evidence of the patentee’s own failures to make and use the later claimed invention at the time of the application. See, e.g., AK Steel Corp. v. Sollac, 344 F.3d 1234, 1244 (Fed. Cir. 2003). Hence, the mere potential need for clinical work, without more, is not dispositive in this case.”

The court held that Watson had not shown that the necessary experimentation would have been “excessive,” such as by being unreasonably time-consuming. Because Watson had not met its burden, the court reversed the district court’s ruling.