[Regarding the undue experimentation aspect of the enablement inquiry under 35 U.S.C. § 112,] the mere potential need for clinical work, without more, is not dispositive.

On February 14, 2013, in, the U.S. Court of Appeals for the Federal Circuit (Reyna, Bryson, Wallach*) reversed-in-part and affirmed-in-part the district court's judgment following a bench trial that Watson did not infringe U.S. Patents No. 6,200,604 and No. 6,974,590, which related to drug delivery via the mucous membrane lining or mucosa in the oral cavity, and that the asserted (Khankari) patents were invalid for lack of enablement. The Federal Circuit stated:

To satisfy section 112 of the 1952 Patent Act, the specification must enable a person of ordinary skill in the art to make and use the invention. This requirement is met when at the time of filing the application one skilled in the art, having read the specification, could practice the invention without "undue experimentation." Whether undue experimentation is required "is not a single, simple factual determination, but rather is a conclusion reached by weighing many factual considerations." The following factors may be considered when determining if a disclosure requires undue experimentation: (1) the quantity of experimentation necessary, (2) the amount of direction or guidance presented, (3) the presence or absence of working examples, (4) the nature of the invention, (5) the state of the prior art, (6) the relative skill of those in the art, (7) the predictability or unpredictability of the art, and (8) the breadth of the claims. What is relevant depends on the facts, and although experimentation must not be undue, a reasonable amount of routine experimentation required to practice a claimed invention does not violate the enablement requirement. The burden of proof here is on Watson to show that the Khankari patents are invalid for lack of enablement by clear and convincing evidence. . . .

Specific to the enablement inquiry, the parties do not dispute that the Khankari patents are enabling as to an effervescent "couple" generating the claimed effervescent reaction, where the soluble acid source and the effervescent agent (carbonate source) are in the same tablet or other dosage form. Instead, the dispute arises from the district court's claim construction requiring effervescent "agent" to be "at least one compound" that evolves gas. This "single compound effervescent agent" construction requires the soluble acid source to be in a separate tablet or dosage form from the effervescent agent. In addition, in order to achieve the claimed effervescent reaction, this construction requires these separate dosage forms to be co-administered. The district court held that the Khankari patents lacked enabling disclosures illustrating a dosage form having only the single compound effervescent agent. Specifically, it held that the disclosures lacked teachings directed to formulating and co-administering two separate dosage forms -- one including a soluble acid source and the other containing the effervescent agent -- to achieve an effervescent reaction. The lack of disclosure of such methods of co-administration would, according to the court, necessitate undue experimentation to practice the invention. . . . The district court's emphasis on the mere fact that experimentation may be necessary is misplaced, however. The question of undue experimentation is a matter of degree, and what is required is that the amount of experimentation not be "unduly extensive." For example, the fact that a clinician's involvement may be necessary to determine effective amounts of the single compound effervescent agent and its corresponding soluble acid source does not itself constitute undue experimentation. In addition, extensive experimentation does not necessarily render the experiments unduly extensive where the experiments involve repetition of known or commonly used techniques. Thus, the focus "is not merely quantitative, since a considerable amount of experimentation is permissible, if it is merely routine, or if the specification in question provides a reasonable amount of guidance . . . ."

Permissible experimentation is, nevertheless, not without bounds. This court has held that experimentation was unreasonable, for example, where it was found that eighteen months to two years' work was required to practice the patented invention. 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. Hence, the mere potential need for clinical work, without more, is not dispositive in this case.

Rather, Watson had the burden to show by way of testimony or documentary evidence the amount of experimentation needed to calculate a formulation for co-administering a soluble acid source in one form of dosage with a carbonate source in another form to achieve the claimed effervescent reaction. As Cephalon avers, the Khankari patents describe multiple embodiments using effervescent formulations for fentanyl citrate (acid) alongside different amounts of sodium carbonate (base). Nonetheless, Watson has not presented evidence showing why these formulations for a "couple" do not provide sufficient guidance for a skilled artisan to calculate formulations for single compound effervescent agents. Nor does Watson show that the resulting experimentation in this case would be excessive, e.g., that it would involve testing for an unreasonable length of time. Unsubstantiated statements indicating that experimentation would be "difficult" and "complicated" are not sufficient. In light of the lack of evidence on the record of undue experimentation, the district court erred as a matter of law in holding that Watson proved its case on enablement by clear and convincing evidence. . . . Thus, we reverse the district court's nonenablement determination.