The High Standard for Inherency

Par Pharmaceutical, Inc. v.TWi Pharmaceuticals, Inc.

Peter M. Jay and Robert M. Joynes

March 13, 2015

Inherency is fundamentally based upon logic. If two things are the same, then they
must necessarily have the same properties. See Ansonia Brass & Copper Co. v. Elec. SupplyCo., 144 U.S. 11 (1892) (“. . . the application of an old process to a new and analogous purpose does not involve invention, even if the new result had not before been contemplated.”). However, in patent law, whether one thing is the same as another thing rests within the specificity—or lack thereof—of the claim language.

For instance, polymorphs have identical chemical formulas but have different crystal
structures. Skilled artisans recognize that two different polymorphs can have wildly different properties—even though they have the same general chemical formula. Thus, if the general chemical formula of the polymorph is disclosed by the prior art, a claim to a particular polymorph of the general chemical formula having particular properties may be patentable over such prior art. However, if a particular polymorph is disclosed by the prior art, a claim to the same particular polymorph that includes some particular property may not be patentable. In other words, the specificity of the claimed language relative to the disclosure of the prior art must be considered in an inherency analysis.

In Par Pharmaceutical Inc. v. TWi Pharmaceuticals, Inc., the Federal Circuit provided that, to rely upon inherency, “the claimed food effect limitations necessarily [must be] present in the prior art combinations.” Par Pharm., Inc. v. TWi Pharm., Inc., No. 2014-1391, slip op. at 17 (Fed. Cir. December 3, 2014) (emphasis in original). Thus, the Federal Circuit indicated that, if the claims require a specified degree of improvement, then that degree of improvement must necessarily be disclosed by the prior art.

The claims-at-issue related to methods of administering nanosized formulations of megestrol acetate to increase body mass in a human patient suffering from anorexia, cachexia, or loss of body mass. The USPTO initially rejected the claims directed to the methods as obvious in view of prior art that discussed micronized megestrol formulations in combination with technology related to the manufacture of drug particles less than either 1000 nm or 400 nm in size. Par Pharm. overcame the rejection by amending the claims to add limitations directed to the formulation’s lack of a food effect (i.e., a comparison of the rate and extent of drug absorption between patients taking the drug in a fed versus fasted state). As such, claim 1 of the eventually issued patent recites the following illustrative food effect limitation:

. . . wherein after a single administration in a human subject of the formulation
there is no substantial difference in the Cmax of megestrol when the formulation
is administered to the subject in a fed versus a fasted state, wherein fasted state
is defined as the subject having no food within at least the previous 10 hours,
and wherein fed state is defined as the subject having a high-calorie meal within
approximately 30 minutes of dosing.

U.S. Patent No. 7,101,576 (hereinafter, “the ‘576 patent”) (emphasis added). Accordingly, the claims do not simply require an improvement in the bioavailability; the claims require that there is no substantial difference in the Cmax (i.e., a quantification of bioavailability) when the formulation is administered to the subject in a fed versus a fasted state.

Except for the food effect limitation, Par Pharm. and TWi appeared to agree that the
combination of various prior art references disclosed the elements of the claims. Indeed, the prior art disclosed that BCS Class II drugs in general could demonstrate a food effect, but the prior art references failed to identify megestrol as a Class II drug that presented such an effect. TWi, however, argued that the food effect limitation was an inherent property in the formulation disclosed by the combination of the prior art elements. Par Pharm. disagreed. The district court sided with TWi.

TWi’s expert testified that an improvement in bioavailability necessarily results in a
decrease in any food effect. However, the claims of the ‘576 patent do not simply require any decrease in food effect. Rather, the claims require no substantial difference in Cmax between the fed and fasted states.

Further, TWi presented evidence that a reduction in particle size improves
bioavailability. Indeed, the claims-at-issue are directed to methods of administering nanosized formulations of megestrol acetate. Thus, it is reasonable to infer that a reduction from particular micronized megestrol, which was disclosed by the prior art, to nanosized megestrol, would improve bioavailability. However, the claims of the ‘576 patent do not simply require any improvement in bioavailability—no substantial difference in Cmax between the fed and fasted states is required.

The Federal Circuit indicated that the district court erred by concluding that references that disclose an improvement in bioavailability inherently disclose no substantial
difference in Cmax between the fed and fasted states. In this regard, the Federal Circuit stated that the

. . . broad diktats regarding the effect of particle size on bioavailability and food
effect are not commensurate with the actual limitations at issue. While it may
be true that a reduction in particle size naturally results in some improvement
in the food effect, the district court failed to conclude that the reduction in
particle size naturally results in “no substantial difference” in the food effect.

Par Pharm., Inc., at 16 (Fed. Cir. December 3, 2014) (emphasis in original). Thus, the Federal Circuit vacated the district court’s inherency analysis, and remanded for further consideration.

The lessons learned from the Federal Circuit’s decision are simple. In order to rely on
inherency to establish the existence of a claim limitation in the prior art in an obviousness analysis, a party must meet a high standard. To establish inherency, the relevant claim limitations must necessarily be present in the prior art or the natural result of the combination of elements explicitly disclosed by the prior art. As the Federal Circuit reiterated, mere probabilities or possibilities are not sufficient to establish inherency. However, even if no prior art of record explicitly discusses the limitation, if the application itself instructs that the limitation is not an additional requirement imposed by the claims on the claimed invention, but rather a property necessarily present in the claimed invention, then the claim limitation can be inherent. In re Kubin, 561 F.3d 1351, 1357-8 (Fed. Cir. 2009).

Moreover, the alleged inherent properties of the prior art must be commensurate in
scope with the actual limitations set forth in the claims. Thus, the specific degree of the claim language must necessarily be present in the prior art. It is not sufficient that the prior art may show that a general function is inherent, such as increased bioavailability or decreased food effect, but rather, one must establish that the specific limitations of the claim (e.g., “no substantial difference in Cmax”) must necessarily be present in the prior art.

The Federal Circuit’s decision may prove valuable in challenging inherency rejections
during prosecution. Indeed, an Examiner has a somewhat lesser burden of proof when relying upon inherency. See MPEP §§ 2112(V) and 2113 (discussing the Examiner’s burden of proof required to establish inherency). However, based upon the Federal Circuit’s decision, Applicants can reasonably argue that, to meet their burden, Examiners must analyze inherency relative to the claim limitations rather than some marginally related improvement. In other words, the inherency analysis must be logically tied to the specific claim language.

Quarterly Newsletter of the AIPLA Chemical Practice Committee, Volume 3, Issue I