In re Couvaras: Limitations of Unexpected Results for Non-Obviousness of Claimed Mechanisms of Action

Authored by Kaitlin Farrell and Stella Vila

On June 14, 2023, the Federal Circuit affirmed the decision of the Patent Trial and Appeal Board upholding an Examiner’s rejection of all pending claims in U.S. Patent Application 15/131,442 (’442 application).1 The Federal Circuit agreed with the Board that the ’442 application’s pending claims were unpatentable as obvious in view of the asserted prior art.2  Notably, the Federal Circuit panel, consisting of Judges Lourie, Dyk, and Stoll,3 clarified the impact of unexpected results on the obviousness analysis when presented in the context of a pharmaceutical combination product versus a mechanism of action.


The pending claims of the ’442 application generally recited “methods of increasing prostacyclin release in the systemic blood vessels of a human with essential hypertension to improve vasodilation,” by co-administering a GABA-a agonist and an Angiotensin II Receptor Blocker (ARB) – two types of antihypertensive agents.4

During prosecution, applicant Couvaras conceded that GABA-a agonists and ARBs “ha[d] been known as essential hypertension treatments for many [] decades.”5 The Examiner agreed, and also found that the claimed results of the compounds’ administration (i.e., increased prostacyclin release, activation of uninhibited GABA-a receptors, and smooth muscle relaxation) were not patentable because they “naturally flowed from the claimed administration of the known antihypertensive agents.”6

Couvaras appealed to the Board, arguing that the Board erred because (1) the prostacyclin increase was unexpected and therefore patentable, and (2) objective indicia overcame any existing prima facie case of obviousness.7 The Board affirmed the Examiner’s rejection,8  and Couvaras appealed to the Federal Circuit.9


On appeal, Couvaras raised three issues: (1) the Board erred in affirming that a skilled artisan would have had a motivation to combine the art asserted by the Examiner; (2) the claimed mechanism of action was unexpected, and that the Board erred in discounting its patentable weight by deeming it simply inherent in the claimed method; (3) the Board erred in its consideration of Couvaras’s objective indicia of nonobviousness, particularly with respect to unexpected results.10

Motivation to Combine

First, the panel rejected Couvaras’s argument that the Board erred in finding that a skilled artisan would not have had a motivation to combine the identified prior art.11 The panel observed that Couvaras did not dispute that GABA-a agonists and ARBs were well-known as useful for alleviating hypertension.12 This fact alone, the panel reasoned, could serve as motivation to combine the art because “the idea of combining [these compounds] flow[ed] logically from their having been individually taught in the prior art.”13 Although Couvaras argued that the Board’s conclusions concerning motivation were too generic to support finding a motivation to combine in the clinical context,14 the panel rejected this suggestion in view of the known uses disclosed in the prior art.15  Additionally, the Court pointed to the Board’s observation that the claimed antihypertensive agents were also taught to be used in combination with other antihypertensive agents to improve treatment.16 In view of these findings, the Court found that the motivation to combine was “not a general motivation to cure hypertension, but, rather, the motivation to create a particular cure by co-administering ARBs with another class of known antihypertensive agents as instructed by [the prior art].”17


Second, Couvaras argued that the Board downgraded the patentable weight of limitations drawn to the antihypertensive agents’ mechanism of action.18 Couvaras alleged that even if the mechanism of action was “inherent,” it resulted in an “unexpected property,” namely, the increased release of prostacyclin, which should be afforded patentable weight.19 The panel disagreed, noting that “unexpected properties may cause what may appear to be an obvious composition to be nonobvious,” not that unexpected mechanisms of action must be found to make the known use of known compounds nonobvious.20 In the prostacyclin mechanism, the two antihypertension agents exert the same ultimate result as the two separate compounds were known to effect – a decrease in blood pressure.21 Quoting In re Montgomery, the panel reiterated that “[n]ewly discovered results of known processes directed to the same purpose are not patentable because such results are inherent.”22 On this basis, the panel agreed with the Board that recitation of the mechanism for known compounds to yield a known result cannot overcome a prima facie case of obviousness, even if the nature of that mechanism was unexpected.23

Objective Indicia

Lastly, Couvaras asserted various other errors in identifying and weighing additional indicia of nonobviousness.24 For example, Couvaras contended that the Board erred in giving no weight to the alleged unexpected results.25 The panel disagreed, focusing on Couvaras’s failure to “show that the co-administration of a GABA-a agonist and an ARB provided an unexpected benefit,” (e.g., better control of hypertension, less toxicity to patients, or the ability to use surprisingly low dosages).26 The panel affirmed that no such benefits had been shown, and therefore, no evidence of unexpected results existed.27

Additionally, Couvaras argued that the Board erred in its consideration of additional indicia of nonobviousness, including teaching away, failure of others, and the length of time elapsed.28 The Court rejected Couvaras’s evidence of teaching away, finding that the cited prior art did not concern the same compounds or the same biological mechanisms.29

With respect to failure of others, Couvaras alleged a failure in the art to increase prostacyclin release.30 However, the Court rejected Couvaras’s evidence on the merits, finding that the art cited involved mere experimentation and therefore did not constitute a “failure of others.”31

Finally, citing Leo Pharmaceutical Products, Ltd. v. Rea,32 Couvaras argued that the length of time elapsed between the prior art and the claimed invention served as an objective indicium of the claims’ nonobviousness.33 The Federal Circuit disagreed, explaining that while “length of the intervening time between the publication dates of the prior art and the claimed invention can qualify as an objective indicator of nonobviousness,” such a finding requires additional evidence of long-felt need and failure of others—evidence Couvaras lacked.34 Thus, the panel upheld the Board’s conclusion that objective indicia did not overcome the prima facie case of obviousness.35


The Court’s opinion underscores the prima facie obviousness framework as a tangled web of factors that each requires its own fact-specific analysis.  In view of Couvaras, practitioners should tailor arguments concerning unexpected results to the claimed invention and be aware of limitations as related to claimed mechanisms of action.

1 In re Couvaras, 2023 WL 3984753, at *1 (Fed. Cir. June 14, 2023).
2 Id.
3 Id.
4 Id.
5 Id.
6 Id.
7 Id.
8 Id. at 2.
9 Id.
10 Id.
11 Id.
12 Id.
13 Id. (quoting In re Kerkhoven, 626 F.2d 846, 850 (CCPA 1980)).
14 In re Couvaras, 2023 WL 3984753, at *3; see Cardiac Pacemakers v. St. Jude Medical, 381 F.3d 1371 (Fed Cir. 2004)
(finding no motivation to combine because it was undisputed that, before the work of the inventor there was no device
capable of treating the conditions of interest).
15 In contrast from the facts in Cardiac Pacemakers, here, it is undisputed that, before the work of Couvaras, the
antihypertensive agents recited in the claims existed and were known to treat hypertension. In re Couvaras,
2023 WL 3984753, at *3.
16 E.g., In re Couvaras, 2023 WL 3984753, at *3.
17 Id.
18 Id.
19 Id.
20 Id. (emphasis in original) (quoting Honeywell International, Inc. v. Mexichem Amanco Holdings S.A., 865 F.3d 1348,
1355 (Fed. Cir. 2017)) (finding that where the recited mechanism was unexpected, it was not dismissed as having no
patentable weight due to inherency).
21 In re Couvaras, 2023 WL 3984753, at *3.
22 Id. (quoting In re Montgomery, 677 F.3d 1375, 1381 (Fed. Cir. 2012)) (citation omitted).
23 In re Couvaras, 2023 WL 3984753, at *4.
24 Id.
25 Id.
26 Id.
27 Id.
28 Id.
29 Id.
30 Id.
31 Id.
32 726 F.3d 1346, 1359 (Fed. Cir. 2013).
33 In re Couvaras, 2023 WL 3984753, at *5.
34 Id.
35 Id.