by Dennis Crouch
The Federal Circuit’s recent decision in In re McLeay offers a glimpse into the evolving relationship between utility and enablement in patent law. Although the decision is short and non-precedential, I think it offers some important insights on how both the USPTO and Federal Circuit judges are thinking about the issues.
In affirming the USPTO’s rejection of claims for treating COVID-19 with aerosolized ribavirin, the court’s February 18, 2025 ruling (No. 23-2338) shows that the Full Scope Enablement Doctrine has effectively assumed the gatekeeping role traditionally assigned to Section 101’s Utility Doctrine — especially for pharmaceutical treatment claims. This shift reflects a broader pattern where enablement requirements under Section 112 are increasingly shouldering the substantive work of ensuring inventions are genuinely useful—work that the relatively permissive Utility Doctrine has largely abandoned. I enjoyed the case also noting that it was argued by the patent applicant’s twin brother Bart McLeay (Kutak Rock LLP).
Background: Dr. Matthew McLeay sought to patent methods of delivering ribavirin via nebulizer to treat SARS-CoV-2 lung infections. The core claim at issue required “administering to a lung of said patient by inhalation a liquid aerosol composition comprising >50% (w/w) water and <50% (w/w) ribavirin, wherein said liquid aerosol is delivered to the lung with a nebulizer.” The claim preamble includes an indication that this is a “method of treating a SARS-CoV-2 lung infection in a patient in need thereof” and so a proper construction of the term may also read this as requiring an effective treatment COVID. In my
Although the <50% ribavirin limitation was disclosed the originally filed specification, the document does not show exactly how this would work in a nebulizer. Here, though the USPTO agreed with the applicant that it would be straightforward to actually make the invention and to perform the claimed steps. The following comes from oral arguments:
Judge Stoll: The claim itself says using this inhaler, using it as an aerosol to treat COVID, right? And I think we can all agree that a person of ordinary skill in the art could make that happen, right?
USPTO Attorney Craven: Could do those steps, Yes
Judge Stoll: But the only question is whether it has utility, whether it actually would treat someone with COVID.
Craven: Right.
But, as discussed below, the USPTO did not reject the claim for lack of utility. Rather, the USPTO’s rejection is for lack of enablement for failing to show utility.
The McLeay decision represents the latest chapter in a longer doctrinal evolution. The Federal Circuit’s treatment of utility and enablement requirements has created doctrinal confusion, particularly in pharmaceutical patent cases where proving therapeutic efficacy at the time of filing presents unique challenges. Two key cases illustrate this problematic conflation:
In In re ‘318 Patent Infringement Litigation, 583 F.3d 1317 (Fed. Cir. 2009), the Federal Circuit considered whether patent applications enabled the use of galantamine to treat Alzheimer’s disease. The court found the applications insufficient because they contained “only a description of the disease state, a suggestion to use galantamine to treat symptoms, and an invitation to determine through experimentation whether galantamine would be effective.” While the court acknowledged that human trials are not required for patentability, it held that the specification must provide some basis for believing the claimed treatment would be effective. The court emphasized that the inventor herself testified she “wasn’t sure” whether the treatment would work when filing the patent. Without experimental proof or a reasonable theoretical basis for believing galantamine would treat Alzheimer’s, the court found the claims non-enabled. The court reached this conclusion despite the fact that galantamine was later proven effective and received FDA approval.
Similarly, in Rasmusson v. SmithKline Beecham Corp., 413 F.3d 1318 (Fed. Cir. 2005), the Federal Circuit upheld rejection of patent claims for treating prostate cancer when the applicant could not demonstrate a reasonable expectation that the treatment would work. The court held that § 112’s enablement requirement incorporates § 101’s utility requirement, stating that “if a patent claim fails to meet the utility requirement because it is not useful or operative, then it also fails to meet the how-to-use aspect of the enablement requirement.” In his article on the cases, Professor Risch argues this doctrinal merger is problematic. See, Michael Risch, A Surprisingly Useful Requirement, 19 George Mason L. Rev. 108 (2011). The Rasmusson specification clearly described how to administer the claimed treatment – satisfying § 112’s requirement to teach others how to use the invention. The real issue should have been whether the invention had demonstrated utility under § 101.
This doctrinal confusion particularly impacts the pharmaceutical industry, where demonstrating therapeutic efficacy often requires extensive testing that may not be complete at the time of filing. The Federal Circuit’s approach effectively requires such testing before filing to satisfy enablement; whereas utility can be proven after filing through later-developed evidence, as long as the underlying science supporting the invention existed at the time of filing. See In re Brana, 51 F.3d 1560, 1567 (Fed. Cir. 1995) (holding that post-filing evidence can demonstrate the utility that existed at the filing date). See also, Biogen Int’l GmbH v. Mylan Pharms., Inc., 28 F.4th 1194, 1200
(Fed. Cir. 2022) (“Under our precedent, ‘it is unnecessary to prove that a claimed pharmaceutical compound actually achieves a certain result.’”), Nuvo Pharms (Ir.) Designated Activity Co. v. Dr. Reddy’s Lab’ys Inc., 923 F.3d 1368 (Fed. Cir. 2019).
At oral arguments, Judges Stoll and Chief Judge Moore delved into these issues — particularly peppering USPTO attorney Sarah Craven who did not fully answer the questions:
Judge Stoll: Why do we inject utility into enablement? Why is that? … Because utility usually falls under 101, right? … Why should that be an enablement issue?
Chief Judge Moore: I think that the PTO is consistently over broadly using 318 and Rasmussen. And I’m bothered by it because I think you suddenly think you’re the FDA and you’re not the FDA. . . . I’m bothered by is this notion that there needs to be some degree of proof that they have actually used [the invention before filing].
Now, I don’t want to unduly defend McLeay’s patent application — its disclosure is thin, especially because it does not provide any real examples toward the upper end of the claimed range <50% ribavirin. Enablement issues in cases with thin disclosures are tricky, particularly where the claims also walk a fine line with obviousness. Here, the very references cited in the specification to show that skilled artisans would not expect success – and thus that the invention was nonobvious – were used by the Board to demonstrate the art was unpredictable and would require undue experimentation to reproduce the invention. This tension between enablement and obviousness often puts inventors in a difficult position: evidence that could help overcome an obviousness rejection by showing skepticism in the field may simultaneously create enablement hurdles under In re Wands, 858 F.2d 731 (Fed. Cir. 1988). Here, the applicant had argued that ribavirin’s “use in treating COVID-19 is not expected by skilled pulmonologists and infectious disease specialists to be successful.” In the appeal, the Board found this acknowledgment helped prove the Wands factor of unpredictability in the art.
In my opinion, whether enablement should incorporate utility depends significantly on claim type and structure. We know that utility patents generally require a useful invention, but that question is answered by the utility doctrine itself. For me, the fundamental question about involving enablement in the utility analysis is whether the claim itself requires utility—whether it includes limitations regarding operability and usefulness. That determination should drive whether enablement doctrine properly encompasses utility concerns. Device and structure claims typically require enabling disclosure of structure and fabrication, with utility playing a secondary role. Method-of-use claims, however, inherently center on “use” which begins to suggest that the purpose becomes essential to the invention itself. However, even there, the underlying utility is often to non-specific to trigger an enablement question.
The claims cross a clear threshold in cases where the claims expressly include a functional outcome limitation – such as providing an “effective treatment.” In that situation, the claimed purpose is not merely incidental but fundamental to the invention’s identity and structure and it becomes fair game to judge that claimed functional outcome according to the standards of the enablement doctrine.
After reviewing the PTAB decision for McLeay’s case, it seems that a critical preliminary step was overlooked: the PTAB never definitively construed whether claim 20 required effectiveness or merely described an intended use. The claim’s preamble states a “method of treating a SARS-CoV-2 lung infection” but doesn’t explicitly require successful or effective treatment. Before applying the heightened enablement standard from In re ‘318 and Rasmusson, the PTAB should have first determined whether the claims actually required effectiveness as an element. Only with that construction established should the analysis have proceeded to whether such effectiveness was enabled by the specification.
= = =
- First, the claimed concentration range (up to 50% ribavirin) far exceeded any demonstrated examples. The prior art, including Dr. McLeay’s own work, only disclosed compositions with 2%, 6%, and 10% ribavirin concentrations. A later study by Messina showed success with 10% ribavirin, but still didn’t support the full claimed range up to 50%.
- Second, while Dr. McLeay argued that pharmaceutical patents need not demonstrate effectiveness to satisfy enablement, the court distinguished between proving efficacy and enabling the full scope of the claims. The Federal Circuit explained that while “utility informs a court in making an enablement determination, a claim’s utility alone should not end the enablement inquiry.”
The Federal Circuit’s holding threads the needle between utility and enablement doctrine. While the court affirmed the Board’s ultimate rejection, it explicitly pushed back against the USPTO’s conflation of utility and enablement requirements. Specifically, the court rejected the USPTO’s argument that the application’s “lack[] of any evidence of ribavirin’s efficacy against COVID-19” was fatal to enablement.
[W]e reject the Board’s overbroad contention that the claim is not enabled because the Application “lacked any evidence of ribavirin’s efficacy against COVID19.” While utility informs a court in making an enablement determination, a claim’s utility alone should not end the enablement inquiry.
Unfortunately, the decision does not explain its reasoning in any further detail. Despite the court’s caveats, the decision is somewhat hard to swallow because the application did teach someone how to make and use the invention, and the failure the lack of evidence that the full scope of the claim was operable. This outcome illustrates how the Full Scope Enablement Doctrine has effectively absorbed much of utility’s traditional gatekeeping role – but with a crucial difference. While utility doctrine would focus simply on whether the invention works for its intended purpose, enablement doctrine demands evidence supporting the full range of what is claimed and limits the evidence available for proof.