Diagnostic claims and products of nature represent two of the most challenging areas for establishing subject matter eligibility under 35 U.S.C. § 101. Both domains sit at the fault line between discovery and invention—the place where patent law must determine whether a claim protects a genuine technological advance or merely appropriates a natural phenomenon. Getting that analysis right, both during prosecution and in crafting the underlying specification, requires a clear understanding of how the USPTO approaches these categories and where the practical opportunities lie.
The USPTO’s Analytical Framework
The USPTO evaluates patent eligibility through a framework established by the Supreme Court in Mayo Collaborative Services v. Prometheus Laboratories (2012) and Alice Corp. v. CLS Bank (2014), and refined by the USPTO’s 2019 Revised Patent Subject Matter Eligibility Guidance. Under that framework, the first inquiry is whether a claim recites a judicial exception—a law of nature, natural phenomenon, or abstract idea. If it does, the analysis proceeds to Step 2A, Prong 2: whether the additional claim elements integrate the exception into a practical application, meaning they impose a meaningful limit on the exception beyond merely linking it to a particular field or applying it using well-understood, routine, or conventional techniques. Where that integration cannot be established, the examiner will then assess under Step 2B whether the claim adds significantly more than the exception itself.
That structure is systematic in theory. In practice, it presents significant interpretive challenges, particularly for life sciences claims where the line between a natural correlation and a patentable invention is rarely clear.
Diagnostic Method Claims
The Core Tension
Diagnostic claims are especially challenging because they often implicate multiple judicial exceptions simultaneously. A claim directed to identifying a disease state through a biomarker may be characterized as a law of nature (the natural correlation between the biomarker and the condition), an abstract idea (the mental act of comparing data and reaching a conclusion), or both. The central challenge is distinguishing claims that merely instruct a practitioner to observe and apply a natural correlation from those that integrate the correlation into a genuinely patent-eligible method.
The difficulty is not theoretical. In Ariosa Diagnostics v. Sequenom (Fed. Cir. 2015), the Federal Circuit invalidated a method for detecting cell-free fetal DNA in maternal plasma—a genuinely innovative diagnostic advance—because the court found that the additional method steps were routine and conventional, and that the claim was therefore directed to a natural phenomenon without adding significantly more. Ariosa illustrates the core risk: even a discovery of real scientific significance may not survive § 101 scrutiny if the implementation steps are not themselves unconventional. That outcome continues to define the practical landscape for diagnostic method claims.
Why Specificity in Detection Matters
Specificity in the detection methodology is often outcome-determinative. Generic claim language—such as “detecting whether JUL-1 is present in the plasma sample”—frequently fails to establish eligibility. The USPTO’s published subject matter eligibility guidance examples illustrate the contrast: using a porcine anti-JUL-1 antibody to detect a human protein (an unconventional cross-species application), employing a specific monoclonal antibody such as mAb-D33, or utilizing scanning near-field optical microscopy rather than routine autoradiography have all been presented as examples likely to fare better in examination.
The principle is whether the detection step represents an instruction to apply a judicial exception using well-understood, routine, and conventional techniques—or whether it embodies something non-conventional that extends beyond the correlation itself. Claims that clearly land on the latter side of that line stand on stronger footing, though the Federal Circuit has applied this standard strictly and specificity alone is no guarantee of survival.
Diagnostic-Treatment Integration
An alternative path to eligibility involves pairing diagnostic steps with specific treatment interventions. Here too, however, the distinction between generic and specific language is critical. A limitation such as “administering an appropriate treatment” adds little. By contrast, specifying a particular treatment—especially one that is unconventional for the diagnosed condition—may support eligibility. USPTO guidance examples include topical vitamin D administration for conditions where such treatment is non-standard, and the use of anti-TNF antibodies tied directly to the diagnostic determination.
This approach carries significant practical risk and an inherent conceptual tension. Federal Circuit decisions have applied the “routine and conventional” standard strictly to treatment steps, and a conventional therapeutic intervention will not rescue an otherwise ineligible diagnostic claim even when the underlying biomarker correlation is genuinely novel. More fundamentally, this approach conditions eligibility on the novelty of the detection technique or the therapeutic step, rather than the diagnostic insight itself. The biomarker correlation remains largely unprotectable under this framework, which is a significant limitation practitioners and their clients should understand when evaluating claim strategy.
Some claims have avoided characterization as directed to a judicial exception by focusing exclusively on detection or measurement steps without formally reciting the diagnostic correlation. A claim directed solely to obtaining a sample and detecting a biomarker through specific means does not, on its face, recite the law of nature connecting that biomarker to disease. The practical concern is that such claims may be of limited commercial value, failing to capture the diagnostic significance that motivated the invention, or may meet standards for novelty and nonobviousness.
More broadly, claims that emphasize process implementation—the “how” rather than the “what”—tend to receive more favorable treatment. That principle favors claims with unconventional implementation details: specific reagents, conditions, contexts, or techniques that distinguish the method from routine practice. Where a detection method demonstrably improves accuracy, speed, or reliability over conventional approaches, arguments framing those advances as practical applications or improvements to technology can be persuasive, though they require claims narrowly tailored to the specific implementation.
Product of Nature Claims
The Marked Difference Standard
For nature-based products, eligibility turns on whether the claimed composition exhibits markedly different characteristics from its naturally occurring counterpart, a standard rooted in the Supreme Court’s decision in Association for Molecular Pathology v. Myriad Genetics (2013) and elaborated through subsequent USPTO guidance. That standard applies to individual natural ingredients and to combinations alike, with “markedly different characteristics” encompassing structural, functional, or combined differences.
Why Purification Is Not Enough
Mere purification, isolation, or extraction of a naturally occurring compound does not confer eligibility. Myriad established this principle directly in holding that isolated DNA sequences matching naturally occurring genes were not patent-eligible subject matter. The USPTO’s hypothetical guidance examples extend the same logic: purified amazonic acid isolated from Amazonian cherry tree leaves, despite the difficulty of purification and its novelty, is presented as ineligible because it remains structurally and functionally identical to the naturally occurring form. For cosmetic extracts and purified natural ingredients, the effort expended in isolation is legally irrelevant absent actual structural or functional differentiation.
Chemical Modification as a Path to Eligibility
Structural modification of natural molecules presents a more promising avenue. The USPTO’s guidance examples recognize that chemical derivatives may constitute patent-eligible subject matter. In one such example, deoxyamazonic acid, created by removing a hydroxyl group from naturally occurring amazonic acid, is presented as eligible based on structural modification alone, on the rationale that it creates a unique molecule that is distinct from naturally occurring amazonic acid and does not prevent others from using it. The claim on the derivative cannot block access to the natural molecule, which is central to why the modification satisfies the eligibility threshold.
The analysis becomes more complex when claims are broad enough to encompass both modified and unmodified forms. Such claims face eligibility challenges even where the specific derivative, if claimed narrowly, would qualify. Whether particular claim language reads on the naturally occurring form is a highly fact-specific determination requiring careful attention to claim scope.
Structural Differences Without Functional Changes
Notably, structural differences alone can be sufficient for eligibility, even absent functional changes. Chemical structure modifications (altered amino acid sequences or different glycosylation patterns) establish the requisite difference, as do physical structure changes such as different crystal forms. In another USPTO guidance example, an antibiotic in a tetrahedral crystal form is presented as eligible over the natural hexagonal-pyramidal form, despite identical chemical composition. For formulated products, the physical architecture of a composition—an encapsulated delivery system, a gel matrix, or a specific emulsion structure—may itself constitute a structural difference relative to the natural ingredients in their native state.
Functional Differentiation
Functional differences provide an independent basis for eligibility. Properties that differ from the natural counterpart, such as improved solubility, modified release profiles, enhanced bioavailability, or altered organoleptic properties, can establish the requisite marked difference. USPTO guidance examples present amazonic acid stabilized in water (where the natural form is insoluble) and a sweetener formulated without its natural bitter aftertaste as eligible on functional grounds. Quantifiable differences are generally stronger than qualitative characterizations, though both may support eligibility under the right circumstances.
Combination Products
Combination products present distinct analytical considerations. The eligibility inquiry focuses on whether the combination itself exhibits markedly different characteristics relative to its constituent components—not just the components in isolation. One USPTO guidance example involves texiol, water, and Compound N combined in specific amounts that neutralize the bitter aftertaste naturally present in texiol, producing emergent properties that differ from the sum of the parts. By contrast, in another guidance example, a simple combination of texiol and water, where each component retains its natural properties, is presented as ineligible. The distinction is between synergistic or emergent properties and mere aggregation of naturally occurring components.
Claim Drafting and Specification Strategy
Diagnostic and Predictive Methods
Specifications supporting diagnostic method claims need to do more than describe the discovery. Generic language provides inadequate support for subsequent eligibility arguments. Detailed descriptions of specific antibodies, assays, or instruments, with explanation of their innovative or unconventional characteristics, create a stronger foundation. Comparative data demonstrating methodological advantages over conventional approaches in speed, accuracy, or cost supports practical application arguments during prosecution.
Surprising aspects of the invention deserve explicit documentation: unexpected biomarker correlations, unanticipated detection sensitivity, or unforeseen clinical utility. Connecting the diagnostic method to concrete clinical decision-making, for example, describing how results guide treatment selection, provides material for practical application arguments that can prove valuable when responding to rejections.
Product of Nature Claims
Specifications for nature-based products should explicitly characterize the natural counterpart, describing the properties of natural ingredients in their native state and providing baseline data for comparative analysis. Comprehensive documentation of markedly different characteristics then becomes essential.
Structural documentation should include crystal structure data where relevant, formulation architecture characterized through microscopy or particle sizing, and chemical structure modifications confirmed by spectroscopic analysis. Functional characterization should encompass comparative dissolution or release studies, stability data contrasted with natural forms, sensory or organoleptic testing results, bioavailability or penetration studies, and solubility comparisons. Mere assertion of differences is insufficient. For example, rather than stating “controlled release,” the specification should explain why the difference is marked and practically significant—for instance, that “the controlled release formulation extends sweetness perception over 20 minutes versus the immediate burst characteristic of natural texiol, enabling practical use in chewing gum applications.” This kind of contextual framing demonstrates practical importance in a way that generic characterizations do not.
For combination products, specifications should address component interactions directly, documenting synergistic or emergent properties that distinguish the combination from simple aggregation. Multiple embodiments across a range of formulations provide flexibility for claim amendments during prosecution. Where factually supportable, explicit statements that a composition does not occur in nature or has no known natural counterpart can assist in establishing eligibility at the outset, though such statements are most effective when supported by concrete comparative data rather than standing alone.
Prosecution Strategy
Effective responses to Section 101 rejections require careful analysis of the specific basis of the rejection—whether grounded in laws of nature, abstract ideas, or products of nature—with arguments tailored accordingly. The USPTO has published extensive subject matter eligibility examples for life sciences applications. Citing relevant hypothetical examples that parallel the applicant’s fact pattern demonstrates consistency with Office practice and can provide persuasive precedent examiners are likely to find familiar.
Optimal responses frequently combine claim amendments with arguments addressing existing claim limitations, since amendments alone may prove insufficient without accompanying explanation of their significance. For particularly complex Section 101 issues, examiner interviews offer an opportunity to understand specific concerns and explore amendment options before formal response, often improving both efficiency and outcomes.
Conclusion
Section 101 doctrine in diagnostic methods and product of nature claims reflects ongoing tensions between encouraging innovation and preventing the appropriation of natural phenomena and fundamental truths. The Supreme Court’s decisions have produced a framework that is demanding to navigate, particularly for diagnostic method claims, where even genuinely innovative advances have struggled to survive eligibility scrutiny. While the strategies described above provide structure for prosecution and specification drafting, every patent application presents unique facts, and outcomes depend heavily on specific claim language, the underlying specification, and the examiner’s application of the law to those particular circumstances. This article is intended as general guidance only and does not constitute legal advice. Section 101 jurisprudence continues to evolve, making ongoing attention to Federal Circuit decisions and USPTO policy guidance an important part of effective life sciences patent practice.
Conley Rose’s life sciences practice regularly assists clients in navigating subject matter eligibility challenges, from specification drafting through prosecution and beyond. Contact Conley Rose to discuss how your organization can develop a strategy for protecting diagnostic and nature-based innovations under Section 101.