The day after the Supreme Court issued its unanimous decision in Mayo Collaborative Services v. Prometheus Laboratories, Inc., the USPTO issued a letter to the Patent Examining Corps that provides preliminary guidance to examiners and promises that more detailed guidance is forthcoming.

The Problem With Prometheus’ Claims

The USPTO summarizes the Supreme Court’s rationale for invalidating Prometheus’ claims as follows:

[T]he claims inform a relevant audience about certain laws of nature. Any additional steps consist of well-understood, routine, conventional activity already engaged in by the scientific community. Those steps, when viewed as a whole, add nothing significant beyond the sum of their parts taken separately. …. Essentially, appending conventional steps, specified at a high level of generality, to laws of nature, natural phenomena, and abstract ideas cannot make those laws, phenomena, and ideas patent-eligible. 

The Problem With The Machine-Or-Transformation Test

The USPTO cites Prometheus for poking this hole in the machine-or-transformation test:

A claim that recites a law of nature or natural correlation, with additional steps that involve well-understood, routine, conventional activity previously engaged in by researchers in the field is not patent-eligible, regardless of whether the steps result in a transformation.

The Preliminary Guidance—Back To Bilski

The letter advises examiners to continue applying the Interim Bilski Guidance issued July 27, 2010, but factoring in “additional considerations” set forth in the letter. As I summarized previously, the Interim Bilski Guidance sets forth a number of factors that may be considered when evaluating patent-eligibility under § 101. With regard to laws of nature, the Interim Bilski Guidance highlights the following issues:

(1) The particularity or generality of the application of the law of nature. 
(2) Whether the claimed method recites an application of a law of nature solely involving subjective determinations; e.g., ways to think about the law of nature. 
(3) Whether its involvement is extrasolution activity or a field-of-use, i.e., the extent to which (or how) the application imposes meaningful limits on the execution of the claimed method steps.

The Interim Bilski Guidance lists the following factors as potentially supporting patent-eligibility:

  • the law of nature is practically applied
  • the application meaningfully limits the execution of the steps

On the other hand, the following factors are listed as potentially undermining patent-eligibility:

  • the claim is not directed to an application of a law of nature
  • the claim would monopolize a natural force or patent a scientific fact; e.g., by claiming every mode of producing an effect of that law of nature
  • the law of nature is applied in a merely subjective determination
  • the law of nature is merely nominally, insignificantly, or tangentially related to the performance of the steps

In this letter, the USPTO adds the following guidance based on Prometheus:

Examiners must continue to ensure that claims, particularly process claims, are not directed to an exception to eligibility such that the claim amounts to a monopoly on the law of nature, natural phenomenon, or abstract idea itself. In addition, to be patent-eligible, a claim that includes an exception should include other elements or combination of elements such that, in practice, the claimed product or process amounts to significantly more than a law of nature, a natural phenomenon, or an abstract idea with conventional steps specified at a high level of generality appended thereto.

The Prometheus Process

The letter instructs examiners to reject claims under 35 USC § 101 if they are “effectively directed” to a law of nature. If that happens, the applicant will have an opportunity to explain why the claim is not drawn solely to the law of nature and point to limitations in the claim that apply the law of nature.

The Practicalities Of Prometheus

Only time will tell if examiners—and applicants—find this guidance to be practical. Evaluating Prometheus’ claims under this guidance shows how it still could be difficult to apply. Representative claim 1 of Prometheus’ U.S. Patent 6,355,623 reads:

1. A method of optimizing therapeutic efficacy for treatment of an immune-mediated gastrointestinal disorder, comprising: 
(a) administering a drug providing 6-thioguanine to a subject having said immune-mediated gastrointestinal disorder; and
(b) determining the level of 6-thioguanine in said subject having said immune-mediated gastrointestinal disorder,
wherein the level of 6-thioguanine less than about 230 pmol per 8 X 10(8) red blood cells indicates a need to increase the amount of said drug subsequently administered to said subject and
 wherein the level of 6-thioguanine greater than about 400 pmol per 8 X 10(8) red blood cells indicates a need to decrease the amount of said drug subsequently administered to said subject.

Perhaps an examiner would reject this claim because it is not directed to an application of a law of nature. As many commentators have pointed out, the “wherein” clauses do not recite any active steps that hinge on the determined level of metabolite. It might be possible to overcome such a rejection by amending the claims to recite specific steps that transform the claims into a “particular, useful application” of the law of nature.

Perhaps an examiner would reject this claim because it would monopolize scientific facts—the relationship between 6-thioguanine levels and safety and efficacy. Such a rejection might be more difficult to overcome while preserving a meaningful scope of patent protection, because any additional steps likely would flow from that relationship or could leave the claims vulnerable to design-around.

While examiners will be applying this guidance in the first instance, patent applicants are likely to appeal rejections to the Board and then to the Federal Circuit in order to obtain final resolution—and perhaps more specific guidance—on these issues.