Until 5 years ago, the boundary in the USA was very wide for what was accessible to patent protection. This contrasts with Europe, where the technicality of the new claim features has always been decisive. With the decision in Mayo v. Prometheus, the Supreme Court has restricted this liberal practice.
The core of the disputed invention lay in the indication of the range within which the level of the active ingredient in the patient’s blood must lie for the thiopurine treatment to be effective.
The disputed Patents US 6,355,623 claimed a “method for optimizing the therapeutic efficiency” of an immune-mediated gastrointestinal disorder. The first two method steps of the claim were known per se and read as follows:
a) dispensing a drug containing the active substance 6-thioguanine to the patient and
b) the measurement of the level of this active substance in the patient.
The actual new feature that characterized the invention was formulated as follows:
“wherein a level of 6-thioguanine of less than about 230 pmol per 8×108 red blood cells indicates a need to subsequently increase the amount of drug administered to the subject, and wherein a level of 6-thioguanine of greater than about 400 pmol per 8×108 red blood cells indicates a need to subsequently decrease the amount of drug administered.”
Prometheus Labs. was the exclusive licensee of this patent and sued Mayo for patent infringement. In turn, Mayo sued for invalidity of the patent.
At first instance, the court ruled that the first two steps only served to “collect data” and that the third step was a purely mental act that established the natural connection between the metabolites produced in the body and the therapeutic efficacy. This step covers all possibilities for realizing the natural connection and is not patentable.
The appeal to the Court of Appeals for the Federal Circuit (CAFC) led to the first-instance judgment being set aside. All process steps had to be taken into account for patentability. The fact that a single step contains an inherently unpatentable law of nature or a mental act does not preclude patentability.
The US Supreme Court took up this case and disagreed with the CAFC ruling.
The court considers the correlation between the naturally produced metabolites and therapeutic efficacy to be a non-patentable law of nature. According to the Supreme Court, the first two steps are not “genuine applications of the law of nature”, but merely efforts by the patentee to monopolize the law of nature with clever claim formulations. The first two procedural steps are common in the art and are not sufficient to transform the knowledge of a law of nature into a patentable application.
The result of this judgment is that a claim is not patentable if, in addition to a feature that is excluded from patent protection and constitutes a mental act or a law of nature, it only has generally accepted technical features. It is noteworthy that this is in principle in line with the European Patent Office’s line.