Patenting Medical Diagnostic Procedures


There is a string of cases holding patents invalid on the basis that the patent is merely claiming an aspect of natural law.  This involves patents pertaining to medical diagnostics. Patents for medical diagnostic procedures may involve a dependency upon reactions or results that are a function of natural law (35 U.S.C. Section 101).  For example, claiming that a disease or malady can be detected by observing the existence of a chemical or medical agent that causes a reaction signaling the presence of a disease or DNA sequence is not patent eligible.

Note this is different from invalidating a patent on the basis that the invention has already been disclosed (Section 102) or that the invention was would in fact be obvious to a person skilled in the art, and therefore not really innovative (Section 103)

If the diagnostic technique comprises merely a test regarding whether or not a particular reaction occurs, it is deemed not patentable. This is because whether or not the reaction occurs is a function of natural law, e.g., the reaction occurs because the correct reactants are present.  The subject of the claimed invention is merely observation of whether or not the reaction can occur.  A simple example is that if methane CH4 exists in the presence of oxygen O2, then the reactants may combust to create carbon dioxide CO2 and water H2O.  This is an example of a natural law.

But implementation of a process or action that utilizes a natural law may be patentable.  The classic example is the decision of Diamond v. Diehr stating that use of the Arrhenius equation to control manufacturing equipment in the production of rubber was patentable. 


In 2012, it was determined that a diagnostic test that measured the level of reaction product in the human body (metabolites) based upon the administration of a therapeutic agent was not patentable since the reaction product was a function of a natural law.  See Mayo v. Prometheus.  The court stated that “laws of nature, natural phenomena, and abstract ideas” are not patentable.

The decisions that methods merely employing natural law have been grouped with decisions that methods employing an abstract idea, and that both are unpatentable under 35 U.S.C. Section 101.  This grouping has resulted in the creation of the Mayo/Alice test.  This topic is however, the subject of recent USPTO guidelines and my article Clarifying What are Patent Ineligible Abstract Ideas.

This first Mayo decision was grouped with latter decisions regarding a computerized business method for mitigating trading risk, see Alice Corp v CLS Bank International.  This grouping resulted in the so-called Mayo/Alice two step test for determining subject matter eligibility for patent protection.  The two step test involves first looking whether the patent is directed to laws of nature.  If yes, then the second step is to determine if the patent subject matter includes limitations that, considered individually and as an ordered combination, transform the patent into eligible subject matter.  Stated differently, does the patent subject matter add “significantly more” than mere application of a natural law.  Returning to Diamond v. Diehr, the subject matter for controlling the manufacturing process based upon use of the Arrhenius created the “significantly more” to be deemed patentable.  

In the second Mayo case decided yesterday, February 6, 2019, determined that the diagnostic mechanism focused upon the interaction of 125I-labeled MuSK with MuSK autoantibodies in bodily fluid, an interaction which occurs naturally.  Also it was determined that the patent at issue lacked an inventive concept since the diagnostic steps needed to observe the interaction involved only standard techniques known in the art.  


Briefly, the patent in issue pertained to diagnosis of the neurological disorder known as myasthenia gravis.  Prior art disclosed the condition was an autoimmune disease caused by a patient generating antibodies against the patient’s acetylcho-line receptors.  The patent disclosed that 20% of patients suffering from myasthenia gravis did not produce the autoantibodies but instead generated autoantibodies to a membrane protein called MuSK.  The inventors therefore claimed patent protection for diagnosis of myasthenia gravis by detecting man-made labeled autoantibodies that bind to MuSk protein.  


The court agreed with Mayo that the patent essentially covered only the correlation between the presence of naturally occurring MuSK autoantibodies in bodily fluid and MuSK related neurological diseases like myasthenia gravis.  The patent holder sought to distinguish the patent subject matter by pointing to the fact that the invention required use of new laboratory techniques to make use of man-made molecules, i.e., the labeled antibodies.  Therefore, the patent holder argued that the patent did not preempt the use of the natural law by others, but rather only those that followed the procedures disclosed in the patent.  

The court distinguished the patent from a prior court decision that held a patent that claimed discovery of a method of preserving hepatocyte cells for later use.  The method utilized multiple freeze thaw cycles.  The ability of the cells to survive the multiple freeze thaw cycles was deemed to be natural law.  However the claims of the patent were viewed as reciting a new and improved way of preserving hepatocyte cells for later use, in contrast to merely observing or detecting the ability of hepatocytes cells to survive multiple freeze-thaw cycles. 

In my view, the distinctions are subtle.  The distinction illustrates the significance of careful claim drafting.  In my view this subtlety may also be easily lost upon the USPTO examiner and perhaps only illuminated in an appeal to the Patent Trial and Appeals Board (PTAB).   

Continuing, however, the court sought support in an earlier decision of Cleveland Clinic that observing naturally occurring biological correlations “with no meaningful non-routine steps in between” are directed to natural law and therefore not patentable subject matter.  Recall the need for something “substantially more” as referenced above.  Again, this points to the need for careful claim drafting. The court is clear that conventional “concrete steps” used to facilitate the observation of the natural law are not “substantially more”.  In this second Mayo decision, the concrete steps were labeling the MuSK protein. The court appears to emphasize the requirement of “non routine” steps to meet the substantially more criteria of the second step of the Mayo/Alice test.  .

The court also asserts that the patent at issue merely recites a natural law and conventional methods for observing it.  The court distinguishes this from applications of natural law, which are patent eligible.   

“Claiming a natural cause of an ailment and well-known means of observing it is not eligible for patent because such a claim in effect only encompasses the natural law itself.  But claiming a new treatment for an ailment, albeit using a natural law, is not claiming the natural law.” 

Finally, the court rejected that the “man-made” molecules, i.e., labeled MuSK, were analogous to the cDNA protein created by the patent holder in Association for Molecular Pathology v. Myriad Genetics, Inc.  Recall Myriad Genetics distinguished isolation of naturally occurring DNA sequence (non-patentable) to a man-made cDNA sequence in detecting BRCA1 and BRCA2 genes.  


I think this decision illustrates the need for careful understanding of the invention and methodology utilized in performing the invention.  It also illustrates that this understanding is essential in drafting the claims intended to define the invention.  As always, there is no bright line test provided for guiding the determination of what is (or is not) patent eligible.  

Copyright David McEwing, 2019