Document ID: ./input/supremecourt_opinions/opinions/11pdf/10-1150.pdf
Page Number: 12

8 

MAYO COLLABORATIVE SERVICES v. PROMETHEUS 

LABORATORIES, INC.
 
Opinion of the Court 

nonetheless led to the “clear and compelling conclusion . . .
that the . . . claims . . . do not encompass laws of nature or
preempt  natural  correlations.”    628  F. 3d  1347,  1355 
(2010).  Mayo again filed a petition for certiorari, which we
granted. 

II 

Prometheus’  patents  set  forth  laws  of  nature—namely, 

relationships  between  concentrations  of  certain  metabo­
lites  in  the  blood  and  the  likelihood  that  a  dosage  of  a 
thiopurine  drug  will  prove  ineffective  or  cause  harm.
Claim  1,  for  example,  states  that  if  the  levels  of  6–TG  in 
the  blood  (of  a  patient  who  has  taken  a  dose  of  a  thiopu­
rine drug) exceed about 400 pmol per 8x108 red blood cells, 
then  the  administered  dose  is  likely  to  produce  toxic  side
effects.  While it takes a human action (the administration
of  a  thiopurine  drug)  to  trigger  a  manifestation  of  this 
relation in a particular person, the relation itself exists in
principle apart from any human action.  The relation is a 
consequence  of  the  ways  in  which  thiopurine  compounds
are  metabolized  by  the  body—entirely  natural  processes. 
And  so  a  patent  that  simply  describes  that  relation  sets
forth a natural law. 

The question before us is whether the claims do signifi­
cantly  more  than  simply  describe  these  natural  relations.
To put the matter more precisely, do the patent claims add 
enough to their statements of the correlations to allow the 
processes  they  describe  to  qualify  as  patent-eligible  pro­
cesses  that  apply  natural  laws?    We  believe  that  the  an­
swer to this question is no. 

A 
If  a  law  of  nature  is  not  patentable,  then  neither  is  a
process  reciting  a  law  of  nature,  unless  that  process  has
additional  features  that  provide  practical  assurance  that
the  process  is  more  than  a  drafting  effort  designed  to