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

Cite as:  566 U. S. ____ (2012) 

7 

Opinion of the Court 

not  limited  to  instances  in  which  the  doctor  actually  de­
creases  (or  increases)  the  dosage  level  where  the  test 
results suggest that such an adjustment is advisable.  Id., 
at  107a–109a;  see  also  Brief  for  Respondent  i  (describing
claimed  processes  as  methods  “for  improving  . . .  treat­
ment  . . .  by  using  individualized  metabolite  measure­
ments  to  inform  the  calibration  of  . . .  dosages  of  . . .
thiopurines” (emphasis added)).

Nonetheless  the  District  Court  ultimately  granted 
summary  judgment  in  Mayo’s  favor.    The  court  reasoned 
that  the  patents  effectively  claim  natural  laws  or  natural
phenomena—namely  the  correlations  between  thiopurine
metabolite  levels  and  the  toxicity  and  efficacy  of  thiopu­
rine drug dosages—and so are not patentable.  App. to Pet. 
for Cert. 50a–83a. 

On appeal, the Federal Circuit reversed.  It pointed out
that in addition to these natural correlations, the claimed 
processes specify the steps of (1) “administering a [thiopu­
rine] drug” to a patient and (2) “determining the [resulting 
metabolite]  level.”    These  steps,  it  explained,  involve  the
transformation  of the  human  body or of blood taken from 
the  body.  Thus,  the  patents  satisfied  the  Circuit’s  “ma­
chine  or  transformation  test,”  which  the  court  thought 
sufficient  to  “confine  the  patent  monopoly  within  rather 
definite bounds,” thereby bringing the claims into compli­
ance  with  §101.    581  F. 3d  1336,  1345,  1346–1347  (2009) 
(internal quotation marks omitted).

Mayo  filed  a  petition  for  certiorari.    We  granted  the
petition, vacated the judgment, and remanded the case for
reconsideration  in  light  of  Bilski,  561  U. S.  ___,  which 
clarified that the “machine or transformation test” is not a 
definitive  test  of  patent  eligibility,  but  only  an  important 
and  useful  clue.  Id.,  at  ___–___  (slip  op.,  at  7–8).    On 
remand  the  Federal  Circuit  reaffirmed  its  earlier  conclu­
sion. 
It  thought  that  the  “machine-or-transformation
test,” understood merely as an important and useful clue,