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MAYO COLLABORATIVE SERVICES v. PROMETHEUS 

LABORATORIES, INC.
 
Syllabus
 

these thresholds “indicate a need” to decrease or increase (respective-
ly) the drug dosage. 

Petitioners Mayo Collaborative Services and Mayo Clinic Rochester 
(Mayo)  bought  and  used  diagnostic  tests  based  on  Prometheus’  pa-
tents.  But in 2004 Mayo announced that it intended to sell and mar-
ket  its  own,  somewhat  different,  diagnostic  test.    Prometheus  sued 
Mayo contending that Mayo’s test infringed its patents.  The District 
Court found that the test infringed the patents but granted summary
judgment  to  Mayo,  reasoning  that  the  processes  claimed  by  the  pa-
tents  effectively  claim  natural  laws  or  natural  phenomena—namely,
the correlations between thiopurine metabolite levels and the toxicity
and  efficacy  of  thiopurine  drugs—and  therefore  are  not  patentable.
The Federal Circuit reversed, finding the processes to be patent eligi-
ble under the Circuit’s “machine or transformation test.”  On remand 
from  this  Court  for  reconsideration  in  light  of  Bilski  v.  Kappos,  561 
U. S. ___, which clarified that the “machine or transformation test” is 
not  a  definitive  test  of  patent  eligibility,  id.,  at  ___–___,  the  Federal 
Circuit reaffirmed its earlier conclusion. 

Held: Prometheus’ process is not patent eligible.  Pp. 8–24.

(a) Because  the  laws  of  nature  recited  by  Prometheus’  patent 
claims—the  relationships  between  concentrations  of  certain  metabo-
lites  in  the  blood  and  the  likelihood  that  a  thiopurine  drug  dosage 
will prove ineffective or cause harm—are not themselves patentable,
the claimed processes are not patentable unless they have additional
features that provide practical assurance that the processes are genu-
ine applications of those laws rather than drafting efforts designed to
monopolize  the  correlations.    The  three  additional  steps  in  the 
claimed  processes  here  are  not  themselves  natural  laws  but  neither
are  they  sufficient  to  transform  the  nature  of  the  claims.    The  “ad-
ministering”  step  simply  identifies  a  group  of  people  who  will  be  in-
terested  in  the  correlations,  namely,  doctors  who  used  thiopurine
drugs  to  treat  patients  suffering  from  autoimmune  disorders.    Doc-
tors had been using these drugs for this purpose long before these pa-
tents  existed.    And  a  “prohibition  against  patenting  abstract  ideas 
‘cannot be circumvented by attempting to limit the use of the formula
to  a  particular  technological  environment.’ ”  Bilski,  supra,  at  ___. 
The “wherein” clauses simply tell a doctor about the relevant natural 
laws, adding, at most, a suggestion that they should consider the test 
results  when  making  their  treatment  decisions.    The  “determining”
step  tells  a  doctor  to  measure  patients’  metabolite  levels,  through 
whatever  process  the  doctor  wishes  to  use.    Because  methods  for 
making  such  determinations  were  well  known  in  the  art,  this  step 
simply  tells  doctors  to  engage  in  well-understood,  routine,  conven-
tional activity previously engaged in by scientists in the field.  Such