March
14­
15,
2006
FIFRA
Scientific
Advisory
Panel
Regarding
Scientific
Issues
Associated
with
MIR604
Modified
Cry3A
Protein
Bt
Corn
Human
Health
and
Environmental
Assessments
 
Questions
to
the
Panel
MIR604
Environmental
Assessment
1.
The
weight
of
evidence
from
the
reviewed
data
indicates
that
there
will
not
be
a
hazard
to
wildlife
from
the
commercialization
of
Event
MIR604
corn.
Although
the
mCry3A
protein
expressed
by
Event
MIR604
corn
is
known
to
affect
only
coleopteran
insect
species,
EPA
assessed
the
potential
risks,
to
a
wide
variety
of
non­
target
organisms
(
i.
e.
mammals,
birds,
fish,
invertebrates
and
plants),
that
could
potentially
result
from
exposure
to
this
Bt
protein.
The
emphasis
of
this
non­
target
risk
assessment,
however,
was
on
invertebrate
species
that
dominate
corn
agroecosystems.
The
Agency
also
evaluated
a
soil
fate
study
that
was
intended
to
provide
information
on
the
persistence
and
rate
of
degradation
of
mCry3A
protein
in
the
soil
environment.
After
reviewing
data
submitted
in
support
of
the
Event
MIR604
Bt
corn
registration,
EPA
concluded
that
aquatic
and
terrestrial
wildlife,
including
soil
organisms,
were
not
likely
to
be
adversely
affected
and
that
this
Bt
corn
product
is
not
likely
to
threaten
the
longterm
survival
of
any
non­
target
wildlife
populations.

The
Panel
is
requested
to
comment
on
the
Agency's
analysis
of
the
currently
available
data
on
the
potential
impacts
of
Event
MIR604
corn
on
non­
target
species.

MIR604
Human
Health
and
Characterization
(
1)
Previously
submitted
studies
for
Event
MIR604
demonstrated
the
equivalence
of
the
plantand
bacterial­
produced
test
substances
by
showing
similar
molecular
weights,
purity
of
90.3%,
a
lack
of
post­
translational
glycosylation
of
mCry3A
from
either
source,
and
comparable
toxicities
toward
western
corn
rootworm
(
WCRW).
However,
two
forms
of
mCry3A
(
designated
as
mCry3A­
sf
and
mCry3A­
lf)
were
found
in
the
bacterial­
produced
test
material
(
MCRY3A­
0102).
The
molecular
weights
of
the
short
and
long
form
of
mCry3A
were
67.5
kDa
and
69.1
kDa,
respectively,
determined
via
SDS­
PAGE
and
MALDI­
TOF
Mass
spectrometry.
The
lesser
of
the
two
components,
with
the
lower
molecular
weight,
corresponded
to
the
intended
mCry3A
protein
with
598
amino
acids.
The
other
component
contained
the
same
598
amino
acids
as
the
first
component
but
also
contained
an
additional
16
amino
acids
at
the
N 
terminal
end
of
the
protein.
Both
mCry3A
forms
were
insecticidally
active
against
WCRW.
On
this
basis,
and
taking
into
account
the
high
degree
of
structural
homology
(
97.4%
amino
acid
identity),
the
two
forms
of
mCry3A
in
test
material
MCRY3A­
0102
were
considered
to
be
equivalent.

Please
comment
on
the
Agency's
conclusion
that
the
mCry3A
proteins
from
corn
event
MIR604
and
from
recombinant
E.
coli
are
substantially
the
same
for
the
purpose
of
the
Agency's
risk
assessment;
and
that
the
equivalence
is
confirmed
for
the
two
forms
of
the
bacterial­
produced
mCry3A
test
material
(
MCRY3A­
0102).

(
2)
Previously
submitted
studies
demonstrated
the
lack
of
toxicity
of
the
mCry3A
protein
following
acute
oral
high­
dose
exposure
to
mice,
rapid
degradation
of
mCry3A
upon
exposure
to
simulated
mammalian
gastric
fluid,
and
the
lack
of
significant
amino
acid
sequence
homology
of
2
the
mCry3A
protein
to
proteins
known
to
be
mammalian
toxins
or
human
allergens.
Moreover,
little
to
no
human
dietary
exposure
to
mCry3A
protein
is
expected
to
occur
via
transformed
corn.
Therefore,
dietary
exposure
to
mCry3A
is
not
anticipated
to
pose
any
dietary
risk
to
the
U.
S.
population.

Please
comment
on
the
Agency's
conclusions
regarding
the
lack
of
mammalian
toxicity
and
allergenicity
of
mCry3A.
