DUAL RUN CASSETTE FOR THE SYNTHESIS OF 18F-LABELLED COMPOUNDS
Technical Field of the Invention
The present invention concerns devices and methods for the automated
synthesis of [1 F]-labelled compounds, in particular those suitable for use as in
vivo imaging agents for positron emission tomography (PET). In particular, the
focus of the present invention is for the automated synthesis of more than one
batch of an [1 F]-labelled compound using just one disposable cassette.
Description of Related Art
Radiolabeled compounds for use as in vivo imaging agents are currently
typically prepared by means of an automated synthesis apparatus (alternatively
"radiosynthesizer"). Such automated synthesis apparatuses are commercially
available from a range of suppliers, including: GE Healthcare; CTI Inc.; Ion
Beam Applications S.A. (Chemin du Cyclotron 3, B-1 348 Louvain-La-Neuve,
Belgium); Raytest (Germany) and Bioscan (USA). The radiochemistry takes
place in a "cassette" or "cartridge" designed to fit removably and
interchangeably onto the apparatus, in such a way that mechanical movement
of moving parts of the apparatus controls the operation of the cassette.
Suitable cassettes may be provided as a kit of parts that is assembled onto the
apparatus in a number of steps, or may be provided as a single piece that is
attached in a single step, thereby reducing the risk of human error. The single
piece arrangement is generally a disposable single use cassette which
comprises all the reagents, reaction vessels and apparatus necessary to carry
out the preparation of a given batch of radiopharmaceutical.
The commercially-available GE Healthcare FASTlab™ cassette is an example
of a disposable single piece type of cassette pre-loaded with reagents
comprising a linear array of valves, each linked to a port where reagents or
vials can be attached. Each valve has a male-female joint which interfaces with
a corresponding moving arm of the automated synthesis apparatus. External
rotation of the arm thus controls the opening or closing of the valve when the
cassette is attached to the apparatus. Additional moving parts of the apparatus
are designed to clip onto syringe plunger tips, and thus raise or depress syringe
barrels. The FASTlab cassette has 25 identical 3-way valves in a linear
array, examples of which are shown in Figures 1 and 2 . Figure 1 illustrates the
commercially-available FDG Phosphate FASTlab™ cassette, and Figure 2 the
commercially-available FDG Citrate FASTlab™ cassette.
Synthesis of [1 F]fluorodeoxyglucose ([1 F]FDG) on the cassettes of Figures 1
and 2 is carried out by nucleophilic fluorination with [1 F]fluoride produced by a
1 O(p,n) 1 F reaction. The [1 F]fluoride so-produced enters the cassette at
position 6 and travels to a QMA (quaternary methyl ammonium anion
exchange) solid phase extraction (SPE) column placed at position 4 via tubing
at position 5 . The [1 F]fluoride is retained by an ion-exchange reaction and the
1 O-water is allowed to flow through the common pathway of the cassette to be
recovered at position 1. [1 F]Fluoride retained on the QMA is then eluted with
an eluent solution (acetonitrile solution of Kryptofix™ 222 and potassium
carbonate at position 2) withdrawn in the syringe at position 3 and into the
reaction vessel (connected by three tubings, one leading to each of positions 7,
8 and 25). Water is evaporated and mannose triflate precursor (from position
12) is added to the reaction vessel. Then the [1 F]-labelled mannose triflate
([1 F]fluorotetraacetylglucose, FTAG) is trapped and so separated from
[1 F]fluorides on an environmental tC1 8 SPE column at position 18 via tubing at
position 17 to undergo hydrolysis with NaOH (from the vial at position 14) to
remove acetyl protecting groups. The resulting hydrolyzed basic solution is
then neutralized in the syringe placed at position 24 with phosphoric acid in the
case of phosphate configuration (Figure 1) or hydrochloric acid present in a
citrate buffer in the case of citrate configuration (Figure 2). Potential residual
[1 F]fluoride removal takes place on an alumina SPE column at position 20 via
tubing at position 2 1 and removal of weakly hydrophilic impurities on an HLB
SPE column (for the phosphate cassette of Figure 1) or a tC1 8 SPE column (for
the citrate cassette of Figure 2) at position 22 via tubing at position 23. The
final purified solution of [1 F]FDG is transferred to a collection vial via long
tubing connected at position 19 .
2 positions on the FASTlab™ cassette are free in the case of each of the known
[1 F]FDG cassettes illustrated in Figures 1 and 2, i.e. positions 9 and 10 . Caps
are placed on the valves at these positions.
A typical [1 F]FDG production site produces minimum 2 batches of [1 F]FDG in
a day. However, because of the residual activity on the FASTlab™ cassette,
transfer line and the shadow from the waste bottle after completion of a batch, it
is impossible for safety reasons to carry out back to back runs of the abovedescribed
process on the same apparatus. This, in combination with the
relatively large size of the FASTlab™ apparatus, means that in order to produce
a second batch of [1 F]FDG in the same day using this process, it is necessary
to have a second apparatus in a second hot cell.
It would be desirable to have a means to produce more than one batch of
[1 F]FDG using the FASTlab™ on the same day and in only one hot cell. For
both of the above-described commercially-available FASTlab™ [1 F]FDG
cassettes, 23 of the total 25 positions are used. It is therefore not possible to fit
all the duplicate components for a second batch onto the same cassette.
Summary of the Invention
In one aspect the present invention provides a cassette ( 1 ) for the synthesis of
a plurality of batches of an [1 F]-labelled positron-emission tomography (PET)
tracer wherein said cassette comprises:
(i) an anion exchange column (3, 4) for each of said plurality of
batches;
a reaction vessel (5);
(iii) a vial (2) containing an aliquot of eluent for each of said plurality
of batches;
(iv) a vial (6) containing an aliquot of a precursor compound for each
of said plurality of batches;
(v) reagent vials (7, 8, 9) wherein each reagent vial contains an
aliquot of reagent for each of said plurality of batches;
(vi) optionally, a solid-phase extraction (SPE) column for deprotection
( 10) and/or one or more SPE columns for purification ( 1 1, 12);
and
(vii) means for cleaning said reaction vessel and said SPE columns.
In another aspect the present invention provides a method for the synthesis of a
plurality of batches of an [1 F]-labelled PET tracer wherein said method
comprises:
(a) trapping a first aliquot of [1 F]fluoride onto a first anion exchange
column(3);
(b) providing a first aliquot of a precursor compound in a reaction
vessel (5);
(c) passing a first aliquot of eluent through said first anion exchange
column (3) to elute said first aliquot of [1 F]fluoride into said
reaction vessel (5);
(d) heating the reaction vessel (5) for a predetermined time to obtain
crude [1 F]-labelled PET tracer;
(e) optionally deprotecting said crude [1 F]-labelled PET tracer on a
SPE column (10);
(f) optionally purifying said crude [1 F]-labelled PET tracer on one or
more SPE columns ( 1 1, 12);
(g) cleaning said reaction vessel (5) and said SPE columns (10, 11,
12);
(h) repeating steps (a)-(g) one or more times, each time using a
subsequent aliquot of [1 F]fluoride, a subsequent anion exchange
column (4) and a subsequent aliquot of an [1 F]FDG precursor
compound;
wherein said method is carried out on a single cassette ( 1 ) .
In another aspect the present invention provides a non-transitory storage
medium comprising computer readable program code, wherein execution of the
computer readable program code causes a processor to carry out the steps of
the method of the invention as defined hereinabove.
The present invention allows one synthesizer in one hot cell to produce
sequentially multiple batches of an [1 F]-labelled PET tracer. It has been
demonstrated herein that good yields are achieved for each of two sequential
[1 F]FDG batches as well as good trapping and elution of the incoming activity.
Quality control analyses of the two batches described in Example 1
hereinbelow demonstrate that each batch meets the pharmacopeia
requirements for [1 F]FDG.
Brief Description of the Figures
Figure 1 and Figure 2 illustrate examples of known cassettes for the production
of one batch per cassette of an [1 F]-labelled compound.
Figure 3 illustrates a cassette suitable for carrying out two [1 F]FDG runs on
FASTlab™.
Figure 4 illustrates the workflow for producing two [1 F]FDG batches on
FASTlab™ using a single cassette such as that illustrated in Figure 3 .
Detailed Description of the Preferred Embodiments
By the term "cassette " is meant a single-use piece of apparatus designed to fit
removably and interchangeably onto an automated synthesis apparatus, in
such a way that mechanical movement of moving parts of the synthesizer
controls the operation of the cassette from outside the cassette, i.e. externally.
The term "single-use " as used in the context of a cassette of the present
invention means that the cassette is intended to be used once prior to disposal
for the production of a plurality of batches of an [1 F]-labelled PET tracer.
Suitable cassettes comprise a linear array of valves, each linked to a port
where reagents or vials can be attached, by either needle puncture of an
inverted septum-sealed vial, or by gas-tight, marrying joints. In one
embodiment each valve is a 3-way valve. In one embodiment each valve is a
stopcock valve comprising a rotatable stopcock. Each valve has a male-female
joint which interfaces with a corresponding moving arm of the automated
synthesis apparatus. External rotation of the arm thus controls the opening or
closing of the valve when the cassette is attached to the automated synthesis
apparatus. Additional moving parts of the automated synthesis apparatus are
designed to clip onto syringe plunger tips, and thus raise or depress syringe
barrels. The cassette is versatile, typically having several positions where
reagents can be attached, and several suitable for attachment of syringe vials
of reagents or chromatography columns. The cassette always comprises a
reaction vessel, generally configured such that 3 or more ports of the cassette
are connected thereto to permit transfer of reagents or solvents from various
ports on the cassette. Cassettes need to be designed to be suitable for
radiopharmaceutical manufacture and are therefore manufactured from
materials which are of pharmaceutical grade as well as resistant to radiolysis.
In one embodiment of the present invention the single-use cassette is a
FASTlab™ cassette, i.e. one which is suitable for use with a FASTIab™
automated synthesis apparatus.
In one embodiment of the present invention the various elements of the
cassette are selectively fluidly connected. The term "selectively fluidly
connected " means that it is possible to select whether or not fluid can pass to
and/or from the feature to another feature of the invention, e.g. by use of a
suitable valve. In one embodiment of the invention a suitable valve is a 3-way
valve having three ports and means to put any two of the three associated ports
in fluid communication with each other while fluidly isolating the third port. In
another embodiment of the invention a suitable valve is a stopcock valve
comprising a rotatable stopcock. In one embodiment, the components of the
cassette are selectively fluidly connected along a common pathway. The term
"common pathway" is to be understood to be a fluid pathway to which the other
components of the system or of cassette of the present invention are selectively
fluidly connected. In one embodiment, the common pathway is a linear fluid
pathway. In one embodiment, the common pathway is made from a rigid
pharmaceutical grade polymeric material that is resistant to radiation. Nonlimiting
examples of suitable such materials include polypropylene,
polyethylene, polysulfone and Ultem®. In one embodiment, said common
pathway is made from polypropylene or polyethylene.
By the term "automated synthesis apparatus " is meant an automated module
based on the principle of unit operations as described by Satyamurthy et al
(1999 Clin Positr Imag; 2(5): 233-253). The term 'unit operations " means that
complex processes are reduced to a series of simple operations or reactions,
which can be applied to a range of materials. Such automated synthesis
apparatuses are preferred for the method of the present invention especially
when a radiopharmaceutical composition is desired. They are commercially
available from a range of suppliers (Satyamurthy et al, above), including: GE
Healthcare; CTI Inc; Ion Beam Applications S.A. (Chemin du Cyclotron 3, B-
1348 Louvain-La-Neuve, Belgium); Raytest (Germany) and Bioscan (USA).
Automated synthesis apparatuses are designed to be employed in a suitably
configured radioactive work cell, or "hot cell " , which provides suitable radiation
shielding to protect the operator from potential radiation dose, as well as
ventilation to remove chemical and/or radioactive vapours. Using a cassette
the automated synthesis apparatus has the flexibility to make a variety of
different radiopharmaceuticals with minimal risk of cross-contamination, by
simply changing the cassette. This approach also has the advantages of
simplified set-up hence reduced risk of operator error, improved GMP (good
manufacturing practice) compliance, multi-tracer capability, rapid change
between production runs, pre-run automated diagnostic checking of the
cassette and reagents, automated barcode cross-check of chemical reagents
vs the synthesis to be carried out, reagent traceability, single-use and hence no
risk of cross-contamination, tamper and abuse resistance.
The term "plurality " used herein in the context of batches of an [1 F]-labelled
PET tracer is intended to refer to more than one batch, where that more than
one batch is synthesised on one single-use cassette. In one aspect the term
plurality refers to two batches, i.e. a first batch and a second batch. The terms
"first batch" and "second batch" represent two separate consecutive syntheses
of [1 F]-labelled PET tracer produced on the same cassette, the second batch
being produced only after production of the first batch has been completed, i.e.
the product has been collected in the product collection vial. The term "batch"
is used to refer a batch of the final synthesised [1 F]-labelled PET tracer. It is
intended that the plurality of batches can be produced on the same day and
without need to open the hot cell in which the cassette and automated
synthesiser are present.
An "[1 F1-labelled PET tracer" is a chemical compound that comprises an 1 F
atom and is suitable for use as a PET tracer. Non-limiting examples of [1 F]-
labelled PET tracers include [1 F]fluorodeoxyglucose ([1 F]FDG),
[1 F]Fluoromisonidazole ([1 F]FMISO), [1 F]fluorothymidine ([1 F]FLT),
[1 F]Fluoroazomycin arabinofuranoside ([1 F]FAZA), [1 F]Fluoroethyl-choline
([1 F]FECH), [1 F]fluorocyclobutane-1 -carboxylic acid ([1 F]FACBC),
[1 F]flumanezil ([1 F]FMZ), [1 F]tyrosine, [1 F]altanaserine, 4-[ 1 F]fluoro-3-
iodobenzyl guanidine ([1 F]FIBG), e a-[1 F]fluorobenzylguanidine ([1 F]mFBG)
and [1 F]5-fluorouracil. In one embodiment of the present invention the 1 Flabelled
compound is selected from [1 F]FDG, [1 F]FMISO, [1 F]FLT and
[1 F]FACBC. In another embodiment of the present invention the 1 F-labelled
compound is [1 F]FDG.
A "reaction vessel " in the context of the present invention is a container of the
cassette of the invention where the reactants and reagents required for the
synthesis can be sent and the product(s) removed in an appropriate order. The
reaction vessel has an internal volume suitable for containing the reactants and
reagents and is made from pharmaceutical grade materials resistant to
radiation.
An "aliquot " in the context of the method of the present invention is a sufficient
quantity of a particular reagent for use in the synthesis of one batch of a PET
tracer.
A "precursor compound " is to be understood herein as a non-radioactive
derivative of a radiolabelled compound, designed so that chemical reaction with
a convenient chemical form of the detectable label occurs site-specifically in the
minimum number of steps (ideally a single step) to give the desired
radiolabelled compound. To ensure site-specific labelling a precursor
compound may have protecting groups. Such precursor compounds are
synthetic and can conveniently be obtained in good chemical purity. A number
of precursor compounds are well known to be suitable for the synthesis of [1 F]-
labelled compounds, as taught for example in Chapter 7 of "Handbook of
Radiopharmaceuticals: Radiochemistry and Applications" (2003 John Wiley &
Sons Ltd., Wench & Redvanly, Eds.).
The term "protecting group " refers to a group which inhibits or suppresses
undesirable chemical reactions, but which is designed to be sufficiently reactive
that it may be cleaved from the functional group in question to obtain the
desired product under mild enough conditions that do not modify the rest of the
molecule. Protecting groups and methods for their removal (i.e. "deprotection ")
are well known to those skilled in the art and are described in 'Protective
Groups in Organic Synthesis', Theorodora W. Greene and Peter G. M. Wuts,
(Fourth Edition, John Wiley & Sons, 2007).
The term "reagent " used herein is a term intended to refer to solvents and
reactants used in the synthesis of a particular [1 F]-labelled PET tracer.
Suitably these are stored in a reagent vial. The term "reagent vial " is taken to
mean a vial containing one of the reagents for use in the production of the [1 F]-
labelled PET tracer, sufficient for the production of the desired plurality of
batches. The term "sufficient " means a suitable amount of a reagent to ensure
that the plurality of batches can be obtained. Generally this amount is a little
more than the exact amount required. A typical reagent vial is made from a
rigid pharmaceutical grade polymer resistant to radiation. Suitable reagents
contained in said reagent vials include ethanol, acetonitrile, deprotecting agents
and buffers. In one embodiment said deprotecting agent is selected from HCI,
NaOH and H3PO4. In one embodiment said deprotecting agent is NaOH. In
one embodiment said buffer is based on a weak acid, for example selected
from citrate, phosphate, acetate and ascorbate. For example where the [1 F]-
labelled compound of the present invention is [1 F]FDG, the single-use cassette
comprises a reagent vial containing ethanol, one containing acetonitrile,
another containing NaOH and another containing a buffer based on a weak
acid selected from citrate or phosphate.
The term "solid phase extraction (SPE)" refers to the sample preparation
process by which compounds in a solution are separated from each other
based on their respective affinities for a solid (the "solid phase" , or "stationary
phase") through which the sample is passed and the solvent (the "mobile
phase" or "liquid phase") in which they are dissolved. The result is that a
compound of interest is either retained on the solid phase or in the mobile
phase. The portion that passes through the solid phase is collected or
discarded, depending on whether it contains the compound of interest. If the
portion retained on the stationary phase includes the compound of interest, it
can then be removed from the stationary phase for collection in an additional
step, in which the stationary phase is rinsed with another solution known as an
"eluent" . For the present invention SPE is suitably carried out using an "SPE
column" (also often referred to as an "SPE cartridge "), which is readily available
commercially and is typically in the form of a syringe-shaped column packed
with solid phase. Most known solid phases are based on silica that has been
bonded to a specific functional group, e.g. hydrocarbon chains of variable
length (suitable for reverse-phase SPE), quaternary ammonium or amino
groups (suitable for anion exchange), and sulfonic acid or carboxyl groups
(suitable for cation exchange).
The term "eluting " refers to passing a solution through an SPE column with the
aim to release a compound or compounds of interest that has or have been
bound to the solid phase.
The term "eluent" used hereinabove in connection with SPE generally is also
specifically used in connection with the single-use cassette of the present
invention to refer to the eluent used to elute [1 F]fluoride trapped on the anion
exchange column. [1 F]fluoride suitable for use in the synthesis of an [1 F]-
labelled compound is normally obtained as an aqueous solution from the
nuclear reaction 1 O(p,n) 1 F. In order to increase the reactivity of [1 F]fluoride
and to reduce or minimise hydroxylated by-products resulting from the
presence of water, water is typically removed from [1 F]fluoride prior to the
reaction, and fluorination reactions are carried out using anhydrous reaction
solvents (Aigbirhio et al 1995 J Fluor Chem; 70: 279-87). A further step that is
used to improve the reactivity of [1 F]fluoride for radiofluorination reactions is to
add a cationic counterion prior to the removal of water. This cationic counterion
is dissolved in an organic-aqueous solution and this solution is used as an
eluent for eluting [1 F]fluoride from an anion exchange column on which the
[1 F]fluoride has been trapped. In one embodiment said organic-aqueous
solution is an aqueous solution of acetonitrile or methanol. In one embodiment
said organic-aqueous solution is an aqueous solution of acetonitrile. Suitably,
the counterion should possess sufficient solubility within the anhydrous reaction
solvent to maintain the solubility of the [1 F]fluoride. Therefore, counterions that
are typically used include large but soft metal ions such as rubidium or
caesium, potassium complexed with a cryptand such as Kryptofix™ 222, or
tetraalkylamnnoniunn salts, wherein potassium complexed with a cryptand such
as Kryptofix™ 222, or tetraalkylamnnoniunn salts are preferred. The term
Kryptofix™ 222 (or K222) refers herein to a commercially-available preparation
of the compound 4,7,1 3,1 6,21 ,24-Hexaoxa-1 , 10-
diazabicyclo[8.8.8]hexacosane.
An "SPE column for deprotection " in the context of the present invention is an
SPE column having a solid phase on which a precursor compound having
protecting groups is retained following the [1 F]-labelling reaction in order to
remove the protecting groups and obtain the desired [1 F]-labelled PET tracer.
In one embodiment the SPE column for deprotection is a reversed-phase SPE
column as defined herein.
"Reversed-phase SPE" makes use of a nonpolar modified solid phase and a
polar mobile phase. Compounds are retained by hydrophobic interactions and
eluted using a non-polar elution solvent to disrupt the forces that bind the
compound to the solid phase. Non-limiting examples of reversed-phase SPE
columns include C 18, tC18, C8, CN, Diol, HLB, Porapak, RDX, and NH2 SPE
columns. In one embodiment of the present invention the reversed-phase SPE
column is a tC18 or a HLB SPE column. In one embodiment, said reversephase
SPE column is a HLB SPE column. In another embodiment of the
present invention the reversed-phase SPE column is a tC1 8 column. In some
embodiments of the present invention the tC18 column is an environmental
tC1 8 column, sometimes referred to as a long tC1 8 column or a tC1 8 plus
column. In one embodiment the reverse-phase SPE column used for
deprotection is an environmental tC1 8 column.
"Normal-phase SPE" makes use of a polar modified solid phase and a nonpolar
mobile phase. Compounds are retained by hydrophilic interactions and
eluted using a solvent that is more polar than the original mobile phase to
disrupt the binding mechanism. Non-limiting examples of normal-phase SPE
columns include alumina, diol and silica SPE columns. In one embodiment of
the present invention said normal-phase SPE column is an Alumina SPE
column.
"Anion exchange SPE" utilises electrostatic attraction of charged group on
compound to a charged group on the sorbent's surface and can be used for
compounds that are charged in solution. The primary retention mechanism of
the compound is based mainly on the electrostatic attraction of the charged
functional group on the compound to the charged group that is bonded to the
silica surface. A solution having a pH that neutralizes either the compound's
functional group or the functional group on the sorbent surface is used to elute
the compound of interest. A non-limiting example of an anion exchange SPE
column is a quaternary ammonium anion exchange (QMA) SPE column.
The term "means for cleaning " refers to a source of reagent selectively fluidly
connected to the component to be cleaned. The selective fluid connection
suitably comprises a valve and length of flexible tubing. Suitable reagents for
cleaning include ethanol and acetonitrile, aqueous solutions thereof, and water.
The term "cleaning " in the context of the present invention refers to the process
of passing a suitable amount of one or more reagents through a component to
be cleaned in order to render it suitable for use in preparation of a subsequent
batch of [1 F]-labelled PET tracer. In one embodiment said means for cleaning
said reaction vessel and said SPE columns comprises a source of water fluidly
connected to said reaction vessel and to said SPE columns. A suitable source
of water is water for injection. In one embodiment said source of water is a
water bag fluidly connected to said cassette. In one embodiment said means
for cleaning said reaction vessel and said SPE columns comprises a source of
acetonitrile fluidly connected to said SPE column for deprotection. In one
embodiment said means for cleaning said reaction vessel and said SPE
columns comprises a source of ethanol fluidly connected to said SPE columns
for purification. Said sources of reagents are in one embodiment present in
vials comprised in the cassette of the invention.
The term "trapping " refers to the process wherein a particular compound or
compounds binds to the solid phase of an SPE column.
The term "passing " refers to the act of allowing a reactant, reagent or reaction
solution to flow through a particular component by the selective opening of
valves.
The term "heating " herein means application of heat in order to promote a
particular chemical reaction to take place. In the context of [1 F]-labelling as
envisaged herein heat is suitably a temperature in the region of 100-1 50°C for a
short duration of around 2-1 0 minutes.
The term "purifying " or "purification " as used herein may be taken to mean a
process to obtain substantially pure [1 F]-labelled compound. The term
"substantially " refers to the complete or nearly complete extent or degree of an
action, characteristic, property, state, structure, item, or result. The term
"substantially pure" can be taken to mean completely pure [1 F]-labelled
compound, which would be ideal, but also [1 F]-labelled compound that is
sufficiently pure to be suitable for use as a PET tracer. The term "suitable for
use as a PET tracer " means that the substantially pure [1 F]-labelled compound
is suitable for intravenous administration to a mammalian subject followed by
PET imaging to obtain one or more clinically-useful images of the location
and/or distribution of the [1 F]-labelled compound. In one embodiment of the
present invention purification is carried out by means of a reverse-phase SPE
column and/or a normal-phase SPE column, each as defined hereinabove.
The term "cleaning " in the context of the present invention refers to the process
of passing a suitable amount of one or more reagents through a component to
be cleaned in order to render it suitable for use in preparation of a subsequent
batch of [1 F]-labelled PET tracer. In one embodiment, the cleaning step in the
context of the method of the present invention comprises rinsing the reaction
vessel and SPE columns with water. In another embodiment of the method of
the present invention said cleaning step comprises rinsing the SPE column with
acetonitrile prior to rinsing with water. In another embodiment of the method of
the present invention said cleaning step comprises rinsing said SPE columns
( 11, 12) with ethanol prior to rinsing with water.
In one embodiment of the method of the present invention the steps are carried
out in sequence.
An illustrative example of the present invention is the synthesis of [1 F]FDG on
the FASTIab™ (GE Healthcare). The first [1 F]FDG synthesis is similar to the
current [1 F]FDG process on FASTlab™, it uses the same amount of reagents.
At the end of the first [1 F]FDG process, the first batch is sent to a first product
collection vial. At this stage there is enough residual reagents in the different
vials for a second [1 F]FDG synthesis. The FASTlab™ stays in waiting mode
after the delivery of the first [1 F]FDG batch. From this moment the FASTlab™
is ready to receive the radioactivity from the cyclotron for a second [1 F]FDG
synthesis. Once the [1 F]fluoride solution from the cyclotron is arrives in the
conical vial of the cassette, the operator can start the second [1 F]FDG process,
which starts with the cleaning of the tC1 8 column with 1ml of acetonitrile and
the rinsing with water for injection of the purification columns. The reaction
vessel has already been washed during the first synthesis. A second QMA
column and tubing is added to the cassette to ensure a proper trapping and
elution of the [1 F]fluoride, prior to the drying step. After the elution of the
[1 F]fluoride into the reactor, the rest of the [1 F]FDG process is performed the
same way that the first [1 F]FDG synthesis. A separate outlet line is used. The
cassette allows the two [1 F]FDG bulks to have their own outlet lines,
sterilization filters and product collection vials, so the separation of the batch is
clear.
Figure 3 is a schematic drawing of a non-limiting example of a cassette of the
present invention designed for the radiosynthesis of 2 consecutive batches of
[1 F]FDG.
Brief Description of the Examples
Example 1 describes the synthesis of two batches of [1 F]FDG on one
FASTlab™ cassette.
List of Abbreviations used in the Examples
[1 F]FDG [1 F]fluorodeoxyglucose
[1 F]FTAG [1 F]fluorotetraacetylglucose
GC gas chromatography
HLB hydrophilic-lipophilic balance
IC ion chromatography
K222 4,7,1 3,1 6,21 ,24-Hexaoxa-1 , 1 0-diazabicyclo[8.8.8]hexacosane
MeCN acetonitrile
min minute(s)
NCY uncorrected yield
ppm parts per million
QMA quaternary methylammonium
SPE solid-phase extraction
Examples
Example 1: Synthesis of Two Batches of f F1FDG on One FASTlab
Cassette
The cassette configuration as illustrated in Figure 3 was used to produce two
consecutive batches of [1 F]FDG using the following method (numbers in this
method are reference numbers in Figure 3 unless stated as a "position", which
is one of positions 1-25 going from left to right on the cassette of Figure 3):
(i) 800 m I_ MeCN (from vial 7) was used to condition the tC1 8 environmental
SPE column ( 10), and 5 mL H2O was used to condition each of the HLB SPE
column ( 1 1) and the Alumina SPE column (12).
(ii) [1 F]Fluoride was obtained from the bombardment of [1 O]-H2O with a
high-energy proton beam extracted from a Cyclotron Cyclone 18/9 (IBA) and
transferred to the cassette via the conical reservoir at position 6 .
(iii) [1 F]Fluoride was trapped on the QMA column (3) and separated from
the enriched water which was collected in an external vial via a pathway
through positions 5-4-1 .
(iv) Eluent (from vial 2) was withdrawn in the syringe at position 3 and
passed through the QMA column (3) to release [1 F]fluoride and send to the
reaction vessel (5).
(v) Evaporation of the water in the reaction vessel (5) was catalysed by
adding a little quantity of 25 img/mL mannose triflate precursor (vial 6 at position
12 at 120°C.
(vi) Mannose triflate precursor (from vial 6) was withdrawn in the syringe at
position 11 and transferred to the reaction vessel (5) in position 10 where the
labelling reaction was carried out at 125°C for 2 minutes.
(vii) The resulting radiolabelling intermediate, [1 F]FTAG, was trapped and
so, separated from unreacted fluorides, on the upper side of the tC1 8
environmental column ( 10) at position 18 .
(viii) Sodium hydroxide (from vial 8) was passed through the column ( 10) to
convert the [1 F]FTAG to [1 F]FDG collected by the syringe at position 24.
(ix) Neutralization of the resulting basic solution was carried out using
phosphoric acid (from vial 9).
(x) The final product was sent to a first external collection vial (13)
connected in position 2 1 via the two purification columns ( 1 1, 12) in a row (i.e.
HLB in position 23 and Alumina in position 20).
(xi) The tC1 8 environmental was washed with acetonitrile from position 13
(vial 7), and the reactor, purification columns and tubing were rinsed with water
from the water bag connected at the spike at position 15 .
(xii) A second batch of [1 F]fluoride from the cyclotron was transferred to the
cassette as in step (ii).
(xiii) The [1 F]fluoride was trapped on a new QMA column (4) found at
position 8 and separated from the enriched water which is collected in an
external vial via a pathway through positions 7-8-1 9-1 .
(xiv) With [1 F]fluoride from the QMA (4) at position 8, steps (iv)-(ix) were
carried out as for the first batch.
(xv) The second batch of [1 F]FDG was purified via the same columns ( 1 1,
12) in position 23 (HLB) and 20 (Alumina) and then transferred to a new
external collection vial (14) connected by the tubing in position 22.
This cassette configuration has an enriched water recycling pathway on the left
side for the first batch (Figure 4 top) and on the right side for the second batch
(Figure 4 bottom) of the cassette (contamination of the manifold with enriched
water possible) with seven positions on the cassette engaged, i.e. position 6 for
the activity inlet, position 1 with the connection of enriched water vial, position 4
for the QMA 1, position 5 for tubing of QMA 1, position 7 for QMA 2 position 8
for tubing of QMA 2 and position 19 for recovery of enriched water from batch
2 .
Starting activity, final activity and residual activities were measured by a
calibrated ionization chamber VEENSTRA (VIK-202).
To determine yield, the following yield Calculations were made:
- if delta Tf = elapsed time after time at starting of the synthesis in min
- if Af = final activity in mCi
- cAf = corrected final activity in mCi regarding to starting of the
synthesis in min = Af. Exp(ln(2)*(delta Tf/1 10)) where 110 = half-life
of [1 F]fluorine in minutes
- if cAi = corrected starting activity in mCi regarding to starting of the
synthesis in mCi
- if delta Ts = duration of the synthesis
- Corrected yield (CY) = (cAf/cAi)*1 00
- Uncorrected yield (NCY) = CY*Exp(ln(2)*(-delta Ts/1 10))
The results below relating to starting activity, final activity and residual activities
were obtained with this cassette configuration:
Starting Residual Residual activity
Run Non-corrected
activity activity on in [180]-water vial
# Yield (%)
(mCi) QMA (%) (%)
1a 7,845 66.59 0.1 2 0.31
1b 8,936 72.48 0.35 0.37
2a 7,630 68.80 0.1 5 0.1 0
2b 7,678 73.98 0.1 3 0.1 8
3a 7,980 69.86 0.05 0.1 2
3b 8,007 70.54 0.41 0.07
For quality control, measurements of pH, glucose concentration, acetic acid
concentration and K222 concentration were made.
pH was measured using a Metrohm 744 pH meter.
Glucose concentration was determined by ion chromatography (IC) where the
analytical conditions were:
- Dionex IC System
- Column Dionex Carbopak PA10, 4.0*250mm @ 25°C
- Solvent KOH 10OmM @ 1mL/min
- Electrochemical detector @ 30°C
The composition of the standard for FDG used was:
- Glucose = 25 g/mL
- FDM = 50 pg/mL
- FDG = 50 pg/mL
- CIDG = 50 pg/mL
The determination of acetic acid amount was evaluated using gas
chromatography (GC) carried out on a Varian CP-3800 equipped with a CP-
8400 autosampler and the following parameters:
- Column: Macherey-Nagel Optima® 624-LB column, 30 m * 0.32 mm ID,
1.80 mhh film
- Injection: volume 1 m I_, split ratio 1:1 0, injector at 250°C
- Carrier gas: Helium 10 PSI 5 mL/min
- Temperature: 80°C from 0 to 3 min, 80 to 200 °C from 3 to 9 min at
20°C/min and finally 200°C from 9 to 10 min.
- Detector: FID at 250°C (He 20 mL/min, H2 30 mL/min and Compressed
air 260 mL/min)
- Reference used: Acetic acid solution at 500 ppm w/w (which
corresponds to a tenth of the limit, 5000ppm).
The amount of K222 in the final product was determined by spotting the sample
on a TLC plate which is impregnated by a revealing solution of iodoplatinate
(0,5 g of Chloroplatinic acid hexa-hydrated: H2PtCI6.6H2O (!highly
hygroscopic!), 9 g of potassium iodide: Kl, 200 ml_ of distilled water) and
comparing this with standard solutions of K222 1, 5, 10, 50 and 100 ppm).
Colour intensity of the obtained stains is proportional to the amount of K222
present in the solution.
The results below were obtained:

Claims
1. A cassette ( 1 ) for the synthesis of a plurality of batches of an [1 F]-
labelled positron-emission tomography (PET) tracer wherein said
cassette comprises:
(i) an anion exchange column (3, 4) for each of said plurality of
batches;
(ii) a reaction vessel (5);
(iii) a vial (2) containing an aliquot of eluent for each of said plurality
of batches;
(iv) a vial (6) containing an aliquot of a precursor compound for each
of said plurality of batches;
(v) reagent vials (7, 8, 9) wherein each reagent vial contains an
aliquot of reagent for each of said plurality of batches;
(vi) optionally, a solid-phase extraction (SPE) column for deprotection
(10) and/or one or more SPE columns for purification ( 11, 12);
and,
(vii) means for cleaning said reaction vessel and said SPE columns.
2. The cassette as defined in Claim 1 wherein said PET tracer is selected
from [1 F]fluorodeoxyglucose ([1 F]FDG), [1 F]Fluoromisonidazole
([1 F]FMISO), [1 F]fluorothymidine ([1 F]FLT), [1 F]Fluoroazomycin
arabinofuranoside ([1 F]FAZA), [1 F]Fluoroethyl-choline ([1 F]FECH),
[1 F]fluorocyclobutane-1-carboxylic acid ([1 F]FACBC), [1 F]flumanezil
([1 F]FMZ), [1 F]tyrosine, [1 F]altanaserine, 4-[ 1 F]fluoro-3-iodobenzyl
guanidine ([1 F]FIBG), e a-[1 F]fluorobenzylguanidine ([1 F]mFBG) and
[1 F]5-fluorouracil.
3. The cassette as defined in Claim 2 wherein said PET tracer is selected
from [1 F]FDG [1 F]FLT, [1 F]FMISO and [1 F]FACBC.
4. The cassette as defined in Claim 3 wherein said PET tracer is [1 F]FDG.
5. The cassette as defined in any one of Claims 1-3 wherein said anion
exchange column (3, 4) is a quaternary ammonium anion exchange
(QMA) column.
(6) The cassette as defined in any one of Claims 1-5 wherein said eluent
comprises a cationic counterion dissolved in an organic-aqueous
solution.
(7) The cassette as defined in Claim 6 wherein said cationic counterion is
selected from rubidium, caesium, potassium complexed with a cryptand,
and a tetraalkylammonium salt.
(8) The cassette as defined in Claim 7 wherein said cationic counterion is
potassium complexed with a cryptand.
(9) The cassette as defined in Claim 8 wherein said cryptand is
4,7,1 3,1 6,21 ,24-Hexaoxa-1 , 1 0-diazabicyclo[8.8.8]hexacosane (Kryptofix
2.2.2).
( 10) The cassette as defined in any one of Claims 6-9 wherein said organic
aqueous solution is an aqueous solution of acetonitrile or methanol.
( 1 1) The cassette as defined in Claim 10 wherein said organic aqueous
solution is an aqueous solution of acetonitrile.
( 12) The cassette as defined in any one of Claims 1- 1 1 wherein said SPE
column ( 10) for deprotection is a reversed-phase SPE column.
( 13) The cassette as defined in Claim 12 wherein said reversed-phase SPE
column is a C18 column.
(14) The cassette as defined in any one of Claims 1- 13 wherein said one or
more SPE columns for purification ( 11, 12) comprises a normal-phase
SPE column.
( 15) The cassette as defined in Claim 14 wherein said normal-phase SPE
column is an Alumina SPE column.
( 16) The cassette as defined in any one of Claims 1- 15 wherein said one or
more SPE columns for purification ( 11, 12) comprises a reversed-phase
SPE column.
( 17) The cassette as defined in Claim 16 wherein said reversed-phase
column is a HLB SPE column.
( 18) The cassette as defined in any one of Claims 1-17 wherein said means
for cleaning said reaction vessel and said SPE columns comprises a
source of water fluidly connected to said reaction vessel and to said SPE
columns.
( 19) The cassette as defined in Claim 18 wherein said means for cleaning
said reaction vessel and said SPE columns comprises a source of
acetonitrile fluidly connected to said SPE column for deprotection ( 10).
(20) The cassette as defined in Claim 18 or Claim 19 wherein said means for
cleaning said reaction vessel and said SPE columns comprises a source
of ethanol fluidly connected to said SPE columns for purification.
(21 ) A method for the synthesis of a plurality of batches of an [1 F]-labelled
PET tracer wherein said method comprises:
(a) trapping a first aliquot of [1 F]fluoride onto a first anion exchange
column(3);
(b) providing a first aliquot of a precursor compound in a reaction
vessel (5);
(c) passing a first aliquot of eluent through said first anion exchange
column (3) to elute said first aliquot of [1 F]fluoride into said
reaction vessel (5);
(d) heating the reaction vessel (5) for a predetermined time to obtain
crude [1 F]-labelled PET tracer;
(e) optionally deprotecting said crude [1 F]-labelled PET tracer on a
SPE column ( 10);
(f) optionally purifying said crude [1 F]-labelled PET tracer on one or
more SPE columns ( 1 1, 12);
(g) cleaning said reaction vessel (5) and said SPE columns ( 10, 11,
12);
(h) repeating steps (a)-(g) one or more times, each time using a
subsequent aliquot of [1 F]fluoride, a subsequent anion exchange
column (4) and a subsequent aliquot of an [1 F]FDG precursor
compound;
wherein said method is carried out on a single cassette ( 1 ) .
(22) The method as defined in Claim 2 1 wherein said PET tracer is selected
from [1 F]fluorodeoxyglucose ([1 F]FDG), [1 F]Fluoromisonidazole
([1 F]FMISO), [1 F]fluorothymidine ([1 F]FLT), [1 F]Fluoroazomycin
arabinofuranoside ([1 F]FAZA), [1 F]Fluoroethyl-choline ([1 F]FECH),
[1 F]fluorocyclobutane-1-carboxylic acid ([1 F]FACBC), [1 F]flumanezil
([1 F]FMZ), [1 F]tyrosine, [1 F]altanaserine, 4-[ 1 F]fluoro-3-iodobenzyl
guanidine ([1 F]FIBG), e a-[1 F]fluorobenzylguanidine ([1 F]mFBG) and
[1 F]5-fluorouracil.
(23) The method as defined in Claim 22 wherein said PET tracer is selected
from [1 F]FDG [1 F]FLT, [1 F]FMISO and [1 F]FACBC.
(24) The method as defined in Claim 23 wherein said PET tracer is [1 F]FDG.
(25) The method as defined in any one of Claims 2 1-23 wherein each of said
first anion exchange column (3) and said subsequent anion exchange
column (4) is a quaternary ammonium anion exchange (QMA) column.
(26) The method as defined in any one of Claims 2 1-25 wherein said eluent
comprises a cationic counterion dissolved in an organic-aqueous
solution.
(27) The method as defined in Claim 26 wherein said cationic counterion is
selected from rubidium, caesium, potassium complexed with a cryptand,
and a tetraalkylammonium salt.
(28) The method as defined in Claim 27 wherein said cationic counterion is
potassium complexed with a cryptand.
(29) The method as defined in Claim 28 wherein said cryptand is
4,7,1 3,1 6,21 ,24-Hexaoxa-1 , 1 0-diazabicyclo[8.8.8]hexacosane (Kryptofix
2.2.2).
The method as defined in any one of Claims 26-29 wherein said organic
aqueous solution is an aqueous solution of acetonitrile or methanol.
The method as defined in Claim 30 wherein said organic aqueous
solution is an aqueous solution of acetonitrile.
32. The method as defined in any one of Claims 2 1-31 wherein said SPE
column for deprotecting (10) is a reversed-phase SPE column.
33. The method as defined in Claim 32 wherein said reversed-phase SPE
column is a C18 column.
34. The method as defined in any one of Claims 2 1-33 wherein said one or
more SPE columns for purifying ( 1 1, 12) comprises a normal-phase SPE
column.
35. The method as defined in Claim 34 wherein said normal-phase SPE
column is an Alumina SPE column.
36. The method as defined in any one of Claims 2 1-35 wherein said one or
more SPE columns for purifying ( 1 1, 12) comprises a reversed-phase
SPE column.
37. The method as defined in Claim 36 wherein said reversed-phase column
is a HLB SPE column.
38. The method as defined in any one of Claims 2 1-37 wherein said cleaning
step comprises rinsing said reaction vessel (5) and said SPE columns
( 10, 11, 12) with water.
39. The method as defined in Claim 38 wherein said cleaning step
comprises rinsing said SPE column ( 10) with acetonitrile prior to rinsing
with water.
40. The method as defined in either Claim 38 or Clam 39 wherein said
cleaning step comprises rinsing said SPE columns ( 1 1, 12) with ethanol
prior to rinsing with water.
41. A non-transitory storage medium comprising computer readable program
code, wherein execution of the computer readable program code causes
a processor to carry out the steps as defined in any one of claims 2 1-40.