FIELD OF THE INVENTION

The present invention relates to a triazolo[4,5-d]pyrimidine derivative for use in prognosis and/or diagnosis in-vivo of a bacterial infection in a host mammal, particularly a deep-seated bacterial infection. The present invention also relates to a method of imaging said bacterial infection and to the use of triazolo[4,5- d]pyrimidine derivative in prognosis and/or diagnosis in-vitro of a bacterial infection.

INTRODUCTION Bacterial infection is a major cause of morbidity and mortality, particularly when there is a deep-seated infection.

Deep-seated infections are difficult to diagnose from other causes of inflammation. Current practice relies on biopsy, blood, urine sample analysis or radiological technics such as for example magnetic resonance imaging (MRI), X- Ray, ultrasound (US), X-ray computerized tomography (CT) and the like that allow the infection to be localized and detect morphological changes related to the infection, the host reaction or both. Unfortunately such morphological changes may not be different from inflammation or cancer tumors. Moreover these morphological changes may not be detectable in the early stages of an infection, and remain unspecific when they are present.

Deep-seated infection may also been identified using a tracer labeled with a radioelement and is then called a radiomarker. The radiomarker also called radiotracer can be detected by nuclear imaging techniques such as on single photon Emission Computer Tomography (SPECT) or positron emission tomography (PET). Examples of radiotracers are ¹⁸ F-fluorodeoxyglucose PET, ⁶⁷ Ga-citrate SPECT or radiolabeled leukocyte SPECT but they are not specific to bacterial infection and cannot distinguish infection from sterile inflammation or cancer. There is therefore an urgent need in the art for a new tracer for use in prognosis or diagnosis of bacterial infection, particularly deep-seated infection in a host mammal. There is a need for a tracerthat would be bacteria specific and sensitive but also non-toxic, affordable, widely available and easily and rapidly prepared.

SUMMARY OF THE INVENTION

We have surprisingly found that triazolo[4,5-d]pyrimidine derivatives or a composition thereof can be used as a tracer in the prognosis and/or diagnosis of bacterial infection in a host mammal. Triazolo[4,5-d]pyrimidine derivatives have the advantage to rapidly and non-invasively target early infection and therefore to discriminate between infection and sterile inflammation or cancer. The triazolo[4,5-d]pyrimidine derivatives have also the advantage to diagnose or prognose a large spectrum of bacteria belonging to Gram-positive or Gram negative species.

The triazolo[4,5-d]pyrimidine derivatives can be absorbed by the bacterial cell and can therefore be used as a tracer for in-vivo or in-vitro prognosis and/or diagnosis of bacterial infection.

DETAILLED DESCRIPTION In one aspect, the invention provides a triazolo[4,5-d]pyrimidine derivative of formula (I) for use in prognosis and/or diagnosis in-vivo of bacterial infection in a host mammal.

In another aspect the invention provides the use of triazolo[4,5-d]pyrimidine derivative of formula (I) in in-vitro prognosis and/or diagnosis of bacterial infection.

The term "bacterial infection" refers for example to pneumonia, septicemia, endocarditis, osteomyelitis, meningitis, urinary tract, skin, and soft tissue infections, but also to cardiac-implant-related infective endocarditis, to prosthetic valve endocarditis or periprosthetic joint infection that occurs in 1 or 2 percent of joint replacement surgeries.

The bacterial infection may be caused for example by one or more of S. aureus, S. epidermidis, E. faecalis, E. faecium, methicillin-resistant S. aureus (MRSA), methicillin-resistant S. epidermidis (MRSE), glycopeptide intermediate S. aureus (GISA), Coagulase-negative staphylococci (CoNS), Vancomycin-resistant enterococci (VRE), beta-hemolytic Streptococcus agalactiae (Group B Streptococcus, GBS) or other streptococci that belong to Gram-Positive bacteria or by one or more of Acinetobacter baumannil, Pseudomonas aeruginosa, carbapenem-resistant Pseudomonas aeruginosa, Enterobacteriaceae, and 3 ^rd generation cephalosporin-resistant Enterobacteriaceae (Klebsiella pneumonia, Escherichia coli, Enterobacter spp, Serratia spp, Proteus spp, Providentia spp, and Morganella spp) that belong to Gram-Negative bacteria.

The term diagnosis as used herein refers to identifying a bacterial infection in the host mammal.

The term prognosis as used herein refers to determining intensity of a bacterial infection in the host mammal at any stage, particularly at an early stage.

The term host mammal as used herein refers preferably to a human but also to an animal. In a particular embodiment the triazolo[4,5-d]pyrimidine derivative of formula (I) comprises a detectable marker.

In another particular embodiment the triazolo[4,5-d]pyrimidine derivative of formula (I) is bound to a detectable marker.

The term "detectable marker" as used herein refers to any type of tag, which is detectable and thus allows the determination of the presence of the triazolo[4,5- d]pyrimidine derivative:

- either directly for example as a radiolabeled triazolo[4,5-d]pyrimidine derivative wherein for example one atom of the derivative has been replaced by one radioisotope marker selected from the group ² H, ³ H, ¹³ F- ¹⁸ F, ¹⁹ F, ¹¹ C, ¹³ C, ¹⁴ C, ⁷⁵ Br, ⁷⁶ Br, ¹²⁰ l , ¹²³ l, ¹²⁴ l, ¹²⁵ l, ¹³¹ l, ¹⁵ 0, ¹³ N, ⁷⁸ Br and the like; preferably one halogen atom is replaced by one radioisotope selected from ¹³ F, ¹⁸ F, ¹⁹ F, ⁷⁵ Br, ⁷⁶ Br, ¹²⁰ l , ¹²³ l, ¹²⁴ l ' ¹²⁵ l, ¹³¹ l, ⁷⁸ Br and the like;

- or directly as a radiolabeled triazolo[4,5-d]pyrimidine derivative wherein the derivative may be complexed with a radiomarker such as "Tc , ⁶³ Ga, ⁶⁷ Ga, ¹¹¹ IN and the like;

- or indirectly for example via a transporter comprising a signal amplifier. The triazolo[4,5-d]pyrimidine derivative is then chemically bound to the transporter and the derivative may be considered as a sensor of bacterial infection.

The term of "signal amplifier" as used herein refers to any agent that would amplify a return on signal at a bacterial infected tissue or implant.

The signal amplifier may for example enhance reflection, refraction, scattering, transmission or attenuation of an ultrasound wave in a US imaging tomography at a bacterial infected tissue or implant; or enhance a resonance or different hydrogen alignment in reaction to a radiofrequency pulse emitted by a magnetic field in magnetic resonance imaging at a bacterial infected tissue or implant; or enhance a proportion of X-ray absorbed or scattered at the bacterial infected tissue or implant in X-Ray computed tomography (CT).

The term "transporter" as used herein refers for example to a body which acts as a signal amplifier orjnto which the signal amplifier may be incorporated, such as a micelle, microsphere, liposome, polymeric particle, nanosphere, nanosuspension, nano emulsion, nanocapsule and the like.

The triazolo[4,5-d]pyrimidine derivative that comprises a detectable marker via a radioisotope or is bound to a detectable marker either via a complex with the detectable marker or via a transporter comprising the detectable marker is also called hereafter a detectable triazolo[4,5-d]pyrimidine derivative. In a particular embodiment, the detectable marker is a signal amplifier that is indirectly associated to the triazolo[4,5-d]pyrimidine derivative to be used in a detection method that will depend on the nature of the marker.

The triazolo[4,5-d]pyrimidine derivative may be associated with a signal amplifier such as for example gadolinium (e.g. ⁶⁴ Gd) chelates that are ferromagnetic compounds able to enhance magnetic resonance imaging. Gd chelates can be an ionic (e.g. meglumine or sodium salt) or non-ionic signal amplifier. Iron oxide may also be used as signal amplifier for MRI. For example, Manganese doped superparamagnetic iron oxide nanoparticle may be used to form ultrasensitive MRI contrasts agents. Such Mn-SPIO nanoparticles are then self-assembled into clusters inside micelles that will be detectable by MRI. Other signal amplifiers for MRI are for example a manganese chelate, iron platinum (FePt) alloy nanocrystal, manganese ferrite (MnO-Fe ₂ O3 ) nanocrystal, or other metal-doped iron oxide nanoparticle such as Co-Fe ₂ O ₃ and Ni0-Fe ₂ O ₃ . The triazolo[4,5-d]pyrimidine derivative may also be associated with a signal amplifier such as a microbubble to be used in contrast-enhanced ultrasound imaging (US).

The triazolo[4,5-d]pyrimidine derivative may also be associated with a signal amplifier also called contrast agent containing Iodine or Barium for X-Ray computed tomography (CT). The contrast agent should increase the absolute CT attenuation difference between the target bacterial infection and the surrounding tissue. Examples of a suitable contrast agent for X-Ray computer tomography are iohexol (Omnipaque™, GE Healthcare); iopromide (Ultravist™, Bayer Healthcare); iodixanol (Visipaque™, GE Healthcare); ioxaglate (Hexabrix™, Mallinckrodt Imaging); iothalamate (Cysto-Conray II™, Mallinckrodt Imaging); and iopamidol (Isovue™, Bracco Imaging).

In another particular embodiment, the detectable marker is an isotope which allows the use of the triazolo[4,5-d]pyrimidine derivative as a tracer in a detection method that will depend on the nature of the marker. Accordingly, the triazolo[4,5-d]pyrimidine derivative comprising at least one detectable isotope can be detected by using beta, gamma, positron or x-ray imaging wherein, for example beta or gamma irradiation is provided by the relevant isotope and is detected at an appropriate wavelength.

The triazolo[4,5-d]pyrimidine derivative comprising at least one detectable isotope may be used for example with magnetic resonance spectroscopy (MRS) or imaging (MRI), X-Ray computed tomography (CT), positron emission tomography (PET) and single emission computed tomography (SPECT) . The detectable triazolo[4,5-d]pyrimidine derivative may be detected through isotope ¹⁹ F or ¹³ C or a combination thereof for MRS/MRI by well-known organic chemistry techniques.

Other detectable triazolo[4,5-d]pyrimidine derivatives may also be detected by isotope selected from ¹⁹ F, ¹¹ C, ⁷⁵ Br, ⁷⁶ Br or ¹²⁰ l or a combination thereof for PET techniques.

Other detectable triazolo[4,5-d]pyrimidine derivatives may also be detected by an isotope selected from ¹⁸ F or ¹¹ C or a combination thereof for PET in-vivo imaging and may be prepared as described in Bengt Langstrom in Acta Chemica Scandinavia, 53:651-669 (1999) or the journal of Nuclear Medicine 58(7): 1094- 1099(2017) A.M.J.Paans in https://cds.cern.ch/record/1005065/files/p363.pdf

Other detectable triazolo[4,5-d]pyrimidine derivatives may be detected by ¹²³ l and ¹³¹ l for SPECT imaging and may be prepared as described by Kulkarni, lnt.J.Rad.Appl.& Inst (partB)18:647(1991).

Other detectable triazolo[4,5-d]pyrimidine derivatives may also be detected with technetium-99m(" ^m Tc), ¹²³ l and ¹¹¹ IN for SPECT imaging. The triazolo[4,5- d]pyrimidine derivative that is radiolabeled accordingly may be easily prepared by a man skilled in the art by techniques well known in the art and described by Zhuang in Nuclear Medicine & Biology 26(2):217-24 (1999) or by Kulkarni in Nuclear Medicine & Biology 18(6):647-654 (1991) or in technical reports 466 published by the International Atomic Energy Agency in 2008.

The triazolo[4,5-d]pyrimidine derivative wherein one or more atoms are replaced by a radionuclide or isotope may be used as a radiotracer to test cells, tissues or fluids from a host mammal and identify the presence and importance of a bacterial infection in the host for example at the surface of a prosthetic valve.

The term "host mammal", as used herein refers preferably to a human, but also to an animal.

The term triazolo[4,5-d]pyrimidine derivative refers to a compound of the following formula (I)

wherein R ¹ is C3-5 alkyl optionally substituted by one or more halogen atoms; R ² is a phenyl group, optionally substituted by one or more halogen atoms; R ³ and R ⁴ are each hydroxyl; R is XOH, where X is CH2, OCH2CH2, or a bond; or a pharmaceutical acceptable salt or solvate thereof, or a solvate thereof or a solvate of such a salt provided that when X is CH2 or a bond, R ¹ is not propyl; when X is CH2 and R ¹ is CH2CH2CF3, butyl or pentyl, the phenyl group at R ² must be substituted by fluorine; when X is OCH2CH2 and R ¹ is propyl, the phenyl group at R ² must be substituted by fluorine.

Alkyl groups whether alone or as part of another group are straight chained and fully saturated. In some embodiments, R ¹ may represent a C3-5 alkyl optionally substituted by one or more fluorine atoms. Preferably R ¹ is 3,3,3-trifluoropropyl, butyl or propyl.

In some embodiments, R ² may represent phenyl or phenyl substituted by one or more halogen atoms. Preferably R ² is phenyl substituted by one or more fluorine atoms. Most preferably R ² is 4-fluorophenyl or 3,4-difluorophenyl.

In some embodiments, R may represent XOH, where X is CH2, OCH2CH2, or a bond; preferably R is OH or OCH2CH2OH.

Most preferred triazolo[4,5-d]pyrimidine derivatives are compounds of formula (I) where R ² represents 4-fluorophenyl or 3,4-difluorophenyl and/or where R represents OCH2 CH2OH.

Triazolo[4,5-d]pyrimidine derivatives are well-known compounds. They may be obtained according to the method described in US6,525,060 which is described at column 3 line 26 to column 8 line 14 which is incorporated herein by reference.

Prefered triazolo[4,5-d]pyrimidine derivatives are derivatives where R represents OH or OCH2CH2OH and/or R ² represents 4-fluorophenyl or 3,4- difluorophenyl.

Most preferred triazolo[4,5-d]pyrimidine derivatives are: (lR-(la, 2a, 3b(1R*, 2*),5b))-3-(7-((2-(3,4-difluorophenyl)cyclopropyl)amino)-5-( (3,3,3- trifluoropropyl)thio)-3/-/-l,2,3-triazolo[4,5-d]pyrimidin-3- yl)-5- (hydroxy)cyclopentane-l,2-diol;

(lS-(la, 2a, 3b(1R*, 2*),5b))-3-(7-((2-(3,4-difluorophenyl)cyclopropyl)amino)-5- (propylthio)-3/-/-l,2,3-triazolo[4,5-d] pyrimidin-3-yl)-5-(2- hydroxyethoxy)cyclopentane-l,2-diol;

(lS,2S,3R,5S)-3-[7-[(lR,2S)-2-(3,4-difluorophenyl)cyclopr opylamino]-5-

(propylthio)-3/-/-[l,2,3]triazolo[4,5-d]pyrimidin-3-yl]-5 -(2-hydroxyethoxy)-l,2- cyclopentanediol; (lS,2S,3R,5S)-3-[7-[(lR,2S)-2-(4-fluorophenyl)cyclopropylami no]-5-(propylthio)-

3/-/-[l,2,3]triazolo[4,5-d]pyrimidin-3-yl]-5-(2-hydroxyet hoxy)-l,2- cyclopentanediol) or a pharmaceutical acceptable salt or solvate thereof, or a solvate thereof or a solvate of such a salt.

The most preferred triazolo[4,5-d]pyrimidine derivative to be used in prognosis and/or diagnosis is (lS,2S,3R,5S)-3-[7-[(lR,2S)-2-(3,4- difluorophenyl)cyclopropylamino]-5-(propylthio)-3/-/-[l,2,3] triazolo[4,5- d]pyrimidin-3-yl]-5-(2-hydroxyethoxy)-l,2-cyclopentanediol) as defined in formula (II) (and also called Triafluocyl hereafter):

or a pharmaceutical acceptable salt or solvate thereof, or a solvate thereof or a solvate of such a salt.

Another most preferred triazolo[4,5-d]pyrimidine derivative to be used in prognosis and/or diagnosis is (lS,2R,3S,4R)-4-[7-[[(lR,2S)-2-(3,4- difluorophenyl)cyclopropyl]amino]-5-(propylthio)-3/-/-l,2,3- triazolo[4,5- d]pyrimidin-3-yl]-l,2,3-cyclopentanetriol as defined in formula (III) (and also called Fluometacyl):

or a pharmaceutical acceptable salt or solvate thereof, or a solvate thereof or a solvate of such a salt.

In some embodiment, one atom of the triazolo[4,5-d ]pyrimidine derivative of formula (I) is selected from the group consisting of ³ H, ¹³ F - ¹⁸ F, ¹⁹ F, ^{1 1} C, ¹³ C, ¹⁴ C,

⁷⁵ Br, ⁷⁶ Br, ¹²⁰ Ί, ¹²³ l, ¹²⁴ l, ¹²⁵ l, ¹³¹ l, ¹⁵ O, ¹³ N, ⁷⁸ Br.

In some embodiment, one halogen substituent of the triazolo[4,5-d]pyrimidine derivative of formula (I) may be ¹⁸ F or ¹²³ l.

In some embodiment, one halogen substituent of the Triazolo(4,5-d)pyrimidine derivative of formula (I) may be ¹⁸ F. In some embodiment, one halogen substituent of R ² in the triazolo[4,5- d]pyrimidine derivative of formula (I) may be ¹⁸ F.

In a further aspect, the present invention provides a pharmaceutical composition comprising the triazolo[4,5-d]pyrimidine derivative of formula (I) thereof and a pharmaceutically acceptable additive, for use in diagnosing and/or prognosing in-vivo bacterial infection in a host mammal;

In a still further aspect, the present invention provides the use of a pharmaceutical composition comprising the triazolo[4,5-d]pyrimidine derivative of formula (I) thereof and a pharmaceutically acceptable additive, in in-vitro prognosis and/or diagnosis of bacterial infection. The pharmaceutical composition may be a dry powder or a liquid composition having physiological compatibility. In some embodiments, the pharmaceutically acceptable additive may be an auxiliary substance, preservative, solvent and/or viscosity modulating agent.

By solvent, is meant any suitable physiologically compatible solvent such as for example water, saline or any other physiological solution, ethanol, glycerol, oil such as vegetable oil or a mixture thereof. By viscosity modulating agent is meant for example sugar polymer such as carboxymethylcellulose, polysaccharide such as saccharine, and the like.

In some embodiments, the triazolo[4,5-d]pyrimidine derivative or pharmaceutical composition thereof comprising a detectable marker and used as radiotracer may be administered locally or systemically by inhalation, ingestion or injection at a dose that is relevant to a selected imaging device. The administration may be orally, parenterally, topically, rectally, nasally, vaginally.

By parenterally is meant subcutaneously, intravenously, intraarterially, intraperitoneally, intrathecally, intraventricularly and the like.

Dose levels of administration to the host mammal depend upon its age, weight, general health, sex, time of administration, form of administration and the like and would be well known by the one skilled in the art. They may vary between 0.001mg/kg/day and 10,000mg/kg/day according to the imaging technique selected.

In other embodiments, the triazolo[4,5-d]pyrimidine derivative or pharmaceutical composition thereof comprising a detectable marker and used as radiotracer may be added to a sample obtained from the host mammal, in an effective amount that is relevant to a selected imaging device.

By sample obtained from the host mammal is meant any sampling of cells, tissues, or body fluids, in which bacterial infection can be determined. Examples of such samples include blood, lymph, urine, biopsies, or bone marrow.

Sample may also refers to an implant, the surface on which bacterial infection can be determined.

By implant, one means all implantable foreign material for clinical use in host mammals such as for prosthetic joints, pacemakers, implantable cardioverter- defibrillators , intravascular or urinary catheters, stent including coronary stent, prosthetic heart valves, intraocular lens, dental implants and the like.

In still another aspect, the present invention also provides a method of imaging a bacterial infection in a host mammal which method comprises a step of administering a detectable amount of triazolo[4,5-d]pyrimidine derivative to the host mammal. In a further aspect, the present invention also provides the use of triazolo[4,5- d]pyrimidine derivatives in an in-vitro method of imaging a bacterial infection.

In some embodiments, the method of imaging may comprise the following steps:

(a) administering to the host mammal a detectable amount of triazolo[4,5- d]pyrimidine derivative of formula (1) comprising a detectable marker as described above or of the pharmaceutical composition; or adding to a sample obtained from the host mammal a detectable amount of triazolo[4,5- d]pyrimidine derivative of formula (1) comprising a detectable marker as described above or of the pharmaceutical composition ; and

(b) tracking said detectable triazolo[4,5-d]pyrimidine derivative by an imaging technique such as for example Magnetic Resonance imaging (MRI), single-photon emission computer tomography (SPECT), positron emission tomography imaging (PET), positron emission tomography with computer tomography imaging, positron emission tomography with magnetic resonance imaging; and displaying an image of said bacterial infection. In a particular embodiment the imaging technique is positron emission tomography PET or Single Photon Emission Computed Tomography (SPECT).

The use of a detectable triazolo[4,5-d]pyrimidine derivatives of formula (I) or composition thereof is useful for displaying bacterial infection but also to monitor treatment of bacterial infection in a host. Indeed, with a better knowledge of the bacterial infection severity, it is possible to better select an appropriate treatment and to reduce a potential development of bacterial resistance.

If a detectable triazolo[4,5-d]pyrimidine derivatives of formula (I) or composition thereof is administered or added to a sample obtained from the host before treatment of the infection (e.g. by administration of an antibiotic), it will be possible to administer the right effective amount of antibiotic to the host.

In still another aspect, the present invention also provides a tracer, preferably a positron emission tomography (PET) tracer or a single-photon emission computer tomography (SPECT) tracer comprising a triazolo[4,5-d]pyrimidine derivative of formula (I) for prognosis and/or diagnosis in-vivo of bacterial infection, or for in-vitro prognosis and/or diagnosis of bacterial infection.

In some embodiments, the tracer may be an imaging tracer. In some embodiments, the tracer may comprise the pharmaceutical composition.

The invention will now be illustrated with reference to the following Figures of the accompanying drawings which are not intended to limit the scope of the claimed invention:

Figure 1 shows a reaction scheme illustrating the synthesis of a labelling precursor detailed in step (i) of Example 1; and

Figure 2 shows a reaction scheme illustrating the synthesis of further labelling precursors detailed in step (ii) of Example 1.

The present invention will be illustrated in more detail in the following examples, which are not intended to limit the scope of the claimed invention in any way.

Example 1: preparation of ¹⁸ F-Triafluocyl as triazolo[4,5-d]pyrimidine derivative comprising the detectable marker ¹⁸ F. i) synthesis of a first labelling precursor illustrated in figure 1 : tert-butyl (3-

((3aS,4R ,6S,6aR )-6-(2-((tert-butoxycarbonyl)oxy)ethoxy)-2,2- dimethyltetrahydro-3a/-/-cyclopenta[d][l,3]dioxol-4-yl)-5-(p ropylthio)-3/-/- [l,2,3]triazolo[4,5-d]pyrimidin-7-yl)((lR , 25)-2-(3-fluoro-4- (trimethylstannyl)phenyl)cyclopropyl)carbamate (5).

In a first step (i), 2-(((3aR ,4S,6R ,6aS)-6-((5-Amino-6-chloro-2-

(propylthio)pyrimidin-4-yl)amino)-2,2-dimethyltetrahydro- 3a/-/- cyclopenta[d][l,3]dioxol-4-yl)oxy)etanol (1) is obtained by reaction of 2- (((3aR ,4S,6R ,6aS)-6-amino-2,2-dimethyltetrahydro-3a/-/- cyclopenta[d][l,3]dioxol-4-yl)oxy)ethanol with 4,6-dichloro-2-

(propylthio)pyrimidin-5-amine and is carried out in acetonitrile in a sealed vessel at 110 ^° C.

The next step (ii) consists in a ring closure reaction of the intermediate 1 by means of a diazotization reaction with sodium nitrite in acetic acid at a temperature from 5°C to 20°C (step ii) leading to 2-(((3aR ,4S,6R ,6aS)-6-(7-chloro- 5-(propylthio)-3/-/-[l,2,3]triazolo[4,5-d] pyrimidin-3-yl)-2,2-dimethyltetrahydro- 3a/-/-cyclopenta[d][l,3]dioxol-4-yl)oxy)etanol (2).

In step iii, 2-(((3aR ,4S,6R ,6aS)-6-(7-(((lR ,2S)-2-(4-bromo-3- fluorophenyl)cyclopropyl)amino)-5-(propylthio)-3/-/-[l,2,3]t riazolo[4,5- d]pyrimidin-3-yl)-2,2-dimethyltetrahydro-3a/-/-cyclopenta[d] [l,3]dioxol-4- yl)oxy)ethanol (3) is obtained by nucleophilic substitution of the chlorine atom of intermediate 2 by 2-(4-bromo-3-fluorophenyl)cyclopropanamine hydrochloride at a temperature of for example 20°C.

The sensitive amino and hydroxyl functions of 3 are then protected by a tert- butoxycarbonyl group (step iv) after reaction of 3 with di-tert-butyl dicarbonate in tetrahydrofuran at a temperature of for example 20°C to give tert-butyl ((lR ,2S)-2-(4-bromo-3-fluorophenyl)cyclopropyl)(3-((3aS,4R ,6S,6aR )-6-(2-((tert- butoxycarbonyl)oxy)ethoxy)-2,2-dimethyltetrahydro-3a/-/- cyclopenta[d][l,3]dioxol-4-yl)-5-(propylthio)-3/-/-[l,2,3]tr iazolo[4,5-d]pyrimidin- 7-yl)carbamate (4).

The labelling position is activated in a next step (step v) by nucleophilic substitution of the bromine atom of (4) by a trimethylstannyl group using hexamethyldistannane in the presence of tetrakis(triphenylphosphine)palladium(0) as a catalyst to give tert-butyl (3- ((3aS,4R ,6S,6aR )-6-(2-((te/T-butoxycarbonyl)oxy)ethoxy)-2,2- dimethyltetrahydro-3a/-/-cyclopenta[d][l,3]dioxol-4-yl)-5-(p ropylthio)-3/-/- [l,2,3]triazolo[4,5-d]pyrimidin-7-yl)((1R, 2S)-2-(3-fluoro-4-

(trimethylstannyl)phenyl)cyclopropyl)carbamate (5).

The intermediate products (1) to (5) illustrated in figure 1 are hereafter called

Intermediate (1) to intermediate (5)

Intermediate (1) is obtained as follows: a mixture of 4,6-dichloro-2- (propylthio)pyrimidin-5-amine (1.0 g, 4.2 mmol), 2-(((3aR ,4S,6R ,6aS)-6-amino- 2,2-dimethyltetrahydro-3a/-/-cyclopenta[d][l,3]dioxol-4-yl)o xy)ethanol (1.17 g, 5.4 mmol) and triethylamine (0.6 mL, 4.2 mmol) in acetonitrile (10 mL) is introduced in a sealed vessel and heated overnight at 110°C. After evaporation of the solvent, the residue is purified by silica gel column chromatography.

Yield: 77%.

Melting point: 112-114°C.

Intermediate (2) is obtained as follows: to a solution of (1) (1.0 g, 2.4 mmol) in acetic acid (10 mL) cooled on an ice bath is added NaNO ₂ (225 mg, 3.2 mmol). The resulting mixture is allowed to reach room temperature within 1 hour and water (40 mL) is then added. The resulting mixture is extracted with ethyl acetate (3 x 50 mL) and the combined organic layers are dried over MgSO ₄ and evaporated to give an oily residue.

Yield: 94%.

Melting point: oil.

Intermediate (3) is obtained by a mixing (2) (0.5 g, 1.16 mmol), 2-(4-bromo-3- fluorophenyl)cyclopropanamine hydrochloride (0.3 g, 1.16 mmol) with triethylamine (0.21 mL, 1.45 mmol) in acetonitrile (10 mL) and the resulting mixture is left to react at room temperature for 2 hours. After evaporation of the solvent, the residue is purified by silica gel column chromatography.

Yield: 98%.

Melting point: 122-124°C.

Intermediate (4) is obtained by mixing (3) (0.62 g, 1.0 mmol), di-tert-butyl dicarbonate (1 g, 4.6 mmol), with 4-(dimethylamino)pyridine (30 mg, cat.) in tetrahydrofuran (10 mL) and the resulting mixture is left to react overnight at room temperature. After evaporation of the solvent, the residue is purified by silica gel column chromatography.

Yield: 56%

Melting point: 156-158°C.

Precursor 1: tert-butyl (3-((3aS,4R, 6S,6aR )-6-(2-((tert- butoxycarbonyl)oxy)ethoxy)-2,2-dimethyltetrahydro-3a/-/- cyclopenta[d ][1,3]dioxol-4-yl)-5-(propylthio)-3/-/-[1,2,3]triazolo[4,5-d ]pyrimidin- 7-yl)((1R ,2S)-2-(3-fluoro-4-(trimethylstannyl)phenyl)cyclopropyl)carb amate (5), is obtained by mixing (4) (0.41 g, 0.5 mmol), hexamethyldistannane (0.49 g, 1.5 mmol), with tetrakis(triphenylphosphine)palladium(0) (10 mg, cat.) in dry toluene (5 mL) and introduced in a sealed vessel and heated overnight at 100°C under nitrogen. After cooling, ethyl acetate (50 mL) is added and the insoluble is filtered off. The filtrate is evaporated to dryness and the resulting residue is purified by silica gel column chromatography.

Yield: 65%

Melting point : 60-62 °C.

ii) Synthesis of further labelling precursors as illustrated in figure 2

Other precursors can be synthesized from (5) using hydroxy(tosyloxy)iodobenzene (step vi) to give the corresponding iodonium tosylate (6), or using iodine (step vii) to give (7) followed by addition of Meldrum's acid (step viii) to give the iodonium ylide (8).

Labelling precursor (6) is obtained by adding hydroxy(tosyloxy)iodobenzene (0.13 g, 0.33 mmol) to a solution of (5) (0.27 g, 0.3 mmol) in dichloromethane (5 mL) at 0°C. The resulting mixture is left to react at room temperature for 1 hour. After evaporation of the solvent, the residue is purified by silica gel column chromatography.

Yield: 72%.

Melting point: 92-95°C.

Labelling precursor tert-butyl (3-((3aS,4R, 6S,6aR )-6-(2-((tert- butoxycarbonyl)oxy)ethoxy)-2,2-dimethyltetrahydro-3aH- cyclopenta[d][l,3]dioxol-4-yl)-5-(propylthio)-3H-[l,2,3]tria zolo[4,5- d]pyrimidin-7-yl)((lR, 2S)-2-(3-fluoro-4-iodophenyl)cyclopropyl)carbamate (7) is obtained by adding Iodine (0.15 g, 0.6 mmol) to a solution of (5) (0.27 g, 0.3 mmol) in dichloromethane (5 mL). The resulting mixture is left to react at room temperature for 1 hour. After evaporation of the solvent, the residue is purified by silica gel column chromatography.

Yield: 61%.

Melting point: 151-153°C.

iii) conversion of labelling precursors 6 and 8 into ¹⁸ F-Triafluocyl.

the iodonium group of both labelling precursor 6 and 8 are converted into ¹⁸ F- Triafluocyl according to described processes in the literature:

Regarding precursor 6 in Copper-Mediated Radiofluorination of Arylstannanes with [18F]KF; by Makaravage, Katarina J.; Brooks, Allen F.; Mossine, Andrew V.; Sanford, Melanie S.; Scott, Peter J. H.(from Organic Letters (2016), 18(20), 5440- 5443).

Regarding precursor 8 in Spirocyclic hypervalent iodine(lll)-mediated radiofluorination of non-activated and hindered aromatics; by Rotstein, Benjamin H.; Stephenson, Nickeisha A.; Vasdev, Neil; Liang, Steven H.

(From Nature Communications (2014), 5, 4365).

Example 2: comparison of in vitro ¹⁸ F-Triafluocyl and ¹⁸ F-FDG uptake assay

In order to assess the selective uptake of ¹⁸ F-Triafluocyl into bacteria and its utility for the specific diagnosis of bacterial infections, we performed an in vitro assay in which we compared the uptake of ¹⁸ F-triafluocyl and ¹⁸ F-FDG into bacteria.

For this purpose, S. epidermidis bacteria were incubated with ¹⁸ F-FDG or ¹⁸ F- Triafluocyl, and the relative radioactivity associated with the bacterial cells was determined as follows. S. epidermidis bacteria were grown overnight in tryptic soy broth (TSB) at 37°C, with shaking at 250 rpm. The overnight culture was diluted to OD6oo 0.1 and incubated until mid-exponential phase was reached. 1x10 ⁸ CFU were resuspended in 1 ml of a cell culture medium RPMI 1640 provided by Sigma- Aldrich (R7638).

Bacteria and control without bacteria were incubated with 2 MBq ¹⁸ F-FDG or 2 MBq ¹⁸ F-Triafluocyl prepared as described in Example 1 for 1 h at 37°C. Bacteria were harvested by centrifugation (600x g, 5 min) and washed three times by successive centrifugations. After washing, the cells were transferred into scintillation vials. The supernatants were also collected in scintillation vials. Bacteria and supernatants were counted by gamma counter ( 2470 Wizard ^2™ (Perkin Elmer))

Results were obtained as counts per min. Results were normalised for controls (no bacteria) and by calculating the percentage of activity in the cells-containing scintillation vials compared to the total counts (cells and supernatants combined).

After incubation with the bacteria, we found that the relative activity of ¹⁸ F- triafluocyl associated with the bacterial cells was 1.5 to 2-fold higher than the activity of ¹⁸ F-FDG.

Example 3: use of in-vitro ¹⁸ F-Triafluocyl for prognosis and/or diagnosis of bacterial infection from a blood sample obtained from a host mammal (human). Since it is well-known in the art that Triafluocyl (also called Ticagrelor), binds the platelet P2Y12 receptor reversibly , and platelets accumulate at sites of bacterial infection (as described in Hamzeh-Cognasse H, Damien P, Chabert A, Pozzetto B, Cognasse F, Garraud O. Platelets and infections - complex interactions with bacteria. Front Immunol. 2015;6:82. Published 2015 Feb 26. doi:10.3389/fimmu.2015.00082), we also compared radiotracer uptake into human platelets in the presence or in the absence of bacteria.

Preparation of human washed platelets: a Blood sample was collected from healthy volunteers on Acid Citrate Dextrose (ACD: 93 mM Na3-citrate, 7 mM citric acid, 14 mM dextrose, pH 6.0) containing lU/ml apyrase in a volume ratio of ACD to blood of 1:6. Blood was centrifuged for 5 s at 800 x g followed by 5 min at 100 x g to obtain platelet rich plasma (PRP). PRP was diluted 3-fold in ACD containing lU/ml apyrase ((Apyrase from potatoes, Grade I (A6132 Sigma-Aldrich)) and centrifuged at 1000 x g to obtain a platelet pellet. The platelet pellet was resuspended at a concentration of 3 x 10 ⁸ ml ^-1 in Tyrode's buffer (137 mM NaCI, 12 mM NaHCOs, 2 mM KCI, 0,34 mM Na ₂ HP0 ₄ , 1 mM MgCI ₂ , 5.5 mM glucose, 5 mM Hepes, 0.35% Bovine Serum Albumine from Sigma Aldrich A3294) and Hepes refers to 4-(2-Hydroxyethyl)piperazine-l-ethanesulfonic acid, N-(2- Hydroxyethyl)piperazine-N'-(2-ethanesulfonic acid)

(H4034, Sigma-Aldrich).

Bacteria, platelets and controls without bacteria were incubated with 2 MBq ¹⁸ F- FDG or 2 MBq ¹⁸ F-Triafluocyl for 1 h at 37°C. Bacteria and platelets were harvested by centrifugation (1000 x g, 10 min) and washed three times by successive centrifugations (1000 x g for 10 min). Supernatants were collected in scintillation vials. After washing, the cells were transferred into scintillation vials. Cells and supernatants were counted by gamma counter (2470 Wizard ^2™ (Perkin Elmer)) Results were obtained as counts per min. Results were normalised for controls (no cells) and by calculating the percentage of activity in the cell containing scintillation vials compared with the total counts (cells and supernatants combined). Results confirm ¹⁸ F-triafluocyl uptake into platelets, while ¹⁸ F-FDG was not transported into these cells. Moreover, after incubation with platelet suspensions containing bacteria, we found that the relative activity of ¹⁸ F- triafluocyl associated with the cell mixture was about 10-fold higher than the activity of ¹⁸ F-FDG.

Example 4: Selective use of ¹⁸ F- Triafluocyl for prognosis and/or diagnosis of bacterial infection over mammalian cells obtained from a human host S. epidermidis bacteria were grown overnight in tryptic soy broth (TSB) at 37°C, with shaking at 250 rpm. The overnight culture was diluted to OD6oo 0.1 and incubated until mid-exponential phase was reached. lxlO ⁸ CFU were resuspended in 1 ml RPMI 1640.

THP1 (ATCC ^® TIB-202 ^TM) and HL60 (ATCC ^® CCL-240 ^™} cell lines were grown in RPMI 1640 tissue culture medium supplemented with L-glutamine, 10% foetal calf serum and 1% penicillin/streptomycin at 37°C and 5% CO2. HT29 cell line ( ATCC ^® HTB-38) was grown in McCoy's 5A medium and 10% foetal bovine serum at 37°C and 5% CO2. Non-adherent cell lines (HL60, THP1; 1 x 10 ⁶ cells ml ^-1 ) were harvested, washed and resuspended in 1 ml tissue culture medium. The adherent cells HT29 were maintained in 6-well plates at 80% confluence.

Bacteria, cell lines and controls without cells were incubated with 2 MBq ¹⁸ F-FDG or 2 MBq ¹⁸ F-ticagrelor for 1 h at 37°C. Bacteria and non-adherent cells were harvested by centrifugation (600x g, 5 min) and washed three times by successive centrifugations. Cell supernatants were collected in scintillation vials. After washing, the cells were transferred into scintillation vials. Adherent cells were washed three times with fresh medium (McCoy's 5A medium plus 10% foetal bovine serum). Supernatants were collected into scintillation vials. Adherent cells were detached by trypsin treatment and placed into scintillation vials. The scintillation vials for cells and supernatants were counted by gamma counter. Results were obtained as counts per min. Results were normalised for controls (no cells) and by calculating the percentage of activity in the cell containing scintillation vials compared with the total counts (cells and supernatant combined).

Results confirm ¹⁸ F-Triafluocyl uptake into bacteria while no uptake was observed into any of the mammalian cells, leukocytic (THP1 and HL-60) or tumor (HT29) cells. In contrast, we observed an uptake of ¹⁸ F-FDG into the three lines of mammalian cells. ¹⁸ F-Triafluocyl can thus be used for the specific in vitro detection of bacterial infection in a sample of human origin.

Example 5: Protocol of in-vivo prognosis and/or diagnosis

A protocol of test for in-vivo prognosis and/or diagnosis of bacterial infection in a patient has been established and adapted to the use of ¹⁸ F-Triafluocyl as radiotracer.

The protocol hereafter has been developed for PET-CT imaging but may easily be extrapolated by the man skilled in the art, to other imaging technics such as SPECT.

The protocol is based on the same image acquisition for each patient:

After a minimum of 6h fasting, 3.7 MBq ¹⁸ F-Triafluocyl /Kg body weight (mean activity/patient: 277 MBq, range: 202-394 MBq) is injected through a peripheral vein catheter. The patient is placed into a quiet room and instructed not to move. Approximately lh (mean: 69 min, range: 54-100 min) after injection of 18F- Triafluocyl, static whole-body examination is performed with a PET-CT scanner. Volumetric low-dose axial CT images are acquired. Then, emission raw data images are recorded at each bed and reconstructed as overlapping coronal slices after CT attenuation model-based scatter correction (convolution subtraction) and normalization correction. The protocol can be applied to patients suffering from a bacterial infection allowing a deep-seated location in all tissues of the patient's body such as muscle, epithelial, connective and nervous, whereas patients suffering from cancer or sterile inflammation are less detectable by the present protocol.