Triglyceride analogs

Abstract

The present invention relates to triglyceride analogs labeled with radioisotopes, or salts thereof, for positron emission tomography (PET) or single-photon emission computed tomography (SPECT) imaging. In addition, the present invention relates to compositions comprising the radiolabeled triglyceride analog, or a salt thereof, and methods for preparing the same. Further, methods of imaging using the radiolabeled triglyceride analog and uses of the radiolabeled triglyceride analog are disclosed herein. The invention also relates to an intermediate triglyceride analog for synthesis of the radiolabeled triglyceride analog.

Description

[0001] Triglyceride analogs

[0002] The present invention relates to triglyceride analogs labeled with radioisotopes, or salts thereof, for positron emission tomography (PET) or single-photon emission computed tomography (SPECT) imaging. In addition, the present invention relates to compositions comprising the radiolabeled triglyceride analog, or a salt thereof, and methods for preparing the same. Further, methods of imaging using the radiolabeled triglyceride analog and uses of the radiolabeled triglyceride analog are disclosed herein. The invention also relates to an intermediate triglyceride analog for synthesis of the radiolabeled triglyceride analog.

[0003] Background

[0004] Brown adipose tissue (BAT) is a highly active metabolic tissue found in most mammals and is involved in thermogenesis. Brown adipocytes take up glucose and fatty acids (FAs) from the circulation to fuel thermogenesis via mitochondrial uncoupling protein 1 (UCPI)-mediated pathways.

[0005] Individuals with detectable BAT activity have lower plasma triglycerides (TG), and lower prevalence of type 2 diabetes (T2D) and cardiovascular disease (CVD). Activation of BAT in metabolic dysfunction-prone rodents by cold or p3-adrenergic receptor (P3-AR) agonism attenuates diet-induced adiposity, insulin resistance, and atherosclerosis. BAT activation is proposed to be a potential therapeutic strategy to prevent and / or treat cardiometabolic diseases including T2D and atherosclerotic CVD.

[0006] A triglyceride is an ester derived from glycerol and three fatty acids. Triglycerides are the main constituents of fat in humans and other vertebrates, as well as vegetable fat. Triglycerides store fatty acids that are derived from intestine or liver. Fatty acids from adipocytes are transported to the liver as bound to albumin. Many types of (naturally occurring) triglycerides exist, comprising different variations of aliphatic chains, e.g. in length, branching, and saturation of carbon bonds.

[0007] Visualization of BAT and quantification of BAT activity is typically performed via [18F]fluorodeoxyglucose ([18F]FDG) positron emission tomography (PET)-computed tomography (CT). Alternatively, [18F]fluoro-6-thia-heptadecanoic acid (FTHA) as a FA tracer is used to trace activated BAT. T2D and aging largely reduce the cold-induced uptake of [18F]FDG by BAT, but not that of [18F]FTHA (Blondin et al., 15). Hence, [18F]FDG is inappropriate to assess metabolic activity of cold-activated BAT especially in aged people and individuals with obesity or T2D, who would benefit most from BAT-activating strategies. [18F]FTHA is also less suitable as it does not take advantage of high lipoprotein lipase (LPL) expression by active BAT to facilitate uptake of triglyceride-derived fatty acids, and is bound to albumin within the circulation, resulting in the delivery of the vast majority of [18F]FTHA to the liver (lozzo et al., 16).

[0008] Thus, there is a need for a novel radiolabeled triglyceride-based compound for PET or SPECT imaging with improved properties for tracing activated BAT. Brief description of the invention

[0009] The present invention discloses a novel radiolabeled triglyceride analog for PET or SPECT imaging. Subsequent incorporation of the radiolabeled triglyceride analog in the form of glycerol tri[18F]oleate ([18F]TO) into TG-rich lipoprotein (TRL)-like particles showed that [18F]TO outperforms the standard compound in the art, [18F]FDG, for example in tracing activated BAT. Similar suitable radiolabeled triglyceride analogs may be synthesized. Hence, the compounds of the invention are ideally suited for PET or SPECT imaging and are useful in the study of relevant diseases and treatment thereof, and for the development of drugs for e.g. activating BAT.

[0010] The object of the present invention is therefore to provide a radiolabeled triglyceride analog or salt thereof represented by formula (I): wherein each of R1, R2, and R3are independently linear or branched C1.40 alkyl, linear or branched C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of any one of R1, R2, and R3is substituted by a group comprising a radioisotope suitable for positron emission tomography (PET) or single-photon emission computed tomography (SPECT).

[0011] In another aspect, the present invention provides a radiolabeled triglyceride analog or salt thereof represented by formula (la): wherein at least one of X1, X2, and X3is a group comprising a radioisotope suitable for PET or SPECT, and the other of X1, X2, and X3is methyl.

[0012] In yet another aspect, the present invention provides a radiolabeled triglyceride analog or salt thereof represented by formula (lb):

[0013] It is another object of the invention to provide a triglyceride analog or salt thereof represented by formula (II): wherein each of R4, R5, and R6are independently linear or branched C1.40 alkyl, linear or branched

[0014] C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen of R4, R5, and R6is substituted by a leaving group.

[0015] In another aspect, the invention provides a labeled triglyceride analog or salt thereof represented by formula (IV): wherein each of R7, R8, and R9are independently linear or branched C1-40 alkyl, linear or branched

[0016] C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of any one of R7, R8, and R9 is substituted by a group comprising a stable isotope.

[0017] It is another object of the invention to provide a composition comprising lipid particles, the lipid particles comprising: the radiolabeled triglyceride analog according to the invention or the labeled triglyceride analog according to the invention, and optionally one or more additional lipid species. In another aspect, the invention provides a pharmaceutical composition comprising an effective amount of the radiolabeled triglyceride analog according to the invention, the labeled triglyceride analog according to the invention, or the composition according to the invention; the pharmaceutical composition further comprising a pharmaceutically acceptable carrier, and / or diluent, and / or excipient.

[0018] It is another object of the invention to provide a method of synthesizing the radiolabeled triglyceride analog of formula (I), the method comprising: a. providing the triglyceride analog of formula (II) comprising a leaving group; b. allowing an [18F] comprising species to react with the triglyceride analog, thereby removing the leaving group and providing the radiolabeled triglyceride analog of formula (I).

[0019] It is another object of the invention to provide a method of imaging at least a part of the body of a subject comprising using the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention, optionally wherein the imaging is in vivo.

[0020] In another aspect, the invention provides a method of diagnosis comprising the method of imaging according to the invention.

[0021] In another aspect, the invention provides a use of the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention as an imaging agent.

[0022] In another aspect, the invention provides a use of the radiolabeled triglyceride analog according to the invention or the triglyceride analog according to the invention for manufacturing a composition for imaging.

[0023] In another aspect, the invention provides a use of the radiolabeled triglyceride analog according to the invention, the labeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention in detection, diagnosis, prognosis, prediction of outcome, surgery, staging, treatment, therapy, radiotherapy, monitoring of treatment, monitoring of disease progression, or monitoring therapy.

[0024] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps.

[0025] Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0026] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. The patent, scientific, and technical literature referred to herein establish knowledge that was available to those skilled in the art at the time of filing. The entire disclosures of the issued patents, published, and pending patent applications, and other publications that are cited herein are hereby incorporated by reference to the same extent as if each was specifically and individually indicated to be incorporated by reference. In the case of any inconsistencies, the present disclosure will prevail.

[0027] Various aspects of the invention are described in further detail below.

[0028] Brief description of the figures

[0029] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which:

[0030] Figure 1 shows that incorporation of glycerol tri[19F]oleate ([19F]TO) does not affect size, kinetics and biodistribution of TRL-like particles in mice.

[0031] Figure 2 shows time-dependent biodistribution of the PET tracer glycerol tri[18F]oleate incorporated into lipoprotein-like particles in mice.

[0032] Figure 3 shows PET-CT images of representative mice injected with glycerol tri[18F]oleate-labeled lipoprotein-like particles or [18F]fluorodeoxyglucose.

[0033] Figure 4 shows PET-CT imaging of glycerol tri[18F]oleate incorporated into lipoprotein-like particles vs. [18F]fluorodeoxyglucose in mice.

[0034] Figure 5 shows that incorporation of glycerol tri[19F]oleate does not affect blood clearance of triglyceride-rich lipoprotein-like particles in mice.

[0035] Figure 6 shows time-dependent biodistribution of the PET tracer glycerol tri[18F]oleate incorporated into triglyceride-rich lipoprotein-like particles in mice.

[0036] Figure 7 shows PET-CT imaging of glycerol tri[18F]oleate incorporated into triglyceride-rich lipoprotein-like particles vs. [18F]fluorodeoxyglucose in mice.

[0037] Figure 8 shows regions-of-interest (ROI) of organs and tissues.

[0038] Figure 9 shows a scheme of the synthesis of glycerol tri[18F]oleate (19).

[0039] Figure 10 shows a scheme of the synthesis of glycerol tri[19F]oleate (16).

[0040] Figure 11 shows an analytical HPLC chromatogram of glycerol tri[18F]oleate (19) co-injected with glycerol tri[19F]oleate (16).

[0041] Figure 12 shows the detectability of brown adipose tissue (BAT) with [18F]TO PET-CT in diet-induced obese mice.

[0042] Figure 13 compares the detectability of browning in white adipose tissue of diet-induced obese mice with [18F]TO vs [18F]FDG in PET-CT.

[0043] Detailed description of the invention

[0044] The present invention relates to a radiolabeled triglyceride analog or salt thereof represented by formula (I): wherein each of R1, R2, and R3are independently linear or branched C1.40 alkyl, linear or branched C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of any one of R1, R2, and R3is substituted by a group comprising a radioisotope suitable for positron emission tomography (PET) or single-photon emission computed tomography (SPECT).

[0045] The radiolabeled triglyceride analog or salt thereof preferably mimics biological characteristics of naturally occurring triglycerides. Biological characteristics may for example include, but are not limited to interaction with cells, interaction with other molecules (in vivo), such as lipids, peptides, proteins, and nucleic acids, metabolism, cellular transport, in vivo distribution, cellular distribution, etc. The carbon chains of each of R1, R2, and R3may therefore suitably mimic biological characteristics of naturally occurring fatty acids, in particular the aliphatic chains of naturally occurring fatty acids.

[0046] Suitably, each of R1, R2, and R3may be independently linear or branched C5-35 alkyl, linear or branched C5-35 alkenyl, or linear or branched C5-35 alkynyl. Suitably, each of R1, R2, and R3may be independently linear or branched C7-33 alkyl, linear or branched C7-33 alkenyl, or linear or branched C7-33 alkynyl. Suitably, each of R1, R2, and R3may be independently linear or branched Cg. 29 alkyl, linear or branched C9.29 alkenyl, or linear or branched C9.29 alkynyl. Suitably, each of R1, R2, and R3may be independently linear or branched C11.25 alkyl, linear or branched C11.25 alkenyl, or linear or branched Ci 1-25 alkynyl. Suitably, each of R1, R2, and R3may be independently linear or branched C11.21 alkyl, linear or branched C11.21 alkenyl, or linear or branched C11.21 alkynyl. Suitably, each of R1, R2, and R3may be independently linear or branched C13-21 alkyl, linear or branched C13- 21 alkenyl, or linear or branched C13-21 alkynyl. Suitably, each of R1, R2, and R3may be independently linear or branched C15-19 alkyl, linear or branched C15-19 alkenyl, or linear or branched C15-19 alkynyl. Suitably, each of R1, R2, and R3may be independently linear or branched C15-40 alkyl, linear or branched C15-40 alkenyl, or linear or branched C15-40 alkynyl.

[0047] Suitably, each of R1, R2, and R3may be linear.

[0048] Suitably, each of R1, R2, and R3independently may comprise the aliphatic chain of a fatty acid.

[0049] Suitably, each of R1, R2, and R3may comprise the same number of carbon atoms. Suitably, each of R1and R2may comprise the same number of carbon atoms. Suitably, each of R1and R3may comprise the same number of carbon atoms. Suitably, each of R2, and R3may comprise the same number of carbon atoms. Suitably, each of R1, R2, and R3may comprise a different number of carbon atoms. Suitably, each of R1and R2may comprise a different number of carbon atoms. Suitably, each of R1and R3may comprise a different number of carbon atoms. Suitably, each of R2and R3may comprise a different number of carbon atoms.

[0050] Suitably, each of R1, R2, and R3may be independently linear C1.40 alkyl or linear C2-40 alkenyl. Suitably, the C2-40 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C2-40 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C9.29 alkyl or linear C9.29 alkenyl. Suitably, the C9.29 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C9.29 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C13-19 alkyl or linear C13-19 alkenyl. Suitably, the C13-19 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C13-19 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C15-40 alkyl or linear C15-40 alkenyl. Suitably, the C15-40 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C15-40 alkenyl may have one, two, three, four, or five C=C bonds.

[0051] Suitably, the branched C1.40 alkyl, C2-40 alkenyl, or C2-4o alkynyl may be respectively mono- or polymethyl C1.40 alkyl, mono- or polymethyl C2-40 alkenyl, or mono- or polymethyl C2-40 alkynyl. Suitably, the branched C5-35 alkyl, C5-35 alkenyl, or Cs-35 alkynyl may be respectively mono- or polymethyl C5-35 alkyl, mono- or polymethyl C5-35 alkenyl, or mono- or polymethyl C5-35 alkynyl. Suitably, the branched C7-33 alkyl, C7-33 alkenyl, or C7-33 alkynyl may be respectively mono- or polymethyl C7-33 alkyl, mono- or polymethyl C7-33 alkenyl, or mono- or polymethyl C7-33 alkynyl. Suitably, the branched C9.29 alkyl, C9.29 alkenyl, or Cg.29 alkynyl may be respectively mono- or polymethyl C9.29 alkyl, mono- or polymethyl C9.29 alkenyl, or mono- or polymethyl C9.29 alkynyl. Suitably, the branched C11.25 alkyl, C11.25 alkenyl, or C11.25 alkynyl may be respectively mono- or polymethyl C11.25 alkyl, mono- or polymethyl C11.25 alkenyl, or mono- or polymethyl C11.25 alkynyl. Suitably, the branched C11.21 alkyl, C11.21 alkenyl, or Cn.21 alkynyl may be respectively mono- or polymethyl C11.21 alkyl, mono- or polymethyl C11.21 alkenyl, or mono- or polymethyl C11.21 alkynyl. Suitably, the branched C13-21 alkyl, C13-21 alkenyl, or Ci3-2i alkynyl may be respectively mono- or polymethyl C13-21 alkyl, mono- or polymethyl C13-21 alkenyl, or mono- or polymethyl C13-21 alkynyl. Suitably, the branched C15-19 alkyl, C15-19 alkenyl, or C15-19 alkynyl may be respectively mono- or polymethyl C15-19 alkyl, mono- or polymethyl C15-19 alkenyl, or mono- or polymethyl C15-19 alkynyl. Suitably, the branched C15-40 alkyl, C15-40 alkenyl, or C15-40 alkynyl may be respectively mono- or polymethyl C15-40 alkyl, mono- or polymethyl C15-40 alkenyl, or mono- or polymethyl C15-40 alkynyl.

[0052] Preferably, at least one hydrogen atom of any one of R1, R2, and R3may be substituted by a group comprising a radioisotope suitable for PET. Suitably, one hydrogen atom of any one of R1, R2, and R3may be substituted by a group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET.

[0053] Suitably, at least one hydrogen atom of R1may be substituted by the group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET. Suitably, at least one hydrogen atom of R2may be substituted by the group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET. Suitably, at least one hydrogen atom of R3may be substituted by the group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET.

[0054] Suitably, at least one hydrogen atom of the terminal carbon atom of any one of R1, R2, and R3may be substituted by the group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET. Suitably, at least one hydrogen atom of the terminal carbon atom of R1may be substituted by the group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET. Suitably, at least one hydrogen atom of the terminal carbon atom of R2may be substituted by the group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET. Suitably, at least one hydrogen atom of the terminal carbon atom of R3may be substituted by the group comprising a radioisotope suitable for PET or SPECT, preferably a radioisotope suitable for PET.

[0055] Suitably, the at least one hydrogen atom may be one hydrogen atom.

[0056] The invention also relates to a radiolabeled triglyceride analog or salt thereof represented by formula (la): wherein at least one of X1, X2, and X3is a group comprising a radioisotope, and the other of X1, X2, and X3is methyl.

[0057] Suitably, X1may be a group comprising a radioisotope and X2and X3may be methyl.

[0058] Suitably, X2may be a group comprising a radioisotope and X1and X3may be methyl. Suitably, X3may be a group comprising a radioisotope and X1and X2may be methyl.

[0059] The invention also relates to a radiolabeled triglyceride analog or salt thereof represented by formula (lb):

[0060] The radioisotope of the radiolabeled triglyceride analog or salt thereof is suitable for positron emission tomography (PET) or single-photon emission computed tomography (SPECT).

[0061] Preferably, the radioisotope may be a positron-emitting radioisotope. Suitably, the radioisotope may be a gamma-emitting radioisotope.

[0062] The skilled person can suitably select an appropriate radioisotope that can be used for PET or SPECT, and is suited for incorporation into a triglyceride, e.g. suited for labeling the triglyceride analogs of the present invention as set out in the following section “Intermediate compounds”.

[0063] Suitably, the radioisotope may be a radioisotope of carbon, fluorine, or iodine. Preferably, the radioisotope may be a radioisotope of fluorine or iodine. More preferably, the radioisotope may be a radioisotope of fluorine.

[0064] Suitably, the radioisotope may be11C,18F,123l, or125l. Suitably, the radioisotope may be123l,125l, or18F. Preferably, the radioisotope may be123l or18F. More preferably, the radioisotope may be

[0065] 18p

[0066] Intermediate compounds

[0067] The invention also pertains to an intermediate compound for synthesis of the radiolabeled triglyceride analog according to the invention. Accordingly, the invention also relates to a triglyceride analog or salt thereof represented by formula (II): wherein each of R4, R5, and R6are independently linear or branched C1-40 alkyl, linear or branched

[0068] C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of R4, R5, and R6is substituted by a leaving group. Suitably, each of R4, R5, and R6may be independently linear or branched C5-35 alkyl, linear or branched C5-35 alkenyl, or linear or branched C5-35 alkynyl. Suitably, each of R4, R5, and R6may be independently linear or branched C7-33 alkyl, linear or branched C7-33 alkenyl, or linear or branched C7-33 alkynyl. Suitably, each of R4, R5, and R6may be independently linear or branched Cg. 29 alkyl, linear or branched C9.29 alkenyl, or linear or branched C9.29 alkynyl. Suitably, each of R4, R5, and R6may be independently linear or branched C11.25 alkyl, linear or branched C11.25 alkenyl, or linear or branched C11.25 alkynyl. Suitably, each of R4, R5, and R6may be independently linear or branched C11.21 alkyl, linear or branched C11.21 alkenyl, or linear or branched C11.21 alkynyl. Suitably, each of R4, R5, and R6may be independently linear or branched C13-21 alkyl, linear or branched C13- 21 alkenyl, or linear or branched C13-21 alkynyl. Suitably, each of R4, R5, and R6may be independently linear or branched C15-19 alkyl, linear or branched C15-19 alkenyl, or linear or branched C15-19 alkynyl. Suitably, each of R4, R5, and R6may be independently linear or branched C15-40 alkyl, linear or branched C15-40 alkenyl, or linear or branched C15-40 alkynyl.

[0069] Suitably, each of R4, R5, and R6may be linear.

[0070] Suitably, each of R4, R5, and R6independently may comprise the aliphatic chain of a fatty acid.

[0071] Suitably, each of R4, R5, and R6may comprise the same number of carbon atoms. Suitably, each of R4and R5may comprise the same number of carbon atoms. Suitably, each of R4and R6may comprise the same number of carbon atoms. Suitably, each of R5and R6may comprise the same number of carbon atoms. Suitably, each of R4, R5, and R6may comprise a different number of carbon atoms. Suitably, each of R4and R5may comprise a different number of carbon atoms. Suitably, each of R4and R6may comprise a different number of carbon atoms. Suitably, each of R5and R6may comprise a different number of carbon atoms.

[0072] Suitably, each of R1, R2, and R3may be independently linear C1.40 alkyl or linear C2-40 alkenyl. Suitably, the C2-40 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C2-40 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C9.29 alkyl or linear C9.29 alkenyl. Suitably, the C9.29 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C9.29 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C13-19 alkyl or linear C13-19 alkenyl. Suitably, the C13-19 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C13-19 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C15-40 alkyl or linear C15-40 alkenyl. Suitably, the C15-40 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C15-40 alkenyl may have one, two, three, four, or five C=C bonds.

[0073] Suitably, the branched C1.40 alkyl, C2-40 alkenyl, or C2-4o alkynyl may be respectively mono- or polymethyl C1.40 alkyl, mono- or polymethyl C2-40 alkenyl, or mono- or polymethyl C2-40 alkynyl. Suitably, the branched C5-35 alkyl, C5-35 alkenyl, or Cs-35 alkynyl may be respectively mono- or polymethyl C5-35 alkyl, mono- or polymethyl C5-35 alkenyl, or mono- or polymethyl C5-35 alkynyl. Suitably, the branched C7-33 alkyl, C7-33 alkenyl, or C7-33 alkynyl may be respectively mono- or polymethyl C7-33 alkyl, mono- or polymethyl C7-33 alkenyl, or mono- or polymethyl C7-33 alkynyl. Suitably, the branched C9.29 alkyl, C9.29 alkenyl, or Cg.29 alkynyl may be respectively mono- or polymethyl C9.29 alkyl, mono- or polymethyl C9.29 alkenyl, or mono- or polymethyl C9.29 alkynyl. Suitably, the branched C11.25 alkyl, C11.25 alkenyl, or C11.25 alkynyl may be respectively mono- or polymethyl C11.25 alkyl, mono- or polymethyl C11.25 alkenyl, or mono- or polymethyl C11.25 alkynyl. Suitably, the branched C11.21 alkyl, C11.21 alkenyl, or Cn.21 alkynyl may be respectively mono- or polymethyl C11.21 alkyl, mono- or polymethyl C11.21 alkenyl, or mono- or polymethyl C11.21 alkynyl. Suitably, the branched C13-21 alkyl, C13-21 alkenyl, or Ci3-2i alkynyl may be respectively mono- or polymethyl C13-21 alkyl, mono- or polymethyl C13-21 alkenyl, or mono- or polymethyl C13-21 alkynyl. Suitably, the branched C15-19 alkyl, C15-19 alkenyl, or C15-19 alkynyl may be respectively mono- or polymethyl C15-19 alkyl, mono- or polymethyl C15-19 alkenyl, or mono- or polymethyl C15-19 alkynyl. Suitably, the branched C15-40 alkyl, C15-40 alkenyl, or C15-40 alkynyl may be respectively mono- or polymethyl C15-40 alkyl, mono- or polymethyl C15-40 alkenyl, or mono- or polymethyl C15-40 alkynyl.

[0074] Suitably, at least one hydrogen atom of R4may be substituted by the leaving group. Suitably, at least one hydrogen atom of R5may be substituted by the leaving group. Suitably, at least one hydrogen atom of R6may be substituted by the leaving group. Suitably, one hydrogen atom of R4may be substituted by the leaving group. Suitably, one hydrogen atom of R5may be substituted by the leaving group. Suitably, one hydrogen atom of R6may be substituted by the leaving group.

[0075] Preferably, at least one hydrogen atom of the terminal carbon atom of any one of R4, R5, and R6may be substituted by the leaving group. Suitably, at least one hydrogen atom of the terminal carbon atom of R4may be substituted by the leaving group. Suitably, at least one hydrogen atom of the terminal carbon atom of R5may be substituted by the leaving group. Suitably, at least one hydrogen atom of the terminal carbon atom of R6may be substituted by the leaving group.

[0076] Suitably, the at least one hydrogen atom may be one hydrogen atom.

[0077] Suitably, the leaving group may be a group suitable for replacement by a nucleophile in a nucleophilic substitution reaction.

[0078] Nucleophilic substitution reactions are well-known in the art. The skilled person can accordingly select suitable nucleophiles and groups suitable for replacement by the nucleophiles in order to create the triglyceride analogs represented by formula (II) according to the invention.

[0079] Suitably, the group suitable for replacement by a nucleophile in a nucleophilic substitution reaction may be a halogen or a sulphone ester. Non-limiting examples of halogens are iodine, bromine, and chlorine. Suitably, the halogen may be iodine, bromine, or chlorine. Non-limiting examples of sulphone esters are mesylate, triflate, tosylate, and nosylate. Suitably the sulphone ester may be mesylate, triflate, tosylate, or nosylate.

[0080] Preferably, the leaving group may be a tosylate group represented by formula (III): wherein denotes the attachment of the group to a carbon atom of any one of R4, R5, and R6.

[0081] Preferably, the leaving group may be a tosylate group represented by formula (III): wherein denotes the attachment of the group to the terminal carbon atom of any one of R4, R5, and R6.

[0082] The invention also relates to a triglyceride analog or salt thereof represented by formula (Ila): wherein at least one of Y1, Y2, and Y3is a group comprising a leaving group, and the other of Y1, Y2, and Y3is methyl.

[0083] Suitably, Y1may be a group comprising a leaving group and Y2and Y3may be methyl.

[0084] Suitably, Y2may be a group comprising a leaving group and Y1and Y3may be methyl. Suitably, Y3may be a group comprising a leaving group and Y1and Y2may be methyl. The invention also relates to a triglyceride analog or salt thereof represented by formula (lib):

[0085] The invention also relates to a triglyceride analog or salt thereof represented by formula (lie):

[0086] (He).

[0087] The invention also relates to a triglyceride analog or salt thereof represented by formula (lid):

[0088] (Hd).

[0089] Compound comprising a stable isotope

[0090] The group comprising a radioisotope suitable for PET or SPECT of the radiolabeled triglyceride analog or salt thereof according to the invention may also be a group comprising a stable isotope. Such a labeled triglyceride analog or salt thereof comprising a stable isotope can be synthesized in a similar manner as the radiolabeled triglyceride analog or salt thereof. Such a labeled triglyceride analog or salt thereof may be useful in for example analysis of metabolism of a subject without directly making use of PET or SPECT, for example alongside PET or SPECT.

[0091] Accordingly, the invention further relates to a labeled triglyceride analog or salt thereof represented by formula (IV): wherein each of R7, R8, and R9are independently linear or branched C1.40 alkyl, linear or branched C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of any one of R7, R8, and R9is substituted by a group comprising a stable isotope. Suitably, each of R7, R8, and R9may be independently linear or branched C5-35 alkyl, linear or branched C5-35 alkenyl, or linear or branched C5-35 alkynyl. Suitably, each of R7, R8, and R9may be independently linear or branched C7-33 alkyl, linear or branched C7-33 alkenyl, or linear or branched C7-33 alkynyl. Suitably, each of R7, R8, and R9may be independently linear or branched C9.29 alkyl, linear or branched C9.29 alkenyl, or linear or branched C9.29 alkynyl. Suitably, each of R7, R8, and R9may be independently linear or branched C11.25 alkyl, linear or branched C11.25 alkenyl, or linear or branched C11.25 alkynyl. Suitably, each of R7, R8, and R9may be independently linear or branched C11-21 alkyl, linear or branched C11.21 alkenyl, or linear or branched C11.21 alkynyl. Suitably, each of R7, R8, and R9may be independently linear or branched C13-21 alkyl, linear or branched C13-21 alkenyl, or linear or branched C13-21 alkynyl. Suitably, each of R7, R8, and R9may be independently linear or branched C15-19 alkyl, linear or branched C15-19 alkenyl, or linear or branched C15-19 alkynyl. Suitably, each of R7, R8, and R9may be independently linear or branched C15-40 alkyl, linear or branched C15-40 alkenyl, or linear or branched C15-40 alkynyl.

[0092] Suitably, each of R7, R8, and R9may be linear.

[0093] Suitably, each of R7, R8, and R9independently may comprise the aliphatic chain of a fatty acid.

[0094] Suitably, each of R7, R8, and R9may comprise the same number of carbon atoms. Suitably, each of R7and R8may comprise the same number of carbon atoms. Suitably, each of R7and R9may comprise the same number of carbon atoms. Suitably, each of R8and R9may comprise the same number of carbon atoms. Suitably, each of R7, R8, and R9may comprise a different number of carbon atoms. Suitably, each of R7and R8may comprise a different number of carbon atoms. Suitably, each of R7and R9may comprise a different number of carbon atoms. Suitably, each of R8and R9may comprise a different number of carbon atoms.

[0095] Suitably, each of R1, R2, and R3may be independently linear C1.40 alkyl or linear C2-40 alkenyl. Suitably, the C2-40 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C2-40 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C9.29 alkyl or linear C9.29 alkenyl. Suitably, the C9.29 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C9.29 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C13-19 alkyl or linear C13-19 alkenyl. Suitably, the C13-19 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C13-19 alkenyl may have one, two, three, four, or five C=C bonds. Suitably, each of R1, R2, and R3may be independently linear C15-40 alkyl or linear C15-40 alkenyl. Suitably, the C15-40 alkenyl may comprise cis and / or trans stereoisomers. Suitably, the C15-40 alkenyl may have one, two, three, four, or five C=C bonds.

[0096] Suitably, the branched C1.40 alkyl, C2-40 alkenyl, or C2-4o alkynyl may be respectively mono- or polymethyl C1.40 alkyl, mono- or polymethyl C2-40 alkenyl, or mono- or polymethyl C2-40 alkynyl. Suitably, the branched C5-35 alkyl, C5-35 alkenyl, or Cs-35 alkynyl may be respectively mono- or polymethyl C5-35 alkyl, mono- or polymethyl C5-35 alkenyl, or mono- or polymethyl C5-35 alkynyl. Suitably, the branched C7-33 alkyl, C7-33 alkenyl, or C7-33 alkynyl may be respectively mono- or polymethyl C7-33 alkyl, mono- or polymethyl C7-33 alkenyl, or mono- or polymethyl C7-33 alkynyl. Suitably, the branched C9.29 alkyl, C9.29 alkenyl, or Cg.29 alkynyl may be respectively mono- or polymethyl C9.29 alkyl, mono- or polymethyl C9.29 alkenyl, or mono- or polymethyl C9.29 alkynyl. Suitably, the branched C11.25 alkyl, C11.25 alkenyl, or C11.25 alkynyl may be respectively mono- or polymethyl C11.25 alkyl, mono- or polymethyl C11.25 alkenyl, or mono- or polymethyl C11.25 alkynyl. Suitably, the branched C11.21 alkyl, C11.21 alkenyl, or Cn.21 alkynyl may be respectively mono- or polymethyl C11.21 alkyl, mono- or polymethyl C11.21 alkenyl, or mono- or polymethyl C11.21 alkynyl. Suitably, the branched C13-21 alkyl, C13-21 alkenyl, or Ci3-2i alkynyl may be respectively mono- or polymethyl C13-21 alkyl, mono- or polymethyl C13-21 alkenyl, or mono- or polymethyl C13-21 alkynyl. Suitably, the branched C15-19 alkyl, C15-19 alkenyl, or C15-19 alkynyl may be respectively mono- or polymethyl C15-19 alkyl, mono- or polymethyl C15-19 alkenyl, or mono- or polymethyl C15-19 alkynyl. Suitably, the branched C15-40 alkyl, C15-40 alkenyl, or C15-40 alkynyl may be respectively mono- or polymethyl C15-40 alkyl, mono- or polymethyl C15-40 alkenyl, or mono- or polymethyl C15-40 alkynyl.

[0097] Suitably, at least one hydrogen atom of R7may be substituted by the group comprising a stable isotope. Suitably, at least one hydrogen atom of R8may be substituted by the group comprising a stable isotope. Suitably, at least one hydrogen atom of R9may be substituted by the group comprising a stable isotope. Suitably, one hydrogen atom of R7may be substituted by the group comprising a stable isotope. Suitably, one hydrogen atom of R8may be substituted by the group comprising a stable isotope. Suitably, one hydrogen atom of R9may be substituted by the group comprising a stable isotope.

[0098] Suitably, at least one hydrogen atom of the terminal carbon atom of any one of R7, R8, and R9may be substituted by the group comprising a stable isotope. Suitably, at least one hydrogen atom of the terminal carbon atom of R7may be substituted by the group comprising a stable isotope. Suitably at least one hydrogen atom of the terminal carbon atom of R8may be substituted by the group comprising a stable isotope. Suitably, at least one hydrogen atom of the terminal carbon atom of R9may be substituted by the group comprising a stable isotope.

[0099] Suitably, the at least one hydrogen atom may be one hydrogen atom.

[0100] Suitably, the group comprising a stable isotope may consist of a stable isotope.

[0101] Suitably, the stable isotope may be a stable isotope of carbon, fluorine, or iodine. Preferably, the stable isotope may be a stable isotope of fluorine or iodine. More preferably, the stable isotope may be a stable isotope of fluorine.

[0102] Suitably, the stable isotope may be127l or19F. Preferably, the stable isotope may be19F.

[0103] The invention also relates to a labeled triglyceride analog or salt thereof represented by formula (IVa):

[0104] Synthesis of compounds

[0105] The invention also provides a method of synthesizing the radiolabeled triglyceride analog of formula (I) according to the invention, the method comprising: a. providing the triglyceride analog of formula (II) according to the invention comprising a leaving group; b. allowing an [18F] comprising species to react with the triglyceride analog, thereby removing the leaving group and providing the radiolabeled triglyceride analog of formula (I) according to the invention.

[0106] Suitably, the [18F] comprising species may be [18F]triflylfluoride.

[0107] Suitably, the method of synthesizing may further comprise purifying the radiolabeled triglyceride analog of formula (I) according to the invention, preferably using high-performance liquid chromatography.

[0108] Suitably, the method of synthesizing may further comprise a step of synthesizing and providing [18F]triflylfluoride, the step comprising: reacting N-phenyl-bis(trifluoromethane)sulfonimide with [18F]fluoride, thereby synthesizing [18F]triflylfluoride. Preferably, the reacting is in the presence of dimethylformamide and a solution of potassium sulfate.

[0109] Suitably, the method of synthesizing may further comprise isolating the synthesized [18F]triflylfluoride in a solution comprising potassium bicarbonate, Kryptofix® 222 (4,7, 13, 16,21 ,24- hexaoxa-1 ,10-diazabicyclo[8.8.8]hexacosane), and acetonitrile.

[0110] A detailed exemplary method of synthesizing the radiolabeled triglyceride analog of formula (I) according to the invention, specifically formula (lb), using the triglyceride analog of formula (II) according to the invention, specifically formula (lib), is disclosed in the Examples section below, summarized in Scheme 1 B and Figure 9B.

[0111] The invention also provides a method of synthesizing the radiolabeled triglyceride analog of formula (la) according to the invention, the method comprising: a. providing the triglyceride analog of formula (Ila) according to the invention comprising a leaving group; b. allowing an [18F] comprising species to react with the triglyceride analog, thereby removing the leaving group and providing the radiolabeled triglyceride analog of formula

[0112] (la) according to the invention.

[0113] The invention also provides a method of synthesizing the radiolabeled triglyceride analog of formula (lb) according to the invention, the method comprising: a. providing the triglyceride analog of formula (lib) according to the invention comprising a leaving group, wherein the leaving group is a tosylate group; b. allowing an [18F] comprising species to react with the triglyceride analog, thereby removing the leaving group and providing the radiolabeled triglyceride analog of formula

[0114] (lb) according to the invention.

[0115] Synthesis of the triglyceride analog of formula (II) according to the invention is disclosed in detail in the Examples section below. The skilled person can accordingly synthesize other triglyceride analogs, such as those comprising different aliphatic chains, using methods and materials known in the art, for example by accordingly selecting other suitable compounds comprising aliphatic chains (e.g. having different lengths, branching, and / or saturation of carbon bonds) and other suitable compounds comprising glycerol groups, glycerol esters, or glycerides such as diacylglycerols.

[0116] A detailed exemplary method of synthesizing the triglyceride analog of formula (II) according to the invention, specifically formula (lib), is disclosed in the Examples section below, summarized in Scheme 1A and Figure 9A.

[0117] The compounds of the invention may be suitable for use alone or comprised in different compositions known in the art. Herein, a particularly suitable composition for the compounds of the invention has been developed comprising lipid particles. The composition resulted in efficient in vivo processing and uptake as the composition mimics the behaviour of endogenous triglyceride-rich lipoprotein (TRL) particles.

[0118] Hence, the present invention also relates to a composition comprising lipid particles, the lipid particles comprising: the radiolabeled triglyceride analog according to the invention or the labeled triglyceride analog according to the invention, and optionally one or more additional lipid species. Suitably, the lipid particles may comprise the radiolabeled triglyceride analog according to the invention. Suitably, the lipid particles may comprise the labeled triglyceride analog according to the invention. Suitably, the lipid particles may comprise one or more additional lipid species. Compositions according to the invention may also comprise a salt of the compound.

[0119] Suitably, the one or more additional lipid species may be selected from triglyceride, phosphatidylcholine, cholesteryl ester, L-a-lysophosphatidylcholine, and cholesterol. Suitably, the one or more additional lipid species may be triglyceride, phosphatidylcholine, cholesteryl ester, L-a- lysophosphatidylcholine, and cholesterol.

[0120] Suitably, the triglyceride may be glyceryl trioleate. Suitably, the cholesteryl ester may be cholesteryl oleate. Suitably, the particles may have a mean diameter of from about 30 nm to about 1000 nm. Suitably, the particles may have a mean diameter of from about 30 nm to about 900 nm, of from about 30 nm to about 800 nm, of from about 30 nm to about 700 nm, of from about 30 nm to about 600 nm, of from about 30 nm to about 500 nm, of from about 30 nm to about 400 nm, of from about 30 nm to about 300 nm, of from about 30 nm to about 200 nm, of from about 30 nm to about 100 nm, of from about 30 nm to about 80 nm, of from about 30 nm to about 70 nm, of from about 30 nm to about 60 nm, of from about 40 nm to about 1000 nm, of from about 40 nm to about 800 nm, of from about 40 nm to about 600 nm, of from about 40 nm to about 400 nm, of from about 40 nm to about 200 nm, of from about 40 nm to about 100 nm, of from about 30 nm to about 1000 nm, or of from about 30 nm to about 1000 nm. Preferably, the particles may have a mean diameter of about 50 nm.

[0121] Suitably, the lipid particles may each comprise of from 60% to 90% by weight of triglyceride, of from 10% to 25% by weight of phosphatidylcholine, of from 2% to 4% by weight of cholesteryl ester, of from 1 .5% to 3.0% by weight of L-a-lysophosphatidylcholine, and of from 1 .5% to 2.5% by weight of cholesterol.

[0122] Suitably, the lipid particles may each comprise of from 60% to 90% by weight of triglyceride. Suitably, the lipid particles may each comprise of from 60% to 85%, of from 60% to 80%, of from 60% to 75%, of from 65% to 90%, of from 65% to 85%, or of from 65% to 75% by weight of triglyceride.

[0123] Suitably, the lipid particles may each comprise of from 10% to 25% by weight of phosphatidylcholine. Suitably, the lipid particles may each comprise of from 10% to 23%, of from 12% to 25%, of from 15% to 25%, of from 18% to 25%, of from 20% to 25%, of from 12% to 23%, of from 15% to 23%, or of from 18% to 23% by weight of phosphatidylcholine.

[0124] Suitably, the lipid particles may each comprise of from 2% to 4% by weight of cholesteryl ester. Suitably, the lipid particles may each comprise of from 2% to 3.5%, of from 2.5% to 4%, or of from 2.5% to 3.5% by weight of cholesteryl ester.

[0125] Suitably, the lipid particles may each comprise of from 1 .5% to 3.0% by weight of L-a- lysophosphatidylcholine. Suitably, the lipid particles may each comprise of from 1.5% to 2.5%, of from 2.0% to 3.0%, or of from 2.0% to 2.5% by weight of L-a-lysophosphatidylcholine.

[0126] Suitably, the lipid particles may each comprise of from 1 .5% to 2.5% by weight of cholesterol. Suitably, the lipid particles may each comprise of from 1 .5% to 2.3%, of from 1 .7% to 2.3%, or of from 1.7% to 2.5% by weight of cholesterol.

[0127] Suitably, the composition according to the invention may further comprise a carrier, and / or diluent, and / or excipient; optionally the composition may be a pharmaceutical composition.

[0128] Pharmaceutical compositions

[0129] The invention also relates to a pharmaceutical composition comprising an effective amount of the radiolabeled triglyceride analog according to the invention, the labeled triglyceride analog according to the invention, or the composition according to the invention; the pharmaceutical composition further comprising a pharmaceutically acceptable carrier, and / or diluent, and / or excipient. Suitably, the pharmaceutical composition may comprise a pharmaceutically acceptable excipient. Suitably, the pharmaceutical composition may comprise a pharmaceutically acceptable adjuvant. Suitably, the pharmaceutical composition may comprise a pharmaceutically acceptable diluent. Suitably, the pharmaceutical composition may comprise a pharmaceutically acceptable carrier.

[0130] As used herein, "pharmaceutically acceptable" refers to a material that is not biologically or otherwise undesirable, i.e. , the material may be administered to an individual along with the selected compound and optionally lipid particles without causing any undesirable biological effects or interacting in a deleterious manner with any of the other components of the pharmaceutical composition in which it is contained.

[0131] The salt of the compound according to the invention (i.e. the radiolabeled triglyceride analog or labeled triglyceride analog) may preferably be a pharmaceutically acceptable salt. Pharmaceutical compositions according to the invention may also comprise a salt of the compound.

[0132] Salts may be pharmaceutically acceptable salts. As used herein, “pharmaceutically acceptable salts” refers to derivatives of the disclosed compounds wherein the parent compound is altered by converting an existing acid or base moiety to its salt form (e.g., by reacting a free base group with a suitable organic acid). Examples of pharmaceutically acceptable salts include, but are not limited to, mineral or organic acid salts of basic residues such as amines; alkali or organic salts of acidic residues such as carboxylic acids; and the like. Representative acid addition salts include acetate, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptonate, glycerophosphate, hemisulfate, heptonate, hexanoate, hydrobromide, hydrochloride, hydroiodide, 2-hydroxy-ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2- naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, toluenesulfonate, undecanoate, valerate salts, and the like. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, magnesium, and the like, as well as nontoxic ammonium, quaternary ammonium, and amine cations, including, but not limited to ammonium, tetramethylammonium, tetraethylammonium, methylamine, dimethylamine, trimethylamine, triethylamine, ethylamine, and the like. The pharmaceutically acceptable salts of the present disclosure include the conventional non-toxic salts of the parent compound formed, for example, from non-toxic inorganic or organic acids. The pharmaceutically acceptable salts of the present disclosure can be synthesized from the parent compound which contains a basic or acidic moiety by conventional chemical methods. Generally, such salts can be prepared by reacting the free acid or base forms of these compounds with a stoichiometric amount of the appropriate base or acid in water or in an organic solvent, or in a mixture of the two; generally, nonaqueous media like ether, ethyl acetate, ethanol, isopropanol, or acetonitrile are preferred. Lists of suitable salts are found in Remington's Pharmaceutical Sciences, 17th ed., Mack Publishing Company, Easton, Pa., 1985, p. 1418, Pharmaceutical Salts: Properties, Selection, and Use, P. H. Stahl and C. G. Wermuth (eds.), Wiley-VCH, 2008, and Berge et al., Journal of Pharmaceutical Science, 66, 1-19, 1977. The compounds according to the invention (i.e. the radiolabeled triglyceride analog or labeled triglyceride analog) and, where appropriate, the tautomers thereof, in each case in free form or in salt form, can be present in the form of one of the stereoisomers which are possible or as a mixture of these, for example in the form of pure stereoisomers, such as antipodes and / or diastereomers, or as stereoisomer mixtures, such as enantiomer mixtures, for example racemates, diastereomer mixtures or racemate mixtures, depending on the number, absolute and relative configuration of asymmetric carbon atoms which occur in the molecule and / or depending on the configuration of non-aromatic double bonds which occur in the molecule; the invention relates to the pure stereoisomers and also to all stereoisomer mixtures which are possible and is to be understood in each case in this sense hereinabove and hereinbelow, even when stereochemical details are not mentioned specifically in each case. It is advantageous to isolate or synthesize in each case the biologically more effective stereoisomer, for example enantiomer or diastereomer, or stereoisomer mixture, for example enantiomer mixture or diastereomer mixture, if the individual components have a different biological activity.

[0133] Compositions, in particular pharmaceutical compositions, may routinely contain pharmaceutically acceptable concentrations of salt, buffering agents, preservatives, compatible carriers, supplementary immune potentiating agents such as adjuvants and cytokines and optionally other therapeutic and / or prophylactic agents.

[0134] Excipients are natural or synthetic substances formulated alongside an active substance, included for the purpose of bulking-up the formulation or to confer a (therapeutic) enhancement on the active substance in the final dosage form, such as facilitating absorption or solubility. Excipients can also be useful in the manufacturing process, to aid in the handling of the active substance concerned such as by facilitating powder flowability or non-stick properties, in addition to aiding in vitro stability such as prevention of denaturation over the expected shelf life. Pharmaceutically acceptable excipients are well known in the art. A suitable excipient is therefore easily identifiable by one of ordinary skill in the art. By way of example, suitable pharmaceutically acceptable excipients include water, saline, aqueous dextrose, glycerol, ethanol, and the like.

[0135] Adjuvants are pharmacological and / or immunological agents that modify the effect of other agents in a formulation. Pharmaceutically acceptable adjuvants are well known in the art. A suitable adjuvant is therefore easily identifiable by one of ordinary skill in the art.

[0136] Diluents are diluting agents. Pharmaceutically acceptable diluents are well known in the art. A suitable diluent is therefore easily identifiable by one of ordinary skill in the art.

[0137] Carriers are non-toxic to recipients at the dosages and concentrations employed and are compatible with other ingredients of the formulation. The term “carrier” denotes an organic or inorganic ingredient, natural or synthetic, with which the active ingredient is combined to facilitate the application. Pharmaceutically acceptable carriers are well known in the art. A suitable carrier is therefore easily identifiable by one of ordinary skill in the art. Preferably, the carrier may be a biocompatible carrier.

[0138] The compositions and pharmaceutical compositions described herein can be administered to the subject by any conventional route, including injection or by gradual infusion over time. The administration may, for example, be by infusion or by intramuscular, intravascular, intracavity, intracerebral, intralesional, rectal, subcutaneous, intradermal, epidural, intrathecal, percutaneous, intraperitoneal, intravitreal, subretinal, subconjunctival, peribulbar, posterior juxlascleral, transscleral, subrachoroidal, retrobulbar, intravitreous, itratumor, inhalation, intratracheal intranasal, oral, or intraarticular administration.

[0139] The compositions and pharmaceutical compositions described herein may be in any form suitable for the above modes of administration. For example, compositions comprising lipid particles may in any form suitable for infusion. As further examples, suitable forms for parenteral injection (including, subcutaneous, intramuscular, intravascular or infusion) include a sterile solution, suspension or emulsion; suitable forms for topical administration include an ointment or cream; and suitable forms for rectal administration include a suppository. Alternatively, the route of administration may be by direct injection into the target area, or by regional delivery or by local delivery. The identification of suitable dosages of the compositions of the invention is well within the routine capabilities of a person of skill in the art.

[0140] The pharmaceutical composition is preferably for, and therefore formulated to be suitable for, administration to a subject, preferably a human or animal subject. Preferably, the administration is parenteral, e.g., intravenous, subcutaneous, intramuscular, intradermal intracutaneous and / or intratumoral administration, i.e., by injection.

[0141] The compounds according to the invention (i.e. the radiolabeled triglyceride analog or labeled triglyceride analog), compositions, and pharmaceutical compositions described herein are for administration in an effective amount. An “effective amount” is an amount that alone, or together with further doses, produces the desired (therapeutic or non-therapeutic) response. The effective amount to be used will depend, for example, upon the (therapeutic or non-therapeutic) objectives, the route of administration, and the condition of the patient / subject. For example, the suitable dosage of the composition or pharmaceutical composition of the invention for a given patient / subject will be determined by the attending physician (or person administering the composition), taking into consideration various factors known to modify the action of the composition of the invention for example severity and type of haematological malignancy, body weight, sex, diet, time and route of administration, other medications and other relevant clinical factors. The dosages and schedules may be varied according to the particular condition, disorder or symptom the overall condition of the patient / subject. Effective dosages may be determined by either in vitro or in vivo methods. A particularly preferred objective for administration in an effective amount is PET or SPECT imaging.

[0142] Methods of imaging and uses

[0143] The compounds and compositions of the invention can be used for imaging a subject. As disclosed in the Examples, the compounds and compositions of the invention provide higher sensitivity and specificity in tracing activated BAT via PET imaging compared to the standard in the art [18F]TO. The compounds and compositions of the invention are therefore particularly suitable for tracing human BAT activity, especially in metabolically compromised conditions including ageing, obesity and T2D, and dyslipidemia and atherosclerotic CVD, but can also be used for imaging other (metabolically active) tissues of a subject as is evident from Figures 2-4, 6, and 7. The compounds and compositions of the invention are thus suitable for diagnosing diseases or disorders in a subject. When administration of the compounds or compositions of the invention is combined with treatment of a subject, the progress of the disease or disorder and / or the efficacy of the treatment modality can be also be imaged and monitored.

[0144] Hence, the invention also provides a method of imaging at least a part of the body of a subject comprising using the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according the invention, optionally wherein the imaging is in vivo.

[0145] Suitably, the method of imaging may further comprise: a. administering an effective amount of the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention to the subject; and / or b. wherein the imaging is positron emission tomography (PET) imaging or single-photon emission computed tomography (SPECT) imaging; and / or c. wherein the at least a part of the body is a tissue of interest.

[0146] Suitably, the method of imaging may further comprise: administering an effective amount of the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention to the subject.

[0147] Suitably, the imaging may be positron emission tomography (PET) imaging or single-photon emission computed tomography (SPECT) imaging.

[0148] Suitably, the at least a part of the body may be a tissue of interest.

[0149] Suitably, the method of imaging may further comprise: a. administering an effective amount of the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention to the subject; b. detecting emission from the radioisotope; and c. generating an image of the at least a part of the body from the emission of step b.

[0150] One embodiment of the invention is a method of imaging at least a part of the body of a subject comprising using the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according the invention, the method comprising: a. administering an effective amount of the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention to the subject; b. detecting emission from the radioisotope; and c. generating an image of the at least a part of the body from the emission of step b. Suitably, the imaging may be for obtaining an image of brown adipose tissue, subcutaneous and visceral white adipose tissue, skeletal muscle, heart, liver, blood, heart, spleen, kidney, lung, bladder, adrenal glands, skull bone, stomach, duodenum, or skin. Suitably, the imaging may be for obtaining an image of brown adipose tissue, subcutaneous and visceral white adipose tissue, skeletal muscle, heart, or liver. Preferably, the imaging may be for obtaining an image of brown adipose tissue. Suitably, the imaging may be for obtaining an image of subcutaneous and visceral white adipose tissue. Suitably, the imaging may be for obtaining an image of skeletal muscle. Suitably, the imaging may be for obtaining an image of heart. Suitably, the imaging may be for obtaining an image of liver. Suitably, the imaging may be for the localization or distribution of triglycerides.

[0151] Suitably, the brown adipose tissue may be supraclavicular brown adipose tissue. Suitably, the brown adipose tissue may be active brown adipose tissue.

[0152] Suitably, the method of imaging may be used to assist in detection, diagnosis, prognosis, prediction of outcome, surgery, staging, treatment, therapy, radiotherapy, monitoring of treatment, monitoring of disease progression, or monitoring therapy.

[0153] Suitably, the subject may be suffering from a disease.

[0154] Suitably, the disease may be a metabolic disease or a cardiometabolic disease. Suitably, the disease may be metabolic syndrome, type 2 diabetes, (combined) dyslipidemia, hypertriglyceridemia, obesity, metabolically associated fatty liver disease (MASLD), metabolically associated steatohepatitis (MASH), (congenital generalized) lipodystrophy, or atherosclerotic cardiovascular diseases, including coronary heart disease and stroke.

[0155] The invention also provides a method of diagnosis comprising the method of imaging according to the invention.

[0156] Suitably, the method of diagnosis may further comprise comparing the image of at least a part of the body of a subject with an image of the at least a part of the body of the subject that has been obtained previously, preferably wherein the image of the at least a part of the body of the subject that has been obtained previously has been obtained using the method of imaging according to the invention.

[0157] Suitably, the method of diagnosis may further comprise comparing the image of at least a part of the body of a subject with a reference image. Suitably, the method of diagnosis may further comprise comparing the image of at least a part of the body of a subject with reference data.

[0158] The invention also provides a use of the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention as an imaging agent.

[0159] The invention also provides the radiolabeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention for use as an imaging agent. The invention also provides a use of the radiolabeled triglyceride analog according to the invention or the triglyceride analog according to the invention for manufacturing a composition for imaging.

[0160] The invention also provides the radiolabeled triglyceride analog according to the invention or the triglyceride analog according to the invention for use in manufacturing a composition for imaging. The invention also provides a use of the radiolabeled triglyceride analog according to the invention, the labeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention in detection, diagnosis, prognosis, prediction of outcome, surgery, staging, treatment, therapy, radiotherapy, monitoring of treatment, monitoring of disease progression, or monitoring therapy.

[0161] The invention also provides the radiolabeled triglyceride analog according to the invention, the labeled triglyceride analog according to the invention, the composition according to the invention, or the pharmaceutical composition according to the invention for use in detection, diagnosis, prognosis, prediction of outcome, surgery, staging, treatment, therapy, radiotherapy, monitoring of treatment, monitoring of disease progression, or monitoring therapy.

[0162] General definitions

[0163] As used herein, the term “ex vivo” refers to “outside” the body. The term “in vitro” can be used to encompass “ex vivo” components, compositions and methods.

[0164] Unless defined otherwise herein, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. For example, Singleton and Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d Ed., John Wiley and Sons, NY (1994); and Hale and Marham, The Harper

[0165] Collins Dictionary of Biology, Harper Perennial, NY (1991) provide those of skill in the art with a general dictionary of many of the terms used in the invention. Although any methods and materials similar or equivalent to those described herein find use in the practice of the present invention, the preferred methods and materials are described herein. Accordingly, the terms defined immediately below are more fully described by reference to the Specification as a whole. Also, as used herein, the singular terms "a", "an," and "the" include the plural reference unless the context clearly indicates otherwise. It is to be understood that this invention is not limited to the particular methodology, protocols, and reagents described, as these may vary, depending upon the context they are used by those of skill in the art.

[0166] As used herein, the terms “treat”, “treating” and "treatment" are taken to include an intervention performed with the intention of preventing the development or altering the pathology of a condition, disease, disorder, or symptom. Accordingly, "treatment" refers to both therapeutic treatment and prophylactic or preventative measures, wherein the object is to prevent or slow down (lessen) the targeted condition, disease, disorder, or symptom (e.g. a cancer or viral infection). “Treatment” therefore includes a reduction, slowing, or inhibition of the amount or concentration of malignant, virally infected, or diseased cells, for example as measured in a sample obtained from the subject, of at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or 100% when compared to the amount or concentration of malignant cells, virally infected cells, or diseased cells before treatment. Methods of measuring the amount or concentration of malignant cells, virally infected, or diseased cells include, for example, qRT-PCR, and quantification of specific biomarkers in a sample obtained from the subject.

[0167] As used herein, the term “subject” refers to an organism to which a composition according to the invention may be administered. This may for example be for experimental, diagnostic, prophylactic, and / or therapeutic purposes. Typical subjects include animals (e.g., mammals such as mice, rats, rabbits, cats, dogs, horses, non-human primates, and humans). As used herein, the term “subject” may further refer to an individual, e.g., a human, having or at risk of having a specified condition, disease, disorder, or symptom. The subject may be a patient i.e. a subject in need of treatment in accordance with the invention. The subject may have received treatment for the condition, disease, disorder, or symptom. Alternatively, the subject has not been treated prior to treatment in accordance with the present invention. Preferably, the subject is a human subject.

[0168] The term "alkyl" as used herein, in isolation or as part of a chemical group, represents straight-chain or branched hydrocarbons including one or more carbon atoms (e.g., one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, twenty, or more carbon atoms). As used herein, the term "C1-40 alkyl" refers to a straight or branched hydrocarbon, containing no unsaturation, having from one to forty carbon atoms.

[0169] The term "alkenyl" as used herein, in isolation or as part of a chemical group, represents straight-chain or branched hydrocarbons including two or more carbon atoms (e.g., two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, twenty, or more carbon atoms) and at least one double bond. As used herein, the term "C2-40 alkenyl" refers to a straight or branched hydrocarbon having from two to forty carbon atoms and at least one carbon-carbon double bond. An alkenyl group may include one, two, three, four, or more carbon-carbon double bonds.

[0170] The term "alkynyl" as used herein, in isolation or as part of a chemical group, represents straight-chain or branched hydrocarbons including two or more carbon atoms (e.g., two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, seventeen, eighteen, nineteen, twenty, or more carbon atoms) and at least one triple bond. As used herein, the term "C2-40 alkynyl" refers to a straight or branched hydrocarbon having from two to forty carbon atoms and at least one carbon-carbon triple bond. An alkynyl group may include one, two, three, four, or more carbon-carbon triple bonds.

[0171] The terminal carbon atom of an alkane, alkene, or alkyne is also known as the omega carbon.

[0172] Detailed description of the figures

[0173] The invention will now be disclosed with reference to the figures, which show preferred exemplary embodiments of the subject invention.

[0174] Figure 1 shows that incorporation of [19F]TO does not affect size, kinetics and biodistribution of TRL-like particles in mice. Glycerol tri[3H]oleate and [14C]cholesteryl oleate double-labeled lipoprotein-like particles were prepared without or with the addition of glycerol tri[19F]oleate ([19F]TO). (A) Particle size distribution was measured using Zetasizer Nano ZSP. Particles were intravenously injected (0.7 mg TG / mouse) into 4-hour fasted male C57BI / 6J mice that were treated daily with vehicle or CL316,243 during 8 days. Fifteen minutes after particle injection, blood was drawn, mice were killed and perfused with PBS, and organs / tissues were collected to measure (B)3H activity and (C)14C activity. Values are means ± SEM (A, n=1 preparation; B-C, n=4 or 6 per group). *P<0.05, **P<0.01 and ***P<0.001 (Tukey’s test). gWAT, gonadal white adipose tissue; iBAT, interscapular brown adipose tissue; sBAT, subscapular brown adipose tissue; sWAT, subcutaneous white adipose tissue.

[0175] Figure 2 shows time-dependent biodistribution of the PET tracer glycerol tri[18F]oleate incorporated into lipoprotein-like particles in mice. Glycerol tri[18F]oleate-labeled lipoprotein-like particles were prepared and intravenously injected (0.7 mg / mouse) into 4-hour fasted male C57BI / 6J mice that had been treated daily with vehicle or CL316,243 during 8 days. At (A) 5 min, (B) 10 min or (C) 15 min after particle injection, blood was drawn, mice were killed and perfused with PBS, and organs / tissues were collected to measure18F activity. Values are means ± SEM (A-C, n=4 per group). *P<0.05, **P<0.01 and ***P<0.001 (Student's t-test). gWAT, gonadal white adipose tissue; iBAT, interscapular brown adipose tissue; sBAT, subscapular brown adipose tissue; sWAT, subcutaneous white adipose tissue.

[0176] Figure 3 shows PET-CT images of representative mice injected with glycerol tri[18F]oleate- labeled lipoprotein-like particles or [18F]fluorodeoxyglucose. Glycerol tri[18F]oleate ([18F]TO)-labeled lipoprotein-like particles or [18F]fluorodeoxyglucose ([18F]FDG) were intravenously injected into 4- hour fasted male C57BI / 6J mice that were treated daily with vehicle or CL316,243 during 8 days. Subsequently, 60 min of dynamic image acquisition was performed using small animal nano PET- CT. Data from the 60-min scanning of representative mice were reconstructed into static images. Interscapular brown adipose tissue (iBAT), subscapular brown adipose tissue (sBAT), subcutaneous white adipose tissue (sWAT).

[0177] Figure 4 shows PET-CT imaging of glycerol tri[18F]oleate incorporated into lipoprotein-like particles vs. [18F]fluorodeoxyglucose in mice. Glycerol tri[18F]oleate ([18F]TO)-labeled lipoprotein-like particles or [18F]fluorodeoxyglucose ([18F]FDG) were intravenously injected into 4-hour fasted male C57BI / 6J mice that were treated daily with vehicle or CL316,243 during 8 days. Subsequently, 60 min of dynamic image acquisition was performed using small animal nano PET-CT. Time-activity curves of18F activity are shown in (A) the heart, (B) interscapular brown adipose tissue (iBAT), (C) subcutaneous white adipose tissue (sWAT) and (D) liver (n=2-4 per group). Values are means ± SEM.

[0178] Figure 5 shows that incorporation of glycerol tri[19F]oleate does not affect blood clearance of triglyceride-rich lipoprotein-like particles in mice. Glycerol tri[3H]oleate and [14C]cholesteryl oleate double-labeled triglyceride-rich lipoprotein (TRL)-like particles were prepared without or with the addition of glycerol tri[19F]oleate ([19F]TO), and intravenously injected (0.7 mg TG / mouse) into 4-hour fasted male C57BI / 6J mice that had been treated daily with vehicle or CL316,243 during 8 days. At 2, 5, 10 and 15 min after particle injection, blood was collected from a tail vein. Plasma was then obtained to measure3H and14C activity, and results were calculated back into blood (A)3H activity and (B)14C activity. Values are means ± SEM (n=4-6 per group). **P<0.01 and ***P<0.001 (Tukey’s test for main effects between groups within each particle type).

[0179] Figure 6 shows time-dependent biodistribution of the PET tracer glycerol tri[18F]oleate incorporated into triglyceride-rich lipoprotein-like particles in mice. Glycerol tri[18F]oleate-labeled triglyceride-rich lipoprotein (TRL)-like particles were prepared and intravenously injected into 4-hour fasted male C57BI / 6J mice that had been treated daily with vehicle or CL316,243 during 8 days. At (A) 5 min, (B) 10 min or (C) 15 min after particle injection, blood was drawn, mice were killed and perfused with PBS, and organs / tissues were collected to measure18F activity. Values are means ± SEM (A-C, n=4 per group). *P<0.05, **P<0.01 and ***P<0.001 (Student's t-test).

[0180] Figure 7 shows PET-CT imaging of glycerol tri[18F]oleate incorporated into triglyceride-rich lipoprotein-like particles vs. [18F]fluorodeoxyglucose in mice. Glycerol tri[18F]oleate ([18F]TO)-labeled triglyceride-rich lipoprotein (TRL)-like particles or [18F]fluorodeoxyglucose ([18F]FDG) were intravenously injected into 4-hour fasted male C57BI / 6J mice that had been treated daily with vehicle or CL316,243 during 8 days. Subsequently, 60 min of dynamic image acquisition was performed using small animal nano PET-CT. (A-E) Time-activity curves of18F activity in organs (n=2-4 per group). Values are means ± SEM.

[0181] Figure 8 shows regions-of-interest (ROI) of organs and tissues. Interscapular brown adipose tissue (i BAT), subscapular brown adipose tissue (sBAT), subcutaneous white adipose tissue (sWAT).

[0182] Figure 9 shows a scheme of the synthesis of glycerol tri[18F]oleate (19). (A) Synthesis of precursor 9: (a) 3,4-dihydro-2H-pyran, pyridinium p-toluene sulfonate, dichloromethane, rt, 4.5 h; (b) triphenylphosphine, acetonitrile, 90°C, 24 h; (c) Methyl-9-oxo-nonanoate (4; Scheme S1 , Materials and Methods), sodium bis(trimethylsilyl)amide, tetrahydrofuran, -78°C to 0°C, 2 h; (d) potassium hydroxide, methanol / water, 100°C, 2 h; (e) 1 ,3-diolein, 1 -ethyl-3-(3- dimethylaminopropyl)carbodiimide, 4-dimethylaminopyridine, dichloromethane, rt, 2 h; (f) p- toluenesulfonic acid, methanol, rt, 2 h; (g) p-toluenesulfonyl chloride, di-isopropylethylamine, 4- dimethylaminopyridine, dichloromethane, 40°C, 72 h. (B) Triflyl fluoride labeling of precursor 9: (a) [18F]_(aqueous), potassium sulfate (0.1 M, aqueous), dimethtylformamide, 50°C, 1 min; (b) potassium bicarbonate, kryptofix, acetonitrile, rt, 5 min; (c) [18F]_(dry), potassium bicarbonate, kryptofix, acetonitrile / tetrahydrofuran, 80°C, 10 min.

[0183] Figure 10 shows a scheme of the synthesis of glycerol tri[19F]oleate (16). (a) p- toluenesulfonic acid, methanol, rt, 2 h; (b) p-toluenesulfonyl chloride, triethylamine, dichloromethane, rt, 24 h; (c) tetrabutylammonium tetra(tert-butyl alcohol) fluoride; (d) potassium hydroxide, methanol / water, 100 °C, 2 h; (e) 1 ,3-diolein, 1 ,3-diolein, 1 -ethyl-3-(3- dimethylaminopropyl)carbodiimide, 4-dimethylaminopyridine, dichloromethane, rt, 2 h.

[0184] Figure 11 shows an analytical HPLC chromatogram of [18F]19 co-injected with [19F]16. Top panel: UV at 210 nm; bottom panel: radioactivity measurement.

[0185] Further details of the figures are disclosed in the Examples below. Figure 12 shows the detectability of brown adipose tissue (BAT) with [18F]TO PET-CT in diet-induced obese mice. Further details of the figures are disclosed in the Examples below.

[0186] Figure 13 compares the detectability of browning in white adipose tissue of diet-induced obese mice with [18F]TO vs [18F]FDG in PET-CT. Further details of the figures are disclosed in the Examples below.

[0187] Examples

[0188] Aspects of the invention are demonstrated by the following non-limiting examples.

[0189] All chemicals and solvents were obtained from commercial suppliers and were used without further purification. Air and moisture-sensitive reactions were performed under argon atmosphere. All1H- NMR and13C-NMR spectra were recorded on a Brucker Avance II 500 MHz (1H = 500 MHz,13C = 126 MHz) spectrometer in chloroform-d (CDCh). Chemical shifts are reported in parts per million (ppm). Coupling constants ( ) are reported in hertz (Hz). Abbreviations used to describe multiplicities: s (singlet), d (doublet), t (triplet), dd (double doublet), dt (double triplet), m (multiplet). High-resolution mass spectrometry (HRMS) was performed on a Bruker impact II, LC-QTOF MS using positive (ESI+) or negative (ESI-) electrospray ionization. Thin layer chromatography (TLC) was performed using TLC plates from Merck (silica gel 60 coated aluminum sheets with F254 fluorescence indicator) and visualized using UV light at 254 nm and / or potassium permanganate stain. Preparative HPLC was performed on Knauer Bluehshadow 40P HPLC system equipped with a Knauer 40D UV detector set to 210 nm and an in house build radiodetector using a Phenomenex Luna C18(2) 5 pm, 100A, 250 mm x 10 mm column with acetone / acetonitrile 80:20 as mobile phase with a flow of 5 mL / min. Analytical HPLC was performed on a Shimadzu LC-20AT HPLC equipped with a SPD-20A UV / VIS detector set to 210 nm and an Elysia Raytest Sockel 2” GABI Nova radiodetector on a Phenomenex Luna C18(2) 5 pm, 100 A, 250 mm x 10 mm column with acetone / acetonitrile 80:20 as mobile phase with a flow of 1 mL / min. Detailed synthetic procedure and structural data of intermediate compounds are given below.

[0190] Synthesis of precursor 9 2-(9-bomononyloxy)tetrahydro-2 / 7-pyran (2), ad Grube et al., 29.

[0191] To a solution of 9-bromo-1 -nonanol (1) (5.0 g, 22.4 mmol) in dichloromethane (75 mL) was added 2,3- dihydropyran (3.05 mL, 33.61 mmol) and pyridinium p-toluenesulfonate (63 mg, 0.25 mmol). The solution was stirred overnight before the reaction mixture was washed with water (2x 50 mL) and saturated aqueous sodium bicarbonate (2x 50 mL). The organic layer was dried over sodium sulfate, filtered and evaporated in vacuo. The residue was purified using silica gel column chromatography (gradient of diethyl ether in hexane 0-10%). The product was obtained as a colourless oil (5.29 g, 17.20 mmol, 76.8%).1H N MR (500 MHz, CDCI3) 5 = 4.55 (t, J = 2.8 Hz, 1 H, OCHO), 3.88 - 3.82 (m, 1 H, OCH2(THP)), 3.71 (dt, J=9.6 Hz, 6.9 Hz, 1 H, CH2OCH), 3.51 - 3.45 (m, 1 H, OCH2(THP)), 3.41 - 3.33 (m, 3H, BrCH2, CH2OCH), 1 .87 - 1 .77 (m, 3H), 1 .73 - 1 .66 (m, 1 H), 1.61 - 1.47 (m, 6H), 1.43 - 1.26 (m, 10H, (CH2)5);13C NMR (126 MHz, CDCI3) 5 99.02 (OCHO), 67.80 (OCH2(THP)), 62.53 (CH2OCH), 34.20, 32.96, 30.94, 29.87, 29.50, 28.85, 28.30, 27.06, 26.34, 25.65, 19.86. Mass not found.

[0192] 9-((tetrahydro-2 / 7-pyran-2-yl)oxy)nonyl-triphenylphosphonium (3), ad Capon et al., 30.

[0193] To a solution of 2-(9-bomononyloxy)tetrahydro-2H-pyran (2) (6.12 g, 19.92 mmol) in acetonitrile (50 mL) was added triphenylphosphine (5.75 g, 21 .92 mmol). After reflux overnight the mixture was cooled to room temperature and the solvent was evaporated in vacuo. The residue was purified using silica gel column chromatography (gradient of methanol in dichloromethane 1 - 10%) which afforded the product as a thick colourless oil (6.32 g, 12.91 mmol, 64.8%).1H NMR (500 MHz, CDCI3) 5 = 7.89 - 7.83 (m, 6H, Ph-H), 7 80 - 7.76 (m, 3H, Ph-H), 7.72 - 7.67 (m, 6H, Ph-H), 4.56 - 4.52 (m, 1 H, OCHO), 3.88 - 3.80 (m, 3H, CH2OCHOCH2), 3.69 (dt, J=9.6 Hz, 6.9 Hz, 1 H, CH2PPh3), 3.51 - 3.45 (m, 1 H, CH2OCHOCH2), 3.34 (dt, J=9.6 Hz, 6.7 Hz, 1 H, CH2PPh3), 1 .84 - 1 .77 (m, 1 H), 1.73 - 1.67 (m, 1 H), 1.66 - 1.58 (m, 4H), 1.56 - 1.47 (m, 6H), 1.31 - 1.17 (m, 8H, (CH2)4);13C NMR (126 MHz, CDCI3) 5 135.06 (Ph-CH), 135.04 (Ph-CH), 133.90 (Ph-CH), 133.83 (Ph-CH), 130.63 (Ph-C / 7), 130.53 (Ph-C / 7), 118.99 (Ph-C), 118.31 (CH2PPh3), 99.08 (OCHO), 67.80 (OCH2(THP)), 62.62 (CH2OCH), 32.70, 30.94, 30.56, 30.44, 29.81 , 29.47, 29.32, 29.21 , 29.02, 26.25, 25.61 , 23.08, 22.77, 19.92; HRMS (ESI): m / z: [M]+calc, for C32H42O2P+ 489.2917; Found 489.2915.

[0194] Methyl (Z)-18-((tetrahydro-2H-pyran-2-yl)oxy)octadec-9-enoate (5), ad Gung et al., 31 , Kai et al., 32, Suganuma et al., 33. Scheme S1: Synthesis of methyl-9-oxononanoate 4. Reagents and conditions: (a) Borane tetrahydrofuran complex, tetra hydro furan, 0 °C, 30 min, rt, 4 h; (b) pyridinium chlorochromate, celite, dichloromethane, rt, 1.5 h.

[0195] To a solution of mono-methyl azelate (10) (2.5 g, 12.4 mmol) in tetrahydrofuran (25 mL) was added borane tetrahydrofuran complex (12.4 mL 1.0 M in tetrahydrofuran, 12.4 mmol) dropwise over 30 minutes under argon atmosphere while maintaining the temperature at 0°C. After stirring for 4 hours at room temperature the reaction was quenched with water (50 mL). Potassium carbonate (3.0 g, 21 .7 mmol) was added while stirring at 0°C. The reaction mixture was extracted with diethyl ether (2x50 mL). The organic layers were dried over sodium sulfate, filtered and evaporated in vacuo which afforded methyl-9-hydroxynonanoate (11) as a colourless oil (1 .39 g). The crude intermediate was used immediately in the next reaction without purification.1H NMR (500 MHz, CDCh) 6 3.64 - 3.59 (m, 3H), 3.58 - 3.54 (m, J = 8.4 Hz, 4.5 Hz, 1 .8 Hz, 2H), 2.25 (t, J = 7.5 Hz, 2H), 1 .61 - 1 .46 (m, 4H), 1.26 (s, 8H). To an orange suspension of pyridinium chlorochromate (2.39 g, 11.07 mmol) and celite (2.39 g) in dry dichloromethane (25 mL) was added crude methyl-9-oxo-nonanoate (5) (1 .39 g) in dry dichloromethane (6 mL) dropwise while stirring at room temperature. After stirring for 1 .5 hours the reaction mixture was diluted with diethyl ether (25 mL) and the mixture was filtered through a pad of silica. The filtrate was evaporated in vacuo which afforded the crude methyl-9-oxo- nonanoate (4) as a green oil (0.63 g). Again, this intermediate was used immediately in the next reaction without purification.1H-NMR (500 MHz, CDCI3) 6 9.74 (t, J = 1.8 Hz, 1 H), 3.64 (s, 4H), 2.40 (td, J = 7.3 Hz, 1 .8 Hz, 2H), 2.28 (t, J = 7.5 Hz, 1 .9 Hz, 3H), 1 .64 - 1 .55 (m, 5H), 1 .34 - 1 .24 (m, 8H).

[0196] 5

[0197] To a solution of 3 (4.0 g, 8.2 mmol) in dry tetrahydrofuran (30 mL) was added sodium bis(trimethylsilyl)amide (8.2 mL 1.0 M in tetrahydrofuran, 8.2 mmol) dropwise at O °C under argon atmosphere. After stirring for 1 hour at 0°C the mixture was cooled to -78°C. Methyl-9-oxo- nonanoate (4) (0.63 g) was dissolved in dry tetrahydrofuran (5 mL) and added dropwise. After stirring for 1 hour at -78°C the mixture was allowed to warm to 0°C over 2 hours. The reaction was quenched with 40 mL saturated aqueous ammonium chloride and washed with diethyl ether (3x 50 mL). The organic layers were combined, washed with brine, dried over sodium sulfate, filtered and evaporated in vacuo. The residue was purified using silica gel column chromatography (gradient of methanol in dichloromethane 0 - 0.5%) which afforded the product as a colorless oil (552 mg, 1 .39 mmol, 11 .2% yield over three steps).1H-NMR (500 MHz, CDCh) 6 = 5.38 - 5.31 (m, 2H, -CHCH-), 4.59 - 4.55 (m, 1 H, OCHO), 3.90 - 3.84 (m, 1 H, CH2OCH (THP)), 3.72 (dt, J=9.6 Hz, 6.9 Hz, 1 H, CH2OCH), 3.66 (s, 3H, CH3), 3.53 - 3.47 (m, 1 H, CH2OCH (THP)), 3.38 (dt, J=9.6 Hz, 6.7 Hz, 1 H, CH2OCH), 2.30 (t, J=7.6 Hz, 2H, CH2COOCH3), 2.05 - 1 .95 (m, 4H, CH2CHCHCH2), 1 .87 - 1 .79 (m, 1 H), 1 .75 - 1 .67 (m, 1 H), 1 .64 - 1 .55 (m, 6H), 1 .37 - 1 .26 (m, 20H);13C-NMR (126 MHz, CDCh) 6 130.11 (-CHCH-), 129.94 (-CHCH-), 99.01 (OCHO), 67.85 (OCH2(THP)), 62.50 (CH2OCH), 51.58 (CH3), 35.17, 30.97, 29.93, 29.91 , 29.84, 29.65, 29.62, 29.42, 29.31 , 29.28, 29.25, 27.37, 27.33, 26.40, 25.68, 25.11 , 19.87; HRMS (ESI): m / z: [M+Na]+calc, for C24H44O4Na 419.3132; Found 419.3161.

[0198] (Z)-18-((tetrahydro-2H-pyran-2-yl)oxy)octadec-9-enoic acid (6), ad DeGrado et al., 35.

[0199] To a solution of 5 (552 mg, 1.0 mmol) in methanol / water (150 mL 2:1) was added potassium hydroxide (140 mg, 2.5 mmol). After stirring for 2 hours under reflux the reaction was cooled to room temperature. Saturated aqueous ammonium chloride (150 mL) was added. Diethyl ether (150 mL) and brine (50 mL) were added. The organic layer was separated and washed with Et2O (2x 50 mL). The organic layers were combined, dried over sodium sulfate, filtered and evaporated in vacuo. The residue was purified using silica gel column chromatography (gradient of ethyl acetate in hexane 0 - 20%) which afforded the product as a colorless oil (348 mg, 0.91 mmol, 91.1 %).1H-NMR (500 MHz, CDCI3) 6 5.38 - 5.30 (m, 2H, -CHCH-), 4.61 - 4.56 (m, 1 H, OCHO), 3.91 - 3.84 (m, 1 H, CH2OCH (THP)), 3.72 (dt, J = 9.6 Hz, 6.9 Hz, 1 H, CH2OCH), 3.53 - 3.48 (m, 1 H, CH2OCH (THP)), 3.38 (dt, J = 9.6 Hz, 6.7 Hz, 1 H, CH2OCH), 2.34 (t, J = 7.5 Hz, 2H, CH2COOH), 2.04 - 1 .97 (m, 4H, CH2CHCHCH2), 1 .87 - 1 .78 (m, 1 H), 1 .75 - 1 .68 (m, 1 H), 1 .66 - 1 .49 (m, 8H), 1 .40 - 1 .23 (m, 19H).13C-NMR (126 MHz, CDCI3) 6 179.70 (COOH), 130.37 (-CHCH-), 130.16 (-CHCH-), 99.25 (OCHO), 68.13 (OCH2(THP)), 62.74 (CH2OCH), 34.37, 31.15, 30.13, 30.12, 30.04, 29.87, 29.85, 29.63, 29.53, 29.44, 29.42, 27.58, 27.53, 26.61 , 25.87, 25.08, 20.06. HRMS (ESI): m / z: [M+Na]+calc, for C23H42O4Na 405.2975; Found 405.3010.

[0200] 2-(((Z)-18-((tetrahydro-2H-pyran-2-yl)oxy)octadec-9-enoyl)oxy)propane-1 ,3-diyl dioleate (7), ad Kristinsson et al., 34.

[0201] To a solution of 1 ,3-diolein (170 mg, 274 pmol) and 6 (217 mg, 547 pmol) in dry dichloromethane (1 .5 mL) under argon atmosphere was added 4-dimethylaminopyridine (27 mg, 318 pmol) in dry dichloromethane (0.5 mL) in one portion. 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (85 mg, 547 pmol) in dry dichloromethane (1.5 mL) was added dropwise while stirring at room temperature. After stirring for 2 hours the reaction was poured onto a silica gel column and purified using a gradient of diethyl ether in petroleum ether (100 - 90%) affording the product as a colorless oil (250 mg, 0.25 mmol, 92.5%).1H-NMR (500 MHz, CDCI3) 6 5.39 - 5.30 (m, 6H, -CHCH-), 5.29 - 5.24 (m, 1 H, CHCOO (glycerol)), 4.59 - 4.55 (m, 1 H, OCHO), 4.29 (dd, J = 11 .9 Hz, 4.3 Hz, 2H, COOCH2CH (glycerol)), 4.14 (dd, J = 11.9 Hz, 6.0 Hz, 2H, COOCH2CH (glycerol)), 3.90 - 3.83 (m, 1 H, CH2OCH (THP)), 3.73 (dt, J = 9.6 Hz, 6.9 Hz, 1 H, CH2OCH), 3.53 - 3.46 (m, 1 H, CH2OCH (THP)), 3.38 (dt, J = 9.6 Hz, 6.7 Hz, 1 H, CH2OCH), 2.34 - 2.27 (m, 6H, COOCH2CH2), 2.05 - 1 .95 (m, 12H, CH2CHCHCH2), 1 .87 - 1 .79 (m, 1 H), 1 .75 - 1 .67 (m, 1 H), 1 .64 - 1 .49 (m, 13H), 1 .39 - 1 .20 (m, 61 H), 0.88 (t, J = 6.9 Hz, 6H, CH3).13C-NMR (126 MHz, CDCI3) 5 173.90 (COO), 173.00 (COO), 130.16 (-CHCH-), 130.12 (-CHCH-), 129.86 (CH2CHCHCH2), 99.00 (OCHO), 69.01 (CH2CHO (glycerol)), 67.84 (OCH2(THP)), 62.50 (CH2OCH (glycerol)), 62.24 (CH2CHO (glycerol)), 34.34, 34.18, 32.06, 30.94, 29.91 , 29.87, 29.86, 29.68, 29.66, 29.63, 29.47, 29.43, 29.37, 29.33, 29.29, 29.27, 29.24, 29.20, 27.37, 27.34, 27.32, 26.39, 25.66, 25.03, 24.99, 22.83, 19.86, 14.27 (CH3). Mass not found.

[0202] 2-(((Z)-18-hydroxyoctadec-9-enoyl)oxy)propane-1 ,3-diyl dioleate (8), ad Adlof et al., 36.

[0203] To a solution of 7 (180 mg, 182 pmol) in methanol (10 mL) was added p-toluenesulfonic acid (52 mg, 274 pmol) in methanol (2 mL) in a few portions while stirring at room temperature. After stirring for 1 hour the solvent was evaporated. The crude product was poured directly on a silica gel column and purified using a gradient of diethyl ether in petroleum ether (100% - 80%) affording the product as a colorless oil (94.5 mg, 104 pmol, 57.6%).1H-NMR (500 MHz, CDCh) 6 5.38 - 5.30 (m, 6H. - CHCH-), 5.26 (p, J = 5.7 Hz, 5.1 Hz, 1 H, CHCOO (glycerol)), 4.29 (dd, J = 11.9 Hz, 4.3 Hz, 2H, COOCH2CH (glycerol)), 4.14 (dd, J = 11 .9 Hz, 5.9 Hz, 2H, COOCH2CH (glycerol)), 3.64 (t, J = 6.6 Hz, 2H, CH2OH), 2.34 - 2.28 (m, 6H, CH2COO), 2.01 (q, J = 6.4 Hz, 12H, CH2CHCHCH2), 1 .66 - 1 .52 (m, 9H), 1 .39 - 1 .20 (m, 62H), 0.88 (t, J = 6.9 Hz, 6H, CH3).13C-NMR (126 MHz, CDCh) 6 173.43 (COO), 173.03 (COO), 130.16 (-CHCH-), 130.10 (-CHCH-), 129.90 (-CHCH-), 129.86 (- CHCH-), 69.01 (CH2CHO (glycerol)), 63.22 (CH2OCH (glycerol)), 62.24 (CH2OCH (glycerol)), 34.34, 34.18, 32.96, 32.06, 29.91 , 29.87, 29.86, 29.68, 29.64, 29.56, 29.47, 29.37, 29.35, 29.33, 29.27, 29.24, 29.20, 27.32, 25.89, 24.99, 22.83, 14.27 (CH3). HRMS (ESI): m / z: [M+H]+calc. for CsyH sOy 901.7855; Found 901.7756.

[0204] 2-(((Z)-18-(tosyloxy)octadec-9-enoyl)oxy)propane-1 ,3-diyl dioleate (9), ad DeGrado et al., 35.

[0205] To a solution of 8 (80 mg, 89 pmmol) in dry dichloromethane (5 mL) at 0°C was added diisopropylethylamine (76 pL, 445 pmol) and p-toluenesulfonyl chloride (21 mg, 107 pmol). The reaction mixture was warmed to 40 °C and 4-dimethylaminopyridine (2 mg, 244 mmol) was added. After stirring for 2 h the solvent was evaporated and the residue was purified using silica gel column chromatography (gradient of ethyl acetate in hexane 0 - 20%) which afforded the product as a yellow oil (72.5 mg, 68 pmol 77.2%).1H-NMR (500 MHz, CDCI3) 6 = 7.79 (d, 2H, Ph-H), 7.34 (d, J=8.0 Hz, 2H, Ph- / - / ), 5.38 - 5.30 (m, 6H, -CHCH-), 5.29 - 5.23 (m, 1 H, CHCOO (glycerol)), 4.29 (dd, J=11.9 Hz, 4.3 Hz, 2H, COOCH2CH (glycerol)), 4.14 (dd, =11 .9 Hz, 5.9 Hz, 2H, COOCH2CH (glycerol)), 4.01 (t, J=6.5 Hz, 2H, CH2OTs), 2.45 (s, 3H, CH3(tosyl)), 2.31 (td, J=7.6 Hz, 2.9 Hz, 6H, CH2COO), 2.04 - 1.96 (m, 12H, CH2CHCHCH2), 1.61 (ddd, J=11.3 Hz, 8.0 Hz, 5.5 Hz, 8H), 1.35 - 1.20 (m, 63H), 0.88 (t, J=6.8 Hz, 6H, CH3).13C-NMR (126 MHz, CDCI3) 6 173.42 (COO), 173.00 (COO), 130.16, 129.99, 129.95, 129.93, 129.86, 128.04 (-CHCH- and Ph-CH), 70.82 (CH2Ots), 69.02 (CH2CHO (glycerol)), 62.23 (CH2CHO (glycerol)), 34.34, 32.06, 29.91 , 29.86, 29.84, 29.68, 29.47, 29.37, 29.33, 29.29, 29.27, 29.24, 29.20, 29.06, 28.97, 27.37, 27.34, 27.32, 25.48, 25.03, 24.99, 22.83, 21.78 (CH3(tosyl)), 14.27 (CH3). HRMS (ESI): m / z: [M+H]+calc, for C64H111O9S 1055.7943; Found 1055.8361.

[0206] Glycerol tri^FJoleate (19) radiosynthesis procedure

[0207] Scheme S2 (Figure 9B): Triflyl fluoride labeling of precursor 9. Reagents and conditions: (a) [^F]- (aqueous), Potassium sulfate (0.1M, aqueous), dimethtylformamide, 50°C, 1 min; (b) potassium

[0208] [18F]Fluoride was produced by the18O(p,n)18F nuclear reaction on an IBA Cyclone 18 / 9 cyclotron using a [18O]H2O liquid target. The18F-fluoride is trapped on a Chromafix 2O-PS-HCO318F separation cartridge. A 0.1 M solution of potassium sulfate (500 pL) and a helium flow of 5 mL / min were used to elute the [18F]fluoride into a heated (50°C) solution of A / -phenyl- bis(trifluoromethanesulfonimide) (17) (5 mg, 14 pmol) in dimethylformamide (1 mL).1 O [18F]Triflylfluoride (18) was formed and distilled for 5 minutes into the reaction vessel in which it is trapped in 250 pL of a heated (25°C) solution of acetonitrile containing potassium bicarbonate (0.6 mg, 6 pmol) and kryptofix (2.2 mg, 6 pmol). Precursor 9 (1 mg, 0.1 pmol) was dissolved in 100 pL dry tetrahydrofuran and added to the reaction vessel. After stirring for 10 minutes at 80°C the reaction mixture was cooled to 20°C and 1.5 mL of 80:20 acetone / acetonitrile was added. The crude product was purified using semi-preparative HPLC (Phenomenex Luna 5 pm, 100 A, 250 x 10 mm, 80:20 acetone / acetonitrile, 210 nm, 5 mL / min). The desired radiolabeled product ([18F]19) is obtained in a radiochemical purity greater than 99% and an average decay corrected radiochemical yield of 14.3±3.4% (n=7) in about 1 hour. Methyl-18-hydroxyoctadec-9-enoate (12), ad Adlof et al., 36.

[0209] To a solution of 5 (457 mg, 1.15 mmol) in dry methanol (5 mL) was added p-toluenesulfonic acid (242 mg, 1 .27 mmol). After stirring at room temperature for 3 hours the reaction mixture was diluted with dichloromethane (10 mL). The organic layer is washed with water (15 mL) and brine (15 mL). The organic layer was separated, dried over anhydrous sodium sulfate, filtered and evaporated in vacuo. The residue was purified using silica gel column chromatography (gradient of ethyl acetate in hexane 0 - 20%) which afforded the product as a yellow oil (228 mg, 0.73 mmol, 63.5%).1H-NMR (500 MHz, CDCI3) 5 = 5.38 - 5.30 (m, 2H, -CHCH-), 3.66 (s, 3H, CH3), 3.63 (t, J=6.6 Hz, 2H, CH2OH), 2.30 (t, J=7.6 Hz, 2H, CH2OC), 2.05 - 1 .95 (m, 4H, CH2CHCHCH2), 1 .65 - 1 .58 (m, 2H), 1.58 - 1.52 (m, 2H), 1.35 - 1.26 (m, 19H).13C NMR (126 MHz, CDCI3) 5 174.76 (COOCH3), 130.33 (-CHCH-), 130.22 (-CHCH-), 63.49 (CH2OH), 51.87 (CH3), 34.51 , 33.21 , 30.12, 30.07, 29.88, 29.80, 29.61 , 29.56, 29.53, 29.48, 27.58, 27.56, 26.14, 25.35. HRMS (ESI): m / z: [M+H]+calc. for Ci9H3603312.2664; Found 313.2752

[0210] Methyl-18-(tosyloxy)octadec-9-enoate (13), ad DeGrado et al., 35.

[0211] To a solution of 12 (93.4 mg, 0.3 mmol) in dichloromethane (5 mL) was added triethylamine (64 pL, 0.45 mmol) and p-toluenesulfonyl chloride (69 mg, 0.36 mmol). After stirring at room temperature for 72 h the reaction mixture was diluted with dichloromethane (10 mL). The mixture is washed with water (3 x 10 mL). The organic layer was separated, dried over anhydrous sodium sulfate, filtered and evaporated in vacuo. The residue was purified using silica gel column chromatography (gradient of ethyl acetate in hexane 0 - 20%) which afforded the product as a colorless oil (61 mg, 0.13 mmol, 43.6%).1H-NMR (500 MHz, CDCI3) 5 = 7.79 (d, 2H, Ph-H), 7.34 (d, J=8.1 Hz, 2H, Ph-H), 5.36 - 5.30 (m, 2H, -CHCH- ), 4.01 (t, J=6.5 Hz, 2H, CH2OTs), 3.66 (s, 3H, CH3OCO), 2.45 (s, 3H, CH3(tosyl)), 2.30 (t, J=7.6 Hz, 2H, CH2CO), 2.03 - 1 .96 (m, 4H, CH2CHCHCH2), 1 .65 - 1 .59 (m, 4H), 1 .35 - 1 .20 (m, 20H).13C-NMR (126 MHz, CDCI3) 5 174.71 (COOCH3), 144.99, 133.71 , 130.28, 130.23, 130.19, 128.29 (-CHCH- and Ph-CH), 71.08 (CH2OTs), 51.84 (CH3), 34.51 , 30.09, 30.07, 29.69, 29.56, 29.54, 29.52, 29.49, 29.31 , 29.22, 27.57, 25.73, 25.35, 22.03 (CH3(tos)). HRMS (ESI): m / z: [M+H]+calc, for C26H42O5S 466.2753; Found 467.2860.

[0212] Methyl-18-fluorooctadec-9-enoate (14), ad Kim et al., 38. To a solution of 13 (138 mg, 0.3 mmol) in dry tetra hydrofuran (4 mL) was added TBAF(tBuOH)4 (Kim et al., 38) (335 mg, 0.6 mmol). After stirring for 1 hour at 60°C water was added (10 mL). The mixture was extracted with diethyl ether (3x 10 mL). The organic layer was dried over anhydrous sodium sulfate, filtered and evaporated in vacuo. The residue was purified using silica gel column chromatography (gradient of ethyl acetate in hexane 0 - 10%) which afforded the product as a colorless oil (59.6 mg, 0.19 mmol, 63.8%).1H-NMR (500 MHz, CDC ) 5 = 5.38 - 5.30 (m, 2H, - CHCH-), 4.43 (dt, J=47.4 Hz, 6.2 Hz, 2H, CH2F), 3.66 (s, 3H, CH3), 2.30 (t, J=7.6, 2H, CH2CO), 2.07 - 1 .94 (m, 4H, CH2CHCHCH2), 1 .79 - 1 .57 (m, 4H), 1 .44 - 1 .23 (m, 20H).13C-NMR (126 MHz, CDCI3) 5 174.73 (COOCH3), 130.29 (-CHCH-), 130.24 (-CHCH-), 84.65 (d, J= 163.9 Hz, CH2F), 51 .85 (CH3), 34.51 , 30.89, 30.73, 30.11 , 30.08, 29.81 , 29.62, 29.58, 29.56, 29.53, 29.49, 27.59, 27.57, 25.56, 25.52, 25.35. HRMS (ESI): m / z: [M+H]+calc for C19H35FO2 314.2621 ; Found 315.2698.

[0213] 18-Fluorooctadec-9-enoic acid (15), ad DeGrado et al., 35.

[0214] To a solution of 14 (54 mg, 0.18 mmol) in a mixture of methanol and water (27 mL, 2:1) was added potassium hydroxide (24 mg, 0.42 mmol). After stirring for 2 hours under reflux the reaction mixture was left to cool to room temperature before 25 mL saturated aqueous ammonium chloride was added. The mixture was extracted with diethyl ether (3x 50 mL). The organic layer was dried over anhydrous sodium sulfate, filtered and evaporated which afforded the product as a colourless oil (50 mg, 0.17 mmol, 94.2%).1H-NMR (500 MHz, CDCI3) 5 = 5.39 - 5.30 (m, 2H, -CHCH-), 4.44 (dt, J=47.4 Hz, 6.2 Hz, 2H, CH2F), 2.35 (t, J=7.5 Hz, 2H, CH2COOH), 2.01 (m, 4H, CH2CHCHCH2), 1.78 - 1 .59 (m, 4H), 1 .42 - 1 .15 (m, 20H).13C-NMR (126 MHz, CDCI3) 5 179.46 (COOH), 130.06 (- CHCH-), 84.40 (d, J= 163.9 Hz, CH2F), 34.04, 30.63, 30.47, 29.86, 29.81 , 29.55, 29.36, 29.33, 29.28, 29.21 , 29.17, 27.33, 27.30, 25.31 , 25.27, 24.81. HRMS (ESI): [M+Na]+calc, for Ci8H33FNaO2323.2357; Found 323.2359.

[0215] 2-((18-fluorooctadec-9-enoyl)oxy)propane-1 ,3-diyl dioleate (16), ad Kristinsson et al., 34.

[0216] 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimde (12 mg, 79 pmol) in dichloromethane (1 mL) was added dropwise to a stirred solution of 15 (25 mg, 79 pmol), 4-dimethylaminopyridine (4 mg, 31 pmol) and 1 ,3-diolein (25 mg, 39 pmol) in dichloromethane (3 mL). After stirring for 3 hours the reaction mixture was poured directly onto a silica gel column and purified using a gradient of diethyl ether in petroleum ether (0 - 10%) affording the product as a colorless oil (35 mg, 38 pmol, quantitative).1H-NMR (500 MHz, CDCh) 6 = 5.40 - 5.29 (m, 6H, -CHCH-), 5.29 - 5.23 (m, 1 H, CHCOO (glycerol)), 4.43 (dt, J=47.3 Hz, 6.2 Hz, 2H, CH2F), 4.34 - 4.10 (m, 4H, COOCH2CH (glycerol)), 2.39 - 2.25 (m, 6H, CH2COO), 2.07 - 1.93 (m, 12H, CH2CHCHCH2), 1.74 - 1.56 (m, 8H), 1.36 - 1.23 (m, 63H), 0.88 (t, J=6.9, 6H, CH3).13C NMR (126 MHz, CDC ) 6 173.42 (COO), 173.00 (COO), 130.17, 130.06, 129.92, 129.86 (-CHCH-), 84.38 (d, J= 163.9 Hz, CH2F), 69.01 (CH2CHO (glycerol)), 34.34, 34.18, 32.06, 29.92, 29.86, 29.68, 29.57, 29.48, 29.37, 29.34, 29.29, 29.27, 29.24, 29.20, 27.38, 27.33, 25.03, 25.00, 22.84, 14.27 (CH3). HRMS (ESI): m / z: [M+H]+calc, for C57HIO3F06902.7739; Found 903.7811 .

[0217] Animals and treatment

[0218] Eight-week-old male C57BI / 6J mice (Charles River Laboratories, St. Germain Nuelles, France) were group-housed under standard conditions with a 12h: 12h light-dark cycle (light period, 7 AM - 7 PM) at a room temperature of around 21 °C and with ad libitum access to water and chow. After one week of acclimatization, for experiments 1 , 2 and 3 (see below), mice were randomized into two treatment groups based on body weight and received daily subcutaneous injections around 4 PM with the p3- AR agonist CL316,243 (0.8 mg / kg body weight) or the vehicle (PBS) for 7 days. On day 8, directly after the last dosing of CL316,243 or vehicle at 9 AM, mice were fasted for 4 hours and then anesthetized with isoflurane (1 .5-2% in oxygen at 0.4 L / min) while their body temperature was maintained using heating pads. Thereafter, mice were injected with radiolabeled TRL-like particles as elaborated in the following sections.

[0219] Preparation and characterization of TRL-like particles

[0220] TO (T7140), L-a-lysophosphatidylcholine (L4129), cholesteryl oleate (CO; C9253), and cholesterol (C8667) were purchased from Sigma-Aldrich. Egg yolk phosphatidylcholine (98%) was obtained from Lipoid (Steinhausen, Switzerland). [3H]TO (ET431 L005MC) and [14C]CO (NEC638250UC) were obtained from PerkinElmer.

[0221] TRL-like particles were prepared as previously described by Ying et al., 28 with slight modifications. Briefly, TO (50 mg), egg yolk phosphatidylcholine (16.21 mg), lysophosphatidylcholine (1.64 mg), CO (2.14 mg) and cholesterol (1.43 mg) (all from stock solutions in CH3OH:CHCI31 :1 v / v were added into a 20 mL glass flat-bottom vial (6000096, Perkin Elmer). In addition, [3H]TO (100 pCi) and [14C]CO (10 pCi) with or without 30 pg of [19F]TO were additionally added (experiment 1), or 30 pg [18F]TO was additionally added (experiments 2 and 3). After evaporation of the solvent by a gentle stream of N2, the lipid mixture was sonicated in 10 mL regular saline for 2 x 15 min at 10 pm output, using a Soniprep 150 (MSE Scientific Instruments, UK) equipped with a water bath at 54°C. Evaporated water was compensated for by adding water to the sonication product. The crude emulsion was centrifuged (30 sec at 300g) at room temperature to remove titanium fragments derived from the sonotrode tip, and the resulting TRL-like particles were injected into mice within 2 hours. The size distribution of TRL-like particles was measured by dynamic light-scattering using a fixed- angle Zetasizer Nano ZSP (Malvern Instruments) and expressed as distribution of number. Biodistribution of I3H]TO and [14C]CO double-labeled TRL-like particles without or with [^FJTO In experiment 1 , vehicle-treated mice and CL316,243-treated mice were injected via the tail vein with 200 pL of [3H]TO and [14C]CO double-labeled TRL-like particle emulsion ( / .e., equivalent to 0.7 mg TG; 30 kBq3H-activity and 5.6 kBq14C-activity) without or with [19F]TO (n=6 per group). Blood samples were taken from the tail vein at 2, 5, 10, and 15 min after particle injection, and plasma was obtained after centrifugation (5 min, 12000g, 4°C). Mice were euthanized by CO2 inhalation and perfused with ice-cold PBS for 5 min to remove the blood and noninternalized particles from organs. Organs and tissues were collected and weighed, and approx. 70 mg dissolved overnight at 55°C in 0.5 mL Solvable (Perkin Elmer).3H and14C activity (disintegrations per minute, dpm) in obtained plasma and dissolved organs / tissues were quantified in 2.5 mL and 5 mL Ultima Gold liquid scintillation cocktail (PerkinElmer), respectively, using a Tri-Carb 2910TR Low Activity Liquid Scintillation Analyzer (PerkinElmer). Blood volume was estimated by dividing plasma volume by 0.5850, and then converted into weight (g) based on blood density 1 .06 g / mL. Results were expressed as percentages of the injected radioactive dose per gram of blood or wet tissue (% ID / g). Two mice were excluded from vehicle + [19F]TO particle group due to particle injection failure. Biodistribution of[18F]TO incorporated in TRL-like particles

[0222] In experiment 2, mice treated with vehicle or CL316,243 were injected with [18F]TO-containing TRL- like particle emulsion ( / .e., 150 pL; 0.7 mg TG; 6.5-13 MBq) as described above (n=4 mice per group, per time point). At 5, 10 and 15 min after particle injection, mice were killed by cervical dislocation. Thereafter, blood was collected via heart puncture, and mice were perfused with 10 mL ice-cold PBS. Finally, (parts of) organs and tissues were collected and weighed.18F activity (counts per minute, cpm) was determined using Wizardll 2480 (PerkinElmer). Results were expressed as %

[0223] In experiment 3, mice treated with vehicle or CL316,243 were injected with [18F]TO-containing TRL- like particle emulsion (150 pL; 0.7 mg TG; 6.5-13 MBq) or with [18F]FDG (100 pL; 11 .5 - 14.5 MBq) via a tail vein catheter (n=4 mice per group), after which dynamic image acquisition for 60 min posttracer injection was performed using small animal nano PET / CT (Mediso Ltd.). Mice were positioned on the scanner double-bed and their respiratory rate was monitored during the entire scan. PET scans were acquired in list mode and rebinned into the following frame sequence: 4x5, 4x10, 2x30, 3x60, 2x300, 3x600 and 1 x900. Reconstruction was performed using a fully three-dimensional reconstruction algorithm (Tera-TomoTM, Mediso Ltd.) with 4 iterations and 6 subsets, and an isotropic 0.4 mm voxel dimension. Regions-of-interest (ROI) were drawn manually on the different organs (Fig. 8). The brain ROI was drawn by applying a brain atlas for the different brain regions. Images were analyzed and quantified using the VivoQuant software (Invicro), and ROI were applied using VivoQuant-integrated brain atlas fitting CT. One mouse from CL316,243 + [18F]FDG group, two mice from vehicle + [18F]TO group and two mice from CL316,243 + [18F]TO group were excluded due to failed tracer injection. Statistics

[0224] Data, except for particle size, were presented as mean ± SEM, and statistical analyses were performed using GraphPad Prism 9. In experiment 1 , time-activity curves of3H and14C activity in blood were analyzed by repeated measures two-way ANOVA followed by Tukey’s test for main effects between groups, and organ distribution of3H and14C were analyzed by one-way ANOVA with Tukey’s test. In experiment 2, data were analyzed by unpaired Student’s T-test. P values less than 0.05 were considered statistically significant.

[0225] To obtain a [18F]TO, the inventors identified the terminus of the central alkyl chain as a suitable position for the introduction of a fluorine-18 atom. Radiolabeling was envisioned by nucleophilic aliphatic substitution on precursor 9 (Scheme 1 A, Figure 9A). The synthesis started with the protection of the 9-bromo-1-nonanol (1) hydroxyl group with a tetrahydropyranyl (THP) ether (Grube et al., 29). Compound 2 was converted to its corresponding Wittig reagent 3 using triphenylphosphine (Capon et al., 30). Wittig reaction of 3 and of the formed aldehyde in 4 after reduction and subsequent oxidation of mono-methyl azelate (10) following a previously described procedure (Scheme S1 , Materials and Methods) (Gung et al., 31 , Kai et al., 32), produced THP- protected methyl-Z-octadecenoate (5) in a yield of 11 .2% over three steps (Suganuma et al., 33). After saponification of the methyl ester, the unsaturated FA was introduced on the free hydroxyl group of commercially available 1 ,3-diolein using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC) as a coupling agent in the presence of 4-dimethylaminopyridine (DMAP), affording THP protected TG 7 in an high yield of 92.5% (Kristinsson et al., 34). Removal of the THP protective group using p-toluene sulfonic acid, and final tosylation of the free hydroxyl group on 8 produced precursor 9 in an overall yield of 2.7% over 7 reaction steps (DeGrado et al., 35, Adlof et al., 36). To introduce a fluorine-18 atom in precursor 9 (Scheme 1 B and S2, Figure 9B), [18F]triflylfluoride (18) was formed instantaneously by eluting cyclotron prepared [18F]fluoride into a solution of N- phenyl-bis(trifluoromethane)sulfonimide (17) in dimethylformamide using an aqueous solution of potassium sulfate (Pees et al., 37). The [18F]triflylfluoride is trapped in a solution of potassium bicarbonate and kryptofix in acetonitrile. The reaction of precursor 9 and [18F]triflylfluoride was carried out using a low precursor amount of 1 mg per reaction. Purification using semi-preparative HPLC resulted in the desired [18F]TO 19 in radiochemical purities greater than 99% and an average radiochemical yield of 14.3±3.4% (n=7).

[0226]

[0227] Synthesis of glycerol tri ^FJoleate

[0228] In order to test whether fluorinated glycerol trioleate (triolein, TO) affects the size and in vivo behavior of TRL-like particles, the inventors additionally synthesized the non-radiolabeled glycerol tri[19F]oleate ([19F]TO; i.e., reference compound 16; Scheme S3, Materials and Methods, Figure 10). The synthesis started from the THP protected methyl-Z-octadecenoate 5. Removal of the THP protective group resulted in alcohol 12, which was tosylated giving compound 13 (DeGrado et al., 35, Adlof et al., 36). Compound 13 was fluorinated using tetrabutylammonium tetra (terf-butyl alcohol)-coordinated fluoride (prepared as described previously, Kim et al., 38) to afford fluorinated methyl ester 14 in a yield of 63.8%. After removal of the methyl group from the methyl ester the fluorinated FA chain was introduced on the free hydroxyl group of 1 ,3-diolein to give [19F]TO 16 in an overall yield of 0.9% over 8 reaction steps (Kristinsson et al, 34, DeGrado et al., 35).

[0229] Incorporation of ^FJTO does not affect size, kinetics and biodistribution of TRL-like particles in mice The inventors continued by generating [3H]TO and [14C]CO double-labeled TRL-like particles without or with the addition of the same amount of [19F]TO compared to the amount of [18F]TO that will later be used in PET-CT scanning. Incorporation of [19F]TO did not affect particle size distribution, and the mean diameter of [19F]TO-containing TRL-like particles (47.9 nm) was comparable with that of control TRL-like particles (50.7 nm) (Fig. 1A).

[0230] The incorporation of [3H]TO and [14C]CO into TRL-like particles allowed the inventors to trace uptake of liberated FAs by LPL-mediated lipolysis ( / .e., [3H]oleate) as well as uptake of the TRL core remnants ( / .e., [14C]CO). The TRL-like particles were intravenously injected into mice that have been treated with vehicle or the P3-AR agonist CL316,243 for 8 days to activate BAT and promote browning of white adipose tissue (WAT). Compared to vehicle treatment, CL316,243 treatment accelerated the clearance of [3H]TO from plasma, irrespective of incorporation of [19F]TO (Fig. 5A). In line with the increased plasma clearance, CL316,243 treatment vs. vehicle treatment largely increased the uptake of [3H]TO-derived [3H]oleate by iBAT (6.3-fold; 114.7 vs. 18.1% I D / g), sBAT (5.9-fold; 104.0 vs. 17.8% ID / g), gWAT (6.6-fold; 5.6 vs. 0.8% ID / g) and sWAT (6.9-fold; 10.6 vs. 1.5% ID / g), and reduced uptake of [3H]TO-derived [3H]oleate by the liver (-60.1%; 5.6 vs. 14.1 % ID / g) and spleen (-55.5%; 2.5 vs. 5.7% ID / g) at 15 min after injection, with similar results observed after incorporation of [19F]TO (Fig. 1 B). Neither the treatment nor the various particle preparations affected the uptake of [3H]TO-derived activity by quadriceps, the heart, kidneys and the lung.

[0231] CL316,243 treatment as compared to vehicle treatment accelerated the plasma clearance of [14C]CO, which was irrespective of incorporation of [19F]TO (Fig. 5B), although CL316.243 treatment did not grossly affect the biodistribution of [14C]CO (Fig. 1 C).

[0232] Taken together, incorporation of [19F]TO into TRL-like particles does not affect the size distribution of the TRL-like particles nor the in vivo kinetics and biodistribution of the TRL-derived FAs and core remnants without and with activation of BAT by P3-AR agonism.

[0233] The inventors next evaluated the effect of P3-AR agonism on the in vivo biodistribution of [18F]TO incorporated into TRL-like particles in mice at 5 min (Fig. 2A), 10 min (Fig. 2B) and 15 min (Fig. 2C) after TRL-like particle injection in the mouse model described above. CL316.243 treatment, as compared to vehicle treatment, time-dependently increased the uptake of [18F]TO-derived [18F]oleate by iBAT (7- to 26-fold), sBAT (7- to 57-fold), gWAT (6- to 10-fold) and sWAT (4- to 10-fold) (Fig. 2A- C). Notably, after 15 min the average uptake of [18F]oleate by iBAT (223.2% ID / g) and sBAT (265.7% ID / g) (Fig. 2C) was approximately twice as high as the uptake of [3H]oleate by iBAT (114.7% ID / g) and sBAT (104.0% ID / g) (Fig. 1 B) upon CL316.243 treatment. This may reflect accumulation of18F in contrast to3H that is easily secreted from thermogenic adipose tissues as3H2O following p- oxidation of FAs.

[0234] CL316.243 treatment also consistently increased [18F]TO-derived [18F]oleate uptake by quadriceps (Fig. 2A-C) and adrenals (Fig. 6A-C) as compared to vehicle treatment, although total uptake was much lower than that of BAT. No to little uptake of [18F]oleate was observed in the gastrointestinal tract, pancreas, skull bone, brain, urine and skin (Fig. 6A-C). CL316,243 treatment reduced [18F]oleate uptake by heart, liver, spleen and lung at 5 and / or 10 min (Fig. 2A-B), while increasing uptake of [18F]oleate by these tissues at 15 min (Fig. 2C). This time-dependent change is likely explained by initial binding of TRLs to LPL within capillaries of BAT and WAT to supply FAs for thermogenesis, followed by detachment of TG-containing remnants for uptake elsewhere.

[0235] Taken together, P3-AR agonism causes a time-dependent large increase in the uptake of TRL- [18F]TO-derived [18F]oleate by BAT and WAT to an even higher extent than [3H]TO-derived [3H]oleate.

[0236] The inventors followed up on evaluating the performance of the newly developed [18F]TO incorporated into TRL-like particles with the current gold standard [18F]FDG to trace metabolic BAT activity with nano PET-CT imaging in mice after vehicle or P3-AR agonism treatment.

[0237] PET-CT images, constructed from 60 min of dynamic image acquisition (Fig. 3), showed that in vehicle-treated mice [18F]FDG is taken up in high quantities by the heart with low uptake being observed in BAT. CL316.243 treatment to some extent increased the uptake of [18F]FDG by iBAT and sBAT, but [18F]FDG was still prominently shuttled towards the heart. In favorable contrast, uptake of [18F]TO-derived [18F]oleate by the heart was low in both vehicle- and CL316,243-treated mice, while CL316.243 largely increased uptake of [18F]TO-derived [18F]oleate by both iBAT and sBAT. [18F]TO was also taken up by the liver, which likely reflects hepatic uptake of TRL core remnants and spillover of FAs from LPL-mediated lipolysis.

[0238] Examination of the time-dependent uptake of18F by the various organs in vehicle-treated mice revealed a progressively increasing uptake of [18F]FDG by the heart (up to 74.0% ID / mL; Fig. 4A), which apart from the bladder was higher than in any other organ examined. CL316,243 treatment modestly increased the uptake of [18F]FDG by iBAT (2.6-fold; ~7.0 vs. ~2.7% ID / mL; Fig. 4B) and sWAT (2-fold; ~2.8 vs. ~1.4% ID / mL; Fig. 4C). When using [18F]TO incorporated in TRL-like particles as the tracer,18F activity observed in the heart was very low (~4.6% ID / mL) in either vehicle- and CL316,243-treated mice (Fig. 4A). Most strikingly, CL316.243 treatment highly increased the uptake of [18F]TO-derived [18F]oleate by iBAT (4-fold; -16.5 vs. -4.1% ID / mL; Fig. 4B) and sWAT (4.9-fold; -10.3 vs. -2.1 % ID / mL; Fig. 4C). It should be noted that CL316.243 treatment induced a very rapid uptake of [18F]TO-derived [18F]oleate by iBAT and sWAT, reaching peak uptake within -5 min after injection, and that the18F label showed retention in both tissues within the 60 min scanning period. Likewise, uptake of [18F]TO-derived [18F]oleate by the liver was both rapid and substantial, reflecting rapid hepatic uptake of [18F]TO-containing TRL remnants in addition to [18F]oleate as spillover from extrahepatic LPL-mediated lipolysis. Examination of other tissues shows higher uptake of [18F]TO- derived [18F]oleate by skeletal muscle ( / .e., quadriceps) and lower uptake by brain, kidneys and bladder, compared to [18F]FDG (Fig. 7).

[0239] The inventors furthermore investigated the detectability of brown adipose tissue with [18F]TO PET- CT in diet-induced obese mice. Diet-induced obese C57BL / 6J mice were treated with vehicle (saline) or the p3-adrenergic receptor agonist CL316,243 for 8 days, prior to intravenous administration of [18F]TO incorporated in triglyceride-rich lipoprotein-like particles and PET-CT scanning. As shown in Fig. 12 (left), it was found that in obese mice, brown adipose tissue (BAT) can reliably be detected using [18F]TO. Most strikingly, as show in Fig. 12 (right), activation of BAT with CL316.243 was found to cause a pronounced increase in the Standard Uptake Value (SUV; data presented as mean ±SD, and with individual dot plots) compared to vehicle treatment.

[0240] The detectability of browning in white adipose tissue with [18F]TO versus [18F]FDG in PET-CT was also investigated. Diet-induced obese C57BL / 6J mice were treated with vehicle (saline) or the p3- adrenergic receptor agonist CL316.243 for 8 days, prior to intravenous administration of [18F]TO incorporated in triglyceride-rich lipoprotein-like particles or [18F]FDG, followed by PET-CT scanning. As shown in Fig. 13 (right), subcutaneous white adipose tissue was basically found undetectable with [18F]FDG, independent of thermogenic activation. Standard Uptake Values (SUV; data presented as mean ±SD, and with individual dot plots) for [18F]TO (Fig. 13, left) were already greater than for [18F]FDG in vehicle-treated animals, and strongly increased upon treatment with CL316,243, consistent with induction of browning.

[0241] Taken together, [18F]TO incorporated into TRL-like particles is superior to [18F]FDG in tracing metabolic activity of the thermogenic tissues BAT and sWAT, and results in lower uptake of18F label by the heart, brain, kidney and bladder.

[0242] DISCUSSION

[0243] BAT activation is regarded as a promising strategy for combating metabolic diseases, including T2D, dyslipidemia and associated atherosclerotic CVD. Activated BAT has a very high capacity for clearing TRL-derived TGs from the circulation as shown in mice, but also in humans. This prompted the inventors to generate [18F]TO as a novel tool for visualisation of metabolic BAT activity as compared to [18F]FDG, the current gold standard to examine BAT metabolic activity by PET-CT in humans. Here, it is reported on the successful synthesis of a previously non-existing [18F]TO tracer and incorporation into recombinant TRLs, and it is demonstrated that [18F]TO outperforms [18F]FDG in tracing activated BAT via PET-CT imaging in mice.

[0244] [18F]FDG PET-CT has been instrumental to reveal that BAT is present and active in human adults just over a decade ago, and has since then been widely adopted to assess BAT metabolic activity in clinical studies. The wide application of [18F]FDG PET-CT in oncology, to identify and monitor tumor growth and metastasis, additionally offered opportunities to retrospectively assess BAT activity in large populations. For example, via retrospectively evaluating 134,529 [18F]FDG PET-CT images from 52,487 patients, Becher et al. revealed that individuals with detectable non-stimulated BAT activity (i.e. , at room temperature) have better cardiometabolic health, as reflected by lower blood glucose and TG levels (Becher et al., 13). The presence of active BAT is also independently associated with lower odds of T2D, dyslipidemia and various CVDs (Becher et al., 13). However, [18F]FDG does underestimate cold-stimulated BAT metabolic activity in at least older individuals and those suffering from T2D (Blondin et al., 15). This phenomenon may be partially explained by the development of insulin resistance of BAT under metabolic challenges as shown in mice, which impairs glucose uptake but not fatty acid uptake or oxidative activity.

[0245] Ideally, a lipid-based tracer formulated in recombinant TRLs should be processed and taken up by BAT just like lipids derived from endogenous TRLs. In a previous attempt, the inventors developed a [18F]BODIPY-TG for incorporation into TRL-like particles and tested its utility in tracing cold-activated BAT (Paulus et al., 43). However, BAT uptake of [18F]BODIPY-TG-derived18F was low, irrespective of housing temperature (i.e., regular room temperature or 4°C), while uptake by organs such as lungs and spleen was high. Incorporation of [19F]TO into recombinant TRLs did not affect their biodistribution, indicating that incorporation of the fluorine into TG does not interfere with LPL- mediated particle processing in the circulation.

[0246] The inventors showed that pharmacological activation of BAT by a P3-AR agonist resulted in a much more pronounced increase in the uptake of [18F]TO-derived [18F]oleate by BAT as compared to [18F]FDG. The inventors thus reason that compared with a glucose analog, TRL-TG-derived FAs are both more selective and sensitive in tracing metabolic activity of activated BAT. Concomitant with a much higher uptake of [18F]TO-derived [18F]oleate by activated BAT as compared to [18F]FDG, a much lower18F-uptake by organs by heart and brain was observed. Indeed, glucose is the preferred energy source of the heart and the brain is known to be strictly dependent on glucose oxidation. The weak [18F]TO-derived signal observed in the brain may be attributed to modest transfer of [18F]TO from recombinant TRLs to high-density lipoproteins (HDL) that have been shown capable of passing the blood-brain barrier. Recombinant TRL-incorporated [18F]TO may show a much higher specific uptake of18F by activated BAT compared to [18F]FDG in humans, resulting in that the radioactive dose and thus radioactive burden on the individual is expected to be strongly reduced, which would allow for repeated assessment on BAT activity in longitudinal clinical studies.

[0247] Interestingly, [18F]TO incorporated in TRL-like particles may hold applications broader than assessing activated BAT, especially given that significant evolution has occurred in PET-CT scanners over the past decades. Emerging digital PET-CT enables reduction of the radiotracer dose and shortening of the image acquisition time, and whole-body PET-CT allows for simultaneous whole-body measurement, both encouraging expansion of PET-CT imaging for wider clinical use and research. For example, assessment of whole-body [18F]TO biodistribution can be used investigate the pathophysiology of dyslipidemia and to identify ectopic lipid deposition in non-adipose organs. Likewise, [18F]TO may be used to gain more insight in the mode of action of recently emerged TG-lowering pharmacological strategies, such ANGPTL3 inhibition. Moreover, pharmacological activation of BAT not only promotes the processing of TRL-TGs to reduce plasma TG levels, but also stimulates hepatic uptake of cholesterol-enriched TRL remnants to lower plasma cholesterol levels. Therefore, development of a PET-compatible cholesteryl ester-based tracer to additionally monitor hepatic remnant uptake might be of high interest. In conclusion, herein a currently non-existing PET-compatible [18F]TO for incorporation into TRL-like particles to trace metabolic BAT activity was successfully developed. As demonstrated in mouse models, incorporated [18F]TO outperforms [18F]FDG in tracing activated BAT via PET-CT imaging, providing both higher sensitivity and specificity. The disclosed data additionally suggest that the current evaluation of (cold-)activated human BAT using [18F]FDG might have underestimated the prevalence, volume and physiological importance of BAT. The tracer can be used for tracing human BAT activity, especially in metabolically compromised conditions including ageing, obesity and T2D. In addition, this tracer will be useful to obtain mechanistic insight e.g., in dyslipidemia and in novel TG-targeted lipid-lowering strategies that are being developed to mitigate atherosclerotic CVD risk.

[0248] References

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[0251] 16. lozzo P, Turpeinen AK, Takala T, Oikonen V, Solin O, Ferrannini E, Nuutila P, Knuuti J. Liver uptake of free fatty acids in vivo in humans as determined with 14(R, S)-[18F]fluoro-6-thia- heptadecanoic acid and PET. Eur J Nucl Med Mol Imaging 2003;30:1160-1164.

[0252] 28. Ying Z, Boon MR, Coskun T, Kooijman S, Rensen PCN. A simplified procedure to trace triglyceride-rich lipoprotein metabolism in vivo. Physiol Rep 2021 ;9:e14820.

[0253] 29. Grube A, Timm C, Kock M. Synthesis and Mass Spectrometric Analysis of CyclostellettaminesH, I, K and L. Wiley Online Library, 2006.

[0254] 30. Capon RJ, Skene C, Liu EH-T, Lacey E, Gill JH, Heiland K, Friedel T. Nematocidal thiocyanatins from a southern Australian marine sponge Oceanapia sp. Journal of natural products 2004;67:1277- 1282.

[0255] 31. Gung BW, Dickson H. Total synthesis of (-)-Minquartynoic Acid: an anti-cancer, anti-HIV natural product. Organic letters 2002;4:2517-2519.

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[0257] 33. Suganuma Y, Kobayashi Y. Formation of COOH-Ylides, and their reactivities and selectivities in Wittig reactions. Synlett 2019;30:333-337.

[0258] 34. Kristinsson B, Linderborg KM, Kallio H, Haraldsson GG. Synthesis of enantiopure structured triacylglycerols. Tetrahedron: Asymmetry 2014;25:125-132.

[0259] 35. DeGrado TR, Bhattacharyya F, Pandey MK, Belanger AP, Wang S. Synthesis and preliminary evaluation of 18-(18)F-fluoro-4-thia-oleate as a PET probe of fatty acid oxidation. J Nucl Med 2010;51 :1310-1317.

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Claims

Claims1 . A radiolabeled triglyceride analog or salt thereof represented by formula (I):wherein each of R1, R2, and R3are independently linear or branched C1-40 alkyl, linear or branched C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of any one of R1, R2, and R3is substituted by a group comprising a radioisotope suitable for positron emission tomography (PET) or single-photon emission computed tomography (SPECT).

2. The radiolabeled triglyceride analog or salt thereof according to claim 1 , wherein each of R1, R2, and R3are independently linear or branched C9-29 alkyl, linear or branched C9-29 alkenyl, or linear or branched C9-29 alkynyl, preferably linear or branched Cn-21 alkyl, linear or branched C11.21 alkenyl, or linear or branched C11.21 alkynyl, more preferably linear or branched C15-19 alkyl, linear or branched C15-19 alkenyl, or linear or branched C15-19 alkynyl.

3. The radiolabeled triglyceride analog or salt thereof according to claim 1 or 2, wherein each of R1, R2, and R3are independently selected from linear C15-40 alkyl or linear C15- 0 alkenyl, preferably wherein the C15-40 alkenyl comprises cis and / or trans stereoisomers and may have one, two, three, four, or five C=C bonds.

4. The radiolabeled triglyceride analog or salt thereof according to any one of claims 1 or 2, wherein the branched C1.40 alkyl, C2- 0 alkenyl, or C2-4o alkynyl is respectively mono- or polymethyl C1-40 alkyl, mono- or polymethyl C2-40 alkenyl, or mono- or polymethyl C2-40 alkynyl.

5. The radiolabeled triglyceride analog or salt thereof according to any one of claims 1 to 4, wherein at least one hydrogen atom of the terminal carbon atom of any one of R1, R2, and R3is substituted by the group comprising a radioisotope suitable for PET or SPECT.

6. A radiolabeled triglyceride analog or salt thereof represented by formula (la):wherein at least one of X1, X2, and X3is a group comprising a radioisotope suitable for PET or SPECT, and the other of X1, X2, and X3is methyl.

7. The radiolabeled triglyceride analog or salt thereof according to any one of claims 1 to 6, wherein the radioisotope is a positron-emitting radioisotope.

8. The radiolabeled triglyceride analog or salt thereof according to any one of claims 1 to 7, wherein the radioisotope is a radioisotope of carbon, fluorine, or iodine.

9. The radiolabeled triglyceride analog or salt thereof according to any one of claims 1 to 8, wherein the radioisotope is a radioisotope of fluorine.

10. The radiolabeled triglyceride analog or salt thereof according to any one of claims 1 to 9, wherein the radioisotope is11C,18F,123l, or125l, preferably wherein the radioisotope is18F.1 1 . A radiolabeled triglyceride analog or salt thereof represented by formula (lb):

12. A triglyceride analog or salt thereof represented by formula (II):wherein each of R4, R5, and R6are independently linear or branched C1-40 alkyl, linear or branched C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of R4, R5, and R6is substituted by a leaving group.

13. The triglyceride analog or salt thereof according to claim 12, wherein each of R4, R5, and R6are independently linear or branched C9-29 alkyl, linear or branched C9-29 alkenyl, or linear or branched C9-29 alkynyl, preferably linear or branched Cn-21 alkyl, linear or branched Cn-21 alkenyl, or linear or branched Cn-21 alkynyl, more preferably linear or branched C15-19 alkyl, linear or branched C15-19 alkenyl, or linear or branched C15-19 alkynyl.

14. The triglyceride analog or salt thereof according to any one of claims 12 or 13, wherein at least one hydrogen atom of the terminal carbon atom of any one of R4, R5, and R5is substituted by the leaving group.

15. The triglyceride analog or salt thereof according to any one of claims 12 to 14, wherein the leaving group is a group suitable for replacement by a nucleophile in a nucleophilic substitution reaction.

16. The triglyceride analog or salt thereof according to any one of claims 12 to 15, wherein the leaving group is a halogen or a sulphone ester.

17. The triglyceride analog or salt thereof according to any one of claims 12 to 16, wherein the leaving group is a tosylate group represented by formula (III):whereindenotes the attachment of the group to a carbon atom of R4, R5, or R6, preferably to the terminal carbon atom of R4, R5, or R6.

18. A labeled triglyceride analog or salt thereof represented by formula (IV):wherein each of R7, R8, and R9are independently linear or branched C1-40 alkyl, linear or branched C2-40 alkenyl, or linear or branched C2-40 alkynyl; and wherein at least one hydrogen atom of any one of R7, R8, and R9is substituted by a group comprising a stable isotope.

19. A labeled triglyceride analog or salt thereof, represented by formula (IVa):

20. A composition comprising lipid particles, the lipid particles comprising: the radiolabeled triglyceride analog according to any one of claims 1 to 11 or the labeled triglyceride analog according to claim 18 or 19, and optionally one or more additional lipid species.21 . The composition according to claim 20, wherein the one or more additional lipid species are selected from triglyceride, phosphatidylcholine, cholesteryl ester, L-a- lysophosphatidylcholine, and cholesterol.

22. The composition according to claim 20 or 21 , wherein the lipid particles each comprise of from 60% to 90% by weight of triglyceride, of from 10% to 25% by weight of phosphatidylcholine, of from 2% to 4% by weight of cholesteryl ester, of from 1 .5% to 3.0% by weight of L-a-lysophosphatidylcholine, and of from 1.5% to 2.5% by weight of cholesterol.

23. A pharmaceutical composition comprising an effective amount of the radiolabeled triglyceride analog according to any one of claims 1 to 11 , the labeled triglyceride analog according to claim 18 or 19, or the composition according to any one of claims 20 to 22; the pharmaceutical composition further comprising a pharmaceutically acceptable carrier, and / or diluent, and / or excipient.

24. A method of synthesizing the radiolabeled triglyceride analog of formula (I) as defined in any one of claims 1 to 11 , the method comprising: a. providing the triglyceride analog of formula (II) comprising a leaving group as defined in any one of claims 12 to 17; b. allowing an [18F] comprising species to react with the triglyceride analog, thereby removing the leaving group and providing the radiolabeled triglyceride analog of formula (I) as defined in any one of claims 1 to 11 .

25. The method according to claim 24, wherein the [18F] comprising species is [18F]triflylfluoride.

26. A method of imaging at least a part of the body of a subject comprising using the radiolabeled triglyceride analog according to any one of claims 1 to 11 , the composition according to any one of claims 20 to 22, or the pharmaceutical composition according to claim 23, optionally wherein the imaging is in vivo.

27. The method according to claim 26, wherein the imaging is for obtaining an image of brown adipose tissue, subcutaneous and visceral white adipose tissue, skeletal muscle, heart, liver, blood, heart, spleen, kidney, lung, bladder, adrenal glands, skull bone, stomach, duodenum, or skin, or for the localization or distribution of triglycerides.

28. The method according to claim 26 or 27 comprising: a. administering an effective amount of the radiolabeled triglyceride analog according to any one of claims 1 to 11 , the composition according to any one of claims 20 to 22, or the pharmaceutical composition according to claim 23 to the subject; b. detecting emission from the radioisotope; and c. generating an image of the at least a part of the body from the emission of step b.

29. A method of diagnosis comprising the method according to any one of claims 26 to 28.

30. Use of the radiolabeled triglyceride analog according to any one of claims 1 to 11 , the composition according to any one of claims 20 to 22, or the pharmaceutical composition according to claim 23 as an imaging agent.

31. Use of the radiolabeled triglyceride analog according to any one of claims 1 to 11 or the triglyceride analog according to any one of claims 12 to 17 for manufacturing a composition for imaging.

Images