WO2018178923A1

WO2018178923A1 - Imaging agent

Info

Publication number: WO2018178923A1
Application number: PCT/IB2018/052185
Authority: WO
Inventors: Daniel VAN DER MERWE; Helgard Pieter MEYER; Jan Rijn Zeevaart; Janine SUTHIRAM; Mike Machaba SATHEKGE; Thomas EBENHAN
Original assignee: The South African Nuclear Energy Corporation Limited; University Of Pretoria
Priority date: 2017-03-31
Filing date: 2018-03-29
Publication date: 2018-10-04
Also published as: GB201705258D0

Abstract

This invention relates to a bioconjugate comprising a chelating agent capable of containing a radionuclide linked to Substance P for use as an imaging agent in a method for detection of increased availability of NK-1 receptors for diagnosing pain, especially chronic pain. The invention also relates to the treatment of pain.

Description

IMAGING AGENT

BACKGROUND TO THE INVENTION

Fibromyalgia was already described as early as the nineteenth century by W.R. Gowers who used the term "fibrositis". In the 1950's, W. Graham described fibrositis as a pain syndrome in the absence of any organic disease. In 1977, Smythe and Moldofsky coined the new term "fibromyalgia" and proposed diagnostic criteria that could be used to identify patients with the fibromyalgia syndrome. In 1990 the American College of Rheumatology (ACR) published a report that aimed to redefine the diagnostic criteria for fibromyalgia by using the recognition of the diseases characteristics. They evaluated patients in 16 different centres across the United States and Canada and proposed that positive diagnosis would consist of a self-report history of widespread pain (above and below the waist and on both sides of the body together with axial skeletal pain) lasting more than three months with the demonstration of at least 1 1 of 18 specific bilateral tender points on examination by digital palpation applying approximately 4 kg of pressure. By 2010 this diagnostic criteria was updated to include fatigue, non-refreshing sleep and other somatic complaints. Usually extensive laboratory testing is not used, however physicians do sometimes run a complete blood cell count, comprehensive metabolic panel, thyroid function test, and measure the erythrocyte sedimentation rate and/or C-reactive protein levels to aid in diagnosis. The lack of absolute, definitive diagnostic criteria that can be applied universally to patients often means that doctors will settle for a fibromyalgia diagnosis following elimination of other conditions. To prevent misdiagnosis physicians must carefully consider many other potential diagnoses such as mental health disorders, hypothyroidism, rheumatoid arthritis, adrenal dysfunction and multiple myeloma.

Diagnosis of fibromyalgia is still predominantly based on the ACR criteria and the amendments that were made in 2010. However there has been much criticism of these criteria over the years due to studies that have failed to show a correlation between tender point counts and clinical pain. Despite all of the information that has been gathered over the years regarding fibromyalgia, it still remains a very complex condition that is associated with persistent and debilitating pain that has a severe impact on a patient's ability to work and carry out every day activities. The awareness and understanding of this condition has improved significantly over the years, yet there are still 3 out of 4 patients that will remain undiagnosed. It is therefore evident that the development of a diagnostic technique, supporting the tender point analysis, would prove extremely beneficial to physicians faced with patients that have a myriad of symptoms.

Substance P belongs to a group of neuropeptides referred to as tachykinins which can be found in mammals and other animal species. Substance P binds preferentially to the NK-1 receptor which is a glycoprotein with an extracellular amino-terminus and intracellular carboxyl tail. It is made up of 407 amino acid residues amounting to a relative molar mass of 46 kDa.20 The second and third domains of the receptor, which are membrane- spanning, are where agonist/antagonist binding takes place. When Substance P binds to the NK-1 receptor rapid endocytosis and internalisation of the receptor takes place followed by rapid recycling to the cell membrane. The Substance P/NK-1 pathway is one of the most studied neurotransmitter pathways in the central nervous system. This is because Substance P has been implicated as playing a role in inflammation and chronic pain. EP 1603598 describes radiolabeled conjugates based on Substance P and the uses thereof for imaging, targeting and treatment of brain tumours. It was found in EP 1603598 that the NK-1 receptor is expressed in brain tumours and can be applied for binding radiolabelled conjugates based on substance P and analogues thereof.

Most imaging studies involving NK-1 receptors have been focused on evaluating the effect of novel NK-1 antagonists in the human brain as part of the demand to develop antagonist-based drugs that will have therapeutic application in a range of disorders including pain and inflammation. The first attempts to develop tracers for in vivo imaging proved unsuccessful. In 2000, two NK-1 receptor antagonists (GR203040 and GR205171 ) were radiolabelled with ¹¹C and used in PET studies in rhesus monkeys. Both compounds were taken up rapidly in the brain with [¹¹C]GR205171 having almost a two-fold higher uptake than that of [¹¹C]GR203040. A pre- treatment of a cold dose of GR205171 was administered in order to carry out quantitation of the receptor binding (Patlak graphical method, cerebellum was chosen as the reference region). A steady time-dependent linear increase in the radioactivity was determined, suggesting a slow dissociation from the receptor which was considered useful for visualising the presence NK-1 receptor. On the other hand, the slow dissociation and high affinity of the tracer indicates that the compound is less likely to be displaced by endogenous Substance P levels. This could make the tracer unsuitable for assessing possible changes in receptor expression that are related to Substance P release when there are physiological concerns. The use of this compound was however limited since it did not reach equilibrium within the maximum scanning time that is possible for a C-1 1 radiolabelled ligand.

In 2002, another radiolabeled NK-1 antagonist - [¹⁸F]SPA-RQ was evaluated in preclinical (guinea pig brain and rhesus monkey) and clinical studies. The compound showed an intense NK-1 receptor-specific binding signal and minimal nonspecific binding. No specific binding was observed in the cerebellum which is an area of the brain known to lack NK-1 receptors. This defined an internal reference region for determination of a background signal (i.e. non-specific accumulation of the tracer) and tracer sensitivity. [¹⁸F]SPA-RQ was able to penetrate the monkey brain but washed out with time from the cerebellum. Pre-treatment with cold antagonist decreased binding in the caudate and cortex and rendered no effect in the cerebellum. The results of the clinical studies confirmed the high selectivity of the tracer for the NK-1 receptor and therefore its usefulness in being able to quantify NK-1 receptor occupancy by varying doses of the cold antagonist. Due to the [¹⁸F]SPA-RQ tracer having a slow clearance, the images obtained in the first 90 minutes were not suitable for NK-1 receptor binding quantification resulting in longer study durations which is not always desirable.

In 2009, Wolfensberger et al evaluated an NK-1 antagonist R1 16301 radiolabeled with C-1 1 as an in vivo tracer of NK-1 receptors in humans for the purpose of exploring the involvement of NK-1 receptors in a variety of neuropsychiatric disorders and to aid in the development of drugs that can effectively target the NK-1 receptor. The biodistribution of the tracer corresponded to the known distribution of NK-1 receptors. Following pre- administration of cold R1 16301 , a substantial reduction in the specific tracer signal to background levels was observed. This served to confirm that the tracer was selective to the NK-1 receptor.

Even though NK-1 receptor antagonists have been proposed for blocking the effects of Substance P, this strategy thus far has failed to show any analgesic effect in the clinical setting.

An object of this invention is to provide a tool that will be useful in the diagnosis of pain, and the treatment of pain, and in particular in the diagnosis, and the treatment, of pain-related diseases such as fibromyalgia. SUMMARY OF THE INVENTION

This invention relates to a bioconjugate comprising a chelating agent capable of containing a radionuclide linked to Substance P for use as an imaging agent in a method for detection of increased availability of NK-1 receptors for diagnosing pain, especially chronic pain.

Types of chronic pain include pain from autoimmune diseases such as spondylitis, and systemic lupus erythematosus, cancer pain, osteoarthritic pain, fibromyalgia, tendinosis, regional pain syndromes, myofascial pain syndromes, chronic pain conditions caused by central sensitization that can be seen in the dorsal horn in the spinal cord.

The invention has particular application in the diagnosis of fibromyalgia.

The chelating agent may be a bifunctional chelating agent (BFCA) which is a compound consisting of a varied number of heteroatoms, generally oxygen (O), nitrogen (N) or sulphur (S) that are able to complex a radioisotope. The BFCAs may be cyclic or acyclic. Examples of cyclic chelators are as follows:

Preferably, the conjugate contains a modified version of substance P which is DOTA-[Thi8, Met(02)1 1 ]-Substance P that contains the following sequence: DOTA - Arg - Pro - Lys - Pro - Gin - Gin - Phe - Thi - Gly - Leu - Met(02)-NH2 (MW = 1772.06 g.mol-1 ).

In accordance with the present invention, Gallium-68 radiolabeled Substance P was evaluated as the imaging agent and the chelating agent is 1 ,4,7,10-tetraazacyclododecane-1 ,4,7,10-tetraacetic acid (DOTA).

Preferably, the ⁶⁸Ga-DOTA-Substance P has a radiochemical purity >95.0%, preferably >98.0%.

The bioconjugate of the present invention is ⁶⁸Ga-DOTA-Substance P PET/CT used for detection of increased availability of NK-1 receptors in chronic pain disorders.

The invention also covers an aqueous composition for injection as a tracer dose in a human or animal patient may containing the bioconjugate described above in a dosage of from 1 MBq/kg to 5 MBq/kg, preferably from 2.4 MBq/kg to 4 MBq/kg.

The injected tracer dose in a human or animal patient may be from 2 mCi to 9.5 mCi, preferably from 4.5 mCi to 7.5 mCi.

The aqueous composition may be an aqueous saline solution with residual solvent content < 3% up to a total volume of 5-10 ml, for administration via an intravenous (IV) bolus injection.

After injection in a human or animal patient, the patient is scanned in a PET scanner to obtain a PET image which is viewed to identify the bio- distribution bioconjugate, and the location of the pain. Fibromyalgia may be identified by identifying symmetrical pain points in one or more of the following areas of the body: the neck (back and front), the chest, the shoulders, the upper back, the lower back, the arms, the hips, the knees. A second embodiment of the invention relates to the bioconjugate defined above comprising a chelating agent capable of containing a radionuclide linked to Substance P for use in a method of treating pain.

The radionuclide may be a therapeutic agent selected from: ¹⁸⁸Re, ¹⁸⁶Re,

The injected therapeutic dose in a human patient may be from 26 MBq/kg to 105 MBq/kg, preferably from 53 MBq/kg to 79 MBq/kg.

The injected therapeutic dose in a human patient may be from 50 mCi to 200 mCi, preferably from 100 mCi to 150 mCi.

The invention also covers an aqueous composition containing the bioconjugate described above for administration via an IV bolus injection.

Preferably, the aqueous solution is saline with residual solvent content < 3% up to a total volume of 5-10 ml.

The invention also covers methods of diagnosis and treatment of pain using the bioconjugate defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 A is a radio-HPLC analysis of 68Ga-DOTA-SP; Figure 1 B is a maximum intensity projection image of the in vivo biodistribution in a healthy dog ;

Figure 1 C shows time-activity-curves yielded from blood and urine

(r=0.981 ) samples;

Figure 2 shows a ⁶⁸Ga-DOTA-SubP-PET/CT baseline scan of a dog presenting with hip dysplasia and lameness in the leg; and

Figure 3 shows a ⁶⁸Ga-DOTA-SubP-PET/CT re-scan of a dog presenting with hip dysplasia and lameness in the leg.

Figure 4 is a drawing of a human patient, with dots showing symmetrical pain points for diagnosing fibromyalgia.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to the use of radionuclide labelled conjugates as imaging agents in the diagnosis of pain, and in particular in the diagnosis of pain-related diseases such as fibromyalgia. An aim of the invention is to identify the pain sensation and not necessarily a disease that causes pain or the origin of the pain.

According to the present invention, it has been found that radionuclide labelled conjugates of Substance P can be used as an imaging agent to detect increased Neurokinin-1 (NK-1 ) receptor availability in disorders which are characterised by chronic pain. Substance P is a neuropeptide that is naturally occurring in the biological system and has long been studied for its role in nociceptive (pain) responses and neurogenic inflammation. Substance P was chosen as the biomarker since it has a natural affinity for the NK-1 receptor in biological systems and has never been used to evaluate NK-1 receptor availability before. A radionuclide conjugate of Substance P has already been used in oncology based applications.

The radionuclide labelled conjugate of Substance P comprises a chelating agent capable of containing a radionuclide bound to Substance P.

Substance P is a linear undecapeptide coding the following amino acid sequence:HOOC-Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ (MW = 1347.6 g.mol^-1)

Below is the structure of Substance P:

A preferred modified version of substance P is DOTA-[Thi8, Met(02)1 1 ]- Substance P available from piCHEM Forschungs-und Entwicklungs GmbH that contains the following sequence: DOTA - Arg - Pro - Lys - Pro - Gin - Gin - Phe - Thi - Gly - Leu - Met(02)-NH2 (MW = 1772.06 g.mol-1 ). The chelating agent may be a bifunctional chelating agent (BFCA) which is a compound consisting of a varied number of heteroatoms, generally 0,N or S that are able to complex a radioisotope. The chelating agent may be cyclic or acylic.

Examples of cyclic chelators are:1 ,4,7-Triazacyc!ononane (TACN);1 ,4,7- triazacyclononane-triacetic acid (NOTA);1 ,4,7-triazacyclononane-N- succinic acid-N',N"-diacetic acid(NOTASA); 1 ,4,7-triazacyclononane-N- glutamic acid-N',N"-diacetic acid(NODAGA);1 ,4,7-triazacyclononane- N,N',N"-tris (methylenephosphonic)(NOTP); 1 ,4,7,10- tetraazacyclododecane ([12]aneN4)(cyclen); 1 ,4,7,10- tetraazacyclotridecane ([13]aneN4); 1 ,4,7,1 1 -tetraazacyclotetradecane (iso- cyclam); 1 ,4,7,10-tetraazacyclododecane-1 ,4,7,10-tetraacetic acid (DOT A); 2-(1 ,4,7,10-tetraazacyclododecan-1 -yl)acetate (D01 A); 2,2'-(1 ,4,7,10- tetraazacyclododecane-1 ,7-diyl) diacetic acid (D02A); 2,2',2"-(1 ,4,7,10- tetraazacyclododecane-1 ,4,7-triyl) triacetic acid (D03A); 1 ,4,7,10- tetraazacyclododecane-1 ,4,7,10-tetra(methanephosphonic acid) (DOTP); 1 ,4,7,10-tetraazacyclododecane-1 ,7-di(methanephosphonic acid) (D02P); 1 ,4,7,10-tetraazacyclododecane-1 ,4,7-tri(methanephosphonic acid) (D03P); 1 , 4,7,10-tetraazacyclo-decane-1 -glutamic acid-4,7,10-triacetic acid(DOTAGA) ; 1 ,4,7, 10-tetraazacyclodecane- 1 -succinic acid-4,7, 10- triacetic acid(DOTASA); 1 ,4,8,1 1 -tetraazacyclotetradecane

([14]aneN4)(cyclam); 1 ,4,8,12-tetraazacyclopentadecane ([15]aneN4); 1 ,5,9,13-tetraazacyclohexadecane ([16]aneN4); 1 ,4-ethano-1 ,4,8,1 1 - tetraazacyclo-tetradecane (et-cyclam); 1 ,4,8,1 1 -15- tetraazacyclotetradecane- 1 ,4,8,1 1 -tetraacetic acid (TETA); 2-(1 ,4,8,1 1 - tetraazacyclotetradecane- 1 -yl) acetic acid (TE1 A); 2,2'-(1 ,4,8,1 1 - tetraazacyclotetradecane-1 ,8-diyl) diacetic acid (TE2A); 4,1 1 - bis(carboxymethyl)-1 ,4,8,1 1 -tetraazabicyclo[6.6.2]-hexadecane(CB- TE2A);3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane(Sar);phthalocyanines and their derivatives; porphyrins and their derivatives. Examples of acyclic chelators are: ethylene-diamine-tetraacetic-acid (EDTA); and diethylene-triamine-penta-acetic acid (DTPA). S- acetylmercaptosuccinic anhydride(SAMSA); (2-mercaptoethyl)(2-((2- mercaptoethyl)amino)ethyl)-carbamic acid(N2S2-DADT); 1 ,1 '-(ethane- 1 ,2- diylbis(azanediyl))bis(2-methylpropane-2-thiol)(N2S2 BAT-TM), (2-(2- mercaptoacetamido)ethyl)-cysteine (N2S2-MAMA);2,3-bis(2- mercaptoacetamido)-propanoic acid(N2S2 DADS);ethylenedicysteine (EC);2,2',2"-nitrilotriethanethiol (NS3);2-ethylthio-N,N-bis(pyridin-2- yl)methyl-ethanamine (N3S);((2-mercaptoacetyl)glycylglycyl)carbamic acid (MAG₃) and 4-(2-(2-(2-mercaptoacetamido)acetamido)-acetamido)butanoic acid (MAG₂-GABA);(1 ,2-bis{[[6-(carboxy)pyridine-2-yl]methyl]- amino}- ethane) (H₂dedpa); Nitrilotris(methylenephosphonic acid) (NTMP);ethylenediaminetetramethylene-phosphonic acid (EDTMP), diethylenetriaminepenta-methylene phosphonic acid (DTPMP); Hydrazinonicotinic acid (HYNIC); N'-{5-[Acetyl(hydroxy)amino]-pentyl}-N-[5- ({4-[(5-aminopentyl)-(hydroxy)amino]-4-oxobutanoyl}amino)pentyl]-/V- hydroxysuccin-amide (Deferoxamine).

The preferred radiolabeled product of the present invention is ⁶⁸Ga-DOTA- Substance P PET/CT used for detection of increased availability of NK-1 receptors in chronic pain disorders.

⁶⁸Ga-DOTA-Substance P was produced with a radiochemical purity >98.0%, and was assessed in healthy dogs and dogs with chronic pain (dysplasia) to determine the biodistribution of the potential imaging agent for the detection of increased presence/expression of NK-1 receptors in chronic pain disorders.

A diseased dog was assessed, presenting with lameness in the back legs. After injection of 133 MBq of the tracer and scanning, the PET image presented unilaterally elevated uptake in the hip (associated to bone and/or soft tissue). This suggests that there was an abnormal presence of NK-1 receptors in the hip area. After two weeks of general pain treatment, rescanning revealed lower uptake in the respective hip area.

Typically the bioconjugate is administered via an IV bolus injection. The compound is formulated in saline with residual solvent content < 3% up to a total volume of 5-10 ml. Any anaesthetics are administered through the arterial port.

Injected tracer dose varied from 2.05 MBq/kg to 9.09 MBq/kg (dogs weighed between 25 kg to 55 kg).

The bioconjugate is injected as an intravenous bolus. Flush the syringe with at least the same volume of saline (NaCI 0.9%). After injection in a human or animal patient, the patient is scanned in a PET scanner to obtain a PET image which is viewed to identify the bio-distribution bioconjugate, and the location of the pain. With reference to Figure 4, fibromyalgia may be diagnosed by identifying symmetrical pain points, indicated by dots, in one or more of the following areas of the body: the neck (back and front), the chest, the shoulders, the upper back, the lower back, the arms, the hips, the knees.

In another embodiment of the invention, there is provided a bioconjugate comprising a chelating agent capable of containing a radionuclide linked to Substance P for use as a therapeutic agent for treating pain, in particular the diagnosis and/or treatment of chronic pain-related diseases, such as fibromyalgia. The radionuclide may be a therapeutic agent selected from:

The accumulation of the radiotracer in the pressure points is expected. It is known that injection of a local anesthetic/anti-inflammatory drug into the pressure points causes pain relief. It is believed that the elimination of cytokine emitting cells causing inter alia pain sensation (more radiation sensitive than normal cells or even cancer cells^*) using a therapeutic radionuclide may alleviate pain or even prove to be longer lasting therapy

Example 1 - Determining ⁶⁸Ga-DOTA-SP biodistribution in healthy dogs

Methods ⁶⁸Ga was obtained by eluate fractionation from a tin-dioxide- based ⁶⁸Ga/⁶⁸Ge generator (0.6M HCI elute); 50 μg of sodium acetate buffered DOTA-SP (pH 3.5-4) was incubated at 95 °C for 15 min followed by purification. The radiochemical purity was determined by HPLC using an Agilent 25 cm SB column with isocratic 75% of 0.1 % TFA/H20 and 25% of 0.1 % TFNacetonitrile. Following sterile filtration, ⁶⁸Ga-DOTA-SP was injected and tracer biodistribution was demonstrated in healthy dogs using 3 static PET/CT image acquisitions up to 150 min. The SUV quantification was achieved by 3D-VOI (volume of interest) analysis. Arterial blood and urine samples were quantified.

Results The final radiochemical purity was≥ 98% (Fig 1A). The highest tracer uptake occurred in the urinary bladder (total activity 5.6 MBq, SUV=44) and kidneys via renal excretion (Fig 1 B). Considerable tracer uptake was noted in liver (3.3 MBq, SUV 3.5) due to first pass effects, and intestines (1 .78 MBq, SUV 0.82), decreasing over 120 min. Other organs showed minimal uptake (SUV≤ 0.50). Calculations made from time-activity- curves (Fig 1 C) yielded a pharmacological half-life of 6 min for 68Ga- DOTA-SP and an excretion rate of 19 MBq/hour; 43% of the activity was recovered at 150 min in urine.

Figure 1 shows (A) radio-HPLC analysis (including UV registration at 214 and 254 nm wavelength) of 68Ga-DOTA-SP (red peak Reg #2), Reg #1 refers to residual free 68Ga, (B) maximum intensity projection image of the in vivo biodistribution in a healthy dog at 60 minutes after probe injection - visible uptake in urinary bladder

(UB)>kidneys(KI)>liver(LI)>intestine(IN)>heart (HE), (C) time-activity- curves yielded from blood (r =0.892) and urine (r=0.981 ) samples.

Conclusion ⁶⁸Ga-DOTA-SP could be achieved with high radiochemical purity. In vivo, the tracer showed rapid renal elimination and minimal organ uptake warranting further preclinical testing.

Example 2 - Determining ⁶⁸Ga-DOTA-SP biodistribution in a dysplastic dog

A dog with suspected hip dysplasia underwent 68Ga-DOTA-SP-PET/CT imaging following bolus tracer injection. The tracer's expected biodistribution was studied along with the determination of any unilateral uptake in the suspected hip area (3 static PET/CT image acquisitions up to 150 min were done). The SUV quantification was achieved by 3D-VOI (volume of interest) analysis.

Figure 2 shows a baseline ⁶⁸Ga-DOTA-SubP-PET/CT scan of a dog presenting with hip dysplasia and lameness in the leg, injected dose was 4.5 mCi

Figure 3 shows ⁶⁸Ga-DOTA-SubP-PET/CT re-scan of a dog presenting with hip dysplasia and lameness in the leg after 14-day non-steroidal antiinflammatory therapy intervention, injected dose was 5.5 mCi.

Claims

1 . A bioconjugate comprising a chelating agent capable of containing a radionuclide linked to Substance P for use as an imaging agent in a method for diagnosing pain.

2. The bioconjugate claimed in claim 1 , wherein the pain is chronic pain.

3. The bioconjugate claimed in claim 2, wherein the pain is autoimmune disease pain, cancer pain, osteoarthritic pain, fibromyalgia, tendinosis, regional pain syndromes, myofascial pain syndromes, chronic pain conditions caused by central sensitization that can be seen in the dorsal horn in the spinal cord

4. The bioconjugate claimed in claim 3, wherein the pain is fibromyalgia.

5. The bioconjugate claimed in any one of the preceding claims, wherein the chelating agent is a bifunctional chelating agent (BFCA).

6. The bioconjugate claimed in claim 5, wherein the bifunctional chelating agent is a cyclic chelator.

7. The bioconjugate claimed in claim 6, wherein the cyclic chelator is selected from:

• 1 ,4,7-Triazacyc!ononane (TACN);

• 1 ,4,7-triazacyclononane-triacetic acid (NOTA);

• 1 ,4,7-triazacyclononane-N-succinic acid-N',N"-diacetic acid(NOTASA);

• 1 ,4,7-triazacyclononane-N-glutamic acid-N',N"-diacetic acid(NODAGA);

• 1 ,4,7-triazacyclononane-N,N',N"-tris (methylenephosphonic)(NOTP)

• 1 ,4,7,10-tetraazacyclododecane ([12]aneN4)(cyclen);

• 1 ,4,7,10-tetraazacyclotridecane ([13]aneN4);

• 1 ,4,7,1 1 -tetraazacyclotetradecane (iso-cyclam);

8. The bioconjugate claimed in claim 5, wherein the bifunctional chelating agent is an acyclic chelator.

9. The bioconjugate claimed in claim 8, wherein the acyclic chelator is selected from:

• (1 ,2-bis{[[6-(carboxy)pyridine-2-yl]methyl]- aminoj-ethane) (H₂dedpa);

• Nitrilotris(methylenephosphonic acid) (NTMP);

• ethylenediaminetetramethylene-phosphonic acid (EDTMP),

• diethylenetriaminepenta-methylene phosphonic acid (DTPMP);

• Hydrazinonicotinic acid (HYNIC); or

• N'-{5-[Acetyl(hydroxy)amino]-pentyl}- N-[5-({4-[(5-aminopentyl)- (hydroxy)amino]-4-oxobutanoyl}amino)pentyl]-N-hydroxysuccin-amide (Deferoxamine).

10. The bioconjugate claimed in claim 9, wherein the radionuclide is an

1 1 . The bioconjugate claimed in claim 10, containing a modified version of substance P, which is DOTA-[Thi8, Met(02)1 1 ]-Substance P that contains the following sequence: DOTA - Arg - Pro - Lys - Pro - Gin - Gin - Phe - Thi - Gly - Leu - Met(02)-NH2 (MW = 1772.06 g.mol-1 ).

12. The bioconjugate claimed in claim 1 1 , wherein the radionuclide is Gallium-68.

13. The bioconjugate claimed in claim 12, comprising

Substance P with a radiochemical purity >95%.

14. The bioconjugate claimed in claim 12, comprising

Substance P with a radiochemical purity >98.0%.

15. An aqueous composition containing the bioconjugate claimed in in one of the preceding claims, for injection as a tracer dose in a patient, containing the bioconjugate in an amount from 1 MBq/kg to 5 MBq/kg.

16. The aqueous composition claimed in claim 15, containing the bioconjugate in an amount from 2.4 MBq/kg to 4 MBq/kg.

17. An aqueous composition containing the bioconjugate claimed in any one of claims 1 to 14, for injection as a tracer dose in a patient, containing the bioconjugate in an amount from 2 mCi to 9.5 mCi.

18. The aqueous composition claimed in claim 17, containing the bioconjugate in an amount from 4.5 mCi to 7.5 mCi.

19. The aqueous composition as claimed in any one of claims 15 to 18 wherein, after injection in a human or animal patient, the patient is scanned in a PET scanner to obtain a PET image which is viewed to identify the bio-distribution bioconjugate, and the location of the pain.

20. The aqueous composition claimed in claim 19, wherein the patient is a human patient and the pain is fibromyalgia which is diagnosed by identifying symmetrical pain points, indicated by dots, in one or more of the following areas of the body: the neck (back and front), the chest, the shoulders, the upper back, the lower back, the arms, the hips, the knees

21 . A bioconjugate comprising a chelating agent capable of containing a radionuclide linked to Substance P for use as a therapeutic agent in a method for treating pain.

22. The bioconjugate claimed in claim 21 , as defined in any one of claims 5-9.

23. The bioconjugate claimed in claim 22, wherein the radionuclide is selected from:¹⁸⁸Re, ¹⁸⁶Re, ¹⁵³Sm, ¹⁶⁶Ho, ⁹⁰Y, ⁸⁹Sr, ¹¹¹ In, ¹⁵³Gd, ²²⁵Ac,

24. The bioconjugate claimed in claim 22, wherein the radionuclide is a

beta, alpha or electron emitting radionuclide selected from ¹⁸⁸Re,

25. An aqueous composition containing the bioconjugate claimed in any one of claims 21 - 24, containing the bioconjugate in an amount for injection as a therapeutic dose in a patient in an amount from 26 MBq/kg to 105 MBq/kg.

26. The aqueous composition claimed in claim 25, containing the bioconjugate in an amount of from 53 MBq/kg to 79 MBq/kg.

27. An aqueous composition containing the bioconjugate claimed in any one of claims 21 - 24, in an amount from 50 mCi to 200 mCi.

28. The aqueous composition claimed in claim 27, containing the bioconjugate in an amount from 100 mCi to 150 mCi.

29. The aqueous composition claimed in any one of claims 15 to 20 or 25 to 28, which is an aqueous saline solution with residual solvent content < 3% up to a total volume of 5-10 ml.

30. The aqueous composition claimed 29, for administration

intravenous (IV) bolus injection.

31 . A method of diagnosing pain in a patient including the step of administering a bioconjugate comprising a chelating agent capable of containing a radionuclide linked to Substance P to the patient.

32. A method of treating pain in a patient including the step of administering a bioconjugate comprising a chelating agent capable of containing a radionuclide linked to Substance P to the patient.