RU2121367C1 - Radionuclide for study of myocardium metabolism - Google Patents

Abstract

FIELD: medicine, biochemistry. SUBSTANCE: invention proposes a radionuclide that is [15^-123]-pentadecanoic acid. Invention describes the developed technological scheme for production of РФП based on isotope exchange of nonactive 15-iodopentadecanoic acid with sodium iodide labeled with iodine-123. Invention provides a study of coronary blood circulation and metabolic processes in myocardium at the stage when structural and anatomical changes in heart muscle are absent. An agent can be used for treatment of patients with cardiac diseases. EFFECT: enhanced effectiveness of radionuclide.

Description

 The invention relates to medicine, more specifically to radionuclide diagnostics, and may find application in the treatment of heart disease.

 In the general complex of radiation studies of the myocardium, radionuclide methods are of great importance. They allow you to specify the focus of myocardial infarction, determine its size, and monitor the progress of thrombolytic therapy. In the study of patients with heart diseases, the determination of coronary blood flow and the assessment of metabolic processes in the myocardium, which are necessary for the detection of myocardiopathies of various genesis, as well as for differential diagnosis between transient ischemia and myocardial infarction, are of considerable interest.

To assess the state of myocardial blood flow, ²⁰¹ Te-chloride is currently widely used [1, 2]. However, its use has limitations due to the complexity of the quantitative assessment of blood flow. In addition, the capture of ²⁰¹ Te-chloride can change with a violation of transport mechanisms, which affects the adequacy of the state of myocardial blood flow.

 In recent years, free fatty acids labeled with cyclotron radionuclides have been used for scintigraphic studies of the heart, the oxidation of which is the main source of energy for the heart under aerobic conditions. Fats provide 60% of the energy needs of the heart muscle. With an increase in myocardial oxygen consumption, utilization of fatty acids increases, while the metabolism of the remaining substrates remains unchanged. That is why fatty acids are used to study the myocardium and assess the intensity of oxygen consumption by it, namely radiopharmaceuticals prepared from them (RFP).

Various iodine isotopes or cyclotron ultrashort-lived (UKZH) radionuclides, such as ¹¹ C and ¹⁸ F, are used as labels. Using the latter, positron emission tomography (PET) is performed by studying the exchange of ¹¹ C or ¹⁸ F palmitic acids in the myocardium. However, the use of PET is limited to large centers that have a cyclotron on their territory, because ¹¹ C and ¹⁸ F have a short half-life and can only be used at the place of production.

In this regard, iodine-labeled compounds have advantages. However, when used, for example, for the diagnosis of ¹³¹ I, a sufficiently large radiation load is created on the patient due to its long half-life and the presence of hard beta radiation in the spectrum. ¹²⁵ I, having low-energy gamma radiation, is not very suitable for clinical studies because of the difficulty of its registration.

The most suitable for its nuclear physical characteristics for the purpose of radionuclide diagnostics of the myocardium is iodine-123, whose half-life is 13.31 hours. In recent years, a large amount of research has been carried out on the pharmacokinetics and biochemical transformations of radiopharmaceuticals based on fatty acids with different chain lengths labeled with iodine-123, with an assessment of their clinical and diagnostic value. The most studied of them are ¹²³ I-heptadecanoic [3], ¹²³ I-hexadecanoic [4], ¹²³ I-phenylpentadecanoic [5], ¹²³ I-phenyltellurpentadecanoic [6] acids.

Coronary heart disease is characterized by a decrease in the accumulation of ¹²³ I-fatty acids in ischemic areas of the myocardium. Moreover, in a number of experimental and clinical studies, a high correlation is shown between the level of myocardial perfusion and the accumulation of fatty acids [4]. The metabolic rate of ¹²³ I-fatty acids in the areas of myocardial ischemia is reduced, while in the area of a heart attack it is increased.

Various forms of myocardiopathies are characterized by a pronounced uneven accumulation of radioactivity in the heart muscle and significant fluctuations in the half-life of ¹²³ I from the myocardium. An analysis of the literature data allows us to conclude that for clinical use, several different ¹²³ I-fatty acids are needed that differ in metabolism and the rate of elimination of ¹²³ I from the myocardium. This allows you to objectively assess the state of myocardial perfusion and lipid metabolism in the heart muscle. Despite the abundance of radiopharmaceuticals for these purposes, the search for new, more advanced diagnostic tools continues.

 The technical result of the present invention is to develop a new effective for the study of myocardial metabolism of the radiopharmaceutical.

This result is achieved by using for these purposes 15- ¹²³ I-pentadecanoic acid having a short half-life and low-energy gamma radiation.

 Chemically, 15-iodopentadecanoic acid is an analogue of natural palmitic acid, which is one of the main energy sources of vital activity of the heart muscle and is currently used to study the metabolism of fatty acids in the myocardium. The use of 15-iodopentadecanoic acid for myocardial research is unknown to us. We conducted these studies, preparing the radiopharmaceutical from it.

The technology of obtaining 15- [ ¹²³ I] -pentadecanoic acid.

The preparation of 15- [ ¹²³ I] -pentadecanoic acid is based on the reaction of isotopic exchange of iodine between 15-iodopentadecanoic acid and Na ¹²³ I in a melt of a radioiodinated substrate.

Гидролиз пентадеканолида гидроокисью калия осуществляют кипячением 1.5 г его с 4.5 г KOH в смеси 30 мл этанола и 45 мл воды в течение 5 часов. Образующуюся калиевую соль 15-гидроксилпентадекановой кислоты обрабатывают раствором 1N соляной кислоты до pH ≈ 3 и выпавший 15-гидроксилпентадекановой кислоты отфильтровывают и высушивают. Выход ее составляет около 1.5 г (95%).The synthesis of 15-iodopentadecanoic acid is carried out from pentadecanolide according to the following scheme

The hydrolysis of pentadecanolide with potassium hydroxide is carried out by boiling 1.5 g of it with 4.5 g of KOH in a mixture of 30 ml of ethanol and 45 ml of water for 5 hours. The resulting potassium salt of 15-hydroxylpentadecanoic acid is treated with a solution of 1N hydrochloric acid to pH ≈ 3, and the precipitated 15-hydroxylpentadecanoic acid is filtered off and dried. Its yield is about 1.5 g (95%).

1.3 g of the obtained acid is heated at 70 ^° C. for 1.5 hours with 3.3 g of potassium iodide and 3.2 g of trimethylchlorosilane in 50 ml of acetonitrile. About 1.7 g of 15-iodopentadecanoic acid are obtained, which are recrystallized twice from 40-50 ml of ethanol and characterized by chemical analysis, UV and IR spectroscopy.

 Elementary analysis: found C - 48.3% (Theor. 48.92), H - 8.0% (Theor. 7.94), I - 35.4% (Theor. 34.45).

 In the UV region, an absorption band is observed with a maximum at 255 ± 2 nm, due to the presence of the C – I bond. The molar absorption coefficient of 15-iodopentadecanoic acid at this wavelength is 558 ± 14, which allows its quantitative measurement by spectroscopic method.

Sodium iodide, ¹²³ I, is obtained without the addition of a carrier by irradiation with protons E = 15-13 MEV at the MGC-20 cyclotron of a target from tellurium oxide enriched in the ¹²³ Te isotope using the reaction ¹²³ Te (p, n) ¹²³ I, followed by thermal sublimation of iodine from tellurium target and its absorption by sodium hydroxide solution. Tellurium oxide enriched in ¹²³ Te of 91-96% is used as the target material. A 0.5 mm thick platinum foil in the form of a container with a diameter of 20 mm and a recess (diameter 10 mm, depth 0.5 mm) is used as the target substrate. A 3-5 micron thick layer of silver is applied to the surface of the recess of this container to increase the adhesion of the target substance to the substrate. A portion of tellurium oxide powder (200-250 mg) is placed in the recess of the substrate and melted to obtain a vitreous mass. The target is placed in a water-cooled device to irradiate a proton beam. From the side of the beam, the target is cooled by a helium current and is separated from the ion duct using a stainless steel foil with a thickness of 15-20 μm. To uniformly irradiate the target, the proton beam is scanned along its surface with a frequency of 8-10 Hz. After irradiation, the target is placed in a quartz glass installation for thermal sublimation of iodine. The iodine released during the sublimation is purged with air and absorbed in 1 ml of a 10 ^-2 M sodium hydroxide solution placed in a penicillin vial, which is then sealed with a rubber stopper and rolled with an aluminum cap. The radiochemical purity of the resulting preparation is> 95%. A stainless steel capillary is inserted through a rubber stopper into this vial, the second end of which is placed in a similar vial, and water is distilled off from the first vial at a temperature of 130-140 ^o C. Then, 4 mg of 15-iodopentadecanoic acid is introduced into the first vial with a sterile syringe 1 ml of chemically pure ethanol and ethanol are distilled off at a temperature of 115 ^o C. Upon completion of the distillation of ethanol, the vial is heated at 115 ^o C for 5 minutes, after which 0.5-1.0 ml of ethanol is added again, the contents are shaken until the precipitate is completely dissolved and the same using a syringe assay for the determination of radiochemical purity of the drug.

 It is a sterile crystals of 15-iodopentadecanoic acid labeled with iodine-123, and has the following characteristics.

Specific activity / at the time of manufacture / - 50-350 MBq / mg
The content of 15-iodopentadecanoic acid - 0.3-3.0 mg
Radionuclide acid
at the time of manufacture - 98.8%
at the end of the expiration date - 94.3%
Radiochemical purity -> 95.0%
Before using the radiopharmaceutical for diagnostic purposes, it is dissolved in a small amount of ethanol and the resulting solution is introduced into a vial with a solution of albumin in a ratio of 1: 9. For sterilization, the resulting solution is filtered through a 0.22 μm Millipore filter or other similar filter, after which the preparation is ready for use.

 For a scintigraphic study of the myocardium on a gamma camera, the activity of the drug is 1-2 MBq per 1 kg of patient body weight. The shelf life of the drug is 30 hours from the time of manufacture.

 The results of a biological study of the drug.

On dogs, rabbits, guinea pigs, rats, mice were studied:
- radiation and chemical toxicity by determining LD ₅₀ and chronic toxicity in experimental groups of animals and in parallel in the control;
- hemolytic effect by determining the number of red blood cells in experimental animals before and at various times after iv administration of the drug, as well as "in vitro" on blood agar with simultaneous testing of the drug for sterility, evaluating the results on a four-point system on day 8;
- allergenic effect by evaluating the skin reaction when applying to the middle part of the body surface of the animal 1 drop of a solution of the drug in a minimum dilution that does not cause a visible reaction in control animals, and previously the experimental animals were injected with a solution of the drug in dilution 1 into the skin of the outer surface of the ear for 10 days : 500, and the control - one solvent in the same volume;
- the safety of the drug with iv administration was evaluated according to the following criteria: changes in body weight and internal organs (heart, lungs, liver, kidneys, spleen, gonads), clinical and biochemical blood tests, urinalysis at various times after drug administration within 30 days;
- temperature reaction before administration and 1/2, 1, 2 and 3 hours after drug administration;
- measurement of blood pressure in a direct way in the carotid artery before and after 1, 5, 15, 30 and 60 minutes after drug administration;
- ECG change by registering it before drug administration and on the 1st, 10th and 30th day after its administration;
- diagnostic suitability by examining key indicators in response to the administration of the drug "in vivo" by scintigraphy and "in vitro" using a well counter after removing the heart. In the first case, the dynamics of the passage of the drug in the body was recorded on the magnetic tape of the VCR, "zones of interest" were noted over the region of the heart, liver, and kidneys, the time of maximum onset (T _max ) and half-life (T _1/2 ) of the drug were determined. In the second case, the extracted heart was radiometrics in a well counter, after which a drug distribution curve was plotted in the myocardium for 15 minutes, which was estimated based on the determination of the maximum onset time (T _max ) and half-life T _1/2 ).

The results of an experimental study of the proposed drug carried out on 5 animal species indicate that the drug
- sterile - in none of the studies was the growth of pathological flora noted;
- does not have a hemolytic effect - in all animals within a month there was no change in the number of red blood cells;
- non-toxic - the introduction of diagnostic amounts of the drug does not cause significant changes in peripheral blood, protein, cholesterol, glucose and urea in blood plasma, pH, as well as body weight of animals and internal organs. The drug does not have a significant effect on the ECG, blood pressure and heart rate. This indicates the toxic harmlessness of the drug;
- has no allergenic effect - tests on sensitized guinea pigs showed the absence of allergic reactions;
- special studies to evaluate the immunogenic and carcinogenic effects were not carried out, because 15-I-pentadecanoic acid is not among the compounds that cause carcinogenic and immunogenic damage;
- on bacterial media, the absence of the mutagenic effect of the drug is shown - no deaths were observed in any of the experimental groups. At autopsy of slaughtered animals, neither macroscopic nor microscopic changes in the heart, liver and thyroid gland were detected;
- according to well-known formulas, the radiation loads on the critical organ and the whole organism as a whole are calculated for one animal species (rats). It is shown that these loads are extremely small;
- in vitro and in vivo studies demonstrated good diagnostic capabilities of the drug. Within 1-2 minutes after intravenous administration, the drug shows maximum accumulation in the myocardium. After this, two periods of excretion come: fast and slow. The half-life ranges from 6.5 to 13 minutes, depending on the type of animal. Drug-induced myocarditis does not affect the absorption rate of the drug and T _max does not change. However, in the case of myocarditis, the excretion rate of the drug lengthens 1.5-2 times;
- comparative studies with ²⁰¹ Te-chloride showed distinct advantages of the proposed drug. So, in animals with adrenal myocarditis, there is a pronounced violation of the scintigraphic picture in the form of heterogeneity of drug accumulation and fuzzy contours when using it. Scintigrams obtained with ²⁰¹ Te-chloride in the case of myocarditis have no pathological signs.

 Thus, the drug is non-toxic, sterile, does not cause a damaging effect and has good diagnostic properties. After a single injection, it makes it possible to visually evaluate 2 indicators: the state of coronary blood flow and quantitative data on the features of metabolic processes in the myocardium at the stage when there are still no structural and anatomical changes in the heart muscle, as well as conduct differential diagnosis of transient ischemia from myocardial infarction and diagnose various myocardiopathies genesis.

 The results obtained in the experiments were presented by us to the Pharmacological Committee of the Ministry of Health of the Russian Federation and its solution (protocol No. 14 dated 07/07/95) was approved for clinical study.

 At present, the drug is undergoing clinical trials at the Department of Isotopic Research Methods at TsNIRRI MH RF, the results of which will be presented to the FC MH PF in 1997 in order to obtain permission for its medical use and industrial production.

 A Temporary Pharmacopoeia article has been developed at the RFP "15-iodopentadecanoic acid, iodine-123", which, together with other documents, will be sent to the Ministry of Health of the Russian Federation.

 The institute has developed the technological scheme for the production of radiopharmaceuticals presented above, which is used to obtain it for diagnostic purposes in clinical practice.

Sources of information
1. Doctore E et al., Am. Heart. J., 1986, Vol. 111, 4, P. 788-791.

 2. Laskin S.A. Medical Radiology, 1989, 6, 68-76.

 3. Muller K.D. et al., Radiology, 25, 1, 78-82, 1985.

 4. Van der Wall E.E. et al., Eur. J. Nucl. Med., 6, 9, 383-389, 1981.

 5. Rellas J.S. at al., Am. J. Cardiol., 52, 10, 1326-1332, 1983.

 6. Okada R. D. at al., Eur. J. Nucl. Med., 11, 4, 156-161, 1985.

Claims (1)

Radionuclide for the study of myocardial metabolism, which is 15 ^-123 1-pentadecanoic acid.