Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K49/00—Preparations for testing in vivo
  • A61K49/04—X-ray contrast preparations
  • A61K49/0433—X-ray contrast preparations containing an organic halogenated X-ray contrast-enhancing agent
  • A61K49/0447—Physical forms of mixtures of two different X-ray contrast-enhancing agents, containing at least one X-ray contrast-enhancing agent which is a halogenated organic compound
  • A61K49/0461—Dispersions, colloids, emulsions or suspensions
  • A61K49/0466—Liposomes, lipoprotein vesicles, e.g. HDL or LDL lipoproteins, phospholipidic or polymeric micelles
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K49/00—Preparations for testing in vivo
  • A61K49/06—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations
  • A61K49/18—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by a special physical form, e.g. emulsions, microcapsules, liposomes
  • A61K49/1806—Suspensions, emulsions, colloids, dispersions
  • A61K49/1812—Suspensions, emulsions, colloids, dispersions liposomes, polymersomes, e.g. immunoliposomes

Definitions

• the invention relates to liposome formulations containing ontrast with a long intravascular residence time, which are suitable for the representation of the intravascular space.
• Liposomes have become increasingly important in recent years as potential carrier systems for the various types of contrast media.
• the use of liposomal contrast medium formulations has been described for all imaging diagnostic methods (X-ray diagnostics, computer tomography, MRI diagnostics, radio diagnostics) (Seltzer, St. E., Liposomes in diagnostic imaging. In: Gregoriadis, G. (ed.), Liposomes as drug carriers, John Wiley & Sons Ltd., Chichester, New York, Brisbane, Toronto, Singapore 1988, p. 509).
• the liposomes enable the inclusion of hydrophilic contrast agents in the water phase as well as the inclusion of lipophilic contrast agents in the bilayer phase (Seltzer, St. E., Radiology 171, 19-21 (1989)).
• liposomes are preferentially enriched in ⁇ en organs of the mononuclear phagocyte system (MPS, also called RES), the highest concentrations being reached in the liver and spleen. This so-called passive targeting is used in the case of contrast medium-containing liposomes in order to achieve a selective enrichment of these substances in the healthy liver.
• MPS mononuclear phagocyte system
• the liposo al-encapsulated X-ray contrast agent Iopro id (Ultravist ® ) was able to differentiate tumorous changes in the liver in the rabbit model (Sachse, A. et al., Invest. Radiol. 28, 838-844 (1993);
• the in vivo behavior of liposomes is high. Influence measurement by changing the chemical composition and the physical properties of vesicles.
• the blood half-life and organ distribution of the liposomes are influenced by parameters such as vesicle size, surface charge (Ze potential), lipid composition and lipid dose (Senior, JH, CRC C ⁇ t. Rev. Therap. Drug Camer Syst. 3, 123-193 (1987) ).
• the blood half-life of liposomes can be reduced by reducing the liposome size or by rigidifying the membrane e.g. can be significantly extended by using saturated phospholipids (e.g. distearoylphosphatidylcholm, DSPC).
• saturated phospholipids e.g. distearoylphosphatidylcholm, DSPC.
• the introduction of a load in turn, can lead to a drastic increase in MPS intake and thus a reduction in the blood half-life.
• the blood retention time is very strongly influenced by the applied lipid dose or number of particles.
• the relative liver uptake probably due to a saturation of the liver uptake mechanism.
• a higher spleen uptake and a prolonged blood retention period are observed.
• This effect of PEGylation is attributed to the formation of a steric barrier on the surface of the liposome, by means of which the interaction of the liposomes with various plasma components (eg plasma proteins or opsonins) is significantly changed.
• the blood half-lives of such sterically stabilized liposomes (SSL) when using PEGs with molecular weights between 1900 and 5000 are in the range of approximately 9 to 16 hours.
• the liver uptake of corresponding liposomes (100 - 200 nm) reached values up to slightly below 25% of the applied dose. It should be noted, however, that the liver and spleen are still the main organs for receiving SSL.
• liposeal preparations are used for imaging the intravascular space (blood pool imaging), it is necessary to largely avoid the liposomes being absorbed into the MPS. Because of the relatively large blood volume, high contrast medium concentrations are required in the vascular system, particularly in CT, in order to enable meaningful imaging. If there is an accumulation of the liposomal contrast medium, for example in the liver and spleen, as part of diagnostic examinations in the area of the vascular system, this can u. U. lead to an adverse impact on the functions of the MPS (eg immune defense).
• mice small to medium doses of placebo liposomes (20 - 80 mg / kg) were able to demonstrate a significant impairment of the MPS absorption capacity for carbon particles (Allen, TM et al., Journ. Pharm. Exper. Therap. 229 , 1984, 267-275). About that In addition, the encapsulated contrast medium can also lead to changes in the RES.
• WO 88/09165 describes sprayable, aqueous liposome preparations with iodine-containing X-ray contrast agents and a method for producing corresponding formulations. Due to the size (0.15 - 3 ⁇ m) and the high contrast medium (iodine / lipid ratio between 1.5 and 6 g / g), appropriate preparations should be particularly suitable for the representation of the liver.
• EP 0160552 A2 describes micellar or liposomal contrast media for magnetic resonance tomography (MRT, MRI).
• MRT magnetic resonance tomography
• the small umlamellar liposomes (SUV 60 ⁇ 10 nm) Application to tumor-bearing mice lead to an increased tumor accumulation of the liposomal Gd-DTPA.
• WO 90/04943 describes liposomal MRI contrast agents, methods for their preparation and applications.
• the liposomes according to the invention have an average diameter below 50 nm and, in addition to being used for imaging tumors of the liver and spleen, should also be suitable for imaging the vascular system, the heart and the perfusion of tissues (blood pool imaging) .
• these small liposomes have the disadvantage that, because of their restricted volume, only small amounts of hydrophilic components can be included.
• a significant reduction in the relaxivity of the encapsulated component was described for MRI contrast media. Recently lipophilic, paramagnetic chelates have therefore become increasingly important.
• Liposome membrane (bilayer) and therefore behave like the lipid membrane with regard to their pharmacokmetic.
• Corresponding liposomes (Memsomes), which extend the Blood half-life additionally surface modified (PEGylilert) are said to be particularly suitable for blood pool imaging due to their high relaxivity (Tilcock, T., J. Liposome Res. 4, 909-936 (1994)).
• the latter author also describes surface-modified (PEG) liposomes for imaging the vascular system in nuclear diagnostics.
• the radioactive component can be included either in the inner water phase or in the membrane phase.
• Radiolabelled liposomes (PE-DTTA and 99mTc) with a mean diameter of approx. 100 nm showed a blood half-life of more than 12 hours with surface hydrophilization with 4 - 6 mol ° ⁇ P ⁇ -PEG 6000 (SSL) . After 8 hours, with appropriate preparations, high activity in the heart and blood vessels could be obtained. At the same time, however, a clear accumulation of liver was detectable.
• New contrast media for a specific visualization of vessels and the heart should remain in the vascular system for a longer period after an intravenous injection.
• This "blood pool effect" of new contrast media could cause many pathological conditions, on the one hand due to a reduction in blood flow (e.g. due to thrombosis, embolism, tumors) or on the other hand due to an abnormal increase in blood flow (e.g. due to a disturbance in capillary integrity) are characterized, can be diagnosed more precisely with non-invasive methods.
• an exact representation of the perfusion of different tissues and organs (e.g. heart, lungs) or of pathological changes in the heart e.g. heart valve defects) could be achieved.
• liposomal contrast media for the representation of the intravascular space, which the above-mentioned. Avoid disadvantages, have an adequate blood half-life and accumulate only to a small extent in the liver, spleen or other organs. This object has been achieved by the present invention, in particular by the liposomal contrast agent formulations as characterized in the claims.
• the invention therefore relates to active substance-containing liposome formulations, characterized in that a) the following mixing ratio of the lipids is present: 40-90% phospholipids or amphiphiles, 10-50% sterols, 0-25% charge carriers, b) the liposomes have an average diameter of 100-400 nm and c) the active substance is an X-ray or MRI contrast medium or a radio diagnostic.
• the invention preferably relates to active substance-containing liposome formulations, characterized in that a) the following mixing ratio of the lipids is present: 40-70% phospholipids or amphiphiles, 30-50% sterols,
• the liposomes have an average diameter of 100-400 nm and c) the active substance is an X-ray or MRI contrast medium or a radio diagnostic agent.
• the invention particularly preferably relates to liposome formulations containing active ingredient, characterized in that a) the following mixing ratio of the lipids is present: 60-70% phosphatidylcholm, 20-30% cholesterol,
• the liposomes have an average diameter of 150-350 nm and c) the active substance is an X-ray or MRI contrast agent or a radio diagnostic agent.
• contrast agent-containing liposome preparations can generally the standard methods known in liposome technology. (e.g. New, R.R.C., Preparation of liposomes. In: New, R.R.C. (ed.), Liposomes: a practical approach, Oxford University Press, New York, 1990).
• continuous high-pressure extrusion is particularly suitable for producing liposome suspensions with the properties according to the invention
• the liposome formulations according to the invention contain, in addition to the encapsulated portion of a hydrophilic (water-soluble) contrast medium, an unencapsulated portion of the same.
• the encapsulated portion is usually between 15 and 95% of the total concentration.
• preparations in which between 30 and 75% are encapsulated are particularly suitable. The best results were achieved with preparations in which 40 to 65% of the contrast medium are encapsulated. It could be shown that, surprisingly, the free contrast agent component has a positive influence on the diagnostic quality of the preparations according to the invention.
• Hydrophilic contrast media (diagnostics) suitable for producing formulations according to the invention are generally known from radiological practice (e.g. CT, MRI, nuclear diagnostics). These include the X-ray contrast agents such as amidotrizoate, metrizoate, iopromide, iohexol, iopamidol, iosimide, ioversol, iomeprol, iopentol, ioxilan, iobitridol, ioxaglate, iotrolan, iodixanol, bis- [ ⁇ 3-D- (2, hydroxyl -carbamoyl) -5- carbamoyl ⁇ -2, 4, 6-tr ⁇ od-N- (2, 3-d ⁇ hydroxypropyl) anilide] - malonic acid and 5-hydroxyacetylammo-2, 4, 6-tr ⁇ od- isophthalic acid- [(2, 3-di-hydroxy-N-methyl-propyl) -
• Non-limiting examples from the field of MRT (NMR) contrast media are, for example, Gd-DTPA, Gd-EOB-DTPA, Gd-DOTA, Gd-BOPTA and Mn-DPDP.
• NMR contrast media compounds based on metal-containing macrocycles, such as, for example, gadobutrol, are particularly suitable for producing formulations according to the invention.
• Substances containing central atoms other than gadolinium can also be used in MRI contrast media.
• Other suitable lanthanides are, for example Dysprosium or ytterbium.
• such substances can also be used as contrast-imparting components for computer tomography.
• the aqueous phase can also contain the auxiliaries known to the person skilled in the art, such as, for example, buffer substances, isotonizing additives or preserving additives.
• the phospholipids are natural or synthetic phospholipids such as phosphatidylcholine, phosphatidylethanolamine or sphingolipids, with naturally occurring phospholipids such as e.g.
• Soy phosphatidylcholine (SPC) and egg phosphatidylcholine (EPC) are preferred. Mixtures of the above components can also be used.
• amphiphilic substances examples include hexadecyl poly (3) glycerol, dialkyl poly (7) glycerol ether and alkyl glucosides. Mixtures of the above components can also be used. In addition, however, other synthetically or biotechnologically obtained amphiphilic substances can also be used for the production of liposomes according to the invention. When using amphiphilic substances, so-called niosomes, i.e. Liposomes obtained from non-ionogenic vesicle formers.
• Cholesterol in particular is used as the sterol.
• Components such as fatty acids (e.g. stearic acid, palmitic acid), dicetyl phosphate, cholesterol isuccinate or natural or synthetic phospholipids such as phosphatidylglycerol, phosphatidylserine, for example, are used as charge carriers.
• fatty acids e.g. stearic acid, palmitic acid
• dicetyl phosphate e.g. stearic acid, palmitic acid
• cholesterol isuccinate e.g. stearic acid, palmitic acid
• natural or synthetic phospholipids such as phosphatidylglycerol, phosphatidylserine, for example, are used as charge carriers.
• Phosphatidic acid or phosphatidylinositol used. Furthermore, charged amphiphilic substances (see above) can also be used as charge carriers. Mixtures of the above components can also be used.
• the liposome membrane can also contain preservative additives such as tocopherol as an antioxidant.
• the liposome preparations according to the invention do not contain any surface-hydrophilizing additives such as DSPE-PEG or GM1 (see above) to prolong the blood half-life. It could be shown that preparations containing DSPE-PEG have a reduced, acute tolerance to unmodified liposomes.
• soy phosphatidycholine a) 60% soy phosphatidycholine, 30% cholesterol, 10% soy phosphatidylglycerol, b) 70% soy phosphatidycholine, 20% cholesterol, 10% soy phosphatidyl glycerol, c) 75% soy phosphatidycholine, 20% cholesterol,
• soy phosphatidylglycerol 50% soy phosphatidycholine, 40% cholesterol, 10% soy phosphatidylglycerol, e) 60% soy phosphatidycholine, 30% cholesterol, 10% distearoylphosphatidylglycerol, f) 70% soy phosphatidroglyphyl, 20% chololol, 20% chololol, 20% Soy phosphatidycholine, 30% cholesterol,
• the average diameter of liposome formulations according to the invention is between 100 and 400 nm (measured by photon correlation spectroscopy (PCS), see examples).
• the liposomes have average diameters between 150 and 250 nm.
• the liposome formulations according to the invention are usually stable for more than 12 months when stored in the refrigerator for a period of at least 9 months. In particularly suitable cases, corresponding formulations are stable over this period even at room temperature.
• the liposome formulations according to the invention can be heat sterilized. Experiments with formulations according to the invention which showed 20 min. were treated at 121 ° C that no significant changes occurred.
• the limited plasma stability (e.g. in human plasma) must be mentioned first of all. It was shown in vitro that the degree of encapsulation decreased by approximately 20 to 30% in the first 2 hours. Up to 6 hours after mixing the liposome suspension with the plasma, the proportion of the encapsulated contrast medium continued to decrease (to approx. 60%).
• the plasma stability of the formulations according to the invention in human plasma after 2 h is preferably in the range from 50-90 or 60-80% of the originally encapsulated portion.
• the maximum contrast enhancement of liposome formulations according to the invention in the liver and spleen within a period of 24 hours is generally below 10%, but always below 20%. At later times, no further increase occurs after the formulations according to the invention have been administered the contrast agent concentration in the liver and spleen compared to the early points in time, ie there is no late enrichment. In spite of the low concentration of formulations according to the invention in the liver and spleen, it is preferred to encapsulate those contrast agents which have a rapid and complete elimination from the MPS and, moreover, do not form any toxic decomposition products.
• liposome preparations according to the invention blood concentrations of up to 75% of the applied dose are found in the blood at an early point in time (15 to 60 min p.i.), generally 30-55%. After 4 hours, however, the mean blood concentration is below 25%, usually 15 to 20%.
• the blood half-lives of the liposomal contrast media according to the invention are generally less than 8 hours, but always less than 16 hours.
• the liposome formulations according to the invention are surprisingly particularly suitable for use in blood pool imaging indications.
• iopromide-containing liposomes in a dose of 200 mg total iodine / kg in rabbits showed a significant increase in X-ray density in the blood over the entire examination period of 20 minutes.
• a significantly higher contrast difference ( ⁇ HU) between the aorta and liver tissue could be detected for the liposomes, for example.
• Blood volume 58 ml / kg obtained after 15 min. This value is in the range of 1.0 to 5.0 mg iodine / g, preferably 1.5 to 3.0 mg iodine / g, which are considered sufficient for diagnostic imaging. At earlier times ( ⁇ 15 min pi), significantly higher iodine concentrations can be reached are also diagnostically advantageous. These are, for example, in the range of a maximum of 10-25 mg iodine / g or 15-20 mg iodine / g.
• the formulations according to the invention with their relatively low iodine / lipid quotients are surprisingly particularly suitable here.
• the ratio of trapped iodine to lipid used in the formulations according to the invention is thus only in the range from about 0.1 to 1.4, preferably 0.2-0.8 mg, particularly preferably 0.25-0.65 mg of encapsulated iodine / mg Lipid.
• the blood concentration was still approximately 1.1 ⁇ mol Gd / g and thus still in the diagnostically relevant concentration range of 0.15-2.5 ⁇ mol / g or preferably 0.5 to 2.0 ⁇ mol / g. Similar to the application in CT described above, here too, significantly higher contrast agent concentrations in the blood can result at early points in time ( ⁇ 15 min).
• Macrocyclic contrast agents such as Gadobutroi are particularly suitable for producing formulations according to the invention for MRI. Appropriate formulations ensure that the contrast medium is excreted quickly and completely.
• the formulations according to the invention are furthermore distinguished by a relaxivity which is not or only slightly changed compared to the free contrast medium.
• iopromide-containing liposomes with different lipid compositions are produced and with regard to examined their properties.
• Liposomes prepared according to Example 1 (SPC / CH / SPG 6: 3: 1, amount of iodine / lipid used 1: 1.5) are stored in the refrigerator or at room temperature and their stability is examined after 9 months.
• Liposomes with Gd-containing MRI contrast media are produced by means of the high-pressure extrusion process described in Example 1.
• Liposome suspensions prepared according to Example 1 were mixed with human plasma, an iodine concentration of about 5 mg / ml being set. Each 1 ml of this plasma contrast medium mixture was then dialyzed in a Dianorm equilibrium dialysis apparatus (Dianorm, Heidelberg) against the corresponding human plasma through dialysis membranes with a cutoff of 5000 Da (Dianorm). At different times, samples were taken from the retentate and permeate side and the iodine content was determined by means of X-ray fluorescence spectroscopy (FEA). The results obtained can be seen in FIG. 1.
• the liposome suspension (approach A) listed in Example 4 was injected at a dose of 250 mg total iodine / kg into 16 male rats (weight: 137-160 g) and 4 animals each 0.25; 1; Killed 4 and 24 hours after the injection.
• the liver, spleen, lungs and blood were then examined for their iodine content by means of FEA.
• the results (% of the dose / organ administered) are shown in the table below.
• a DSPE-PEG-containing liposome suspension (SPC / CH / SPG 6: 3: 1 + 5 mol% DSPE-PEG 2000 - 204 nm, 45% encapsulated) was administered in a dose of 250 mg total iodine / kg to 16 male rats (weight: 136-160 g) and 4 animals 0.25 each; 1; Killed 4 and 24 hours after the injection.
• the liver, spleen, lungs and blood were then examined for their iodine content by means of FEA. The results (% of the dose / organ administered) are shown in the table below.
• the liposome suspension (approach A) listed in Example 4 was examined in a dose of 200 mg total iodine / kg in the rabbit.
• the monomeric X-ray contrast agent Ultravist® (Iopro id (INN)) was used as a control.
• the X-ray density in Hounsfield Units (HU) in the aorta and in the liver tissue was measured from 0 to 20 minutes after a single intravenous application (spiral CT, Somatom plus S, Siemens, at 120 kV). The area under the
• Example 9 Blood level profiles after administration of Gd-EOB-DTPA-containing liposomes to the rat
• Example 8 The liposome suspensions listed in Example 8 (batches A and B) were injected at a dose of 0.3 mmol total Gd / kg into 16 male rats (weight: 137-158 g) and 4 animals each 0.25; 1; Killed 4 and 24 hours after the injection.
• the Gd content in the blood was then determined by means of ICP-AES (inductively coupled plasma atomic emission spectroscopy).
• the liver concentrations were not shown here, since the unencapsulated Gd-EOB-DTPA also accumulates specifically in the liver (liver contrast agent for MRI).
• the results (% of the applied dose / 31ut) are shown in the table below.
• Example 10 Blood-pool enhancement (CT) by Gd-EOB-DTPA
• a Gd-EOB-DTPA-containing liposome suspension (approach A, see Example 8) was administered in a dose of 0.3 mmol Gd / kg i.v. (Anterior vein) administered to an anesthetized rabbit (3 ml / min). Since Gd-EOB-DTPA, which is actually used as an MRI liver contrast medium, also absorbs X-rays, it was possible to use computer tomography (CT) to test the accumulation of the liposomal component in the blood.
• CT computer tomography

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• 1996
  • 1996-02-09 EP EP96904033A patent/EP0806969A2/de not_active Withdrawn
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