Composition for therapeutic use, including an organic lipid phase and a rare-earth radioisotope complex

Abstract

The invention relates to a therapeutic composition including a complex having the following formula (1), including a rare-earth radioisotope in ionic form, said complex being solubilized in an organic lipophilic phase: [M(L).sub.3] in which: M denotes the rare-earth radioisotope in ionic form, and L denotes a tropolone ligand or a ligand derived from tropolone.

Claims

1. A therapeutical composition, comprising a complex having the following formula (1) comprising a rare-earth radioisotope, said complex being solubilized in a lipophilic organic phase:
[M(L).sub.3](1) wherein: M designates the rare-earth radioisotope, wherein the rare-earth radioisotope is .sup.90Y or .sup.47Sc, and L designates a tropolone ligand or a tropolone-derived ligand chosen from amongst halogenotropolone, -methyltropolone, -methyltropolone, -methyltropolone, -isopropyltropolone, -isopropyltropolone, -isopropyltropolone, nootkatin, stipitatic acid, puberulic acid, puberulonic acid, purpurogallin, or colchicine.

2. The therapeutical composition according to claim 1 wherein L is -isopropyltropolone.

3. The therapeutical composition according to claim 1 wherein said lipophilic organic phase is a mixture of iodized methyl esters of poppyseed oil, containing 38% by mass iodine.

4. The therapeutical composition according to claim 1 wherein said lipophilic phase is put into emulsion in an aqueous phase.

5. The therapeutical composition according to claim 4, wherein said aqueous phase is a physiological serum.

Description

5. DESCRIPTION OF ONE EMBODIMENT OF THE INVENTION

(1) The general principle of the invention relies on the labeling of a lipophilic organic phase by an organic complex bearing a rare-earth radioisotopic ion, the lipophilic organic complex being a vector of choice to convey the radioisotopic complex to the cancerous cells and the radioisotope label enabling the specific destruction of the pathological cells.

(2) The following embodiments are given by way of examples of the present invention and in no way constitute a limitation thereof. FIG. 1 is the diagram of the automated method.

EXAMPLE 1

Preparation of the Complex 90Y-Tropolone by Extraction According to the Manual Method

(3) In an appropriate recipient, 1 ml of yttrium-90 (.sup.90Y) chloride, having a radioactivity of 0.8 mCi, is mixed with 1 mL of a 10.sup.2 mol/L tropolone solution in a PBS (phosphate buffered saline, pH 7.4) buffer. After 5 minutes of stirring at ambient temperature, 2 mL of chloroform are added and the phases are separated by centrifugation. The organic phase is collected.

(4) The labeling efficiency in percentage is computed as follows:
Labeling efficiency(%)=[activity of the lipophilic phase(Bq)100]/[activity of the lipophilic phase(Bq)+activity of the aqueous phase(Bq)]

(5) The radiochemical purity compatible with a pharmaceutical application is defined as at least 90% of the complex M(L).sub.3 contained in the lipophilic phase.

(6) Thin-layer chromatographic (TLC) analysis on Whatman paper seeks to determine the radiochemical purity of the prepared solution. The eluent used to carry out the migration is methanol. The chromatography is then carried out according to methods well known to those skilled in the art. Briefly, a drop of radiolabeled solution is deposited on a TLC strip, which is then placed in a development chamber. A solvent, in this case methanol, is disposed in the tank without touching the deposition point. The chamber is closed and the migration of the solvent front takes place, carrying with it the sample of radiolabeled solution. At the end of the migration, the strip is deposited by revelation and viewed on a photo-imaging plate, for example by means of the Cyclone phosphor-imager by Perkin-Elmer.

(7) The radiochemical purity (RCP) is expressed in percentage and computed as follows:
RCP=[activity of the radioactive spot of interest(Bq)100]/[total activity(Bq)]
The ratio of migration by radioactivity Rf=(radioactivity of the migration front of the solvent carrying the compound (Bq))/(total radioactivity of the TLC strip (Bq)).

(8) In this example, the yield is equal to 89.5% and the radiochemical purity (RCP) is equal to 96%.

EXAMPLE 2

Preparation of the Complex 90Y--isopropyltropolone by Extraction According to the Manual Method

(9) In an appropriate recipient, 0.5 mL of yttrium-90 (.sup.90Y) acetate having radioactivity of 1.63 mCi, is mixed with 0.5 mL of a 10.sup.2 mol/L -isopropyltropolone solution in ethanol. After 5 minutes of stirring at ambient temperature, 2 mL of chloroform are added and the phases are separated by centrifugation. The organic phase is collected.

(10) Yield=98.3%

(11) Radiochemical purity (RCP)=99.9%

EXAMPLE 3

Preparation of the Complex 90Y-Tropolone According to the Manual Method

(12) In an appropriate recipient, 1 mL of yttrium-90 chloride having a radioactivity of 1.05 mCi, is mixed with 1 mL of a 10.sup.2 mol/L tropolone solution, in PBS (pH=7.4). After 5 minutes of stirring at ambient temperature, the solution is purified on two Sep-Pak C.sub.18 columns (preliminarily activated by physiological serum), and the complex is eluted by 2 mL of ethanol.

(13) Yield=70%

(14) Radiochemical purity (RCP)=95.1%

EXAMPLE 4

Preparation of the Complex 90Y--isopropyltropolone According to the Manual Method

(15) In an appropriate recipient, 0.5 mL of yttrium-90 acetate having radioactivity of 1.4 mCi, is mixed with a 0.5 mL of a 10.sup.2 mol/L -isopropyltropolone solution, in ethanol. After 5 minutes of stirring at ambient temperature, the solution is purified on an Sep-Pak C8 reverse phase cartridge by 5 mL distilled water. The complex .sup.90Y--isopropyltropolone is eluted from the cartridge by 2 mL of ethanol.

(16) Yield=75%

(17) Radiochemical purity (RCP)=92.7%

EXAMPLE 5

Preparation of the Labeled Compound Marked with 90Y in Solution in Lipiodol

(18) The organic solution obtained in the examples 1 to 4 is evaporated at a temperature of 40 C. to 100 C., and the residue is dissolved in 2 mL of Lipiodol. The mixture is stirred for 5 minutes. The radiolabeled lipiodolized phase is collected.

EXAMPLE 6

Preparation of the labeled compound with 90Y in solution in LabrafacCC

(19) The organic solution obtained in the examples 1 to 4 is evaporated at a temperature of 40 C. to 100 C., and the residue is dissolved in 2 mL of LabrafacCC (caprylic/capric acid triglycerides). The mixture is shaken for 5 minutes. The radiolabeled lipophilic phase is collected.

EXAMPLE 7

Automated Preparation of the Complex 90Y--isopropyltropolone in Elution in Lipiodol

(20) Referring to FIG. 1, a description is provided of the automated preparation of the complex .sup.90Y--isopropyltropolone in solution in Lipiodol. The automated system comprises a set of flasks containing different reagents as well as reactors in which the chemical reactions occur. The circulation of reagents in the set of flasks in reactors is controlled by a system of valves (V1-V15) and pumps (P1, P2). The automated operation of the valves and pumps is programmed and pre-recorded in a control system 4. An automaton suited to implementing the method according to the invention is of the Taddeo automaton type (Comecer, Italy).

(21) In brief, a volume of 0.5 mL of yttrium-90 chloride having radioactivity of 1.61 mCi and contained in a recipient A is transferred into the reactor R. A volume of 0.5 mL of a 10.sup.2 mol/L -isopropyltropolone solution, in ethanol in a recipient B is also transferred into the reactor R. After 5 minutes at ambient temperature, the reaction medium is transferred to a Sep-Pak C.sub.18 type column 1 and then washed with 5 mL of distilled water contained in the flask F3. The complex .sup.90Y--isopropyltropolone is then eluted in the flask C by 2.5 mL of ethanol contained in the flask F5. The ethanol is evaporated at 100 C. and under reduced pressure, and 2 mL of Lipiodol contained in the flask F6 are finally added to give the desired radiolabeled composition. The wastes such as the wash solutions and excess reagents are recovered in a waste container 2. These wastes are especially filtered by a filtration system 3 before being eliminated according to the good laboratory practice.

(22) To improve the progress of the reaction mixture, the water-ethanol mixture contained in the flask F4 can be made to pass through the column. This additional washing depends on the lipiophilicity of the ligand used.

(23) Yield=51.6%

(24) Radiochemical purity (RCP)=99.8%

(25) As can be observed, in the light of the results, the automated method according to the invention gives a composition comprising a lipophilic organic phase in which a rare-earth radioisotope complex is solubilized in a manner that is sure for the user, fast and gives excellent radiochemical purity.

EXAMPLE 8

Biodistribution of Lipiodol Labeled by the Complex 90Y--isopropyltropolone, 72 h Post-injection

(26) A volume of 0.15 mL, having radioactivity of 53 Ci, of radiolabeled Lipiodol was injected into the hepatic artery of rats having contracted hepatocellular cancer (through an injection of N1S1 cells 16 days earlier). 72 h after injection, the rats were euthanized and their organs were weighed and counted.

(27) TABLE-US-00001 Injected Injected activity per Tested tissue activity (%) gram of organ (%) Tumor 30.2 13.4 Tumoral liver 17.1 7.6 Healthy liver 22.2 4 Lungs 1.7 0.8 Heart 0.3 0.3 Spleen 0.4 0.9 Kidneys 4.7 2.6 Stomach 0.7 0.2 Intestines 2.2 0.2 Bones (femur) 1.8 1.7

(28) As can be observed from the results, the radioactive activity is chiefly in the tumor, the affected liver and the healthy liver. The activity in the healthy liver was nevertheless three times lower than in the tumor, indicating a preferential fixation of the composition according to the invention in the hepatic tumor. The fixing in the other organs was also low. The composition of radiolabeled Lipiodol through the complex according to the invention therefore makes it possible to specifically target the liver and the hepatic tumor. The problems of anarchic fixation of radioactive complexes are therefore avoided through the composition of the invention, the complex [M(L).sub.3] being particularly stable. The composition according to the invention is therefore more reliable and more efficacious.