CA2033188A1 - Method for the preparation of active ingredients and pharmaceutical compositions for decorporating radioactive isotopoes from living organisms - Google Patents

Abstract

Pharmaceutical composition for decorporating radioactive isotopes from living organisms comprising as active agent a product prepared by reacting 1,4,10,17-tetraoxa-7,16-diazacyclooctadecane with 2-bromomalonic acid disodium salt.

Description

wo ~0tl4343 PCr/HV90/0003~

- 2~3~8 ~ETHOD ~O~ PREPAR~ IO~ O~ ACTIY~ I~G~lEDIEl~TS
AND PH.~U,I~CEUTIC.~L CO.,IPOSITIO~ :FOR Dr CO~POR~ING
RADIOACTIVE ISOTOPES ~RO~I LIVING ORGANIS~IS

This invention relates the preparation o~ active ingredie~ta and pharmaceutical compositionq ~or decorporating radioactive isotopes from living organism3 ~
Nuclear ~ia~ions i~ the e~perime~tal, iqotope-producing, or energy-supplyin~ ~uclear reac-tor~ and in nuclear ~eapon test3 are accompnn;ed by the formation o~ a con~iderable amount of radio-active by-product9. ~ajority of these hot materials ..... . i . - - . . .
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'' ,~'' involves fiqsion products and acti~ated elements, including e~tremely hazardous radioacti~e isotopes such a9 iodine-131, strontium-89-90, cesium-134 and -137, cerium-141 and -144. ~mltted in~o the en~iron-ment,.they may re~ult in a radio~ctive pollution to the ~ingdom of li~e.
There are three ways, three Oste9, the~e iqotopes can get through enter~ng the human body:
the resplrator~ tract (breathing ~ith air), the digestive tract tingesting ~ith iood~ and dri~s), the epide~ (contacting ~ith harmed or unharmed ~in).
A good deal o~ possibilities are provided for reducing or even preventing injurie~ o~ health.
Some isotopes, e~sentially radiostroncium, ho~ever, can only be protected from by hinderIn~ it~ gastro-lntestinal resorption ~ith peroral ac~inistration o~ ~
suitable adsorbents. I~ the medical aid begins as late as severzl hours after the contamination, no e~icient methods are a~ailable at the pre~qent state o~ the medical art ~or the resorbed proportion o~
the radioisotopes transported by the blood-stream and t~e lymph-flo~ to iD~luence their depo9ition in bones, to pre~c~ thalr hi~tic bl~di~g and to promote their d~corporatln3.
~ his ~act moti~ate~ the research on highly e~ective human and veterinary pharmaceuticals capable , woso/l4~3 pcr/Hu9o~ooo35 (~ 2033~8 o~ bonding radiostrontium in the blood-stre~m ~nd in other e~tracellular regions in ~orm oi ~table comple~es. Thiq ~ould prevent the hi~tic deposition o~ the i~otope and permit ist natural e2cretion (~aeces, urine) irom the organism.
The iollo~ing requirements are established to ~uch a pharmaceuticsl age~t:
(a) tke comple~ formation ta~e~ place in the biological ~ystem even in the preqence of concurrent ionq (such as Ca2~, na+, ~+, etc.) and ligands that are pre~ent in a great amount;
(b) it has an acceptably lo~ level of to~icity (~ide-ra~ge ei~iciency);
(c) it i9 ~ater-soluble; and (d) it can be admi~istered pare~terally ag ~ell.
In the early ~i~ties ~hen the rapid develop-ment o~ coordination chem;~trJ commenced, predominantly the transition metal comple~es ~ere studied, over-shado~ing the ~l~ali and al~ali earth metal ones that either do not ~orm comple2es ~ith the readily scce~sible organic and inorga~ic ligands or these comple~es have very low stability, only electrostatic inter-relations bet~een the met~l ions and the ligands ~eep them together. ~hi9 concept was bro~en through by the dis-covery o~ "crD~ ether" and "cryptate" ligands i~ the late 8i~tie9.

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-wo gO/l4343 4 PCr/HU90/00035 -- 2033i88 Crown ethers contain mainly o~ygen donor atoms ~n~le cryptate~ have both o~yge~ a~d ~itrogen donor~.
Their construction holds the incorporated metal io~a in cav}tie~ of well-de~ined 9ize thus, o~ly metals of certain sizes can fo~m stable comple~e~ ~rith these types of ligands. Consequen~ly, they are much more specific than ligands l~no~rn beIore. Stability co~tallts (10 g X) for some of theae ligands with ql ~aii earth metals in aqueous 901utio~ are preserLted in Table (Coordination Chemlstry o~ acrocyclic Compounds, Ed.
G.~. ~elgoIl, Plenum Pre~, 1979).

Table I

Ligand ca2+ sr2~ Ba~+
15-croum-5 0.5 2.72 3.87 dicyclohe~yl-18-cro~-6 0.4 2.64 3.27 dibenzo-18-cro~-6 - 1.00 1.95 1,10-diaza-4,7,13,16-tetra-o~:ycyclo-oc~;adecane - 2.56 2.97 cryptate-(2.1.1~ 2.50 2.00 2.00 cryptate-(2.2.1) 6.95 7.35 6.30 cryptate-(2.2.2) 4.40 8.00 9.50 cryptate-(3.2.2) 2.00 3.40 6.00 cryptate-(3.3.2) 2.00 2.00 3.65 :. , , ., . ;

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Wo90/l4~3 _ 5 PCT/HU90/00035 (~ A
2~331~8 Date in Table I sho~ a very considerable e~fect of the ~ize of ligand "cavity" on the stability const~ntq. In some cases, quch as for cryptate-(2.2.2), the stability constant ~ith Sr2+ is hi~her by se~eral orders of magnitude than ~ith Ca2+.
Th aDove data motivated ~nimal te~ts ~ith the ligand cryptate-(2.2.2) (4,7,13,16,2~,24-he~ao-2-l,10--dia~Pbicyclo-/8.8.8/-he~acosane) for remo~al of Sr-85, Ra-224, Pb-212, and Ba-140 as well as L~-140 isotopes from the or~zniams (W.H. ~ller, Natur~iss.
57, 2~8 /1970/; W.H. ~ller and ~.A. ~uller, Natu~ s.
61, 455 /1974/; W.H ~ller et al., Naturwiss. 64, 96 /1977/; J. Knajfl et al., 12th An~. ~eeting of ESR~, Budapest, 1976; J. Bar9ch, J. Gei~ler and Z. ~zot, Nu~leoni~a 23, 305 /1978/). The value of their re~ult ~as vitiated by the concept that the metal comple~es were formed in vitro then administered subcutaneously and thei~ purging ~as studied. These e~periments could prove only the fact that no dissociation of the comple~
formed e~ternally from the radioactive metal and the ligand occured in an intricate biolo~yal sy9tem instead of an in ~i~o comple~ation of the rsdioactive isotope e~isting already in the animal ~ith the ligand ad-~inistered sub9equently into a stable comple~ ~hich could be decorporated irom the organism in the natural ~ay9 of e~cretio~. It should be noted on the ba3i~ of real . .

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c 2033188 e~periences that ligand compound3 a~e much leq9 to~ic in com~le~ form than the lig~nà~ themqelve~.
I~ co~trast to kno~n comple~es, stabilitJ consta~ts of rare earth metal comple~e~ of 1,10-diaza-4,7,13,16--tetr~o~acyclooctadecane-N,N'-diPcetic acid, s~nthe-sized from the monocyclic cryptate decrease with the inc~easin~ atomic numDer (decreasing ionic size).
~tability con3tants of Ca2+ and ~r2+ complexes, ho~-ever, are identical within the em?er ental e~or (8.39 and 8.29, r~pectivel-J) (~ hang, Inor~.Chem.
25, 35~ /1986/) ~hile comple~es of non-cyclic ~mino-polycarboz~lic acids (EDTA, ethylenediaminetetraacetic acid, DTP~, diethylenetriQminepentacetic acid, etc.) are consider~bly more stable with Ca2+ than ~ith Sr2+.
~ he purpo9e o~ this invention was the prepa~ation of monocyclic cryptate ligands and their derivatives ~-in order to iniluence in vivo ~tabili~ies of complexes iavourPbly by lin~ing function~I groups to the macro-cycles. ~he final goal wa~ to attain derivati~es that wol-~d be suitable ~or the removal of radio9tro~cium, occaqmonally other radioactive met~l isotope9, irom the living orga~i9m9. It ~as proved b~ several e~peri-mental data that an active sgent based on 1,4,10,13--tetrao~a-7,16-diazacyclooctadecane~ '-dimalonic acid tetrasodium salt was capable of promoting the e~cretion of radiostroncium and radiocerium ~hich had .
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2~31~8 been administ2red into various ~ites (peritoneal cavit-J, ~ubcutaneou3 inter~titial ti~sue, lunO) of the animal body.
~ ke method of thi~ inve~tion comprise~ a new method to the preparation OL compositions containing 1,4,10,13-tetrao~a-7,10-diazac~clooctadecane dimalonic salts.
Preparqtion o~ ~uch a compound ~as described by . de Jon~ et al. (Recl. Trav. ~him. Eay~-3as, 102, 164-173 /1983/). In thi~ procedure, 1,4,10,13-te~ra-o~a-7,10-diazacyclooctadec2ne ~as reacted ~ith alpha--haloge~ated methyl malonate ester ~or ~ub~tituti~g hydrogen atom9 on the nit~ogen atoms and then ester ~a9 hydrolyzed into lithium salt.
~ e ha~e found that alpha-brominated di~odium ma-lonate is more preferable ior sub~tituting hydro~en atom~ on the nitrogen atoms than alphP-halogenated methyl malonate. In this case, hydroly3is is omitted a~d the ~ater-~oluble salt i9 obtained directly. In addition, sodium salt is not hygroscopic in contrast to lithium salt thus, it i9 a more convenient active ingredient ~or the preparation oi pharmaceutical com-positions or the li~e. ~nother sdvantage of aodium salt to lithium o~e is its lo~er price.
I~ the procedure of thi9 invention, the active age~t cont~ining 1,4,10,13-tetrao~a-7,16-diazacyclo-. ' ':
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WO 90/14343 - 8 - PCr~HU90/00035 ~;'?. !
20331~8 octaaecane-N,N'-dimaloniC acid tetra90dium salt iq prepared by react~ng 1,4,1C,13-tetrao~y-7,16-diaza-cyclooctadecane ~ith 2-bromomalonic acid disodlum qalt. Preferably, the reaction i9 carried out in a ~liohtly al~alic aqueous medium at 70 to 80C.
~l~alicity of the reaction mi~ture i9 reaqonably chec~ed With phenolphthalein indicator, adjusting and holding a pPle pi ~ colour of t~e mi~ture durlng the reaction.
The acti~e agent containing 1,4,10,13-tetra-o~:y-7,16-dia~acyclooctadecane-i~,N'-di~alonic acid tetraqodium salt i9 capable of bonding radioactive metal isotopes, principally radio~tr2ncium and radio-cerium, inge9ted i~to a living organism. The stable comple~ ~ormed in vi~o can be decorporated irom the body in the natural ways in form of this comple~
~ he pharmaceutic~l compo~ition of this in~ention compri~es an acti~e ingredient containing 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane-~,N'-dimalonic scid tetrasodium salt prepared by the procedure of this invention alon~ ith a pharmaceutically accepted carrier, ~uch as normal _aline solution or a 5-per cent by volume o~ gluco9e 901ution.
~ he compo9ition comprises irom 100 to 500 mg, preierably 250 mg o~ acti~e ingredient mi~ed prefer-ably ~ith a 5-per cent by volume o~ gluco9e 901ution.

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W090/14~3 _ 9 _ pcT/Huso/ooo3s 2~33188 AUAealing po~er of the compoaitiOAnA h q been evidenced by PAnimal teqts. In thiq ~ay, the mini-mumA aAnd ~verage lethal doses ~LDo 1 arAd ~D50, respectively) have been e9tablished.
~ or the determination of lethal do~e~, the active iAngredieAnAt wa~ a~Amini~tered intravenousl~
at irAcrea~ing concentrations to the 2rAimaiq. ~ini-mum and average lethal doses ~ere calculated from the mortality ~qithin 30 days. ~D50/30 value o~ the active agent contairAin~ 1,4,10,13-tetrao2a-7,16--diazacyclooctadecarAe-N,N'-dimaloAnAic acid tetr~Asodlum (DDIACRYP) salt ~ NaBr (~ = 2,5 - 8) a~ prepared accord-ing to E~ample I ~as 1.05 mmole/~g body ~ei~ht. On every occasion, on2 tenth of thi~ dose ~as intro-duced into each animal in thi~ e~perimeAnAt.

~aborator-~ Small ~nimal ~e~t3 for the ffect of D~IC~ P on the EnhaAnAced Decorooration A
~ he phar~aceutical compositioAn coAAtaining DA.ACRYP
active ingredieAnt waq deA~oted "P~R-23". ~he compo-sition contained a carrier, preferably sterilized normal saline solution or 5-per cent by wei~ht of glucose solution. Preferable ratio oi acti~e agent to car_ier ~as from 100 to 500 mg/cm3 carrier.

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WO 90/14343 PCI`/HU90/00035 20331~8 In order to test the effect of nMCR'fP on en-hancing the decorporation of radiostroncium Pnd the rare earth metal radioceriu~ ~rom the body, ~ale and ~em~le S~iss mice and Wistar rPt9 ~ere 9elected.
The e~periment~ ~ere generally conducted by ad~
;nistration of radio~troncium (85SrC12) or radio- -cerium (144Ce~13) o~ an activity from 37 to 5~ ~Bq (1-2~uCi) into Yarious ~ites of the animal body (peritoneal ca~ity, subcutaneou~ interstitial tissue, lung) followed by an intra~enous injection of P~R-23 30 to 60 minutes later qo that one injection intro-duced 100 ~ ole/~g of active agent. Tn the comparative tests, a ~no~n polyPminopolycarbo~ylic acid-type decorporant (decorporating agent), calcil~m-tri~odium salt of D~P~ (diethylenetriaminopentacetic acid) (Heyl and Co., Berlin) was u~ed at equimolar concentra tion. The amount of re9idual isotopes in the animal org~nisms was dete~mined by whole-body activity measurements in every 1 to 4 day~ and was e~pres~ed as per cent o~ activity introduced.
The effect of PTR-23 administered once (Day 0) intravenously on the enhanced escretion of Sr-85 i~otope introduced into the peritoneal ca~ity i3 illu~trated in ~igure 1 ~here the percentage o~ re-9idual isotope9 in the animal body (~hole-body re-.. ... .. .
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WO 90/14343 PCI/HU90/0003$
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te~tion) is plotted against the d~s of experiment.
~he ef~icie~cy of treatment with the compound of this invention 30 minutes after the admini~qtration o~ the isotope is indicated by the _teep drop of the correqponding curve: o-n the Day 1, 35.8 per cent ~a~ a~tained ~hich i3 le9~ than a half of the Sr-85 co~tent of control animal~ bei~g 73.2 per cent. This ratio ~aq consi~tent throughout the e~periment, reach~
ing 21.2 per cent after the treatment with PTR-23 in contrast to the 45.5 per cent of untreated controls.
~his 9eries of e~periments also illustrates that the decorporant DTPA is inef~ective for remo~al of Sr isotope from the animal body (~. Catsch: Dekorporierung radioa~tiver und stabiler ~etallio~en, K. ~hiemig Ver-lag, ~unche~, 1968).
~ he present invention i~ more particularly illu~trated by the following e~amples ~hich are not inte~ded to limit the qcope of the i~ventio~.
E~ample 1 demonstrates the preparation of the active agent. E~amples 2 through 6 illu~trate the healing power of pharmaceutical compositions prepared therefrom.
Eszmple 1 Preparation of 1,4,10,13-tetrao~a-7,16-diaza-cyclooctadeca~e-N,N'-dimalonic acid tetrasodium salt (D~CRYP) - contai~i~g acti~e agent .

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: . . . ~ . - , WO90/l4~3 PCT/HU90/00035 '~, 2.80 g (15.3 mmole) of 2-bromomalonic acid was dissolved in 2 cm3 o~ water And the solution wa~ titrated with 1.5 to 2 ~ ~aOH solution in the presence o~ 1 drop oi phenolphthalein indicator to a pale pi ~ colour. 1.00 g (3.81 mmole) of 1,4,10,13--tetrao~-7~16-diazacyclooctadeca~e (Eryptofi~ 22, ~erc~) was added to the 901ution. The reaction mi~ture wa~ ~ept at 75 to 80C for 14 hour9 ~hile 8.55 cm3 o~
1.873 ~ NaOH aolution wa~ dropped ~rom a bu~et ~or maintaining the pin~ colour. ~he 901ution was then evaporated in vacuo and dehydrated 8till in vacuo on a water-bath at 80C for 6 hours. ~he residue was ta~en up ~ith 15 cm3 of dichlormethane, filtrated, e~tracted three times with dichlormeth~ne ~nd dried in nitrogen stream. The ~hite solid product ~as e~-tracted with ab901ute ethanol until no con~iderable amount o~ material had been dissolved (15 to 17 times).
~ hite deposit ~as precipitated ~rom the e~tract during the e~traction. The ethanolic e~tract ~aa evaporated, ts~en up ~ith dichlormethane, ~iltered, e~tracted three ti~e9 ~ith dichlormethane a~d dried in nitrogen stream. Yield o~ the product ~a~ 1.447 g.
~ he dichlormethane extract waa e~aporated in nitrogen 3tream and 0.357 g oi highly hygros¢opic yellow~sh crystals ~ere obtained.
~he re9idue irom ethanolic extractio~

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WO 90~14343 - 13 - PCI/HU90/00035 -2~33~ &8 (said white precipitate) ~aq di~olved in 20 cm3 of ~rater arld kept at 80C for 20 rn nute3. The solution waq evaporated in ~acuo and dehydrated atill in vacuo on a ~rater-bath at 80C for 5 hour_.
The ~lLrther proces_ing ~as the s~me as above. ~he ethanolic e2ctract was e~aporated in vacuo, talcen up ~ith dichlormethane, ~iltered, and dried in nitrogen ~tream. 0.430 g solid uas obtained.
Productq ~rom ethanolic e~tracts were com-bined, suqpended in ethanol and ~tirred at 70C for 30 minute~. ~he mi~ture waq then e~raporated, ta~cen up ith dichlormeth~ne, ~iltered, and dried in nitrogen stream. ~as~ o~ the product ~ag 1.830 g at a yield of 58 per cent. The product iq a double sQlt o~ 1,4,10,13--tetrao~ca-7,16-diazacyclooctadecane-N,lT'-dimalonic acid tetra~odium qalt ~rith ~odium bromide (conta~n;ng 33 %
by ~eight sodium bromide).
nalvsis Characteristic I~ bands (in ~Br), cm 1 2950, 2868 tm, \,7 /C-~J) 1605 (~3~ V /COO/a8 ) 1430 (m, ~ /CO08 ) Characteristic unidenti~ied IR bands:
1350 (9), 1320 (~), 1095 (9) 928 (w) 1~ ~IR data (in D20), ppm:

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- WO 90/14343 PCI'/HU90/00035 !^~
2~3318~
2.92 (t, 8H, N-~H2) 3.63 ~t, 8H, O-CH2) 3.70 (gg, 8H, O-CH2-CH2-0) 4.00 (sg, 2H, N-C~).
~ater solubilit~ very soluble.

E~smple 2 The result~ with female ~ristar rat~ are ~how~
in ~igure 2. ~he e~perime~tal srr~geme~t Qnd no-tations are ide~tical to those in the general des-criptio~ and in ~igure 1. The o~ly di~ference was i~ the delay between the introduction o~ the i80-tope i~to the peritoneal cavity and the intrave~ous admi~istratio~ of the active age~t, being 60 ~y9. The compo~ition of thi~ inve~tion was even more ef~icient for rats. On the iirst day after the treatment, the amount of radiostro~cium in the animal bodie~ dropped to 22.0 per cent by virtue of the new comple~i~g ~ge~t as compared to the 69.6 per ce~t ~ith the control which is more than three t~mes higher. 1ike the result~ with mice, the ratio between the curves was consistent throughout the e~periment reaching 13.5 and 36.8 per cent of residue at the e~d of test ~or the treated a~d the co~rol animals, respectively.
Retentio~ values in the DTPA-treated group were lo~er than those in the co~trol but the dif~ere~ce was not statistically sig~ifica~t.

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WO 90/14343 PCI`/HU90/0003 ~,r, ;, ,1,. . .
20331.88 It wa~ clearly demo~strated by the e~peri~en-tal data i~ Example 2 that the composition PT~-23 promoted the decorpor~tio~ of Sr-85 admi~i~tered i~to the peritoneal cavity considerably, reducing thereby the radioactive load o~ the animal organi3m e~posed to a ~ingle relatively lo~ do~e ~hen the agent had been ingested into the blood-Qtream 60 minute~ after the administration of the iqotope.

E~mple 3 I~ thi~ ~eries of e2perimentQ, posQibilities of decorporati~g radio~troncium got into the skin or the subcuta~eous inter~titial ti~uea were qtudied with a ~Qingle intra~e~ous treatment by PTR-23 (Fi-gure 3), ~he reQults demonqtrated that the amount of radiostroncium entered through the hurt epiderm (stabs, bruise~Q, cut~) was mar~edly decreaQed by the compo~itio~ PTR-23. Whole-body retention of the a~imals was 31.5 per cent in contrast to 56.9 per ce~t o~ the co~trol (a gain.of almost 50 per ce~t) on the Day 1 when the t~eatme~t w~a applied 30 mi~uteq ~fter the i~fection. Th~ ratio wa~ co~si~te~t throughout the e2perime~t. ~reatme~t with D~PA wa~ i~e~fective agalnO

E~ample 4 Whole-body retentio~ curve~ igure 4 refer to the elimi~ation of radiostroncium ingested through ''.' ' . '.
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WO90/l4~3 - 16 - PCT/HU90/00035 ~ 2033188 the trachea into the lu~gs of ~i~tar rats after the ad~i~istratio~ o~ the compo~ition PTR-23 intra-venousl~ or i~traperitoneally. It r~as,proved un-equivocally b~ the e~perime~tal data that the efficiency of the a~e~t was ~ot in~luenced by the way of admini~tration, i.e. ide~tical ef~ect was obtsined both with intravenous and with intraperi-tonael treat~e~t.
The e~fect of the composition of this i~ven-tion o~ the promotion of ~r decorporatio~ is shown bg the two lower curves in ~igure 4. It can be seen a8ai~ that the amount of Sr isotope ingeQted into the lungs decreased abruptl~ after the admi~istra-tio~ of the said compositio~. On the Day 1, it dropped to 48.2 per cent while this level was 88.3 per cent in th~ co~trol. The highest di~erence was obtai~ed o~ the Day 18 whe~ the rete~tio~ in the treated a~d control groups ~ere 28.6 a~d 58.7 per ce~t, respectively.

E~ample 5 The dose effect of the decorporant of this i~ven- ', tion wa~ measured on Swiss mice. Retentio~ curves in Pigure 5 represe~t an order of magnitude i~ the co~ce~tration of the agent (from 10 to lO0 pmole/kg) ~ollowi~g the e~cretion of Sr isotope ingested . . ' .
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Wo 90/14343 PCr/~UsO/00035 .~- 2~33188 perito~e~lly. It was established Irom the e cperime~-tal d~ta that, at a co~centration of E19 low as 10 /umole/kg, the ~mou~t of isotope retained in the bod~ ~vas sig~ificantly lower than that i~ the control. The effect i~creased with the doae but above 5O ~mole/kg, the enhancement in the e~cretion ua~ ~ot proportional to the amou~t o~ the active ~ge~t a9 sho~ by retention values at the end of e~c-periments (Day 30) being 40.6 per cent in the co~trol and 34.3, 28 3, 25 2, 23.9 and 21.8 per cent in the order oî increasing dose. C on ~equently, it seemed to be rea~onable to administer lower doses repeatedly for treating an internal in~ection of radiostroncium.

Ezample 6 ~ he pharmaceutical composition of this inverltion wa~ tested to other radioact~ve metsls than radio-~tro~cium, mainly Ito the rare earth metal, cerium-144 for its removal from the animal body. ~erium-144 iso-tope was introduced peritoneall~ into female S~
mice. 3O millute~ after, the animals were treated i~trave~ously with lOO ~umole/~g of P~rR-23 or D~PA.
~reatments were repeated twice, o~ the Days 2 and 4.
The results are shown i~ Eigure 6. Whole-bod;y reten-tion cur~es characteristic to e~cretion of the iso-tope revesled that decorporating OI the active iso--; .
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WO 90/~4343 - 18 -- PCr/HU90/00035 ,,. 2~33188 tope from the animals was relatively ~lo~ in the control ~roup. ~he fir~t treatment v~th DTPA ca~sed a alight decrease in the rete~tion on the Day 2 (72.8 per cent as compared to 85.9 per cent) but the ~econd and third treatment~ were ine~fective, i e.
the further course of the t~ro curves ~ere identical.
On the co~trary, after the administIatio~ of the com-position of this invention, the activity retsined i~
the body ~as only 56.2 per ce~t on the ~ay 2 (at the mome~t of the seco~d tre~tme~t) in contrast to the above rate o~ 85.9 per cent. ~he difference was increas-ing due to the second and third treatments until the Day 7 ~rhe~ the level in the P~R-23 group wa~ 33.4 per ce~t while the control level ~a9 76.3 per cent (i.e.
~early t~Jo a~d a half-fold of the former). ~ro~ this time, the rstes of e~cretion (decorporation) were identical thus, the cour~e of the curves was parallel.
It was u~equivoc;ally demo~trated bg the E~ampies that the compositio~ containing 1,4,10,13-tetraosa--7,16-diazacyclooctadecane-N,N'-dimalo~ic acid tetra-sodium ~alt tD~ICRYP) (PTR-23) a favourabl~ influenced --the mobilization of radiostrorcium a~d radiocerium.
It is efficie~t in a~y case whe~ the radioisotope enter~ the perito~eal cavit~, qubcuta~eous i~terstitial tissues, or lu~g9. Studieg O~ several hu~dreds of test animals have revealed ~o detrimental side-effect thus, ~ . . . . ,.: ~
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WO 90/14343 PCI`/HU90/00035 2~331 88 the compo~itio~ of this i~ve~tio~ is expected to be suitable for curing radioi~otope-infected human patients ~9 well.
Aq it was concluded from the data i~ ~able I, i~ the earlier ~tudies with cryptate-(2~2.2) lig~ud for the removal of radiostroncium ~rom livin~ organi~ms, o~ly the behaviour of metal/ligand comple2 ~ormed i~ vitro ~aq investig~ted when administered into the body (~Uller, 1970; ~Uller et al., 1974 and 1977;
Kuajfl et al., 1976). Ouly J. ~atsch et al. (Nukleo~i-ka 23, 305 /1978/) reported a~ e~perimental arrangeme~t in ~qhich radiostro~cium was in~e~ted intra~e~ou~ly iuto rat~ follo-~ed by posterior treetment ~ith cryp-tate-(2.2.2) perito~eally 0 5, 2, 4, 24, 48, 72, 192 a~d 216 hours later.In order to attain a considerable decorporation, a very high load of the active agent, 10 to 80 mg per snimal, was necessary ~hich was equal to or even higher tha~ thesemilethal dose (~D50/30).
It should be mentio~ed that acute to~icity of cryp-tate-(2.2~2) for rats in term of LD50 is 292/umole/kg (I.C.R.P. Publication No. 20, p. 76 /1972J). Even i~
these treatments, the reduction i~ the retention was ~ever greater than 10 to 12 pe~r cent. On the contrary, the composition of this invention reduced radioactivity in rat3 to 49.6 per cent at a load of 1/10 of the semi-lethai dose (cf. E~ample 2 and ~igure 6) demo~strati~g the highly favourable efficiency of the compo~ition of this i~ve~tio~.

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Claims (6)

What we claim is:

1. Method for preparation of an active agent suitable for decorporating radioactive isotopes from the living organism, characterized by reacting 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane with 2-bromomalonic acid disodium salt and isolating the obtained product.

2. Method of Claim 1 characterized by carrying out the reaction in a slightly alkalic aqueous me-dium at 70 to 80°C.

3. Method of Claim 1 or Claim 2 characterized by checking the alkalicity of the reaction mixture by phenolphthalein indicator added to the system and keeping during the reaction a pale pink colour of the mixture.

4. Pharmaceutical composition for decorporating radioactive metal isotopes from living organisms comprising of an active agent prepared according to any of Claims 1 to 3.

5. Pharmaceutical composition of Claim 4 comprising further a carrier which is a sterilized normal saline solution or a 5-per cent by volume of a glucose solution.

6. Pharmaceutical composition of Claim 4 or Claim 5 comprising 100 to 500 mg of active agent dis-solved in 1 cm3 of carrier which is 5-per cent by volume of glucose solution.