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Abstract

The invention provides polychelant compounds which are useful for example in diagnostic imaging procedures and which are degradable in vivo to release excretable fragments. Such compounds conveniently are of the formula (I): R.sup.1 (X.sup.1 R.sup.2 ((X.sup.2).sub.p L).sub.n).sub.m (where X.sup.1 is a linker moiety metabolically cleavable to release R.sup.1 X.sup.3.sub.m and X.sup.4 R.sup.2 ((X.sup.2).sub.p L).sub.n fragments where X.sup.3 and X.sup.4 are the cleavage residues of X.sup.1 ; R.sup.1 X.sup.3.sub.m is a biotolerable polymer, preferably a substantially monodisperse polymer and especially one with a molecular weight below 40,000 D, particularly below 30,000 D and especially below 20,000 D, for example a first to sixth generation dendrimer; X.sup.4 R.sup.2 ((X.sup.2).sub.p L).sub.n is a polychelant fragment having a molecular weight below 40,000 D, preferably below 30,000 D, especially below 20,000 D, each such moiety preferably being the same; p is 0 or 1; X.sup.2, where present, is a linker moiety metabolically cleavable to release a monochelant fragment; each L is a macrocyclic chelant moiety, wherein the macrocyclic skeleton preferably has 9 to 25 ring members and preferably is an optionally oxygen or sulphur interrupted polyazacycloalkane; R.sup.2 ((X.sup.2).sub.p).sub.n is a straight chain or branched backbone moiety, preferably providing a chain of up to 20 atoms between each L group and the X.sup.1 moiety to which it is joined and a chain of up to 25 atoms between each pair of L groups linked thereby, such chains conveniently being nitrogen and/or oxygen and/or sulphur interrupted carbon chains; each n is an integer having a value of at least 2, preferably a value of 2 to 25, especially 2 to 12; and each m is an integer having a value of at least 2, preferably a value of up to 200, especially 3 to 100, such that the total number of L groups in the polychelant of formula (I) is at least 20, preferably 50 to 200), having a molecular weight of at least 30,000 D, preferably at least 40,000 D, and especially preferably 50,000 to 150,000 D, and metal chelates and salts thereof.

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First Claim