Desferrithiocin analogue uranium decorporation agents

Purpose: Previous systematic structure-activity studies of the desferrithiocin (DFT) platform have allowed the design and synthesis of analogues and derivatives of DFT that retain the exceptional iron-clearing activity of the parent, while eliminating its adverse effects. We hypothesized that a similar approach could be adopted to identify DFT-related analogues that could effectively decorporate uranium.

Materials and methods: The decorporation properties of nine DFT-related analogues were determined in a bile duct-cannulated rat model. Diethylenetriaminepentaacetic acid (DTPA) served as a positive control. Selected ligands also underwent multiple and delayed dosing regimens. Uranium excretion in urine and bile or stool was determined by inductively coupled plasma mass spectroscopy (ICP-MS); tissue levels of uranium were also assessed.

Results: The two best clinical candidates are (S)-4,5-dihydro-2-2-hydroxy-4-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid (S)-4′-(HO)-DADFT-PE (9)], with a 57% reduction in kidney uranium levels on oral (p.o.) administration and (S)-4,5-dihydro-2-2-hydroxy-3-(3,6,9-trioxadecyloxy)phenyl]-4-methyl-4-thiazolecarboxylic acid (S)-3′-(HO)-DADFT-PE (10)], with a 62% renal reduction on p.o. administration. The majority of the metal excretion promoted by these analogues is in the bile, thus further reducing kidney actinide exposure.

Conclusions: While 9 administered p.o. or subcutaneously (s.c.) immediately post-metal is an effective decorporation agent, withholding the dose (s.c.) until 4 h reduced the activity of the compound. Conversion of 9 to its isopropyl ester may circumvent this issue.