Production of 103mRh for cancer therapy

Novel Bifunctional [16]aneS4-Derived Chelators for Soft Radiometals

The field of targeted radionuclide therapy is rapidly growing, highlighting the need for wider radionuclide availability. Soft Lewis acid ions, such as radioisotopes of platinum, rhodium and palladium, are particularly underdeveloped. This is due in part to a lack of compatible bifunctional chelators. These allow for the practical bioconjugation to targeting vectors, in turn enabling radiolabeling. The [16]andS₄ macrocycle has been reported to chelate a number of relevant soft metal ions. In this work, we present a procedure for synthesizing [16]andS₄ in 45% yield (five steps, 12% overall yield), together with a selection of strategies for preparing bifunctional derivatives. An ester-linked N-hydroxysuccimide ester (NHS, seven steps, 4% overall yield), an ether-linked isothiocyanate (NCS, eight steps, 5% overall yield) and an azide derivative were prepared. In addition, a new route to a carbon-carbon linked carboxylic acid functionalized derivative is presented. Finally, a general method for conjugating the NHS and NCS derivatives to a polar peptide (octreotide) is presented, by dissolution in water:acetonitrile (1:1), buffered to pH 9.4 using borate. The reported compounds will be readily applicable in radiopharmaceutical chemistry, by facilitating the labeling of a range of molecules, including peptides, with relevant soft radiometal ions.

A solid support generator of the Auger electron emitter rhodium-103m from [103Pd]palladium

Auger electron therapy is an attractive modality for targeting microscopic tumors. Rhodium-103 m (^103mRh, T_½ = 56.1 min) is a promising Auger electron emitter that can be obtained as the decay product of palladium-103 (¹⁰³Pd, T_½ = 16.99 days). ¹⁰³Pd was chelated in a lipophilic derivative of the 16aneS4 macrocycle and the complex was trapped on a C18 cartridge. Elution with dilute hydrochloric acid gave radiochemically pure ^103mRh. We hypothesize this to be through a combination of the Szilard-Chalmers effect and transient ionization.

Separation of 103Ru from a proton irradiated thorium matrix: A potential source of Auger therapy radionuclide 103mRh

Ruthenium-103 is the parent isotope of ^103mRh (t_1/2 56.1 min), an isotope of interest for Auger electron therapy. During the proton irradiation of thorium targets, large amounts of ¹⁰³Ru are generated through proton induced fission. The development of a two part chemical separation process to isolate ¹⁰³Ru in high yield and purity from a proton irradiated thorium matrix on an analytical scale is described herein. The first part employed an anion exchange column to remove cationic actinide/lanthanide impurities along with the majority of the transition metal fission products. Secondly, an extraction chromatographic column utilizing diglycolamide functional groups was used to decontaminate ¹⁰³Ru from the remaining impurities. This method resulted in a final radiochemical yield of 83 ± 5% of ¹⁰³Ru with a purity of 99.9%. Additionally, measured nuclear reaction cross sections for the formation of ¹⁰³Ru and ¹⁰⁶Ru via the ²³²Th(p,f)^103,106Ru reactions are reported within.