A technetium-99m-labelled cyclam acid porphyrin (CAP) for tumour imaging

A new water-soluble cyclam acid porphyrin (CAP), 5,10,15,20-tetrakis [4-{4′,8′,11′-tris(carboxymethyl)-1′-(1′,4′,8′,11′-tetraazacyclotetradecane)amidomethyleneoxy}phenyl] porphyrin has been synthesised, characterised and labelled with 99mTc. In vivo distribution studies were performed in C6-gliomas and N-nitroso-N-methylurea (NMU) induced mammary tumour bearing rats and scintiimages were obtained at 5 h post-administration of the labelled ligand using gamma camera computer system. Tumour to muscle (T/M) ratios were determined and compared with currently available tumour seeking radiopharmaceuticals such as 99mTc(V)-DMSA, 99mTc-Citrate and 201TlCl. In the case of NMU induced mammary tumour rats the ratios were 6.93, 1.97, 5.30 and 3.29; while in the case of C6-gliomas the ratios were 5.58, 2.18, 3.96 and 3.02 for 99mTc-CAP, 99mTc(V)-DMSA, 99mTc-Citrate and 201TlCl, respectively.