Chromatographic analysis and tissue distribution of radiocopper-labelled haematoporphyrin derivatives

The photosensitizers haematoporphyrin derivative (HPD) and dihaematoporphyrin ether/ester (DHE) have been labelled with the radionuclide copper-64 to allow non-invasive measurement of the concentration of photosensitizer in tumour and normal tissues. The effects of labelling have been assessed by gel and high-performance liquid chromatography.Direct comparison of the tissue uptake and clearance of64Cu-labelled HPD/DHE with those of [14C]HPD/DHE has been made in mice bearing intramuscular radiation-induced fibrosarcoma (RIF) tumours, by gamma and beta counting of tumour, skin, liver, muscle, lung, kidney, brain, and blood samples at 1–72 h after intraperitoneal injection of test and control drug. The uptake and clearance curves of64Cu-labelled HPD or DHE in tumour, liver and blood agree to within 20% with those for the14C-labelled control.Non-invasive quantification of64Cu-labelled DHE by gamma counting in vivo in rabbits bearing VX2 tumours in the ear shows good agreement with the photosensitizer concentrations in tumour and liver measured post-mortem in tissue samples.