Development of 15-(p-123I-phenyl)-pentadecanoic acid for in-vivo diagnosis of the myocardium

Radioiodinated ω-phenylfatty acids were recently proposed as radiopharmaceuticals for determining myocardial metabolic alterations. Therefore uptake and elimination of different radiohalogenated phenylfatty acids were determined in blood and heart muscle of mice. The structure activity dependence i.e. the effect of length of the carbon chain, position of the substituent at the benzene ring and type of radiohalogen was studied. Highest myocardial accumulation was found in case of a phenylfatty acid with 15 carbon atoms in the alkylgroup and the radiohalogen attached to the benzene ring in the para position. No difference was observed between the radiobrominated and radioiodinated substrates. In contrast to aliphatic radioiodinated fatty acids, the radioactivity in the stomach remained almost constant (i.e. below 1% dose/organ). Thus 15-(¹²³I-phenyl)-pentadecanoic acid (IPPA) could be brought into clinical application with success. Blood clearance and urine excretion of the radioactivity were determined and the results found to agree with the expectations based on the principal metabolic path of phenylfatty acids.