Evaluation of radioiodinated ethopabate as a potential tumor targeting agent

Overexpression of folate synthesis and folate receptor in a wide variety of tumors was reported. As a result, folate derivatives have emerged as a potential candidate for tumor imaging and therapy. Ethopabate is a structural analogue of para-aminobenzoic acid (PABA), a precursor of folic acid. Ethopabate was radiolabeled with radioiodine-131 (¹³¹I) via direct electrophilic substitution reaction. Several factors that might affect the radiolabeling yield were studied. Paper chromatography was utilized for testing and evaluation of [¹³¹I]iodoethopabate, and HPLC was used as a co-chromatographic tool to confirm the radiochemical yield. The biodistribution of [¹³¹I]iodoethopabate in normal and tumor-bearing mice was investigated. The radioiodination of ethopabate resulted in a radiochemical yield of 93.70 ± 0.19%. The biodistribution data revealed that [¹³¹I]iodoethopabate was taken up by tumors with promising target/non-target (T/NT) ratios. Where, the tumor to-blood ratios were 3.30 ± 0.40 and 4.06 ± 0.10 at 1 and 4 h post injection, respectively. As a result of these findings, [¹³¹I]iodoethopabate appears to have excellent tumor uptake and adequate stability to be used for diagnostic purpose in the future.