Development of radioimmunoassay for TG-51, a new anti-ulcer drug, and its application.

A sensitive and specific radioimmunoassay for a new anti-ulcer drug TG-51 has been developed and applied to the evaluation of its pharmacokinetics in humans. The antiserum was raised in rabbits against an immunogen of N-Acetyl-TG-51 coupled to human serum albumin. The radioactive compound was prepared by acetylating TG-51 with 3H-Acetic anhydride. The separation of free and antibody-bound N-Acetyl-TG-51 was performed by the dextran coated charcoal technique. TG-51 in biological fluids could be quantitatively converted to N-Acetyl-TG-51 prior to radioimmunoassay. This assay system made it possible to ascertain values of 3 ng/ml of TG-51 in plasma using 100 microliters of samples. Results were in good agreement with a high performance liquid chromatography method (HPLC), and the detection limit was raised 25 fold. The accuracy and repoducibility were also satisfactory. By use of this assay method, plasma levels of TG-51 could be determined after a single oral administration of clinical doses of human volunteers.