DERIVATIVES OF 1,3,5-TRIAMINO-1,3,5-TRIDEOXY-CIS-INOSITAS VERSATILE PENTADENTATE LIGANDS FOR PROTEIN LABELING WITH RE-186 188 - PRELABELING, BIODISTRIBUTION, AND X-RAY STRUCTURAL STUDIES/

The pentadentate H(3)bhci deoxy-1,3-bis((2-hydroxybenzyl)amino)-cis-in istol] and its bifunctionalized analogue H(3)bhci-glu-H 2-hydroxybenzy l)amino)-5-glutaramido-cis-inositol] were synthesized, and their coord ination chemistry was investigated with inactive rhenium, with no carr ier added Re-188 and with carrier added Re-186. The neutral Re(V) comp lexes [ReO-(bhci)] and [ReO(bhci-glu-H)] are formed in good yields sta rting from [ReOCl3(P(C6H5)(3))(2)] or in quantitative yield directly f rom [(ReO4)-Re-186/188](-) in aqueous solution by reduction with Sn(II ) or Sn(0). The X-ray structures of [ReO(bhci)] and [ReO(bhci-glu-H)] were elucidated revealing pentadentate ''side on'' coordination of the ligands to the ''Re=O'' core. The basic cyclohexane frame adopts a ch air form in the case of [ReO(bhci)] and a twisted boat form in the cas e of [ReO(bhci-glu-H)]. [ReO(bhci)] crystallizes in the monoclinic spa ce group C2/c with a = 27.425(3), b = 14.185(1), c = 19.047(2) Angstro m, and beta = 103.64(2)degrees and [ReO(bhci-glu-H)] in the monoclinic space group P2(1)/c with a = 13.056(3), b = 10.180(1), c = 22.378(5) Angstrom and beta = 98.205(9)degrees Both Re-188 complexes are stable in human serum for at least 3 days without decomposition. After inject ion into mice, [ReO(bhci-glu)](-) is readily excreted through the inte stines, while [ReO(bhci)] is excreted by intestines, liver, and the ki dneys. TLC investigations of the urine showed exclusively the complexe s [ReO(bhci-glu-H)] and [ReO(bhci)], respectively, and no decompositio n products. For derivatization of antibodies, the carboxylic group of [ReO(bhci-glu-H)] was activated with N-hydroxysuccinimide, which requi red unusually vigorous reaction conditions (heating). The anti colon c ancer antibody mAb-35 [IgG and F(ab')(2) fragment] was labeled with [( ReO)-Re-186/188(bhci-glu)] to a specific activity of up to 1.5 mCi/mg (55 MBq/mg) with full retention of immunoreactivity. Labeling yields f ollowed pseudo-first-order kinetics in antibody concentration with the ratio of rates between aminolysis and hydrolysis being about 2. Biodi stributions of Re-186-labeled intact mAb-35 as well as of its F(ab')(2 ) fragment in tumor-bearing nude mice revealed good uptake by the tumo r with only low accumulation of radioactivity in normal tissue.