Abstract
Colchicine is a cytotoxic bioactive alkaloid that exhibits its action by microtubular binding. With an aim to develop a tumor targeted radio‐therapeutic agent, colchicine has been functionalized to trimethylcolchicinic acid and conjugated to the isothiocyanato derivative of DOTA (1,4,7,10‐tetraaza cyclododecane tetracetic acid). DOTA coupled colchicine was radiolabeled with ^90^Y, one of the most commonly used therapeutic radioisotope. Complexation of 200 µg of the conjugate with ^90^Y was carried out at pH 4.5 with an incubation time of 45 min at 70°C. Complexation yield of ^90^Y‐DOTA‐NCS‐colchicine was confirmed to be >98% using C‐18 reverse phase HPLC system. ^90^Y‐colchicine complex could be differentiated from ^90^Y‐p‐NCS‐benzyl‐DOTA on the basis of difference in their retention times 8 and 4 min, respectively in a standardized HPLC system. Biodistribution studies in Swiss mice fibrosarcoma tumor model showed an uptake of ∼0.8% ID/g tumor at 3 h.p.i. that was retained till 24 h.p.i. ^90^Y‐DOTA‐NCS‐colchicine complex showed excellent pharmacokinetics with major portion of the radioactivity being excreted out within 3 h.p.i. and no accumulation of radioactivity in vital organs. Copyright © 2006 John Wiley & Sons, Ltd.