Kinetics and Efficiency of a Methyl-Carboxylated 5-Fluorouracil-Bovine Serum Albumin Adduct for Targeted Delivery

5‐Fluorouracil (5‐FU) is a clinically well‐established anti‐cancer drug effectively applied in chemotherapy, mainly for the treatment of breast and colorectal cancer. Substantial disadvantages are adverse effects, arising from serious damage of healthy tissues, and shortcoming pharmacokinetics due to its low molecular weight. A promising approach for improvement of such drugs is their coupling to suitable carriers. Here, a 5‐FU adduct, 5‐fluorouracil acetate (FUAc) is synthesized and covalently coupled to bovine serum albumin (BSA) as model carrier molecule. On average, 12 molecules FUAc are bound to one BSA. Circular dichriosm (CD)‐spectra of BSA and FUAc‐BSA are identical, suggesting no significant conformational differences. FUAc‐BSA is tested on T‐47D and MDA‐MB‐231 breast cancer cells. Proliferation inhibition of membrane albumin‐binding protein (mABP)‐expressing T‐47D cells by FUAc‐BSA is similar to that of 5‐FU and only moderate for MDA‐MB‐231 cells that lack such expression. Therefore, a crucial role of mABP expression in effective cell growth inhibition by FUAc‐BSA is assumed. 5‐Fluorouracil acetate is synthesized and on average twelve molecules are covalently coupled to bovine serum albumin (FUAc‐BSA). FUAc‐BSA strongly inhibits proliferation of T‐47D breast cancer cells that express membrane albumin‐binding protein (mABP) but only moderately influences MDA‐MB‐231 cells that lack such expression. A crucial role of mABP expression in effective cell growth inhibition by FUAc‐BSA is assumed.