Introduction . the ability of the small intestine (internalization) to absorb water-soluble anticancer cytostatics determines the possibility of their oral administration. the ex-vivo express method that simulates the internalization of substances using a modified technique of an isolated «inverted» segment of the rat small intestine with flash chemiluminescence is adequate to solve the problem. Objectives : to evaluate the absorption of the new water-soluble anticancer cytostatics with different properties from the rat small intestine for preclinical study by oral administration. M aterial and methods . conjugated with acridinium ( Acridinium NHS Ester, Toronto Research Chemicals, Canada) cytostatics were studied: low molecular weight (1) anthrafuran-acridinium (MW 0.8 kDa) and high molecular weight (2) aimpila-acridinium (MW 105 kDa) and (3) L-lysine-α-oxidase (LO-acridinium, MW 122 kDa). absorption was determined in a modified model of an isolated «inverted» segment of the rat small intestine using flash-chemiluminescence with the calculation of the relative light units (RLu). Results . It was shown that the absorption level of acridinium-conjugated cytostatics depending on molar concentration ranged from 55 % (1) to 1.7–11 % (2, 3) and 2500 (1) to 9.2–188 nmol/l (2, 3), respectively. the level of internalized anthrafuran-acridinium (55 %) was consistent with the known value of the effective non-conjugated cytostatic oral dose, which was two times higher than equitherapeutical parenteral dose: 100 mg/kg vs 50 mg/kg. Conclusion . the data obtained allow us to consider ex vivo express method for preclinical study of the various water-soluble anticancer cytostatics for screening and identification of an opportunity for oral administration and estimation of starting dose. the method has a good correlation with in vivo tests and economically favorable due to a quick response and small number of the tested agent.