The invention relates to the chemistry of medical compounds, and particularly to a group of chiral conjugates (optically active hybrid molecules) of oligo-ether polyol structure, which are inhibitors of ATP-dependent reverse transporters of cells (OEP inhibitors). An OEP inhibitor is a conjugate having an equimolar ratio of optically active polyoxypropylene hexol and polyoxypropylene glycol. The claimed method by which the conjugate is produced allows the production of a preparation which increases the efficacy of medicines by means of inhibiting the multi-drug resistance mechanisms of cells. The resulting preparation may be used in biology, pharmacology, pharmaceutics, medicine, and agriculture. The OEP inhibitor is produced by hydroxypropylation of a mixture of sorbitol and a bifunctional oxygen-containing compound in the presence of a hydroxide of an alkaline or alkaline earth metal. The bifunctional oxygen-containing compound used may be water, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, hexapropylene glycol, heptapropylene glycol or a mixture thereof. The inhibitor is a conjugate of polyoxypropylene glycol having a molecular mass of from 300 to 500 Da and polyoxypropylene hexol having a molecular mass of from 1000 to 1500 Da in an equimolar ratio, with a hydroxyl value within a range of 215-240 mg KOH/g
