Diaphorase (NQO1, NAD(P)H:quinone oxidoreductase 1) is an important biomarker of the presence and progression of cancer and also plays a key role in the activation of prodrugs used in targeted chemotherapy of tumors. This work aimed to compare data from long-term studies of the role of diaphorase in the intracellular activation of prodrugs used in targeted chemotherapy of oncologic diseases. The review includes data from relevant publications describing the biochemical functions of diaphorase, its role in oncology, and possibilities for increasing the effectiveness of antitumor therapy through induction of this enzyme. Articles published from 2000 to 2025 and indexed in the databases PubMed, ScienceDirect, and eLIBRARY.RU were analyzed. The study used methods of internet analysis, content analysis, and historical and descriptive-analytical approaches. Diaphorase accelerates the two-electron reduction of quinones to hydroquinones, preventing the formation of free radicals whereas simultaneously providing bioreductive activation of a number of cytotoxic drugs. Overexpression of diaphorase in malignant cells makes it possible to use this enzyme as a biocatalytic mechanism for selective delivery and activation of prodrugs, thereby increasing therapeutic effectiveness. The review examines modern enzyme–prodrug strategies, including ADEPT (Antibody-Directed Enzyme Prodrug Therapy), GDEPT (Gene-Directed Enzyme Prodrug Therapy), and PMT (Prodrug Monotherapy), as well as prospects for induction of diaphorase by compounds of the 1,2-dithiole-3-thione class and phytochemical agents. The relationship between NQO1 activity, mitochondrial dysfunction of tumor cells, and initiation of apoptosis is emphasized. Overall, diaphorase is considered a promising molecular target for the development of new bioreductive and mitochondria-targeted antitumor drugs.

INTRODUCTION. This article continues a series of publications on the pharmacokinetics of 5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide (TFISA), a novel compound for the treatment of open-angle glaucoma. The distribution of TFISA and its metabolites in rat organs and tissues has not been previously studied in preclinical trials.AIM. This study aimed to assess the tissue distribution and bioavailability of 5-[5-(trifluoromethyl)-1,2-oxazol-3-yl]-furan-2-sulfonamide and its metabolites in rat organs and tissues and to validate the analytical procedures developed for this purpose. MATERIALS AND METHODS. The study used 60 male Wistar rats. TFISA was administered by bilateral ocular instillation of 1% ophthalmic suspension at a dose of 40 μL (approximately 3.7 mg/kg). Tissue samples (liver, kidney, lung, brain, heart, spleen, skin, muscle tissue, and eyes) were collected 1, 2, 4, 8, 12, 24, 48, 72, 144, and 216 h after instillation (from 6 rats at each time point). The samples were immediately homogenised using methanol and were stabilised with ascorbic acid solutions. High-performance liquid chromatography with tandem mass spectrometric detection was used to quantify TFISA, N-hydroxy-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]furan-2-sulfonamide (M1), and N-acetyl-5-[5-(trifluoromethyl)-1,2-oxazole-3-yl]-furan-2-sulfonamide (M2) in homogenised organ and tissue samples.RESULTS. This study involved full validation of the analytical procedures developed for the quantitative determination of TFISA and its metabolites, which was conducted separately for eye tissues and other biological samples. The tissue bioavailability (f_t) of TFISA decreased from 13.0 to 0.7 in the following order: eye tissues (administration and action site) > spleen > lungs ≥ heart ≥ liver > kidneys > brain > skin ≥ muscles. The f_t values for M1 decreased from 52.0 to 2.5 in the following order: spleen ≥ lungs ≥ heart ≥ liver > kidneys > brain > muscles ≥ eye tissues > skin. The f_t values for M2 were lower than those for TFISA and M1 and decreased from 6.4 to 0.3 in the following order: liver ≥ kidneys > heart > lungs > eye tissues > skin > spleen ≥ muscles > brain.CONCLUSION. The validated bioassays have been successfully applied to study the distribution of TFISA and its metabolites in male rats. TFISA best penetrates into the eyes and well-vascularised organs. M1 is highly bioavailable in the spleen, heart, and lungs. M2 shows the highest bioavailability in the liver and kidneys of rats.