e15011 Background: Poor clinical effects of standard treatment for glioblastoma determine the need for the development of new therapeutic strategies. Aberrant functioning of the proteasome system, as well as activation of the HIF-1α signaling pathway, are characteristic of glial tumor cells; they can be considered as potential therapeutic targets in the treatment of malignant brain tumors. One of the possible options for improving the results of glioblastoma treatment may involve strategies for inhibiting the HIF-1α pathway. Bortezomib, a proteasome inhibitor, can block the biological effects of HIF-1α. Bortezomib showed a pronounced antitumor effect in in vitro testing on various models of solid malignant tumors, giving grounds for further studies of its effectiveness in vivo. Patient-derived xenograft (PDX) models are characterized by a variety of cell subclones and are therefore considered the most reliable tool for predicting therapeutic responses. Methods: A PDX model of glioblastoma was created in 20 Balb/c Nude mice implanted with a subcutaneously inoculated human glioblastoma. Temozolomide (0.5 mg/kg), bortezomib (0.25 mg/kg), or a combination of temozolomide and bortezomib were administered intraperitoneally daily for 21 days. The tumor histotype was confirmed by histological analysis (staining with hematoxylin and eosin). The antitumor effect was determined by the inhibition of tumor growth (ITG%), the volume of tumor nodes, and the index of tumor growth. Results: The highest value of the inhibition of tumor growth (ITG%) was registered in the group of animals receiving a combination of temozolomide and bortezomib – 85.38%. The values in the groups receiving temozolomide or bortezomib monotherapy were 57.32% and 63.11%, respectively. Conclusions: An analysis of the antitumor efficacy of bortezomib combined with temozolomide in human subcutaneous PDX-glioblastomas demonstrated their synergistic effect.