Low molecular weight compounds targeting chaperone proteins Hsp90 and Hsp70 have opened up a new avenue in the therapy of neoplasms. In 2020, we tested 3 Hsp70 inhibitors from the class of 4-aminopiperidine derivatives for their antitumor activity on in vivo models. The list of the tested compounds included N-(2-chlorobenzyl)-N-ethyl-1-(2-(methylthio)pyrimidin-4-yl)piperidin-4-amine (compound 1), 4-((methyl(1-(2-(methylthio)pyrimidin-4-yl) piperidin-4-yl)amino)methyl) benzonitrile (compound 2) and N-(2,6- dichlorobenzyl)-1-(1-(2-(ethylthio)pyrimidin-4-yl)piperidin-4-yl)-N-methylmethaneamine (compound 3). The aim of this study was to compare the efficacy of 4-aminopiperidine derivatives in vivo using the models of transplantable murine L1210 lymphocytic leukemia and B16 melanoma. Compounds 2 and 3 used in combination with cyclophosphamide exhibited high cytotoxic activity (р = 0.05) against L1210 leukemia (an 80-82% increase in survival time) and B16 melanoma (98-99.7% tumor growth delay). For L1210 lymphocytic leukemia, compounds 2 and 3 used in combination with cyclophosphamide fell into the low (+) therapeutic potential category. For B16 melanoma, compounds 1, 2 and 3 used in combination with cyclophosphamide fell into either low (+) or moderate (++) therapeutic potential categories. On the whole, the tested doses of the compounds used in combination with cyclophosphamide hold promise for the therapy of L1210 leukemia and B16 melanoma in mouse models. Our findings confirm the potential of low molecular weight Hsp70 inhibitors for combination chemotherapy against cancer.