Oncological diseases are one of the most common public health problems and second leading cause of death after cardiovascular disease. Natural products or synthetic compounds inspired from natural products continue to be excellent sources for new drug candidates. Pyrrolizidines and 3-azabicyclo[3.1.0]hexanes are important classes of heterocyclic compounds with diverse pharmacological activities including anticancer activity. Here we report study of cytotoxicity of newly developed spirosubstituted with acenaphthylen-1(2H)-one and aceanthrylen-1(2H)-one fragments cyclopropa[a]pyrrolizidines and 3-azabicyclo[3.1.0]hexanes against tumor cell lines. The results of antiproliferative activity study showed that spiroadducts with either acenaphthylen-1(2H)-one or aceanthrylen-1(2H)-one framework have shown significant activity with IC₅₀ up to 1 μg/mL. Confocal microscopy study showed diffuse distribution of granular actin in the cell cytoplasm with disappearance of actin filaments. Number of cells with filopodium-like membrane protrusions was also reduced after treatment with some of tested compounds. The obtained results support the antitumor effect of the studied compounds.