The present invention relates to novel substituted pyrrolo- and pyrazolopyridazinones, as well as pharmaceutical compositions containing at least one of these substituted pyrrolo- and pyrazolo- pyridazinones together with at least one pharmaceutically acceptable carrier, excipient and/or diluent. Said novel substituted pyrrolo- and pyrazolo- pyridazinones are binding to the prenyl binding pocket of PDEδ and therefore, are useful for the prophylaxis and treatment of cancer by inhibition of the binding of PDEδ to K-Ras and of Ras signaling in cells.
