Isoxazolo[3,4-d]pyridazin-7(6H)-one derivatives endowed with anti-proliferative Activity.

Isoxazolo[3,4-d]pyridazin-7(6H)-one derivatives endowed with antiproliferative Activity B. Maggio1, G. Cancemi1, D. Raffa1, M. V. Raimondi1, F. Plescia1, A. D’Anneo2,M. Lauricella3, G. Barone4, R. Bonsignore4, G. Daidone1 1. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Medicinal Chemistry and Pharmaceutical Technologies Section, University of Palermo, ViaArchirafi 32, 90123, Palermo, Italy 2. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Laboratory of Biochemistry, University of Palermo. 3.Department of Experimental Biomedicine and Clinical Neurosciences, Laboratory of Biochemistry, University of Palermo. 4. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo. benedetta.maggio@unipa.it A screening carried out by NCI (Bethesda, USA) on compounds available in our laboratory,in order to ascertain their antiproliferative activity against a panel of 60 human tumor cell lines, allowed to discovery the 3,4-diphenylisoxazolo[3,4-d]pyridazin-7(6H)-one 1a [1] as an hit compound, often showing GI50values at sub-micromolar level. We synthesized some analogs of 1a, i.e.1b-gand other derivatives in which the NHgroup is variably alkylated, with the aim to obtain more active compounds as well as to perform structure-activity relationship(SAR) studies. We obtained a quite active antiproliferative compound, the 3,4-di-p-tolylisoxazolo[3,4-d]pyridazin-7(6H)- one 1d, and verified the importance for the antiproliferative activity of the aril, and not alkyl, groups linked to the isoxazolo-pyridazinone moiety. Studies performed on the cell cycle progression and on some cellular target (ATM, procaspase-2 proteins and H2AX histone) demonstrated that 1d produces an increase of the cell population in pre-G0/G1 and induces cellular death by apoptosis, damaging the DNA by double strand breaks. UV-vis titration and viscosity measurement showed that the compound is able to give an interaction with the B-DNA. 1. Renzi G., Dal Piaz V. (2004)Gazz. Chim. It.95: 1478–1491