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 ActivityB. Maggio1, G. Cancemi1, D. Raffa1, M. V. Raimondi1, F. Plescia1, A. D’Anneo2,M. Lauricella3, G. Barone4, R. Bonsignore4, G. Daidone11. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, Medicinal Chemistry andPharmaceutical Technologies Section, University of Palermo, ViaArchirafi 32, 90123, Palermo, Italy2. 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 ofPalermo.4. Department of Biological, Chemical and Pharmaceutical Sciences and Technologies, University of Palermo.benedetta.maggio@unipa.itA screening carried out by NCI (Bethesda, USA) on compounds available in our laboratory,in order toascertain their antiproliferative activity against a panel of 60 human tumor cell lines, allowed to discoverythe 3,4-diphenylisoxazolo[3,4-d]pyridazin-7(6H)-one 1a [1] as an hit compound, often showing GI50valuesat sub-micromolar level. We synthesized some analogs of 1a, i.e.1b-gand other derivatives in which theNHgroup is variably alkylated, with the aim to obtain more active compounds as well as to performstructure-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 linkedto the isoxazolo-pyridazinone moiety. Studies performed on the cell cycle progression and on some cellulartarget (ATM, procaspase-2 proteins and H2AX histone) demonstrated that 1d produces an increase of thecell population in pre-G0/G1 and induces cellular death by apoptosis, damaging the DNA by double strandbreaks. UV-vis titration and viscosity measurement showed that the compound is able to give an interactionwith the B-DNA.1. Renzi G., Dal Piaz V. (2004)Gazz. Chim. It.95: 1478–1491