: Introduction: Discovering compounds with antibacterial activity is crucial in the current fight against antibiotic-resistance. Material and Methods: We generate two QSAR model to design six new heteroaryl drug candidates; we assessed the antibacterial properties of the compounds against nine ATCC strains, the majority being part of the ESKAPE group, that include Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and also Salmonella enterica and Escherichia coli. We performed a synergic assay in which we combined PB4, a compound that we have previously tested in published studies, with GC-VI-70, one of the new compounds with the best cytotoxicity/MIC profile. We tested sub-MIC concentrations of PB4 with five antibiotics (linezolid, gentamycin, ampicillin, erythromycin, rifampin and imipenem) to examine the synergic effect on the ATCC strains. To evaluate compounds’ cytotoxicity, we performed a 24-hour and 48-hour 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on Colorectal Adenocarcinoma (CaCo-2) cells. The antibiotics were tested, alone and in combination with PB4. Results: PB4 lowered the MIC measured for GC-VI-70 and for the various antibiotics employed in clinical use, and all the compounds presented in this study have cytotoxic activity against cells. Conclusions: These compounds show promising use in combination with antibiotics to improve their effectiveness at low concentrations, to prevent unwanted cytotoxic effects.

Diffuse intrinsic pontine glioma (DIPG), affecting children aged 4-7 years, is a rare, aggressive tumor that originates in the pons and then spreads to nearby tissue. DIPG is the leading cause of death for pediatric brain tumors due to its infiltrative nature and inoperability. Radiotherapy has only a palliative effect in stabilizing symptoms. In silico and preclinical studies identified ONC201, as a cytotoxic agent against some human cancer cell lines, including DIPG ones. Single crystal X-ray analysis of the complex of the human mitochondrial caseinolytic serine protease type C (hClpP) and ONC201 (PDB ID: 6DL7) allowed to identify hClpP as its main target. Hyperactivation of hClpP causes damage to mitochondrial oxidative phosphorylation and cell death. In some DIPG patients, receiving ONC201, an acquired resistance was observed. In this context, a wide program was initiated to discover original scaffolds for new hClpP activators to treat ONC201-non-responding patients. Harmaline, a small molecule belonging to the chemical class of β -carboline, was identified through Fingerprints for Ligands and Proteins (FLAP), a structure-based Virtual Screening approach. Molecular dynamics simulations and a deep in vitro investigation showed interesting information on the interaction and activation of hClpP by harmaline.