Gökçen Eren

On the Way to Selective PARP-2 Inhibitors. Design, Synthesis, and Preliminary Evaluation of a Series of Isoquinolinone Derivatives

PARP‐1 and PARP‐2 are members of the family of poly(ADP‐ribose)polymerases, which are involved in the maintenance of genomic integrity under conditions of genotoxic stimuli. The different roles of the two isoforms under pathophysiological conditions have not yet been fully clarified, and this is partially due to the lack of selective inhibitors. We report herein the synthesis and preliminary pharmacological evaluation of a large series of isoquinolinone derivatives as PARP‐1/PARP‐2 inhibitors. Among them, we identified the 5‐benzoyloxyisoquinolin‐1(2 H)‐one derivative as the most selective PARP‐2 inhibitor reported so far, with a PARP‐2/PARP‐1 selectivity index greater than 60.

Synthesis, biological evaluation, and docking studies of novel heterocyclic diaryl compounds as selective COX-2 inhibitors.

Three novel series of diaryl heterocyclic derivatives bearing the 2-oxo-5H-furan, 2-oxo-3H-1,3-oxazole, and 1H-pyrazole moieties as the central heterocyclic ring were synthesized and their in vitro inhibitory activities on COX-1 and COX-2 isoforms were evaluated using a purified enzyme assay. The 2-oxo-5H-furan derivative 6b was identified as potent COX inhibitor with selectivity toward COX-1 (COX-1 IC(50)=0.061 microM and COX-2 IC(50)=0.325 microM; selectivity index (SI)=0.19). Among the 1H-pyrazole derivatives, 11b was found to be a potent COX-2 inhibitor, about 38 times more potent than Rofecoxib (COX-2 IC(50)=0.011 microM and 0.398 microM, respectively), but showed no selectivity for COX-2 isoform. Compound 11c demonstrated strong and selective COX-2 inhibitory activity (COX-1 IC(50)=1 microM, COX-2 IC(50)=0.011 microM; SI= approximately 92). Molecular docking studies of compounds 6b and 11b-d into the binding sites of COX-1 and COX-2 allowed to shed light on the binding mode of these novel COX inhibitors.

Identification of novel benzimidazole derivatives as inhibitors of leukotriene biosynthesis by virtual screening targeting 5-lipoxygenase-activating protein (FLAP).

Pharmacological suppression of leukotriene biosynthesis by 5-lipoxygenase (5-LO)-activating protein (FLAP) inhibitors is a promising strategy to intervene with inflammatory, allergic and cardiovascular diseases. Virtual screening targeting FLAP based on a combined ligand- and structure-based pharmacophore model led to the identification of 1-(2-chlorobenzyl)-2-(1-(4-isobutylphenyl)ethyl)-1H-benzimidazole (7) as developable candidate. Compound 7 potently suppressed leukotriene formation in intact neutrophils (IC(50)=0.31 μM) but essentially failed to directly inhibit 5-LO suggesting that interaction with FLAP causes inhibition of leukotriene synthesis. For structural optimization, a series of 46 benzimidazole-based derivatives of 7 were synthesized leading to more potent analogues (70-72, 82) with IC(50)=0.12-0.19 μM in intact neutrophils. Together, our results disclose the benzimidazole scaffold bearing an ibuprofen fingerprint as a new chemotype for further development of anti-leukotriene agents.

From Molecular Docking to 3D-Quantitative Structure-Activity Relationships (3D-QSAR): Insights into the Binding Mode of 5-Lipoxygenase Inhibitors.

Pharmacological intervention with 5‐Lipoxygenase (5‐LO) is a promising strategy for treatment of inflammatory and allergic ailments, including asthma. With the aim of developing predictive models of 5‐LO affinity and gaining insights into the molecular basis of ligand‐target interaction, we herein describe QSAR studies of 59 diverse nonredox‐competitive 5‐LO inhibitors based on the use of molecular shape descriptors and docking experiments. These studies have successfully yielded a predictive model able to explain much of the variance in the activity of the training set compounds while predicting satisfactorily the 5‐LO inhibitory activity of an external test set of compounds. The inspection of the selected variables in the QSAR equation unveils the importance of specific interactions which are observed from docking experiments. Collectively, these results may be used to design novel potent and selective nonredox 5‐LO inhibitors.

Synthesis, characterization and preliminary screening of regioisomeric 1-(3-pyridazinyl)-3-arylpyrazole and 1-(3-pyridazinyl)-5-arylpyrazole derivatives towards cyclooxygenase inhibition

In a search for novel compounds with analgesic and anti-inflammatory activity, a series of regioisomeric 1-(3-pyridazinyl)-3-arylpyrazole (5a–f, 6a–f) and 1-(3-pyridazinyl)-5-arylpyrazole (7a–f, 8a–f) derivatives were synthesized. The structure of these regioisomers was confirmed by spectral techniques. The compounds were preliminarily screened at 8 μM concentration for their inhibitory activity against cyclooxygenase enzymes, COX-1 and COX-2, using a human whole blood test. The tested derivatives showed inhibitory activity for both enzymes and are worthy of further investigation for developing better leads.

Charting the Chemical Space of Target Sites: Insights into the Binding Modes of Amine and Amidine Groups

Nowadays there is growing awareness that the translation of the increasing number of lead compounds into clinical candidates is still a slow and often inefficient process. In order to facilitate the lead optimization procedure, due consideration must be given to the use of the right bioisosteric replacements. Very recently, we reported that exploring a chemical space of binding sites is a more effective strategy for studying the bioisosteric relationships existing among functional groups. As a continuation of our work in this field, we report herein the construction of a chemical space covered by binding sites of small molecules containing diverse amine and amidine groups. The analysis of the differences in some properties of the binding sites of these functional groups allow for gaining insights into the binding modes of positively charged groups. In addition, this study pinpoints that different types of interactions and bioisosteric relationships exist among primary, secondary, tertiary, quaternary amine, and amidine moieties.

The crystal structures of 2-(3'-hydroxypropyl)benzimidazolium hexa- and tetrachloroplatinate

2-(3’-Hydroxypropyl)benzimidazolium (Hhpb) hexa- and tetrachloroplatinate (C10H13N2O)2·[PtCl6] 1 and (C10H13N2O)2·[PtCl4] 2 were synthesized and their crystal structures determined. Compound 1 is monoclinic, space group P21/n, a = 8.800(1), b = 14.389(2), c = 10.264(2) Å, β = 98.540(10)°, V = 1285.3(3) Å3, Z = 2 and Dc = 1.959 g cm−3. Compound 2 is triclinic, space group P1̄, a=7.8480(10), b=9.0460(10), c=9.6980(10) Å ,α =65.420(10), β =68.810(10), γ = 76.770(1)°,V =581.26(4) Å3, Z =1 and Dc =1.969 g cm−3. In both compounds, the Pt atoms reside at a centre of inversion. Compounds 1 and 2 are comprised of 2-(3’-hydroxypropyl)benzimidazolium (Hhpb)+: (C10H12N2O)+ and [PtCl6]2− and [PtCl4]2− ions, respectively, linked by intermolecular hydrogen bonds N...Cl [range from 3.428(3) to 3.584(4) Å ], N···O [2.769(5) Å ] and O···Cl [3.338(4) and 3.321(3) Å ] for 1, and N···Cl [3.162(7) Å ], N···O [2.749(8) Å ] and O···Cl [3.289(6) Å ] for 2.