Olga Nyeki

Hit-to-lead optimization of disubstituted oxadiazoles and tetrazoles as mGluR5 NAMs

Here we report the discovery and early SAR of a series of mGluR5 negative allosteric modulators (NAMs). Starting from a moderately active HTS hit we synthesized 3,5-disubstituted-oxadiazoles and tetrazoles as mGluR5 NAMs. Based on the analysis of ligand efficiency and lipophilic efficiency metrics we identified a promising lead candidate as a starting point for further optimization.

Synthesis of peptide and pseudopeptide amides inhibiting the proliferation of small cell and epithelial types of lung carcinoma cells

Small cell lung cancer (SCLC) cell lines produce and secrete various peptide hormones, e.g. bombesin (BN)/gastrin releasing peptide (GRP) like peptides that are proposed to function as their autocrine growth factors. To inhibit the proliferative effect of these hormones we have synthesized short chain BN[7‐14]‐analogues replacing the C‐terminal peptide bond by a methylene‐amino (‐CH2NH‐) unit and introducing d‐Phe or d‐Ser into position 12. As several substance P (SP) analogues were found to inhibit the growth of SCLC cells, some short chain SP‐analogues have been synthesized. (Pseudo)octapeptides were synthesized in solution, by fragment condensation using the DCC/HOPfp method. Fragments and SP‐analogues were synthesized stepwise using pentafluorophenyl esters. The resistance to hydrolysis of the reduced peptide bond made permitted exact quantification of the Leuψ(CH2NH)Leu pseudopeptide in hydrolysates. The binding ability of both types of peptides to BN‐receptors on Swiss 3T3 mouse fibroblast cells and their antiproliferative effect on NCI‐H69 human SCLC cell line have been tested and compared with a short chain SP‐antagonist pHOPA‐d‐Trp‐Phe‐d‐Trp‐Leu‐Leu‐NH2 (R) previously described as a potent inhibitor of SCLC proliferation. While BN‐analogues showed weak activity in inhibition of proliferation of SCLC cells, SP‐analogues 6: d‐MePhe‐d‐Trp‐Phe‐d‐Trp‐Leuψ(CH2NH)‐Leu‐NH2 and 7: d‐MePhe‐d‐Trp‐Phe‐d‐Trp‐Leu‐MPA, in spite of greatly diminished affinity towards the BN‐receptor, inhibited SCLC proliferation more effectively than R (6: IC50=2 μm, 7: IC50=5 μm and R: IC50=10 μm). Moreover, 6 inhibited the respiratory activity of SK‐MES 1 epithelial type of lung carcinoma cells in proliferating but not in the quiescent state, suggesting that the antiproliferative effect of these compounds is not due to simple cytotoxicity. These short chain analogues of SP might be promising candidates as therapeutic agents in the treatment of SCLC.

In Vitro Effects of Tp5 Analogs on E-Rosette Formation and Cell Division

AbstractThe effects of seventeen synthetic analogs of thymopentin (TP-5) have been studied in the active and azathioprine-inhibited E-rosette tests.Thymopentin was gradually shortened from the C terminus to peptides and single amino acids. Thymopoietin 32-34 (Arg-Lys-Asp-RGH-0205-TP-3) (II) and thymopoietin 32-35 (Arg-Lys-Asp-Val-RGH-0206-TP-4) (I) were the most active peptides.Dipeptide Arg-Lys produced significant stimulatory effect on azathioprine (ED75) inhibited E-receptor. Treatment of azathioprine (ED75-inhibited E-rosette forming cells (ERFC) with arginine or especially lysine increased the number of ERFC.Some of TP-4 analogs decreased further the number of ERFC decreased by azathioprine ED30. These “suppressive” peptides as well as TP-3 caused a partial arrest of K 562 cell proliferation up to 96 hours.Results suggest that TP-5 is not the smallest active fragment of thymopoietins, since peptides (TP-3 and TP-4) exhibit similar or higher T-cell membrane activation on E-receptor. Arginine, lysine, ...

Unprecedented transformation of aspartyl peptides by conjugative degradation

Simultaneous covalent conjugation and cleavage of aspartyl peptides observed in model experiments may give an explanation of some aggregative phenomena in defective metabolism as well as of decomposition during processing and storage of peptides and proteins.

Synthesis of biotinylated thymocartins

Four biotinylated derivatives of Arg-Lys-Asp-Val immunostimulating tetrapeptide labelled either at the α-amino group of arginyl or the ϵ-amino moiety for lysyl residue have been synthesized for biological studies using classical methods. Copyright

1H-NMR studies on thymopoietin-type oligopeptides — assignment of the proton resonances and investigation of conformational preferences

The thymopoietin-type tripeptides TP3 (HArg-Lys-AspOH), TP(D-Asp)3(HArg-Lys-D-AspOH) and tetrapeptide TP4 (HArg-Lys-Asp-ValOH) were studied by one- and two-dimensional, 500 MHz 1H-NMR spectroscopy in H2O and D2O solutions at four different pH values. All proton resonances of the three oligopeptides were assigned by two-dimensional phase-sensitive TOCSY experiments at pH 12.2, 9.1, 5.9 and 3.6. At these pH-values well-defined stages of protonation and concomitant molecular charges exist, allowing different possibilities for intra-molecular and inter-residual orientations. Conformation-sensitive rotating frame nuclear Overhauser enhancement (ROESY) two-dimensional experiments were also performed at the above pH values. These experiments indicated no definite solution conformation of any of the molecules at any pH. Standard one-dimensional experiments were also carried out and three-bond coupling constants were measured for the NH--CH and the Asp CH--CH moieties. The coupling constants provided evidence that non-statistical orientations of the functional groups exist which are changed upon protonation of the basic sites.