Design, Synthesis, and Evaluation of Homochiral Peptides Containing Arginine and Histidine as Molecular Transporters.

Linear (HR)n and cyclic [HR]n peptides (n = 4,5) containing alternate arginine and histidine residues were synthesized. The peptides showed 0⁻15% cytotoxicity at 5⁻100 µM in human ovarian adenocarcinoma (SK-OV-3) cells while they exhibited 0⁻12% toxicity in human leukemia cancer cell line (CCRF-CEM). Among all peptides, cyclic [HR]4 peptide was able to improve the delivery of a cell impermeable fluorescence-labeled phosphopeptide by two-fold. Fatty acids of different alkyl chain length were attached at the N-terminal of the linear peptide (HR)4 to improve the molecular transporter property. Addition of fatty acyl chains was expected to help with the permeation of the peptides through the cell membrane. Thus, we synthesized seven fatty acyl derivatives of the linear (HR)4 peptide. The peptides were synthesized using Fmoc/tBu solid phase peptide chemistry, purified by reverse-phase high-performance liquid chromatography (RP-HPLC) and characterized by matrix-assisted laser desorption/ionization (MALDI) spectrometry. The fatty acyl peptides containing C8, C12, C14, and C18 alkyl chain did not show cytotoxicity on SK-OV-3 or CCRF-CEM cell lines up to 50 µM concentration; however, at higher concentration (100 µM), they showed mild cytotoxicity. For example, C16-(HR)4 was also found to reduce the proliferation of SK-OV-3 cells by 11% at 50 µM and C20-(HR)4 showed mild toxicity at 10 µM, reducing the proliferation of SK-OV-3 cells by 21%. Increase in the length of alkyl chain showed cytotoxicity to the cell lines. C20-(HR)4 peptide showed better efficiency in translocation of F'-GpYEEI to SK-OV-3 than the phosphopeptide alone. Further investigation of C20-(HR)4 peptide efficacy showed that the peptide could deliver doxorubicin and epirubicin into SK-OV-3 and also improved the drug antiproliferative ability. These studies provided insights into understanding the structural requirements for optimal cellular delivery of the fatty acyl-(HR)4 peptide conjugates.

Design, Synthesis, and Evaluation of the Kinase Inhibition Potential of Pyridylpyrimidinylaminophenyl Derivatives.

In view of potent kinase inhibitors for the treatment of myriad human disorders, we synthesized some structurally variant amide/cyclic amide derivatives based on pyridylpyrimidinylaminophenyl amine, the key pharmacophore of the kinase inhibitor drug molecule, imatinib, and evaluated their kinase inhibition potency. Among the various synthesized amides, compound 20, a cyclic amide/pyridin-2(1H)-one derivative, exhibited an IC50 value comparable to that of the drug imatinib against c-Src kinase, and another compound (14) containing a 2-((4-methyl-2-oxo-2H-chromen-6-yl)oxy)acetamide demonstrated an IC50 value of 8.39 µM. Furthermore, the constitution of the cyclic amide derivative was confirmed by the single-crystal X-ray diffraction technique. These results may serve as a gateway for developing novel next-generation kinase inhibitors.

Design, synthesis, and evaluation of chitosan conjugated GGRGDSK peptides as a cancer cell-targeting molecular transporter.

Targeting cancer cells using integrin receptor is one of the promising targeting strategies in drug delivery. In this study, we conjugated an integrin-binding ligand (GGRGDSK) peptide to chitosan oligosaccharide (COS) using sulfo-SMCC as a bifunctional linker to afford COS-SMCC-GGRGDSK. The conjugated polymer was characterized by FT-IR, (1)H NMR, (13)C NMR, and SEM. COS-SMCC-GGRGDSK did not show cytotoxicity up to a concentration of 1mg/mL in the human leukemia cell line (CCRF-CEM). The conjugate was evaluated for its ability to enhance the cellular uptake of a cell-impermeable cargo (e.g., F'-G(pY)EEI phosphopeptide) in CCRF-CEM, and human ovarian carcinoma (SK-OV-3) cancer cell lines. Additionally, RGD modified and unmodified COS polymers were used to prepare nanoparticles by ionic gelation and showed particle size ranging from 187 to 338nm, and zeta potential of 12.2-18.3mV using dynamic light scattering. The efficiency of COS-NPs and COS-SMCC-RGDSK NPs was assayed for translocation of two synthetic cytotoxic agents ((2-(2-aminoethylamino)-4-(4-chlorophenyl)-6-(1H-indol-3-yl) nicotinonitrile (ACIN), and 2-(2-aminoethylamino)-6-(1H-indol-3-yl)-4-(4-methoxyphenyl)-nicotinonitrile (AMIN)) into CCRF-CEM and human prostate (DU-145) cancer cell lines. The results showed a dramatic reduction in the cell viability on their treatment with RGD targeted COS NPs in comparison to paclitaxel (PTX), free drug, and drug-loaded COS NPs.

Synthesis and evaluation of c-Src kinase inhibitory activity of pyridin-2(1H)-one derivatives.

Src kinase, a prototype member of the Src family of kinases (SFKs), is over-expressed in various human tumors, and has become a target for anticancer drug design. In this perspective, a series of eighteen 2-pyridone derivatives were synthesized and evaluated for their c-Src kinase inhibitory activity. Among them, eight compounds exhibited c-Src kinase inhibitory activity with IC50 value of less than 25µM. Compound 1-[2-(dimethylamino)ethyl]-5-(2-hydroxy-4-methoxybenzoyl)pyridin-2(1H)-one (36) exhibited the highest c-Src kinase inhibition with an IC50 value of 12.5µM. Furthermore, the kinase inhibitory activity of compound 36 was studied against EGFR, MAPK and PDK, however no significant activity was observed at the highest tested concentration (300µM). These results provide insights for further optimization of this scaffold for designing the next generation of 2-pyridone derivatives as candidate Src kinase inhibitors.

Synthesis of novel ciprofloxacin analogues and evaluation of their anti-proliferative effect on human cancer cell lines.

A series of twenty two novel 1-cyclopropyl-6-fluoro-4-oxo-7-(4-substituted piperazin-1-yl)-1,4-dihydroquinoline-3-carboxylic acid analogues have been synthesized, characterized ((1)H NMR, (13)C NMR and LCMS) and evaluated for their inhibitory activity on the proliferation of human caucasian acute lymphoblastic leukemia cells (CCRF-CEM), breast adenocarcinoma cells (MDA-MB-468) and human colon carcinoma cells (HCT-116). Among all the synthesized ciprofloxacin analogues 3t at 50 µM showed comparable potency to doxorubicin (10 µM) in all three cell lines and 3j inhibited proliferation of MDA-MB-468 up to 35% selectively over other two cell lines.