101,980 research outputs found
PEGylation of a Trail ligand.
No full textThis patent describes the synthesis of a polymeric conjugate of KillerTRAIL suitable for anti-cancer and anti-inflammatory therapies. The synthesis of therapeutic biomacromolecules was carried out by conjugating thiol group (-SH) of cysteine 230 of KillerTRAIL with PEG maleimide and thus obtains mPEG-KillerTRAIL derivative. This approach got the synthesis of stable biomacromolecules which can increase the stability of native KillerTRAIL, prevent its aggregation and improve KillerTRAIL shelf-life as well as other pharmacokinetic, biopharmaceutical parameters and the relative anti-cancer activity in vitro and in vivo
PEG conjugates in clinical development or use as anticancer agents: an overview
No full textDuring the almost forty years of PEGylation, several antitumour agents, either proteins, peptides or low molecular weight drugs, have been considered for polymer conjugation but only few entered clinical phase studies. The results from the first clinical trials have shared and improved the knowledge on biodistribution, clearance, mechanism of action and stability of a polymer conjugate in vivo. This has helped to design conjugates with improved features. So far, most of the PEG conjugates comprise of a protein, which in the native form has serious shortcomings that limit the full exploitation of its therapeutic action. The main issues can be short in vivo half-life, instability towards degrading enzymes or immunogenicity. PEGylation proved to be effective in shielding sensitive sites at the protein surface, such as antigenic epitopes and enzymatic degradable sequences, as well as in prolonging the drug half-life by decreasing the kidney clearance. In this review PEG conjugates of proteins or low molecular weight drugs, in clinical development or use as anticancer agents, will be taken into consideration. In the case of PEG-protein derivatives the most represented are depleting enzymes, which act by degrading amino acids essential for cancer cells. Interestingly, PEGylated conjugates have been also considered as adjuvant therapy in many standard anticancer protocols, in this regard the case of PEG-G-CSF and PEG-interferons will be presented
Improving the Therapeutic Potential of G-CSF through Compact Circular PEGylation Based on Orthogonal Conjugations
No full text: In this study, a circular conjugate of granulocyte colony-stimulating factor (G-CSF) was prepared by conjugating the two end-chains of poly(ethylene glycol) (PEG) to two different sites of the protein. For the orthogonal conjugation, a heterobifunctional PEG chain was designed and synthesized, bearing the dipeptide ZGln-Gly (ZQG) at one end-chain, for transglutaminase (TGase) enzymatic selective conjugation at Lys41 of G-CSF, and an aldehyde group at the opposite end-chain, for N-terminal selective reductive alkylation of the protein. The cPEG-Nter/K41-G-CSF circular conjugate was characterized by physicochemical methods and compared with native G-CSF and the corresponding linear monoconjugates of G-CSF, PEG-Nter-G-CSF, and PEG-K41-G-CSF. The results demonstrated that the circular conjugate had improved physicochemical and thermal stability, prolonged pharmacokinetic interaction, and retained the biological activity of G-CSF. The PEGylation strategy employed in this study has potential applications in the design of novel protein-based therapeutics
Transglutaminase and Sialyltransferase Enzymatic Approaches for Polymer Conjugation to Proteins
No full textProteins hold a central role in medicine and biology, also confirmed by the several therapeutic applications based on biologic drugs. Such therapies are of great relevance thanks to high potency and safety of proteins. Nevertheless, many proteins as therapeutics might present issues like fast kidney clearance, rapid enzymatic degradation, or immunogenicity. Such defects implicate frequent administrations or administrations at high doses of the therapeutics, thus yielding or exacerbating potential side effects. A successful technology for improving the clinical profiles of proteins is the conjugation of polymers to the protein surface. The design of a protein-polymer conjugate presents critical aspects that determine the efficacy and safety of the final product. The control over stoichiometry and conjugation site is a strict criterion on which researchers have been intensively focused during the years, in order to obtain homogeneous and batch-to-batch reproducible products. An innovative site-specific conjugation strategy relies on the use of enzymes as tools to mediate polymer conjugation. Enzymatic approaches are attractive because they allow site-selective polymer conjugation at specific protein amino acids. In these reactions, the polymer is a substrate analog that replaces the native substrate. Furthermore, enzymes can count other advantages such as high yields of conversion and physiological conditions of reaction. This chapter provides a meaningful description of protein-polymer conjugation through transglutaminase-mediated and sialyltransferase-mediated enzymatic strategies, reporting the mechanism of action and some relevant examples
Site-Specific Pegylation of G-CSF by Reversible Denaturation
No full textA new strategy has been developed for extending the possibility of poly(ethylene glycol) (PEG) modification to accessible thiol groups of biologically active proteins. In particular, thiol-reactive PEGs have been coupled to the cysteine 17 of granulocyte colony stimulating factor (G-CSF), which is known to be partially buried in a hydrophobic protein pocket. The PEG linking was accomplished by partial protein denaturation with 3 M guanidine.HCl in the absence of any reducing agent in order to preserve the native protein's disulfide bridges. PEG coupling occurred also, but at a lower degree, by using a 3 M solution of urea as the denaturing agent. Following the PEGylation, which was carried out in the unfolded state, the conjugated protein was refolded using dialysis or gel filtration chromatography to eliminate the denaturant. Different thiol-reactive PEGs and polymer molecular weights (5, 10, or 20 kDa) were investigated for G-CSF conjugation under denaturation. The secondary structure of the protein in the G-CSF-PEG conjugates, evaluated using circular dichroism and biological activity assay in cell culture, was maintained with respect to the native protein. Unexpectedly, conjugation enhanced the G-CSF tendency to aggregate, a problem that was overcome by a proper formulation
Stabilization of a supplemental digestive enzyme by post-translational engineering using chemically-activated polyethylene glycol
No full textMany enzymes used as digestive aids exhibit, at best, moderate stability when incubated under gastrointestinal conditions. A supplemental β-galactosidase administered orally to treat lactose intolerance was conjugated to 40 kDa, branched polyethylene glycol (PEG). PEGylation increased the enzyme's relative activity at lower pH values (2.5-4.5) and doubled enzyme stability at pH 2.5. The PEGylated enzyme retained significantly more residual activity after exposure to simulated gastric conditions (52% versus 31%), a consequence of protection from both pepsin and low pH mediated inactivation. Conjugation also provided significant protection against the proteolytic component of pancreatin. Overall, the PEGylated enzyme retained over twice the levels of residual activity recorded for non-PEGylated enzyme after exposure to complete simulated gastrointestinal conditions. PEGylation also marginally improved the enzyme's kinetic characteristics. When using its physiological substrate (lactose), K(m) values recorded were slightly decreased (from 83 to 60 μM) and k(cat)/K(m) values (M(-1) s(-1)) were increased from 100 to 147. This appears to be the first report of the use of a conjugated PEG to stabilize a digestive enzyme and the first report of the ability of conjugated PEG to stabilize a protein at low pH
Targeting glucose-6-phosphate dehydrogenase with a combination of liposomal cisplatin and 6-amino nicotinamide as new strategy to overcome cisplatin-resistance
No full textComparison of classical, stealth and super-stealth liposomes for intravenous delivery of lumefantrine: Formulation, characterization and pharmacodynamic study
No full textPurpose: To develop and compare classical liposomes (CL), stealth liposomes (SL) and super-stealth liposomes (SSL) encapsulating lumefantrine for intravenous administration. Method: CL, SL or SSL were prepared by thin-layer evaporation method and evaluated for particle size, polydispersity index (PdI), encapsulation efficiency and short-term stability. Pharmacodynamic study using mice infected with Plasmodium berghei was also carried out. Results: The particle sizes (nm) and PDI of the liposomes were: CL (248 ± 44.89; 0.78 ± 0.02), SL (235.8 ± 45.18; 0.39 ± 0.06) and SSL (238.2 ± 23.0; 0.24 ± 0.04). Encapsulation efficiency was highest in SSL (66 %), followed by SL (44.4 %) and then by CL (42.5 %). SSL was the most stable after 72 h of storage. In vivo, lumefantrine produced significant reduction in parasitaemia after 7 days (p < 0.05) by SSL (68.3 ± 8.9 %) followed by CL (55.8 ± 15.2 %) and then SL (53.4 ± 14.9 %). Conclusion: SSL formulation of lumefantrine exhibits good physicochemical and pharmacodynamic potentials and should be further investigated in future studies for the treatment of malaria
The evolution of polymer conjugation and drug targeting for the delivery of proteins and bioactive molecules
No full textPolymer conjugation can be considered one of the leading approaches within the vast field of nanotechnology-based drug delivery systems. In fact, such technology can be exploited for delivering an active molecule, such as a small drug, a protein, or genetic material, or it can be applied to other drug delivery systems as a strategy to improve their in vivo behavior or pharmacokinetic activities such as prolonging the half-life of a drug, conferring stealth properties, providing external stimuli responsiveness, and so on. If on the one hand, polymer conjugation with biotech drug is considered the linchpin of the protein delivery field boasting several products in clinical use, on the other, despite dedicated research, conjugation with low molecular weight drugs has not yet achieved the milestone of the first clinical approval. Some of the primary reasons for this debacle are the difficulties connected to achieving selective targeting to diseased tissue, organs, or cells, which is the main goal not only of polymer conjugation but of all delivery systems of small drugs. In light of the need to achieve better drug targeting, researchers are striving to identify more sophisticated, biocompatible delivery approaches and to open new horizons for drug targeting methodologies leading to successful clinical applications. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Toxicology and Regulatory Issues in Nanomedicine > Regulatory and Policy Issues in Nanomedicine
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