Effect of oriented or random PEGylation on bioactivity of a factor VIII inhibitor blocking peptide

PolyPEGylation of Protein using Semitelechelic and Mid-functional Poly(PEGMA)s synthesized by RAFT polymerization

A series of well defined semitelechelic and mid-functionalized poly(poly(ethylene glycol) methyl ether methacrylate)s (poly(PEGMA)s) were synthesized through reversible addition-fragmentation chain transfer (RAFT) polymerization using thiazolidine-2-thione-functionalized chain transfer agents (CTAs). The thiazolidine-2-thione group was located either at the end or in the middle of polymer chains depending on the different structural CTAs. All polymers were fully analyzed by 1H NMR spectroscopy and GPC, confirming their well-defined structures, such as predesigned molecular weights, narrow polydispersity indices, and high yield chain-end or chain-middle functionalization. The thiazolidine-2-thione functionality located at the end of or at the middle of the polymer chains can react with amine residues on protein surfaces, forming protein-polymer conjugates via amide linkages. The bioactivity of protein conjugates were subsequently tested using micrococcus lysodeikticus cell as substitute. The protein conjugations from the mid-functionalized polymer remained much more protein bioactivity comparing to their semitelechelic counterpart with similar molecular weights, indicating the steric hindrance of the mid-functionalized poly(PEGMA)s lead to the better selective conjugation to protein. The number of polymer chains on the protein surface was additionally evaluated by TNBS analysis, exhibiting that there are less mid-functionalized poly(PEGMA)s linked on the protein surface than the semitelechelic polymers, also supporting the hypothesis that the steric hindrance from branch-structural polymers results in the better reaction selectivity. This synthetic methodology is suitable for universal proteins, seeking a balance between the protein bioactivity and the protein protection by the covalent linkage with polymer, and exhibits promising potential for pharmaceutical protein conjugation.

Bio-reversible polyPEGylation

Protein conjugation with biodegradable polyPEGMA and subsequent release is described.

Modification of antimicrobial peptide with low molar mass poly(ethylene glycol)

PEGylation of peptide drugs prolongs their circulating lifetimes in plasma. However, PEGylation can produce a decrease in the in vitro bioactivity. Longer poly(ethylene glycol) (PEG) chains are favourable for circulating lifetimes but unfavourable for in vitro bioactivities. In order to circumvent the conflicting effects of PEG length, a hydrophobic peptide, using an antimicrobial peptide as a model, was PEGylated with short PEG chains. The PEGylated peptides self-assembled in aqueous solution into micelles with PEG shell and peptide core. In these micelles, the core peptides were protected by the shell, thus reducing proteolytic degradation. Meanwhile, most of the in vitro antimicrobial activities still remained due to the short PEG chain attached. The stabilities of the PEGylated peptides were much higher than that of the unPEGylated peptides in the presence of chymotrypsin and serum. The antimicrobial activities of the PEGylated peptides in the presence of serum, an ex vivo assay, were much higher than that of the unPEGylated peptide.

Reactivity profile of anti-factor VIII antibodies with designed synthetic peptides mimicking epitopes of the C2 and a1 domains

Antibodies (Abs) that block factor VIII (FVIII) activity occur in hemophilia A patients treated with FVIII replacement therapy and severely impair treatment. In this work, we designed and synthesized ten peptides whose sequences are found in putative epitopes at the surface of a1 and C2 domains of the FVIII molecule. These peptides were screened for their ability to inhibit the binding of anti-FVIII Abs from plasmas of hemophilia A patients to FVIII. All peptides were efficient in inhibiting anti-FVIII Abs in plasma from patients with inhibitors, with however different efficiencies. It was found that each tested patient's plasma had a different profile of reactivity with peptides, consistent with an individual anti-FVIII Ab specificity. The profile of recognized peptides was also changing during the treatment of the patients. Three peptides were used in an affinity chromatography assay to attempt to remove anti-FVIII Abs from patients' plasma. Anti-FVIII IgGs were significantly captured by the peptide-Sepharose affinity matrixes as assessed by enzyme-linked immunosorbent assay. However, due to the low level of Abs in the plasma samples, other methods (Chromogenic and Bethesda assays) were not sensitive enough to properly detect the reduction of inhibitors.

Liposomal approach towards the development of a longer-acting factor VIII

Prevention of spontaneous bleeding in patients with severe haemophilia A usually requires therapeutic infusions every 2-3 days because of the short half-life of factor VIII (FVIII). Longer-acting FVIII products that require less frequent infusions would be beneficial and might obviate the need for central catheters in most patients. Liposomal formulation can enhance the efficacy of some therapeutic products. The incorporation of high-molecular weight polyethylene glycol (PEG) can extend the circulatory half-life of the liposome. These combined approaches led to the development of BAY 79-4,980, a PEG-containing liposomal version of Kogenate FS (rFVIII-FS). Results from preclinical models and early clinical trials have shown that BAY 79-4,980 prolongs the time to the next bleed. Further clinical evaluation of the efficacy and long-term safety of BAY 79-4,980 are planned.

A pegylated derivative of alpha-galactosylceramide exhibits improved biological properties

The glycolipid alpha-galactosylceramide (alphaGalCer) has immunomodulatory properties, which have been exploited to combat cancer, chronic inflammatory diseases, and infections. However, its poor solubility makes alphaGalCer a suboptimal compound for in vivo applications. In this study, a pegylated derivative of alphaGalCer is characterized, which exhibits improved physical and biological properties. The new compound, alphaGalCerMPEG, is water-soluble and retains the specificity for the CD1d receptor of alphaGalCer. The in vitro stimulatory properties on immune cells (e.g., dendritic cells and splenocytes) are maintained intact, even when tested at a 33-fold lower concentration of the active moiety than alphaGalCer. NK cells isolated from mice treated with alphaGalCerMPEG also had stronger cytotoxic activity on YAC-1 cells than those obtained from animals receiving either alphaGalCer or CpG. Intranasal immunization studies performed in mice showed that alphaGalCerMPEG exerts stronger adjuvant activities than the parental compound alphaGalCer when tested at 0.35 vs 11.7 nM/dose. Coadministration of beta-galactosidase with alphaGalCerMPEG resulted not only in high titers of Ag-specific Abs in serum (i.e., 1:512,000), but also in the stimulation of stronger Th2 and secretory IgA responses, both at local and remote mucosal effector sites (i.e., nose, lung, and vagina). The new synthetic derivative alphaGalCerMPEG represents a promising tool for the development of immune interventions against infectious and noninfectious diseases.

Two-step fluorescence screening of CD21-binding peptides with one-bead one-compound library and investigation of binding properties of N-(2-hydroxypropyl)methacrylamide copolymer-peptide conjugates

Using the one-bead one-compound (OBOC) combinatorial method, four heptapeptide ligands of CD21 receptor, a cell surface marker of malignant B cell lymphoma, were identified with an innovative two-step fluorescence screening method to overcome the limitation caused by autofluorescence of TentaGel resin. The binding affinities of selected peptides, YILIHRN (B1), PTLDPLP (B2), and LVLLTRE (B3), were in the micromolar region as determined by a fluorescence quenching assay. Peptide B1 was conjugated to N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer via spacers of different lengths, composed of one to four repeats of the 8-amino-3,6-dioxaoctanoic acid (A) group. The evaluation of the biorecognizability of HPMA copolymer-B1 conjugates by the CD21 receptor revealed that increasing the number of repeats of A in the spacer from one to three resulted in continuous improvements in the biorecognition by the CD21 receptor; the increase from three to four repeats showed no significant effect. This work showed the potential of the OBOC combinatorial approach to select peptide ligands as targeting moieties for CD21 specific polymeric drug carriers.