Rational design of a potent, long-lasting form of interferon: a 40 kDa branched polyethylene glycol-conjugated interferon alpha-2a for the treatment of hepatitis C

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.

Early and sustained virological response in non-responders with chronic hepatitis C: a randomized open-label study of pegylated interferon-alpha-2a versus pegylated interferon-alpha-2b

OBJECTIVES

The purpose of this randomized open-label study was to assess the efficacy of treatment with pegylated interferon-alpha-2a versus pegylated interferon-alpha-2b, both plus ribavirin, in inducing early and sustained virological response (EVR and SVR) in chronic hepatitis C non-responders.

PATIENTS AND METHODS

A total of 108 patients with chronic hepatitis C who were non-responders to previous combined therapy (standard interferon-alpha plus ribavirin for > or = 3 months) were enrolled and equally randomized into two groups in this intention-to-treat analysis. The patients exhibited similar baseline features. One group received subcutaneous pegylated interferon-alpha-2a 180 microg once weekly, while the other was treated with subcutaneous pegylated interferon-alpha-2b 1.5 microg/kg once weekly. Ribavirin 15 mg/kg/day was included in both protocols. Treatment duration for EVR was 12 weeks. Patients who demonstrated non-detectable hepatitis C virus (HCV) RNA or a > or = 2 log(10) reduction in viral load at week 12 continued therapy up to 48 weeks, with assessments every 3 months during a follow-up of 24 weeks.

RESULTS

All patients in both groups completed the EVR study, then seven patients receiving pegylated interferon-alpha-2a and seven patients receiving pegylated interferon-alpha2b discontinued treatment as a result of severe adverse effects. After 12 weeks of treatment, viral load reduction was >2 log(10) with both pegylated interferon-alpha-2a (-2.53) and pegylated interferon-alpha-2b (-2.48) with no significant difference. At the end of week 48, HCV RNA was undetectable in 14 of 54 patients (25.9%) receiving pegylated interferon-alpha-2a and in 15 of 54 patients (27.7%) receiving pegylated interferon-alpha-2b. When terminating follow-up, an SVR was observed in 11 of 54 patients (20.4%) who received pegylated interferon-alpha-2a and 10 of 54 patients (18.4%) receiving pegylated interferon-alpha-2b. The incidence and severity of adverse events was similar in both groups.

CONCLUSIONS

Our results seem to show that in chronic hepatitis C patients who are non-responsive to previous therapy, EVR to the two pegylated interferons did not significantly differ with a similar therapeutic efficacy defined as SVR.

Contrast-enhanced MRI-guided photodynamic cancer therapy with a pegylated bifunctional polymer conjugate

PURPOSE

To study contrast-enhanced MRI guided photodynamic therapy with a pegylated bifunctional polymer conjugate containing an MRI contrast agent and a photosensitizer for minimally invasive image-guided cancer treatment.

METHODS

Pegylated and non-pegylated poly-(L-glutamic acid) conjugates containing mesochlorin e6, a photosensitizer, and Gd(III)-DO3A, an MRI contrast agent, were synthesized. The effect of pegylation on the biodistribution and tumor targeting was non-invasively visualized in mice bearing MDA-MB-231 tumor xenografts with MRI. MRI-guided photodynamic therapy was carried out in the tumor bearing mice. Tumor response to photodynamic therapy was evaluated by dynamic contrast enhanced MRI and histological analysis.

RESULTS

The pegylated conjugate had longer blood circulation, lower liver uptake and higher tumor accumulation than the non-pegylated conjugate as shown by MRI. Site-directed laser irradiation of tumors resulted in higher therapeutic efficacy for the pegylated conjugate than the non-pegylated conjugate. Moreover, animals treated with photodynamic therapy showed reduced vascular permeability on DCE-MRI and decreased microvessel density in histological analysis.

CONCLUSIONS

Pegylation of the polymer bifunctional conjugates reduced non-specific liver uptake and increased tumor uptake, resulting in significant tumor contrast enhancement and high therapeutic efficacy. The pegylated poly(L-glutamic acid) bifunctional conjugate is promising for contrast enhanced MRI guided photodynamic therapy in cancer treatment.

Auditing protein therapeutics management by professional APCs: toward prevention of immune responses against therapeutic proteins

Alloimmunization is a crippling concern in the management of patients undergoing administration of protein therapeutics as evidenced in replacement therapy and other treatment procedures. Several issues in the genesis and modulation of such deleterious immune responses have been studied. While authors have focused on the downstream events of the specific immune response and suggested modification of protein therapeutics to eliminate epitopes that interact with B cell receptors, T cell receptors, or MHCII molecules, the mechanisms underlying Ag interaction with APCs, a step upstream of immune effectors, have been grossly neglected. We wish to emphasize that the recent knowledge in understanding the capacities of an APC to handle an Ag and the importance of the surrounding microenvironment in this process are crucial for designing novel protein therapeutics with reduced immunogenicity.

Substantially improved pharmacokinetics of recombinant human butyrylcholinesterase by fusion to human serum albumin

Background

Human butyrylcholinesterase (huBChE) has been shown to be an effective antidote against multiple LD₅₀ of organophosphorus compounds. A prerequisite for such use of huBChE is a prolonged circulatory half-life. This study was undertaken to produce recombinant huBChE fused to human serum albumin (hSA) and characterize the fusion protein.

Results

Secretion level of the fusion protein produced in vitro in BHK cells was ~30 mg/liter. Transgenic mice and goats generated with the fusion constructs expressed in their milk a bioactive protein at concentrations of 0.04–1.1 g/liter. BChE activity gel staining and a size exclusion chromatography (SEC)-HPLC revealed that the fusion protein consisted of predominant dimers and some monomers. The protein was confirmed to have expected molecular mass of ~150 kDa by Western blot. The purified fusion protein produced in vitro was injected intravenously into juvenile pigs for pharmacokinetic study. Analysis of a series of blood samples using the Ellman assay revealed a substantial enhancement of the plasma half-life of the fusion protein (~32 h) when compared with a transgenically produced huBChE preparation containing >70% tetramer (~3 h). In vitro nerve agent binding and inhibition experiments indicated that the fusion protein in the milk of transgenic mice had similar inhibition characteristics compared to human plasma BChE against the nerve agents tested.

Conclusion

Both the pharmacokinetic study and the in vitro nerve agent binding and inhibition assay suggested that a fusion protein retaining both properties of huBChE and hSA is produced in vitro and in vivo. The production of the fusion protein in the milk of transgenic goats provided further evidence that sufficient quantities of BChE/hSA can be produced to serve as a cost-effective and reliable source of BChE for prophylaxis and post-exposure treatment.

Very Early Viral Kinetics on Interferon Treatment in Chronic Hepatitis C virus Genotype 4 Infection

Background

Interferon (IFN)-resistant hepatitis C virus strains limit efficacy of antiviral combination therapy in patients infected with genotypes 1 and 4. A single test dose of IFN was useful to identify non-responders to IFN-α2b/ribavirin (RBV) or likely non-responders to pegylated (PEG)-IFN-α2a/RBV therapy in genotype 1 patients. Our aim was to investigate this approach in genotype 4 patients.

Methods

Viral load was measured in 46 patients before and 24 h after 10 megaunits (MU) IFN-α2b, and before and during 2 weeks of daily 5 MU IFN-α2b administration. Thereafter, patients received 48 weeks combination therapy with either 180 μg PEG-IFN-α2a/week ( n=33), 1.5 μg/kg PEG-IFN-α2b/week ( n=7) or 5 MU IFN-α2b/2 days ( n=6), along with 1–1.2g RBV/day. For prediction analysis the largest group (PEG-IFN-α2a) was evaluated only.

Results

Median 24 h log10 change after 10 MU IFN-α2b was 1.15 (range 0.08–2.48) and after 5 MU IFN-α2b was 0.81 (-0.12–2.22; P<0.0001). Log10 changes after 2 weeks on 5 MU IFN-α2b daily and 24 h after 10 MU were the best predictors of early virological response (defined by negativity of a standard qualitative PCR) to PEG-IFN-α2a/RBV combination therapy (area under curve [AUC]=0.97; P<0.001, receiver operating characteristics), 24 h log10 change after 10 MU was the best predictor of sustained virological response (SVR; AUC=0.91, P=0.001).

Conclusion

As in genotype 1 patients, there is large variation in IFN responsiveness, including the presence of resistant strains, in genotype 4 patients. A 24 h log10 change after 10 MU IFN-α2b is an excellent predictor of SVR on PEG-IFNα2a/RBV combination therapy. This test may be useful to obtain homogeneous groups for clinical studies and could help in clinical decision making.

Distinct Hepatitis C virus Kinetics in HIV-Infected Patients Treated with Ribavirin plus Either Pegylated Interferon α2a or α2b

Background

Pegylated interferon (PEG-IFN) α2a and α2b differ in their pharmacokinetic properties, which might have an effect on their antiviral effects against hepatitis C virus (HCV). Differences between PEG-IFN-α molecules could be more pronounced in HIV-coinfected individuals, in whom response to HCV treatment is impaired.

Methods

All HCV–HIV-coinfected patients included in PRESCO and EXTENT trials recruited at one referral centre were retrospectively analysed. In both trials, ribavirin (RBV) 1,000–1,200 mg/day was prescribed together with standard doses of PEG-IFN-α2a or -α2b. The attainment of serum HCV RNA <10 IU/ml at weeks 4, 12 and 24 was assessed. On-treatment analyses were made to estimate the intrinsic potency of PEG-IFN-α2a versus -α2b.

Results

A total of 218 patients were examined, 138 on PEG-IFN-α2a and 80 on PEG-IFN-α2b. Baseline characteristics were comparable in both groups. Undetectable serum HCV RNA at weeks 4, 12 and 24 was more frequently attained using PEG-IFN-α2a than -α2b (45% versus 27% [ P=0.02]; 65% versus 45% [ P=0.01]; and 75% versus 55% [ P=0.01], respectively), regardless of HCV genotype. Plasma RBV levels did not differ between groups. In multivariate analysis, HCV genotypes 2/3 (odds ratio [OR] 12.5; 95% confidence interval [95% CI] 3.45–33.33; P<0.001), use of zidovudine (OR 0.30; 95% CI 0.11–0.85; P=0.02) and treatment with PEG-IFN-α2a (OR 2.12; 95% CI 1.02–4.54; P=0.04) were independent predictors of undetectable HCV RNA at week 24. Conversely, the incidence of serious adverse events was more common with PEG-IFN-α2a than -α2b (13.2% versus 3.6%; P=0.018).

Conclusions

The antiviral effect against HCV seems to be greater for PEG-IFN-α2a than -α2b in the HIV setting. A shorter half-life of PEG-IFN-α2b could explain this finding.

Preparation and characterization of monopegylated human granulocyte-macrophage colony-stimulating factor

ABSTRACT Conjugates of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) attached to polyethylene glycol (PEG) chains were prepared using amine-reactive chemistry. Molecular masses of the PEGs were 20, 30, and 40 kDa. The monopegylated forms were isolated by anion-exchange chromatography and characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), size-exclusion chromatography, mass spectrometry, reverse-phase high-performance liquid chromatography (HPLC), peptide mapping, in vitro cell proliferation bioassays, and rat pharmacokinetic studies. The pegylation site of the purified monopegylated products was identified as the N-terminus of the protein. All forms of pegylated GM-CSF were able to stimulate TF-1 cell proliferation in a colorimetric bioassay at concentrations equal to or lower than that of GM-CSF. Pharmacokinetic studies in rats demonstrated 32-fold, 27-fold, and 40-fold extensions in elimination half-lives for 20, 30, and 40 kDa PEG-GM-CSF, respectively, as compared with nonmodified GM-CSF.

Reversible pegylation of insulin facilitates its prolonged action in vivo

We attempted to engineer a novel long-acting insulin based on the following properties: (i) action as a prodrug to preclude supraphysiological concentrations shortly after injection; (ii) maintenance of low-circulating level of biologically active insulin for prolonged period; and (iii) high solubility in aqueous solution. A spontaneously hydrolyzable prodrug was thus designed and prepared by conjugating insulin through its amino side chains to a 40kDa polyethylene glycol containing sulfhydryl moiety (PEG(40)-SH), employing recently developed hetero-bifunctional spacer 9-hydroxymethyl-7(amino-3-maleimidopropionate)-fluorene-N-hydroxysucinimide (MAL-Fmoc-0Su). A conjugate trapped in the circulatory system and capable of releasing insulin by spontaneous chemical hydrolysis has been created. PEG(40)-Fmoc-insulin is a water-soluble, reactivatable prodrug with low biological activity. Upon incubation at physiological conditions, the covalently linked insulin undergoes spontaneous hydrolysis at a slow rate and in a linear fashion, releasing the nonmodified immunologically and biologically active insulin with a t(1/2) value of 30h. A single subcutaneous administration of PEG(40)-Fmoc-insulin to healthy and diabetic rodents facilitates prolonged glucose-lowering effects 4- to 7-fold greater than similar doses of the native hormone. The beneficial pharmacological features endowed by PEGylation are thus preserved. In contrast, nonreversible, "conventional" pegylation of insulin led to inactivation of the hormone.

Designing transient binding drugs: a new concept for drug discovery

A multitude of weak, or transient, biological interactions (dissociation constant: K(d)>microM), either working alone or in concert, occur frequently throughout biological systems. We are starting to appreciate their importance in complex biological networks. This realization has important implications to drug discovery as we can question the current paradigm of drug design to find the highest possible binders (drugs) to a given target (receptor). Development of transient drugs, defined by their binding to target, can be based on high-off-rates, multivalent approaches or multiple targets. Now, techniques are available to discover such drug candidates. The greatest problem yet to overcome is probably the mind-set of the individual researcher that weak binders are undesired and therefore of no benefit.

Sustained response to peginterferon alfa-2a (40 kD) with or without lamivudine in Asian patients with HBeAg-positive and HBeAg-negative chronic hepatitis B

PURPOSE

The 2 reported trials investigated the effectiveness of treatment with peginterferon alfa-2a in Asian patients with chronic hepatitis B (CHB).

METHODS

Patients with HBeAg-positive (n = 708) or HBeAg-negative (n = 332) CHB were enrolled in 2 randomized, double blind, placebo-controlled studies. Patients received peginterferon alfa-2a 180 mug once weekly, peginterferon plus lamivudine 100 mg per day, or lamivudine alone for 48 weeks. Patients were followed up at 6 and 12 months posttreatment.

RESULTS

Peginterferon alfa-2a provided significantly higher rates of HBeAg seroconversion (31%) in HBeAg-positive patients than did lamivudine (19%, P = 0.005) 6 months posttreatment, irrespective of genotype. Of these, 83% achieving seroconversion during treatment or early posttreatment sustained their response at 12 months posttreatment. In patients who seroconverted, 69% maintained HBV DNA suppression at <10,000 copies/ml and alanine aminotrasferase (ALT) normalization. In HBeAg-negative patients, peginterferon produced a significantly higher combined response of HBV DNA at <20,000 copies/ml and ALT normalization (45%) than lamivudine (31%, P = 0.032), irrespective of genotype. Almost 80% of these patients sustained their response at 12 months posttreatment.

CONCLUSIONS

In conclusion, a finite course of peginterferon alfa-2a provides significant and sustained treatment benefit in Asian CHB patients, who have traditionally been regarded as difficult to treat.

Capillary electrophoretic separation of high-molecular-weight poly(ethylene glycol)-modified proteins

This study was designed to demonstrate the utility of capillary electrophoresis (CE) for separating high-molecular-weight poly(ethylene glycol) (PEG)-conjugated proteins. As a CE method, sodium dodecyl sulfate-capillary gel electrophoresis (SDS-CGE) was applied to analyze interferon alpha (IFN) modified with branched and trimer-structured PEG molecules. Five mono-PEG-IFN conjugates prepared with two branched PEGs (MW 20 and 40 kDa) and three trimer-structured PEGs (MW 23.5, 43.5, and 47 kDa) were purified by cation-exchange chromatography and their masses were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The SDS-CGE method showed high separation capacity by differentiating PEG-IFN conjugates with small differences in molecular size, such as PEG(40K)-, PEG(43.5K)-, and PEG(47K)-IFNs, and it was useful for checking the purity of each mono-PEG-IFN. This study shows that SDS-CGE can well be utilized in the development and quality control of PEGylated proteins prepared with various types of PEG.

N-glycosylation as novel strategy to improve pharmacokinetic properties of bispecific single-chain diabodies

The therapeutic efficacy of recombinant antibodies such as single-chain Fv fragments and small bispecific or bifunctional molecules is often limited by rapid elimination from the circulation because of their small size. Here, we have investigated the effects of N-glycosylation on the activity and pharmacokinetics of a small bispecific single-chain diabody (scDb CEACD3) developed for the retargeting of cytotoxic T cells to CEA-expressing tumor cells. We could show that the introduction of N-glycosylation sequons into the flanking linker and a C-terminal extension results in the production of N-glycosylated molecules after expression in transfected HEK293 cells. N-Glycosylated scDb variants possessing 3, 6, or 9 N-glycosylation sites, respectively, retained antigen binding activity and bispecificity for target and effector cells as shown in a target cell-dependent IL-2 release assay, although activity was reduced approximately 3-5-fold compared with the unmodified scDb. All N-glycosylated scDb variants exhibited a prolonged circulation time compared with scDb, leading to a 2-3-fold increase of the area under curve (AUC). In comparison, conjugation of a branched 40-kDa PEG chain increased AUC by a factor of 10.6, while a chimeric anti-CEA IgG1 molecule had the longest circulation time with a 17-fold increase in AUC. Thus, N-glycosylation complements the repertoire of strategies to modulate pharmacokinetics of small recombinant antibody molecules by an approach that moderately prolongs circulation time.

Releasable PEGylation of proteins with customized linkers

Releasable PEGylation employs customized linkers that reversibly tether a therapeutic moiety with polyethylene glycol polymers. The choice of releasable PEG linkers may have numerous applications that are insufficiently addressed by stable polymer attachment. Releasable PEGylation provides regeneration of authentic and fully active drug and allows tailored design of critical pharmacological parameters such as the maximal drug concentration and total drug exposure. This provides a prodrug format that combines beneficial attributes of PEGylation with controlled release. The linker release mechanisms are shown to be kinetically controlled by the design of a hydrolytically labile center and side chains for the steric modulation of the intramolecular elimination reactions and linker self-immolation. Recent reports have described both aromatic and aliphatic based customized linkers that release the unaltered original drug under physiological conditions and at therapeutically useful release rates. These studies have examined bioconjugates of cytokines, peptide hormones, immunotoxins, enzymes, and reporter proteins.

Disulfide bridge based PEGylation of proteins

PEGylation is a clinically proven strategy for increasing the therapeutic efficacy of protein-based medicines. Our approach to site-specific PEGylation exploits the thiol selective chemistry of the two cysteine sulfur atoms from an accessible disulfide. It involves two key steps: (1) disulfide reduction to release the two cystine thiols, and (2) bis-alkylation to give a three-carbon bridge to which PEG is covalently attached. During this process, irreversible denaturation of the protein does not occur. Mechanistically, the conjugation is conducted by a sequential, interactive bis-alkylation using alpha,beta-unsaturated-beta'-mono-sulfone functionalized PEG reagents. The combination of: - (a) maintaining the protein's tertiary structure after reduction of a disulfide, (b) bis-thiol selectivity of the PEG reagent, and (c) PEG associated steric shielding ensure that only one PEG molecule is conjugated at each disulfide. Our studies have shown that peptides, proteins, enzymes and antibody fragments can be site-specifically PEGylated using a native and accessible disulfide without destroying the molecules' tertiary structure or abolishing its biological activity. As the stoichiometric efficiency of our approach also enables recycling of any unreacted protein, it offers the potential to make PEGylated biopharmaceuticals as cost-effective medicines.

Hepatitis C virus therapy to date

Chronic hepatitis C is a major contributor to cirrhosis and hepatocellular cancer worldwide, justifying the considerable research effort aimed at understanding the disease and refining its treatment. As a result, significant therapeutic advances have been made in the last decade, particularly with regard to the development of pegylated interferons and ribavirin. This review will discuss the physical properties, pharmacokinetics, viral kinetics and side-effect profiles of the different treatment options and how they have improved, culminating in the use of pegylated interferon and ribavirin combination therapy as the current standard of care.

Targeting IFN-alpha to B cell lymphoma by a tumor-specific antibody elicits potent antitumor activities

IFN-alpha, a cytokine crucial for the innate immune response, also demonstrates antitumor activity. However, use of IFN-alpha as an anticancer drug is hampered by its short half-life and toxicity. One approach to improving IFN-alpha's therapeutic index is to increase its half-life and tumor localization by fusing it to a tumor-specific Ab. In the present study, we constructed a fusion protein consisting of anti-HER2/neu-IgG3 and IFN-alpha (anti-HER2/neu-IgG3-IFN-alpha) and investigated its effect on a murine B cell lymphoma, 38C13, expressing human HER2/neu. Anti-HER2/neu-IgG3-IFN-alpha exhibited potent inhibition of 38C13/HER2 tumor growth in vivo. Administration of three daily 1-microg doses of anti-HER2/neu-IgG3-IFN-alpha beginning 1 day after tumor challenge resulted in 88% of the mice remaining tumor free. Remarkably, anti-HER2/neu-IgG3-IFN-alpha demonstrated potent activity against established 38C13/HER2 tumors, with complete tumor remission observed in 38% of the mice treated with three daily doses of 5 microg of the fusion protein (p = 0.0001). Ab-mediated targeting of IFN-alpha induced growth arrest and apoptosis of lymphoma cells contributing to the antitumor effect. The fusion protein also had a longer in vivo half-life than rIFN-alpha. These results suggest that IFN-alpha Ab fusion proteins may be effective in the treatment of B cell lymphoma.

Free-radical-mediated protein inactivation and recovery during protein photoencapsulation

Photoencapsulation of protein therapeutics is very attractive for preparing biomolecule-loaded hydrogels for a variety of biomedical applications. However, detrimental effects of highly active radical species generated during photoencapsulation must be carefully evaluated to maintain efficient hydrogel cross-linking while preserving the structure and bioactivity of encapsulated biomolecules. Here, we examine the free-radical-mediated inactivation and incomplete release of proteins from photocurable hydrogels utilizing lysozyme as a conservative model system. Various protein photoencapsulation conditions were tested to determine the factors affecting lysozyme structural integrity and bioactivity. It was found that a portion of the lysozyme becomes conjugated to polymer chains at high photoinitiator concentrations and long polymerization times. We also found that the more hydrophilic photoinitiator Irgacure-2959 (I-2959, 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone) causes more damage to lysozyme compared to the hydrophobic photoinitiator Irgacure-651 (I-651, 2,2-dimethoxy-2-phenylacetophenone), even though I-2959 has been previously shown to be more cytocompatible. Furthermore, while nonacrylated PEG provides only limited protection from the denaturing free radicals that are present during hydrogel curing, acrylated PEG macromers effectively preserve lysozyme structural integrity and bioactivity in the presence of either photoinitiator. Overall, these findings indicate how photopolymerization conditions (e.g., photoinitiator type and concentration, UV exposure time, etc.) must be optimized to obtain a functional hydrogel device that can preserve protein bioactivity and provide maximal protein release.

Combination therapy with PEG-IFN-alpha and 5-FU inhibits HepG2 tumour cell growth in nude mice by apoptosis of p53

When the tumour suppressor p53 is activated by DNA damage, it stimulates the transcription of its target genes, which then induce cell cycle arrest or apoptosis. Here, we examined the role p53 plays in the antitumour effect of combination treatment with pegylated interferon (PEG-IFN)-alpha and 5-fluorouracil (5-FU), which has been shown to effectively treat advanced hepatocellular carcinoma (HCC). Nude mice were injected subcutaneously with cultured HepG2 cells, in which p53 is functional. They were treated a week later with PEG-IFN and/or 5-FU for 7 weeks, after which we measured and examined their tumours. Combination groups showed significantly lower tumour volumes and higher tumour cell apoptosis than the other groups. Combination treatment and PEG-IFN monotherapy also significantly elevated the p53 protein and mRNA levels in the tumour but only combination treatment increased the degree of p53 phosphorylation at serine46 and induced p53-regulated apoptosis-inducing protein 1 (p53AIP1) expression. The antitumour effects of combination treatment is due in part to the elevation by PEG-IFN of p53 protein and mRNA expression and in part to the DNA damage that is generated by 5-FU, which induces p53 serine46 phosphorylation, which in turn upregulates p53AIP1 expression.

Effects of a 24-week course of interferon-α therapy after curative treatment of hepatitis C virus-associated hepatocellular carcinoma

AIM: To assess whether a 24-wk course of interferon (IFN) could prevent hepatocellular carcinoma (HCC) recurrence and worsening of liver function in patients with hepatitis C virus (HCV)-infected patients after receiving curative treatment for primary HCC.

METHODS: Outcomes in 42 patients with HCV infection treated with IFN-α, after curative treatment for primary HCC (IFN group), were compared with 42 matched curatively treated historical controls not given IFN (non-IFN group).

RESULTS: Although the rate of initial recurrence did not differ significantly between IFN group and non-IFN group (0%, 44%, 61%, and 67% vs 4.8%, 53%, 81%, and 87% at 1, 3, 5, and 7 years, P = 0.153, respectively), IFN group showed a lower rate than the non-IFN group for second recurrence (0%, 10.4%, 28%, and 35% vs 0%, 30%, 59%, and 66% at 1, 3, 5 and 7 years, P = 0.022, respectively). Among the IFN group, patients with sustained virologic response (SVR) were less likely to have a second HCC recurrence than IFN patients without an SVR, or non-IFN patients. Multivariate analysis identified the lack of SVR as the only independent risk factor for a second recurrence, while SVR and Child-Pugh class A independently favored overall survival.

CONCLUSION: Most intrahepatic recurrences of HCV-related HCC occurred during persistent viral infection. Eradication of HCV is essential for the prevention of HCC recurrence and improvement of survival.

Effect of site-directed PEGylation of trichosanthin on its biological activity, immunogenicity, and pharmacokinetics

Trichosanthin (TCS) is a type I ribosome-inactivating protein (RIP) with multiple biological and pharmacological activities. It has been approved effective in the clinical treatment of AIDS and tumor, but its strong immunogenicity and short plasma half-life have limited the clinical administration. To reduce the immunogenicity and prolong the plasma half-life of this compound, three TCS muteins (M(1), M(2) and M(3)) and two PEGylated TCS muteins (PM(1) and PM(2)) were constructed by site-directed mutagenesis and PEGylation, respectively. Compared with the unmodified TCS, both PEGylated TCS showed a 3- to 4-fold decrease in immunogenicity, a 0.5- to 0.8-fold decrease in non-specific toxicity, and a 4.5- to 6-fold increase in plasma half-life. But there is a problem of activity reduction. The increased circulating half-life in vivo may compensate for the reduced activity. Together with the other benefits of PEGylation such as reduced immunogenicity and toxicity, it is worthwhile to further explore the potential application of the PEGylated TCS as a better therapeutic agent for AIDS and tumor.

Adverse skin reactions due to pegylated interferon alpha 2b plus ribavirin combination therapy in a patient with chronic hepatitis C virus

Pegylated interferon (IFN)-alpha-2b with ribavirin has recently replaced "standard" IFN-alpha for the treatment of chronic hepatitis C. The most common side-effect of pegylated IFN-alpha-2b plus ribavirin combination therapy is localized inflammatory skin lesions at the site of injection. A 66-year-old female treated with once-weekly pegylated IFN-alpha-2b plus ribavirin for active chronic hepatitis C developed inflammatory skin lesions 2 months after starting antiviral treatment. The type of skin reactions observed were vesicle erythematous eruptions at the injection sites, and pruritic papular erythematous eruptions located on the face, neck, distal limbs, dorsa of the hands, trunk and buttocks away from the injection sites. Histological examination was performed on the pruritic papular erythematous eruption located on the left forearm, away from the injection sites. It showed epidermal spongiosis, a spongiotic microvesicle, and perivascular infiltration of the upper dermis with lymphocytes. The treatment was interrupted subsequently and the patient was rechallenged with pegylated IFN-alpha-2b plus ribavirin combination therapy, oral prednisolone with olopatadine hydrochloride and topical 0.1% diflucortolone valerate, which led to a significant improvement of skin lesions. Erythema with infiltration can occur at the injection sites of pegylated IFN-alpha-2b. However, the occurrence of vesicle erythematous eruptions away from the injection sites and autosensitization dermatitis apart from injection sites have not yet been frequently reported.

Interferon-based therapy of hepatitis C

In 2007, the world celebrated the 50th anniversary of the discovery of interferon (IFN). The first clinical trial of recombinant IFN-alpha in patients with chronic hepatitis C was published in 1986. This article reviews the classification of IFNs, IFN production during viral infections, IFN signaling pathways and the mechanisms of their antiviral and immunomodulatory properties. Hepatitis C virus infection treatment is currently based on the combination of pegylated IFN-alpha and ribavirin. The pegylated IFN-alpha molecules are described, as well as the putative mechanisms of action of ribavirin. Current treatment guidelines are discussed and new results suggesting that the treatment schedule should be tailored to the early virological response during therapy are presented. Finally, insights into new hepatitis C drug developments are given.

Early virologic response after peginterferon alpha-2a plus ribavirin or peginterferon alpha-2b plus ribavirin treatment in patients with chronic hepatitis C

Patients infected with hepatitis C virus (HCV) genotype 1 and with serum HCV RNA concentrations over 800 000 IU/mL have relatively low rates of virologic response to pegylated interferons. The 2 forms of pegylated interferon have different pharmacokinetic profiles, and pilot studies comparing them have yielded varying results. We compared the virologic response to 12 weeks of treatment with peginterferon alpha-2a plus ribavirin vs peginterferon alpha-2b plus ribavirin in 380 patients who were infected with HCV genotype 1 and had high viral loads. We observed no between-group differences in viral load reduction over time and no differences in the percentage of patients treated with peginterferon alpha-2a or peginterferon alpha-2b plus ribavirin who achieved early virologic response (EVR), defined as >/=2-log reduction in HCV RNA concentration or undetectable HCV RNA at 12 weeks (66%vs 63%). Serum levels of interferon were more frequently below the level of quantitation in patients treated with peginterferon alpha-2b plus ribavirin (58-68%) than in those treated with peginterferon alpha-2a plus ribavirin (1-2%). Patients treated with peginterferon alpha-2b plus ribavirin had higher rates of discontinuation for safety reasons (6%vs 1%). In conclusion, a substantial percentage of patients infected with HCV genotype 1 and high viral load can achieve EVR when treated with peginterferon and ribavirin. The 2 pegylated interferons showed comparable anti-HCV activity during the first 12 weeks of treatment when combined with the same doses of ribavirin (1000-1200 mg/day), but discontinuations for safety reasons were higher in the patients treated with peginterferon alpha-2b plus ribavirin.

Precisely defined protein-polymer conjugates: construction of synthetic DNA binding domains on proteins by using multivalent dendrons

Nature has evolved proteins and enzymes to carry out a wide range of sophisticated tasks. Proteins modified with functional polymers possess many desirable physical and chemical properties and have applications in nanobiotechnology. Here we describe multivalent Newkome-type polyamine dendrons that function as synthetic DNA binding domains, which can be conjugated with proteins. These polyamine dendrons employ naturally occurring spermine surface groups to bind DNA with high affinity and are attached onto protein surfaces in a site-specific manner to yield well-defined one-to-one protein-polymer conjugates, where the number of dendrons and their attachment site on the protein surface are precisely known. This precise structure is achieved by using N-maleimido-core dendrons that selectively react via 1,4-conjugate addition with a single free thiol group on the protein surface--either Cys-34 of bovine serum albumin (BSA) or a genetically engineered cysteine mutant of Class II hydrophobin (HFBI). This reaction can be conducted in mild aqueous solutions (pH 7.2-7.4) and at ambient temperature, resulting in BSA- and HFBI-dendron conjugates. The protein-dendron conjugates constitute a specific biosynthetic diblock copolymer and bind DNA with high affinity, as shown by ethidium bromide displacement assay. Importantly, even the low-molecular-weight first-generation polyamine dendron (1 kDa) can bind a large BSA protein (66.4 kDa) to DNA with relatively good affinity. Preliminary gene transfection, cytotoxicity, and self-assembly studies establish the relevance of this methodology for in vitro applications, such as gene therapy and surface patterning. These results encourage further developments in protein-dendron block copolymer-like conjugates and will allow the advance of functional biomimetic nanoscale materials.

High-yields and extended serum half-life of human interferon alpha2b expressed in tobacco cells as arabinogalactan-protein fusions

Therapeutic proteins like human interferon alpha2 generally possess short serum half-lives due to their small size, hence rapid renal clearance, and susceptibility to serum proteases. Chemical derivatization, such as addition of polyethylene glycol (PEG) groups overcomes both problems, but at the expense of greatly decreased bioactivity. We describe a new method that yields biologically potent interferon alpha2b (IFNalpha2) in high yields and with increased serum half-life when expressed as arabinogalactan-protein (AGP) chimeras in cultured tobacco cells. Thus IFNalpha2-AGPs targeted for secretion typically gave 350-1400-fold greater secreted yields than the non-glycosylated IFNalpha2 control. The purified AGP domain itself was not immunogenic when injected into mice and only mildly so when injected as a fusion glycoprotein. Importantly, the AGP-IFNalpha2 chimeras showed up to a 13-fold increased in vivo serum half-life while the biological activity remained similar to native IFNalpha2. The use of arabinogalactan glycomodules may provide a general approach to the enhanced production of therapeutic proteins by plants.

Structure-based epitope and PEGylation sites mapping of phenylalanine ammonia-lyase for enzyme substitution treatment of phenylketonuria

Protein and peptide therapeutics are of growing importance as medical treatments but can frequently induce an immune response. This work describes the combination of complementary approaches to map the potential immunogenic regions of the yeast Rhodosporidium toruloides phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) and to engineer the protein as a human therapeutic agent for the treatment of phenylketonuria (PKU), an inherited metabolic disorder. The identification of B and T cell epitopes on the PAL protein was performed by computational predictions based on the antigenicity and hydrophilicity of proteins, as well as by experimental epitope mapping using a PepSpots peptide array (Jerini AG). Human T cell epitope mapping was performed by applying the computational EpiMatrix algorithm (EpiVax, Inc.) for MHC Class I and Class II associated T cell epitopes on PAL, which predicts which sequences are associated with binding to several different HLA alleles, a requirement for antigen presentation and subsequent primary immune response. By chemical modification through PEGylation of surface lysine residues, it is possible to cover the immunogenic regions of a protein. To evaluate this strategy, we used mass spectrometry to determine which of the immunogenic epitopes are covered by the covalent PEGylation modification strategy. This approach has allowed us to determine whether additional lysines are needed in specific residue locations, or whether certain lysine residues can be removed in order to accomplish complete molecular coverage of the therapeutic enzyme.

Radiotherapy of CD45-Expressing Daudi Tumors in Nude Mice with Yttrium-90-Labeled, PEGylated Anti-CD45 Antibody

Studies were performed to determine the suitability of using the polyethylene glycol (PEG)-labeled AHN-12 anti-CD45 monoclonal antibody to deliver the high-energy beta-particle-emitting isotope 90Y to a CD45+ B-cell Daudi lymphoma grown as flank tumors in athymic nude mice. The PEGylated radiolabeled antibody displayed a significantly better antitumor effect in the mouse tumor flank model (p<0.03) and significantly better blood pharmacokinetics in normal rats (p<0.05) than the non-PEGylated radiolabeled antibody. Studies of two different sizes of PEG showed that rats given 43 kDa of PEGylated AHN-12, but not 5 kDa of PEGylated AHN-12, had significantly higher radiolabeled antibody blood levels and, therefore, improved pharmacokinetics, as compared to rodents given non-PEGylated radiolabeled AHN-12 (p<0.05). Surviving mice revealed no signs of kidney, liver, or gastrointestinal damage by histology study. Notably, in vitro studies indicated that PEGylation did not have a major effect on labeling efficiency and the binding of labeled antibody. These findings indicate that PEGylation of radiolabeled anti-CD45 antibody may be a useful and desirable means of extending blood half-life and enhancing efficacy. Also, the final outcome may be impacted by the size of the PEG molecule used for the modification of the blood half-life.

Pharmacodynamics of peginterferon alpha-2a and peginterferon alpha-2b in interferon-naïve patients with chronic hepatitis C: a randomized, controlled study

BACKGROUND

Peginterferon alpha-2a and alpha-2b, the two commercially available pegylated interferons, have different pharmacokinetic properties that produce differing abilities to suppress replication of the hepatitis C virus.

AIM

To compare the pharmacodynamics of peginterferon alpha-2a and peginterferon alpha-2b in interferon-naive patients with chronic hepatitis C.

METHODS

Patients were randomized to receive peginterferon alpha-2a, 180 microg (n = 10) or peginterferon alpha-2b 1.0 microg/kg (n = 12) once weekly. The enzymatic activity of 2'5'-oligoadenylate synthetase and levels of neopterin and beta(2)-microglobulin were measured at baseline and at 24, 48, 120 and 168 h.

RESULTS

Oligoadenylate synthetase activity and serum neopterin and beta(2)-microglobulin concentrations did not differ significantly between the two patient groups at any time point, nor was there a significant correlation between the serum area under the concentration-time curve of either peginterferon and the area under the concentration-time curve for 2',5'-oligoadenylate synthetase, neopterin and beta(2)-microglobulin. The area under the concentration-time curves calculated for these three markers did not correlate with body mass index stratified at <25 and >or=25 kg/m(2) for either peginterferon.

CONCLUSIONS

Despite pharmacokinetic differences between peginterferon alpha-2a and peginterferon alpha-2b, the pharmacodynamic profiles of the two formulations appear to be comparable.

Role of amino acid residue 90 in bioactivity and receptor binding capacity of tumor necrosis factor mutants

We have previously produced two bioactive lysine-deficient mutants of TNF-alpha (mutTNF-K90R,-K90P) and found that these mutants have bioactivity superior to wild-type TNF (wtTNF). Because these mutants contained same amino acid except for amino acid 90, it is unclear which amino acid residue is optimal for showing bioactivity. We speculated that this amino acid position was exchangeable, and this amino acid substitution enabled the creation of lysine-deficient mutants with enhanced bioactivity. Therefore, we produced mutTNF-K90R variants (mutTNF-R90X), in which R90 was replaced with other amino acids, to assay their bioactivities and investigated the importance of amino acid position 90. As a result, mutTNF-R90X that replaced R90 with lysine, arginine and proline were bioactive, while other mutants were not bioactive. Moreover, these three mutants showed bioactivity as good as or better than wtTNF. R90 replaced with lysine or arginine had especially superior binding affinities. These results suggest that the amino acid position 90 in TNF-alpha is important for TNF-alpha bioactivity and could be altered to improve its bioactivity to generate a "super-agonist".

Investigation on PEGylation strategy of recombinant human interleukin-1 receptor antagonist

Although PEGylation is a potential approach to prolong the half-lives and reduce the dosing frequency of therapeutic proteins, conjugation behaviors of polymer have pivotal effects on the remaining bioactivities of the derivatives. In this study, the PEGylation strategy of recombinant human interleukin-1 receptor antagonist was investigated. The random conjugation of polyethylene glycol to amino groups on the protein resulted in a severe loss of activity and only retained 9.8% of the activity. In contrast, the PEGylation at the thiol groups had moderate effects on the bioactivity of protein and 40% of activity was conserved. The results suggested that the thiol-target PEGylation was more beneficial for IL-1ra.

A long-acting, mono-PEGylated human growth hormone analog is a potent stimulator of weight gain and bone growth in hypophysectomized rats

Recombinant human GH is used to treat GH deficiency in children and adults and wasting in AIDS patients. GH has a circulating half-life of only a few hours in humans and must be administered to patients by daily injection for maximum effectiveness. Previous studies showed that longer-acting forms of GH could be created by modification of GH with multiple 5-kDa amine-reactive polyethylene glycols (PEGs). Eight of nine lysine residues and the N-terminal amino acid were modified to varying extents by amine PEGylation of GH. The amine-PEGylated GH product comprised a complex mixture of multiple PEGylated species that differed from one another in mass, in vitro bioactivity, and in vivo potency. In vitro bioactivity of GH was reduced 100- to 1000-fold by extensive amine PEGylation of the protein. Here we describe a homogeneously modified, mono-PEGylated GH protein that possesses near complete in vitro bioactivity, a long half-life, and increased potency in vivo. The mono-PEGylated GH was created by substituting cysteine for threonine-3 (T3C) of GH, followed by modification of the added cysteine residue with a single 20-kDa cysteine-reactive PEG. The PEG-T3C protein has an approximate 8-fold longer half-life than GH after sc administration to rats. Every other day or every third day administration of PEG-T3C stimulates increases in body weight and tibial epiphysis growth comparable with that produced by daily administration of GH in hypophysectomized rats. Long-acting, mono-PEGylated GH analogs such as PEG-T3C are promising candidates for future testing in humans.

Pegylation of IFN-alpha and antiviral activity

The development of pegylated interferons (PEG-IFN) has significantly improved the eradication rates in patients with chronic hepatitis C. Two forms of PEG-IFN have been developed, based on two pegylation chemistries: the 12-kDa linear PEG-IFN-alpha2b and the 40-kDa branched PEG-IFN-alpha2a. We compared the in vitro antiviral activity of linear and branched PEG-IFN using the vesicular stomatitis virus (VSV) cytopathic effect (CPE) reduction assay. The specific antiviral activity of branched PEG-IFN was 7% of that of linear PEG-IFN. A given quantity of linear and of branched PEG-IFN does not represent the same biologic activity. A bioassay could give new insights to compare the pharmacokinetic profile of linear PEG-IFN and of branched PEG-IFN.

Enhanced pharmacological activity of recombinant human interleukin-11 (rhIL11) by chemical modification with polyethylene glycol

In order to improve the pharmacological efficacy of recombinant human interleukin-11 (rhIL11) and to reduce the frequency of administration, we examined the feasibility of chemical modification of rhIL11 by polyethylene glycol. The rhIL11 was chemically modified by using branched type (PEG2), or linear type (PEG) polyethylene glycol-N-hydroxysuccinimide with various molecular weights. Plasma profiles of immunoreactive rhIL11 after i.v. injection of the 20 kDa PEG2 conjugated rhIL11 (PEG2 (20 K)-rhIL11) were determined by ELISA. Peripheral platelet counts after the administration of the various conjugates were measured. Pharmacokinetic analysis revealed that the mean residence time of PEG2 (20 K)-rhIL11 after i.v. injection extensively increased by a factor of ca 60 compared with the native rhIL11. Maximum peripheral platelet increase of 67% for PEG2 (20 K)-rhIL11 and that of 50% for PEG (20 K)-rhIL11 over the control was observed whereas no significant change was associated with the bolus i.v. injection of native rhIL11. On the other hand, the remaining biological activity of these PEGylated-rhIL11s was 14-16% of native rhIL11, suggesting that retention of rhIL11 in plasma is much effective in order to potentiate the pharmacological efficacy of the cytokine. Chemical modification of rhIL11 by PEG is a promising approach for improving the clinical efficacy of rhIL11 by prolonged retention in plasma.

Improved pharmacokinetics of recombinant bispecific antibody molecules by fusion to human serum albumin

Recombinant bispecific antibodies such as tandem scFv molecules (taFv), diabodies (Db), or single chain diabodies (scDb) have shown to be able to retarget T lymphocytes to tumor cells, leading to their destruction. However, therapeutic efficacy is hampered by a short serum half-life of these small molecules having molecule masses of 50-60 kDa. Thus, improvement of the pharmacokinetic properties of small bispecific antibody formats is required to enhance efficacy in vivo. In this study, we generated several recombinant bispecific antibody-albumin fusion proteins and analyzed these molecules for biological activity and pharmacokinetic properties. Three recombinant antibody formats were produced by fusing two different scFv molecules, bispecific scDb or taFv molecules, respectively, to human serum albumin (HSA). These constructs (scFv(2)-HSA, scDb-HSA, taFv-HSA), directed against the tumor antigen carcinoembryonic antigen (CEA) and the T cell receptor complex molecule CD3, retained full binding capacity to both antigens compared with unfused scFv, scDb, and taFv molecules. Tumor antigen-specific retargeting and activation of T cells as monitored by interleukin-2 release was observed for scDb, scDb-HSA, taFv-HSA, and to a lesser extent for scFv(2)-HSA. T cell activation could be further enhanced by a target cell-specific costimulatory signal provided by a B7-DbCEA fusion protein. Furthermore, we could demonstrate that fusion to serum albumin strongly increases circulation time of recombinant bispecific antibodies. In addition, our comparative study indicates that single chain diabody-albumin fusion proteins seem to be the most promising format for further studying cytotoxic activities in vitro and in vivo.

Preparation and characterization of a potent, long-lasting recombinant human serum albumin-interferon-alpha2b fusion protein expressed in Pichia pastoris

A long-lasting recombinant human serum albumin-interferon-alpha2b fusion protein (rHSA/IFNalpha2b) was prepared and its structure and biological activities were studied. rHSA/IFNalpha2b was expressed in methylotrophic yeast Pichia pastoris with HSA's natural signal peptide and purified by dye affinity chromatography, hydrophobic interaction chromatography, ion exchange chromatography and Sephadex G25. Purity of the prepared rHSA/IFNalpha2b was greater than 97% analyzed by non-reduced SDS-PAGE and RP-HPLC. Structure and biological activities of the prepared rHSA/IFNalpha2b were characterized by physical, chemical and biological methods. Its pI was 5.3 and showed a single band on IEF gel. Molecular weight determined by MALDI-TOF was 86004.3+/-29.2. Amino-terminal and carboxyl-terminal amino acid sequences were identical to predicted sequence. Its specific activity in vitro was 6.3+/-0.8x10(5) IU/mg fusion protein, retaining about 1.4% of that of unmodified rIFNalpha on a molar basis. After administered in monkeys, significant increases of 2',5'-oligoadenylate synthetase activity relative to IFN-alpha were maintained for 14 days in serum and the rHSA/IFNalpha2b showed more potent biological activity than IFN-alpha on a molar basis. Therefore, markedly improved in vivo biological activity of rHSA/IFNalpha2b could exhibit more potent antiviral activity than IFNalpha2b in future clinical trials.

Nanomedicines in the treatment of chronic hepatitis C--focus on pegylated interferon alpha-2a

Nanotechnology is the application of nanotechnology within medicine. An illustration of this is the use of pegylation as a means of modifying naturally occurring proteins which may have clinical applications, in order to improve the pharmacodynamics of the protein resulting in an effective medication. An example of this is pegylated interferon. The purpose of this review is to examine the chemistry, clinical pharmacology, pharmacokinetics, pharmacodynamics, and clinical studies with 40 kDa pegylated interferon to illustrate the general principles of pegylated biological proteins. The use in clinical practice is reviewed along with the evidence for both efficiacy, safety, and advantages over standard interferon.