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

Investigations on the Combination of Cationic Ring Opening Polymerization and Single Electron Transfer Living Radical Polymerization to Synthesize 2-Ethyl-2-Oxazoline Block Copolymers

Cationic ring opening polymerization of 2-ethyl-2-oxazoline (EtOx) has been performed using α–bromoisobutyryl bromide (tertiary) and 2-bromopropionyl bromide (secondary) as initiators in acetonitrile. The reaction kinetics have been followed and selected P(EtOx) polymers have been used as macroinitiators for the single electron transfer living radical polymerization (SET-LRP) of methyl acrylate (MA), ethylene glycol methyl ether acrylate and 2-(dimethylamino)ethyl methacrylate. Moreover, the effect of solvent and catalyst concentration have been investigated on the SET-LRP of P(EtOx) initiated MA.

Comparison of peginterferon pharmacokinetic and pharmacodynamic profiles

The pharmacokinetics and in dosing regimens of the currently available pegylated interferon (peginterferon) alfa molecules differ greatly, depending on the size and nature of their polyethylene glycol (PEG) moiety. Peginterferon alfa-2a has a branched 40 kDa PEG chain covalently attached to lysine residues and circulates as an intact molecule. On the other hand, peginterferon alfa-2b has a linear 12 kDa PEG chain covalently attached to interferon-a-2b via an unstable urethane bond that is hydrolysed after injection, releasing native interferon alfa-2b. The difference in pegylation between the two peginterferons has a significant impact on their pharmacokinetic properties. Data from comparative and non-comparative studies indicate that peginterferon alfa-2b has a shorter half-life in serum than peginterferon alfa-2a, and a significant proportion of patients receiving peginterferon alfa-2b may have trough concentrations below the limit of detection during the latter part of the 7-day dosing schedule. However, the pharmacodynamic parameters of the two drugs appear to be similar.

Comparative trials of peginterferon α2a and peginterferon α2b for chronic hepatitis C

Standard of care for patients with chronic hepatitis C is pegylated interferon (pegIFN) combined with ribavirin (Rbv). It results in persistent viral eradication and prevents the progression of liver disease and the associated complications in about 50% of treated patients. Currently, two PegIFNs are available that differ significantly in terms of pharmacokinetic and pharmacodynamic profiles as a consequence of different pegylation chemistries. While the registration trials of the two therapeutic regimens demonstrated the superiority of each PegIFN vs the native IFN α2b, the superiority of one regimen over the other in terms of treatment efficacy remains unknown. Retrospective cohort studies and randomized prospective head-to-head trials have attempted to resolve the considerable controversy over this issue and support evidence-based treatment decisions.

Noninvasive detection of passively targeted poly(ethylene glycol) nanocarriers in tumors

The present studies noninvasively investigate the passive tumor distribution potential of a series of poly(ethylene glycol) (PEG) nanocarriers using a SkinSkan spectrofluorometer and an In Vivo Imaging System (IVIS) 100. Fluorescein conjugated PEG nanocarriers of varying molecular weights (10, 20, 30, 40, and 60 kDa) were prepared and characterized. The nanocarriers were administered intravenously to female balb/c mice bearing subcutaneous 4T1 tumors. Passive distribution was measured in vivo (λ(exc), 480 nm; λ(em), 515-520 nm) from the tumor and a contralateral skin site (i.e., control site). The signal intensity from the tumor was always significantly higher than that from the contralateral site. Trends in results between the two methods were consistent with tumor distribution increasing in a molecular weight-dependent manner (10 < 20 < 30 ≪ 40 ≪ 60 kDa). The 10 kDa nanocarrier was not detected in tumors at 24 h, whereas 40-60 kDa nanocarriers were detected in tumors for up to 96 h. The 30, 40, and 60 kDa nanocarriers showed 2.1, 5.3, and 4.1 times higher passive distribution in tumors at 24 h, respectively, as compared to the 20 kDa nanocarrier. The 60 kDa nanocarrier exhibited 1.5 times higher tumor distribution than 40 kDa nanocarrier at 96 h. Thus, PEG nanocarriers (40 and 60 kDa) with molecular weights close to or above the renal exclusion limit, which for globular proteins is ≥45 kDa, showed significantly higher tumor distribution than those below it. The hydrodynamic radii of PEG polymers, measured using dynamic light scattering (DLS), showed that nanocarriers obtained from polymers with hydrodynamic radii ≥8 nm exhibited higher tumor distribution. Ex vivo mass balance studies revealed that nanocarrier tissue distribution followed the rank order tumor > lung > spleen > liver > kidney > muscle > heart, thus validating the in vivo studies. The results of the current studies suggest that noninvasive dermal imaging of tumors provides a reliable and rapid method for the initial screening of nanocarrier tumor distribution pharmacokinetics.

Pharmacokinetics, tissue distribution, excretion, and antiviral activity of pegylated recombinant human consensus interferon-α variant in monkeys, rats and guinea pigs

The study aims to characterize the pharmacokinetic, tissue distribution, excretion, and antiviral activity properties of a novel pegylated recombinant human consensus interferon-α variant (PEG-IFN-SA) following a single subcutaneous administration to monkeys, rats and guinea pigs. Studies included: (1) pharmacokinetic properties of PEG-IFN-SA and comparison with those of non-pegylated IFN-SA in rhesus monkeys and rats; (2) tissue distribution and urinary, fecal, and biliary excretion patterns of (125)I-PEG-IFN-SA in guinea pigs; and (3) antiviral activity assessment of PEG-IFN-SA in cynomolgus monkeys. The pegylated protein exhibited improved pharmacokinetic properties compared to IFN-SA in both monkeys and rats, with a 12-fold and 15-fold increase in elimination half-life, and a 100-fold and 10-fold decrease in serum clearance, as well as a 2.5-fold and 10-fold increase in the time to reach peak serum concentration, respectively. (125)I-PEG-IFN-SA was found to be distributed to most of the tissues examined and has character of targeting special distribution, and urinary appeared to be a major route for the excretion of PEG-IFN-SA in guinea pigs. Serum sample analysis from PEG-IFN-SA-treated monkeys showed dose-dependent antiviral activity for one week. These findings demonstrate that pegylation of IFN-SA results in more desirable pharmacokinetic properties, enhanced drug exposure and sustained-efficacy of in vivo antiviral action.

The journey of a drug-carrier in the body: an anatomo-physiological perspective

Recent advances in chemistry and material sciences have witnessed the emergence of an increasing number of novel and complex nanosized carriers for the delivery of drugs and imaging agents. Nevertheless, this raise in complexity does not necessarily offer more efficient systems. The lack of performance experienced by several colloidal drug carriers during the preclinical and clinical development processes can be explained by inadequate pharmacokinetic/biodistribution profiles and/or unacceptable toxicities. A comprehensive understanding of the body characteristics is necessary to predict and prevent these problems from the early stages of nanomaterial conception. In this manuscript, we review and discuss the anatomical and physiological elements which must be taken into account when designing new carriers for delivery or imaging purposes. This article gives a general overview of the main organs involved in the elimination of nanosized materials and briefly summarizes the knowledge acquired over more than 30 years of research and development in the field of drug targeting.

A new direction for anticoagulants: inhibiting fibrin assembly with PEGylated fibrin knob mimics

Current anticoagulants target coagulation factors upstream from fibrin assembly and polymerization (i.e., formation of fibrin clot). While effective, this approach requires constant patient monitoring since pharmacokinetics and pharmacodynamics vary from patient to patient. To address these limitations, we developed an alternative anticoagulant that effectively inhibits fibrin polymerization. Specifically, we investigated PEGylated fibrin knob "A" peptides, evaluating the effect of both polyethylene glycol (PEG) chain length (0, 2, 5, and 10-30 kDa) and knob peptide sequence (GPRPAAC, GPRPFPAC, and GPRPPERC) on inhibiting fibrin polymerization (i.e., clot formation). Thrombin-initiated clotting assays with purified fibrinogen were performed to compare clot formation with each peptide-PEG conjugate. Results indicated a biphasic effect of PEG chain length, whereby, active-PEG conjugates demonstrated increasingly enhanced inhibition of fibrin polymerization from 0 to 5 kDa PEG. However, the anticoagulant activity diminished to control levels for PEG chains above 5 kDa. Ultimately, we observed a 10-fold enhancement of anticoagulant activity with active peptides PEGylated with 5 kDa PEG compared to non-PEGylated knob peptides. The sequence of the active peptide significantly influenced the anticoagulant properties only at the highest 1:100 molar ratio where GPRPFPAC-5 kDa PEG and GPRPPERC-5 kDa PEG demonstrated significantly lower percent clottable protein than GPRPAAC-5 kDa PEG. Moreover, human plasma treated with the active 5 kDa PEG conjugate exhibited delayed prothrombin time to within the therapeutic range specified for oral anticoagulants. Collectively, this study demonstrated the utility of PEGylated fibrin knob peptides as potential anticoagulant therapeutics. Biotechnol. Bioeng. 2011;108: 2424-2433. © 2011 Wiley Periodicals, Inc.

Covalent conjugation of poly(ethylene glycol) to proteins and peptides: strategies and methods

PEGylation, the covalent linking of PEG chains, has become the leading drug delivery approach for proteins. This technique initiated its first steps almost 40 years ago, and since then, a variety of methods and strategies for protein-polymer coupling have been devised. PEGylation can give a number of relevant advantages to the conjugated protein, such as an important in vivo half-life prolongation, a reduction or an abolishment of immunogenicity, and a reduction of aggregation. Furthermore, the technique has demonstrated a great degree of versatility and efficacy--not only PEG-protein conjugates have reached the commercial marketplace (with nine types of derivatives), but a PEG-aptamer and PEGylated liposomes are now also available. Most of this success is due to the development of several PEGylation strategies and to the large selection of PEGylating agents presently at hand for researchers. Nevertheless, this technique still requires a certain level of familiarity and knowledge in order to achieve a positive outcome for a PEGylation project. To draw general guidelines for conducting PEGylation studies is not always easy or even possible because such experiments often require case-by-case optimization. On the other hand, several common methods can be used as starting examples for the development of tailor-made coupling conditions. Therefore, this chapter aims to provide a basic introduction to a wide range of PEGylation procedures for those researchers who may not be familiar with this field.

Does interferon and ribavirin combination therapy ameliorate growth hormone deficiency in HCV genotype-4 infected patients?

OBJECTIVES

To explore the impact of response to interferon and ribavirin antiviral therapy on human growth hormone (hGH) levels in Egyptian chronic hepatitis C genotype-4 infected patients.

DESIGN AND METHODS

We studied eighty Egyptian HCV infected patients visiting outpatient clinics of Tropical Medicine and Hepatology Department, El-Kasr El-Aini Hospital, Cairo University, Egypt. HCV patients received treatment of interferon and ribavirin combination therapy for 24 weeks. Clinical, virological, histological characteristics, and biochemical tests including; liver function tests (ALT and AST), prothrombin time (PT), alpha fetoprotein (AFP), complete blood picture (CBC), and hGH were monitored in hepatitis C genotype-4 infected patients before and after interferon therapy, and healthy controls.

RESULTS

Chronic HCV genotype-4 infected patients have high significant decrease of hGH as compared to healthy control individuals. In addition to, there was high significant increase of hGH in responders as compared to non-responders after treatment.

CONCLUSION

We concluded that Egyptian HCV genotype-4 infected patients have growth hormone insufficiency. Besides, we found that response to interferon/ribavirin treatment has an impact on growth hormone levels.

Design, modeling, expression, and chemoselective PEGylation of a new nanosize cysteine analog of erythropoietin

Background:

Recombinant human erythropoietin (rhEPO) is considered to be one of the most pivotal pharmaceutical drugs in the market because of its clinical application in the treatment of anemia-associated disorders worldwide. However, like other therapeutic proteins, it does not have suitable pharmacokinetic properties for it to be administrated at least two to three times per week. Chemoselective cysteine PEGylation, employing molecular dynamics and graphics in in silico studies, can be considered to overcome such a problem.

Methods:

A special kind of EPO analog was elicited based on a literature review, homology modeling, molecular dynamic simulation, and factors affecting the PEGylation reaction. Then, cDNA of the selected analog was generated by site-directed mutagenesis and subsequently cloned into the expression vector. The construct was transfected to Chinese hamster ovary/dhfr⁻ cells, and highly expressed clones were selected via methotrexate amplification. Ion-immobilized affinity and size exclusion (SE) chromatography techniques were used to purify the expressed analog. Thereafter, chemoselective PEGylation was performed and a nanosize PEGylated EPO was obtained through dialysis. The in vitro biologic assay and in vivo pharmacokinetic parameters were studied. Finally, E31C analog Fourier transform infrared, analytical SE-high-performance liquid chromatography, zeta potential, and size before and after PEGylation were characterized.

Results:

The findings indicate that a novel nanosize EPO31-PEG has a five-fold longer terminal half-life in rats with similar biologic activity compared with unmodified rhEPO in proliferation cell assay. The results also show that EPO31-PEG size and charge versus unmodified protein was increased in a nanospectrum, and this may be one criterion of EPO biologic potency enhancement.

Discussion:

This kind of novel engineered nanosize PEGylated EPO has remarkable advantages over rhEPO.

Development of a novel DDS for site-specific PEGylated proteins

Because of the shifted focus in life science research from genome analyses to genetic and protein function analyses, we now know functions of numerous proteins. These analyses, including those of newly identified proteins, are expected to contribute to the identification of proteins of therapeutic value in various diseases. Consequently, pharmacoproteomic-based drug discovery and development of protein therapies attracted a great deal of attention in recent years. Clinical applications of most of these proteins are, however, limited because of their unexpectedly low therapeutic effects, resulting from the proteolytic degradation in vivo followed by rapid removal from the circulatory system. Therefore, frequent administration of excessively high dose of a protein is required to observe its therapeutic effect in vivo. This often results in impaired homeostasis in vivo and leads to severe adverse effects. To overcome these problems, we have devised a method for chemical modification of proteins with polyethylene glycol (PEGylation) and other water-soluble polymers. In addition, we have established a method for creating functional mutant proteins (muteins) with desired properties, and developed a site-specific polymer-conjugation method to further improve their therapeutic potency. In this review, we are introducing our original protein-drug innovation system mentioned above.

Site-specific PEGylation of exenatide analogues markedly improved their glucoregulatory activity

BACKGROUND AND PURPOSE

Exenatide is a 39-amino-acid peptide widely used to manage type 2 diabetes mellitus. However, it has a short plasma half-life and requires a twice daily injection regime. To overcome these drawbacks we used maleimide-polyethylene glycol to induce site-specific PEGylation.

EXPERIMENTAL APPROACH

The analogue PB-105 (ExC39) was produced by replacing cysteine at position 39 of exenatide to provide a free thiol group. PB-105 showed the same glucoregulatory activity as exenatide in mice. Site-specific PEGylation of PB-105 was performed to produce PB-110 (ExC39PEG5kDa), PB-106 (ExC39PEG20kDa), PB-107 (ExC39PEG30kDa) and PB-108 (ExC39PEG40kDa). Their effects on intracellular cAMP, acute glucoregulatory activity and pharmacokinetic profile were compared in mice and rats.

KEY RESULTS

PEGylation shifted the concentration-response curve of PB-105 to the right in a parallel, polyethylene glycol mass-dependent manner but with an inflexion point of at least 20 kDa. The activities of PB-107 and PB-108 but not PB-106 were reduced by 90% and 99%. PEGylation affected in vivo glucoregulatory activity in the same 'Inflexion-Shift' fashion at least at 20 kDa, but linearly increased plasma duration and systemic exposure without inflexion. PB-106 had a plasma t(1/2) approximately 10-fold that of PB-105, and exhibited superior glucoregulatory activity compared with PB-105 in normal and diabetic mice.

CONCLUSIONS AND IMPLICATIONS

Site-specific PEGylation of exenatide with a permanent amide linkage affects its activity in a new type of 'Inflexion-Shift' fashion. PB-106 is a putative new analogue for treating diabetes; it possesses no loss of in vitro activity, prolonged plasma duration and superior, improved in vivo glucoregulatory activity compared with exenatide.

Longer action means better drug: tuning up protein therapeutics

An increasing number of proteins are currently available on the market as therapeutics and this branch of the pharmaceutical industry will expand substantially during the coming years. As many diseases result from dysfunction of proteins forming multicomponent complexes, protein drugs with their inherent high specificity and affinity seem to be optimal medical agents. On the other hand, proteins are often highly instable and sensitive to degradation, which questions their applicability as effective therapeutics. Therefore, redesign and engineering of proteins is usually a required step in the present day drug development. Several approaches have been applied to optimize the protein properties central to their pharmaceutical use. This review focuses on different strategies that improve two crucial factors influencing protein drug efficiency: protein stability and its in vivo half-life. We provide examples of successful genetic and chemical modifications applied in the design of effective protein therapeutics.

PEGylated interferon beta-1a: meeting an unmet medical need in the treatment of relapsing multiple sclerosis

Multiple sclerosis is a chronic autoimmune disease of the central nervous system for which a number of disease-modifying therapies are available, including interferon beta (Avonex®, Rebif®, and Betaseron/Betaferon®), glatiramer acetate (Copaxone®), and an anti-VLA4 monoclonal antibody (Tysabri®). Despite the availability and efficacy of these protein and peptide drugs, there remains a significant number of patients who are untreated, including those with relatively mild disease who choose not to initiate therapy, those wary of injections or potential adverse events associated with therapy, and those who have stopped therapy due to perceived lack of efficacy. Since these drugs have side effects that may affect a patient's decision to initiate and to remain on treatment, there is a need to provide a therapy that is safe and efficacious but that requires a reduced dosing frequency and hence a concomitant reduction in the frequency of side effects. Here we describe the development of a PEGylated form of interferon beta-1a that is currently being tested in a multicenter, randomized, double-blind, parallel-group, placebo-controlled study in relapsing multiple sclerosis patients, with the aim of determining the safety and efficacy of 125 microg administered via the subcutaneous route every 2 or 4 weeks.

HBV life cycle and novel drug targets

With up to 400 million affected people worldwide, chronic hepatitis B virus (HBV) infection is still a major health care problem. During the last decade, several novel therapeutic approaches have been developed and evaluated. In most regions of the world, interferon-α, and nucleos(t)ide analogues (NUCs) are currently approved. Despite major improvements, none of the existing therapies is optimal since viral clearance is rarely achieved. Recently, a better understanding of the HBV life cycle and the development of novel model systems of HBV infection have led to the development of novel antiviral strategies and drug targets. This review will focus on current and potential future drug targets in the HBV life cycle and strategies to modulate the virus-host interaction.

Sortase-catalyzed transformations that improve the properties of cytokines

Recombinant protein therapeutics often suffer from short circulating half-life and poor stability, necessitating multiple injections and resulting in limited shelf-life. Conjugation to polyethylene glycol chains (PEG) extends the circulatory half-life of many proteins, but the methods for attachment often lack specificity, resulting in loss of biological activity. Using four-helix bundle cytokines as an example, we present a general platform that uses sortase-mediated transpeptidation to facilitate site-specific attachment of PEG to extend cytokine half-life with full retention of biological activity. Covalently joining the N and C termini of proteins to obtain circular polypeptides, again executed using sortase, increases thermal stability. We combined both PEGylation and circularization by exploiting two distinct sortase enzymes and the use of a molecular suture that allows both site-specific PEGylation and covalent closure. The method developed is general, uses a set of easily accessible reagents, and should be applicable to a wide variety of proteins, provided that their termini are not involved in receptor binding or function.

Biodegradable nanogels for oral delivery of interferon for norovirus infection

Norwalk virus (NV) replicon-harboring cells have provided an excellent tool to the development of antivirals. Previously we demonstrated that the expression levels of replicon RNA and proteins were significantly reduced in the presence of various interferons (IFNs) including IFN-α and IFN-γ in a dose-dependent manner in the NV replicon-harboring cells, and suggested that IFNs could be therapeutic options for norovirus infection. It was also demonstrated that innate immunity including IFNs is crucial in the replication and pathogenicity of murine norovirus (MNV) in vitro (RAW267.4 cells) and in vivo. IFNs have a short half-life in vitro and in vivo due to low stability. Thus it is important to have a good delivery system to improve the stability of IFNs. Nanogels are nanosized networks of chemically cross-linked polymers that swell in physiologic solutions and provide improved stability and bioavailability to drugs. We have synthesized nanogels based on cross-linked polyethyleneimine (PEI)-polyethylenglycol (PEG). The PEI/PEG nanogels were further acetylated (AcNg) to reduce cellular penetration and cytotoxicity. The IFN-AcNg complex was prepared by incubating two components together at 4 °C and lyophilization. The IFN activity of IFN-AcNg was evaluated in the NV- and HCV-replicon-harboring cells and against MNV-1 in RAW267.4 cells in comparison to IFN without AcNg. The AcNg improved the stability of IFN stored at 4 °C, and was well tolerated in the cells. Furthermore, the activity of IFN was significantly higher when combined with AcNg in the replicon-harboring cells and against MNV-1 in RAW267.4 cells. We concluded that AcNg may be pursued further as a vehicle for oral delivery of IFNs in norovirus infection.

Pegylated human interferon alpha 2a does not induce depression-associated changes in mice

Interferon (IFN) alpha proteins are proinflammatory cytokines having immunomodulating and antiviral properties. States during which cytokine systems are activated (e.g., during viral infection or during treatment of chronic hepatitis C and various malignancies with IFN alpha, etc.) can be associated with depression-like syndromes or even full-blown depressive episodes. Therefore, the role of IFN alpha and other cytokines in the pathogenesis of depressive disorder ("cytokine hypothesis of depression") has been assessed for many years with contradictory results. We have investigated whether intraperitoneal administration of high doses (up to 600 µg/kg body weight) of pegylated, recombinant human IFN alpha 2a in mice induces changes known to be associated with depression using three different readouts: behavior in a model of despair (Porsolt swim test), presence of anhedonia (sucrose preference test), and sensitivity of the hypothalamic-pituitary-adrenal system (dexamethasone suppression test). We also assessed potential IFN-induced changes in gene expression in the liver. In none of the performed experiments, depression-associated effects could be found despite very high serum levels of IFN-induced antiviral activity compared to levels measured in hepatitis C virus (HCV) patients treated routinely with pegylated recombinant human IFN alpha 2a. The lack of such expected effects is probably due to the fact that pegylated human recombinant IFN alpha 2a does not activate the murine class I IFN receptor. Our results do not support the hypothesis that administration of recombinant pegylated human IFN alpha to mice produces a robust model of depression.

Peginterferon and ribavirin treatment for hepatitis C virus infection

Pegylated interferon α (IFNα) in combination with ribavirin is currently recommended as a standard-of-care treatment for chronic hepatitis C virus (HCV) infection. This combination therapy has drastically improved the rate of sustained virological response, specifically in difficult-to-treat patients. Recently, individualized treatment, such as response-guided therapy, is being developed based on host-, HCV- and treatment-related factors. Furthermore, modified regimens with currently available medications, novel modified IFNα and ribavirin or combinations with specifically targeted antiviral therapy for HCV agents, are currently being investigated. The purpose of this review is to address some issues and epoch-making topics in the treatment of chronic HCV infection, and to discuss more optimal and highly individualized therapeutic strategies for HCV-infected patients.

A multiple-dose pharmacokinetics of polyethylene glycol recombinant human interleukin-6 (PEG-rhIL-6) in rats

Radiation therapy has been widely applied in cancer treatment. However, it often causes thrombocytopenia (deficiency of white blood cells) as an adverse effect. Recombinant human interleukin-6 (rhIL-6) has been found to be a very effective way against this thrombocytopenia, but IL-6 has low stability in blood, which reduces its efficacy. To increases the stability and half-life of rhIL-6, it was modified by polyethylene glycol (PEG). The pharmacokinetics and the tissue distribution of PEG-rhIL-6 labeled with (125)I were examined after subcutaneous injection in rats. The pharmacokinetic pattern of PEG-rhIL-6 was defined with linear-kinetics, and we fitted a one-compartment model with half-lives of 10.44-11.37 h (absorption, t(1/2Ka)) and 19.77-21.53 h (elimination, t(1/2Ke)), and peak concentrations at 20.51-21.96 h (t(peak)) in rats. Half-lives and t(peak) of PEG-rhIL-6 were longer than those of rhIL-6 previously reported. In the present study, for deposition of PEG-rhIL-6 in rats, the tissue distribution examination showed that blood was the major organ involved, rather than liver. However, as to the elimination of PEG-rhIL-6, the major organ was the kidney. The excretion fraction of the injection dose recovered from urine was 23.32% at 192 h after subcutaneous administration. Less than 6% of PEG-rhIL-6 was eliminated via the feces at 192 h. These results indicate that PEG-rhIL-6 is a good candidate drug formulation for patients with cancer.

Genetic variation in BCL-2 and response to interferon in hepatitis C virus type 4 patients

The prevalence of hepatitis C virus (HCV) infection varies across the world, with the highest number of infections reported in Egypt. BCL-2 gene polymorphism at codon 43 (127G/A) has been found to be a reliable and sensitive marker for the prediction of response to interferon therapy during viral infections. This study examined the correlation of BCL-2 gene polymorphism with the response to treatment with pegylated-IFN-alfa2b and ribavirin. Eighty patients with type 4 HCV and 40 healthy volunteers as controls were enrolled in a prospective study. Quantification of HCV-RNA by real-time PCR was performed for every patient, and gene polymorphism of BCL-2 (ala 43 Thr) was performed for all patients and controls. There was a statistically significant difference between non-responder patients and control group as regards the 43 Thr genotype and allele (P<0.05). Also, there was a statistically significant difference between responders and non-responders (P<0.05) as regards 43 Thr genotype and alleles. We conclude that BCL-2 gene polymorphism at codon 43 (127G/A) is a new biological marker to potentially identify responders and non-responders of HCV genotype 4 patients to achieving a sustained virological response to treatment with IFN in combination with ribavirin.

Purification of singly PEGylated α-lactalbumin using charged ultrafiltration membranes

One of the challenges in producing a PEGylated therapeutic protein is that the PEGylation reaction typically generates a mixture of both singly and multiply PEGylated species. The objective of this study was to examine the feasibility of using ultrafiltration for the purification of a singly PEGylated protein from the multiply PEGylated conjugates. Data were obtained with α-lactalbumin that was PEGylated with a 20 kDa activated PEG, with the ultrafiltration performed over a range of pH and ionic strength using both unmodified and negatively charged composite regenerated cellulose membranes. Purification of the singly PEGylated α-lactalbumin from the multiply PEGylated species was accomplished using a diafiltration process with a negatively charged membrane at pH 5 and an ionic strength of 0.4 mM, conditions that maximized the electrostatic exclusion of the multiply PEGylated species from the charged membrane. The diafiltration process provided more than 97% yield with greater than 20-fold purification between the singly and doubly PEGylated proteins and nearly complete removal of the more heavily PEGylated species. The singly PEGylated α-lactalbumin was recovered as a dilute filtrate solution, although this dilution could be eliminated using a cascade filtration or the final product could be re-concentrated in a second ultrafiltration as part of the final formulation. These results demonstrate the feasibility of using ultrafiltration for the purification of singly PEGylated protein therapeutics.

PK/PD modelling of comb-shaped PEGylated salmon calcitonin conjugates of differing molecular weights

Salmon calcitonin (sCT) was conjugated via cysteine-1 to novel comb-shaped end-functionalised (poly(PEG) methyl ether methacrylate) (sCT-P) polymers, to yield conjugates of total molecular weights (MW) inclusive of sCT: 6.5, 9.5, 23 and 40kDa. The conjugates were characterised by HPLC and their in vitro and in vivo bioactivity was measured by cAMP assay on human T47D cells and following intravenous (i.v.) injection to rats, respectively. Stability against endopeptidases, rat serum and liver homogenates was assessed. There were linear and exponential relationships between conjugate MW with potency and efficacy respectively, however the largest MW conjugate still retained 70% of E(max) and an EC(50) of 3.7nM. In vivo, while free sCT and the conjugates reduced serum [calcium] to a maximum of 15-30% over 240 min, the half-life (T(1/2)) was increased and the area under the curve (AUC) was extended in proportion to conjugate MW. Likewise, the polymer conferred protection on sCT against attack by trypsin, chymotrypsin, elastase, rat serum and liver homogenates, with the best protection afforded by sCT-P (40kDa). Mathematical modelling accurately predicted the MW relationships to in vitro efficacy, potency, in vivo PK and enzymatic stability. With a significant increase in T(1/2) for sCT, the 40kDa MW comb-shaped PEG conjugate of sCT may have potential as a long-acting injectable formulation.

Human growth hormone expressed in tobacco cells as an arabinogalactan-protein fusion glycoprotein has a prolonged serum life

Therapeutic proteins with molecular weights lower than 40 kDa often have short serum half-lives due to their susceptibility to serum proteases and rapid renal clearance. Chemical derivatization, such as PEGylation, or expression as serum albumin fusions increases molecular mass and overcome these problems but at the expense of decreased bioactivity. Here we applied a new method that yields biologically potent recombinant human growth hormone (rhGH) with increased serum half-life when expressed as an arabinogalactan-protein (AGP) in tobacco BY-2 cells. Thus, rhGH was expressed with 10 repeats of the AGP glycomodule Ser-Hyp (SO) at the C-terminus (rhGH-(SO)(10)). We also expressed rhGH as an AGP-enhanced green fluorescent protein (EGFP) fusion, designated rhGH-(SO)(10)-EGFP, to assess the cellular distribution of the glycoprotein, which was mainly extracellular. Recombinant hGH-(SO)(10) bound the hGH receptor with an affinity similar to that of a rhGH standard, stimulated the same intracellular signaling pathway as hGH, but possessed an in vivo serum half-life more than sixfold that of the hGH control. Furthermore, rhGH-(SO)(10) gave a 500 fold greater secreted yield than the non-glycosylated control rhGH that was also targeted for secretion. Detailed analysis of the rhGH-(SO)(10) glycans indicated a conserved structure with relatively little microheterogeneity and an average size of 25 monosaccharide residues. These results were consistent with earlier work expressing interferon alpha 2b as an AGP chimera and further demonstrate the feasibility of this approach to the production of long-acting, biologically potent therapeutic proteins by plant cells.

Pharmacokinetics and pharmacodynamics of peginterferon and ribavirin: implications for clinical efficacy in the treatment of chronic hepatitis C

The pharmacokinetics and pharmacodynamics of standard interferon alfa-2a and interferon alfa-2b are substantially altered by pegylation. The size, geometry, and site of attachment of the PEG moiety affect the pharmacokinetics and pharmacodynamics as evidenced by the different absorption, volume of distribution, and clearance of the linear 12-kDa peginterferon alfa-2b and the branched 40-kDa peginterferon alfa-2a. Despite these differences, the clinical efficacy, safety, and tolerability of the 2 peginterferons are similar. However, evidence exists that peginterferon alfa-2 plus ribavirin is associated with small but significantly higher sustained virological response rates compared with peginterferon alfa-2b. This article discusses the pharmacokinetics and pharmacodynamics of the 2 peginterferons and their combination with ribavirin.

Pegylated interferons alpha2a and alpha2b in the treatment of chronic hepatitis C

Chronic infection with HCV has an estimated prevalence of 1.6-2.0% worldwide and is a major cause of liver-related death. The first attempts to halt the progression of infection relied on the empirical use of interferon (IFN), a naturally occurring cytokine that is implicated in antiviral innate immunity. The first studies of this treatment in the early 1990s, however, led to disappointing response rates. These response rates subsequently improved with the empirical addition of the guanosine analog ribavirin to the treatment regimen. To improve the effectiveness and tolerability of the three times per week therapeutic schedule of IFN, two forms of pegylated interferon (PEG-IFN) were developed in the early 2000s-PEG-IFN-alpha2a and PEG-IFN-alpha2b. These two compounds differ markedly in size, structure, site of attachment of the polyethylene glycol moiety and type of bond involved in pegylation, which ultimately confer different pharmacokinetics and biological activity. Unsurprisingly, researchers question whether the two PEG-IFNs also differ in clinical effectiveness, but the re-analysis of restrospective studies and the results of three head-to-head studies have left this issue open. We have, therefore, scrutinized the design and conduct of all available studies to unravel the reasons behind the therapeutic differences between PEG-IFN-alpha2a and PEG-IFN-alpha2b.

Pegylated interferon alpha-associated optic neuropathy

A 52-year-old man with chronic hepatitis C presented with painless, bilateral, simultaneous nonarteritic anterior ischemic optic neuropathy (NAION) and peripheral neuropathy. Symptoms began 19 weeks after starting peginterferon alpha-2a. The peripheral neuropathy and vision of the right eye improved, but the vision of the left eye worsened after stopping interferon. We identified 23 additional cases of NAION during interferon alpha therapy. At least 12 of these patients suffered bilateral NAION. Patients lost vision 1-40 weeks after initiating therapy. Of 21 eyes that had documented initial and follow-up acuities, 8 improved, 1 worsened, and the rest remained stable. One patient had a painful peripheral neuropathy. Treatment with interferon alpha may result in NAION. Discontinuation of therapy deserves consideration after weighing individual risks and benefits.