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

[Supramolecular Pharmaceutical Sciences: A Novel Concept for Future Pharmaceutical Sciences]

Supramolecular chemistry is a useful and important domain for understanding pharmaceutical sciences, since various physiological reactions (e.g., protein association) and drug activities (e.g., the substrate/receptor reaction) are based on supramolecular chemistry. Biological components, such as DNA and cells, are also supermolecules. However, supramolecular chemistry to date has not been a major domain in the field of pharmaceutical study. In this article, we propose a new concept in pharmaceutical sciences termed "supramolecular pharmaceutical sciences" which combines pharmaceutical sciences and supramolecular chemistry. "Supramolecular pharmaceutical sciences" could encompass strictly controlled molecular arrangement, stimulus responsible molecular motion, new functions beyond those of existing molecules, more accurate drug design, new active pharmaceutical ingredients, new perspectives for the investigation of the drug mechanisms, and novel pharmaceutical technologies. Moreover, pharmaceutical sciences are useful for supramolecular chemistry, because biological reactions are very accurate reactions, making this a win-win relationship. Thus, supramolecular pharmaceutical sciences could be useful for developing new methods, hypotheses, ideas, materials, mechanisms, and strategies in the realm of pharmaceutical science.

Measuring the Impact of PEGylation on a Protein-Polysaccharide Interaction

PEGylation is the most widely used half-life extension strategy for protein therapeutics. While it imparts a range of attractive attributes PEGylation can impede protein binding and reduce efficacy. A model system to probe the effects of PEGylation on protein binding has practical applications. Here, we present a system based on complex formation between a hexavalent lectin (RSL) and the globular polysaccharide Ficoll PM70 (a type of glycocluster). Mutants of the lectin were used to generate conjugates with 3, 6, or 12 PEG (1 kDa) chains. Using NMR spectroscopy we monitored how the degree of PEGylation impacted the lectin-Ficoll interaction. The binding propensity was observed to decrease with increasing polymer density. Apparently, the extended PEG chains sterically impede the lectin-Ficoll binding. This deduction was supported by molecular dynamics simulations of the protein-polymer conjugates. The implications for protein-surface interactions are discussed.

Site-selective protein conjugation at histidine

Site-selective conjugation generally requires both (i) molecular engineering of the protein of interest to introduce a conjugation site at a defined location and (ii) a site-specific conjugation technology. Three N-terminal interferon α2-a (IFN) variants with truncated histidine tags were prepared and conjugation was examined using a bis-alkylation reagent, PEG(10kDa)-mono-sulfone 3. A histidine tag comprised of two histidines separated by a glycine (His2-tag) underwent PEGylation. Two more IFN variants were then prepared with the His2-tag engineered at different locations in IFN. Another IFN variant was prepared with the His-tag introduced in an α-helix, and required three contiguous histidines to ensure that two histidine residues in the correct conformation would be available for conjugation. Since histidine is a natural amino acid, routine methods of site-directed mutagenesis were used to generate the IFN variants from E. coli in soluble form at titres comparable to native IFN. PEGylation conversions ranged from 28-39%. A single step purification process gave essentially the pure PEG-IFN variant (>97% by RP-HPLC) in high recovery with isolated yields ranging from 21-33%. The level of retained bioactivity was strongly dependent on the site of PEG conjugation. The highest biological activity of 74% was retained for the PEG10-106(HGHG)-IFN variant which is unprecedented for a PEGylated IFN. The His2-tag at 106(HGHG)-IFN is engineered at the flexible loop most distant from IFN interaction with its dimeric receptor. The biological activity for the PEG10-5(HGH)-IFN variant was determined to be 17% which is comparable to other PEGylated IFN conjugates achieved at or near the N-terminus that have been previously described. The lowest retained activity (10%) was reported for PEG10-120(HHH)-IFN which was prepared as a negative control targeting a IFN site thought to be involved in receptor binding. The presence of two histidines as a His2-tag to generate a site-selective target for bis-alkylating PEGylation is a feasible approach for achieving site-selective PEGylation. The use of a His2-tag to strategically engineer a conjugation site in a protein location can result in maximising the retention of the biological activity following protein modification.

Bioconjugation in Drug Delivery: Practical Perspectives and Future Perceptions

For the past three decades, pharmaceutical research has been mainly converging to novel carrier systems and nanoparticulate colloidal technologies for drug delivery, such as nanoparticles, nanospheres, vesicular systems, liposomes, or nanocapsules to impart novel functions and targeting abilities. Such technologies opened the gate towards more sophisticated and effective multi-acting platform(s) which can offer site-targeting, imaging, and treatment using a single multifunctional system. Unfortunately, such technologies faced major intrinsic hurdles including high cost, low stability profile, short shelf-life, and poor reproducibility across and within production batches leading to harsh bench-to-bedside transformation.Currently, pharmaceutical industry along with academic research is investing heavily in bioconjugate structures as an appealing and advantageous alternative to nanoparticulate delivery systems with all its flexible benefits when it comes to custom design and tailor grafting along with avoiding most of its shortcomings. Bioconjugation is a ubiquitous technique that finds a multitude of applications in different branches of life sciences, including drug and gene delivery applications, biological assays, imaging, and biosensing.Bioconjugation is simple, easy, and generally a one-step drug (active pharmaceutical ingredient) conjugation, using various smart biocompatible, bioreducible, or biodegradable linkers, to targeting agents, PEG layer, or another drug. In this chapter, the different types of bioconjugates, the techniques used throughout the course of their synthesis and characterization, as well as the well-established synthetic approaches used for their formulation are presented. In addition, some exemplary representatives are outlined with greater emphasis on the practical tips and tricks of the most prominent techniques such as click chemistry, carbodiimide coupling, and avidin-biotin system.

Pharmacological interventions for acute hepatitis C infection

BACKGROUND

Hepatitis C virus (HCV) is a single-stranded RNA (ribonucleic acid) virus that has the potential to cause inflammation of the liver. The traditional definition of acute HCV infection is the first six months following infection with the virus. Another commonly used definition of acute HCV infection is the absence of HCV antibody and subsequent seroconversion (presence of HCV antibody in a person who was previously negative for HCV antibody). Approximately 40% to 95% of people with acute HCV infection develop chronic HCV infection, that is, have persistent HCV RNA in their blood. In 2010, an estimated 160 million people worldwide (2% to 3% of the world's population) had chronic HCV infection. The optimal pharmacological treatment of acute HCV remains controversial. Chronic HCV infection can damage the liver.

OBJECTIVES

To assess the comparative benefits and harms of different pharmacological interventions in the treatment of acute HCV infection through a network meta-analysis and to generate rankings of the available pharmacological treatments according to their safety and efficacy. However, it was not possible to assess whether the potential effect modifiers were similar across different comparisons. Therefore, we did not perform the network meta-analysis and instead we assessed the comparative benefits and harms of different interventions versus each other or versus no intervention using standard Cochrane methodology.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Science Citation Index Expanded, World Health Organization International Clinical Trials Registry Platform, and randomised controlled trials registers to April 2016 to identify randomised clinical trials on pharmacological interventions for acute HCV infection.

SELECTION CRITERIA

We included only randomised clinical trials (irrespective of language, blinding, or publication status) in participants with acute HCV infection. We excluded trials which included previously liver transplanted participants and those with other coexisting viral diseases. We considered any of the various pharmacological interventions compared with placebo or each other.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We calculated the odds ratio (OR) and rate ratio with 95% confidence intervals (CI) using both fixed-effect and random-effects models based on the available-participant analysis with Review Manager 5. We assessed risk of bias according to Cochrane, controlled risk of random errors with Trial Sequential Analysis, and assessed the quality of the evidence using GRADE.

MAIN RESULTS

We identified 10 randomised clinical trials with 488 randomised participants that met our inclusion criteria. All the trials were at high risk of bias in one or more domains. Overall, the evidence for all the outcomes was very low quality evidence. Nine trials (467 participants) provided information for one or more outcomes. Three trials (99 participants) compared interferon-alpha versus no intervention. Three trials (90 participants) compared interferon-beta versus no intervention. One trial (21 participants) compared pegylated interferon-alpha versus no intervention, but it did not provide any data for analysis. One trial (41 participants) compared MTH-68/B vaccine versus no intervention. Two trials (237 participants) compared pegylated interferon-alpha versus pegylated interferon-alpha plus ribavirin. None of the trials compared direct-acting antivirals versus placebo or other interventions. The mean or median follow-up period in the trials ranged from six to 36 months.There was no short-term mortality (less than one year) in any group in any trial except for one trial where one participant died in the pegylated interferon-alpha plus ribavirin group (1/95: 1.1%). In the trials that reported follow-up beyond one year, there were no further deaths. The number of serious adverse events was higher with pegylated interferon-alpha plus ribavirin than with pegylated interferon-alpha (rate ratio 2.74, 95% CI 1.40 to 5.33; participants = 237; trials = 2; I2 = 0%). The proportion of people with any adverse events was higher with interferon-alpha and interferon-beta compared with no intervention (OR 203.00, 95% CI 9.01 to 4574.81; participants = 33; trials = 1 and OR 27.88, 95% CI 1.48 to 526.12; participants = 40; trials = 1). None of the trials reported health-related quality of life, liver transplantation, decompensated liver disease, cirrhosis, or hepatocellular carcinoma. The proportion of people with chronic HCV infection as indicated by the lack of sustained virological response was lower in the interferon-alpha group versus no intervention (OR 0.27, 95% CI 0.09 to 0.76; participants = 99; trials = 3; I2 = 0%). The differences between the groups were imprecise or not estimable (because neither group had any events) for all the remaining comparisons.Four of the 10 trials (40%) received financial or other assistance from pharmaceutical companies who would benefit from the findings of the research; the source of funding was not available in five trials (50%), and one trial (10%) was funded by a hospital.

AUTHORS' CONCLUSIONS

Very low quality evidence suggests that interferon-alpha may decrease the incidence of chronic HCV infection as measured by sustained virological response. However, the clinical impact such as improvement in health-related quality of life, reduction in cirrhosis, decompensated liver disease, and liver transplantation has not been reported. It is also not clear whether this finding is applicable in the current clinical setting dominated by the use of pegylated interferons and direct-acting antivirals, although we found no evidence to support that pegylated interferons or ribavirin or both are effective in people with acute HCV infection. We could find no randomised trials comparing direct-acting antivirals with placebo or other interventions for acute HCV infection. There is significant uncertainty in the benefits and harms of the interventions, and high-quality randomised clinical trials are required.

A Highly Bioactive Lys-Deficient IFN Leads to a Site-Specific Di-PEGylated IFN with Equivalent Bioactivity to That of Unmodified IFN-α2b

Although conjugation with polyethylene glycol (PEGylation) improves the pharmacokinetics of therapeutic proteins, it drastically decreases their bioactivity. Site-specific PEGylation counters the reduction in bioactivity, but developing PEGylated proteins with equivalent bioactivity to that of their unmodified counterparts remains challenging. This study aimed to generate PEGylated proteins with equivalent bioactivity to that of unmodified counterparts. Using interferon (IFN) as a model protein, a highly bioactive Lys-deficient protein variant generated using our unique directed evolution methods enables the design of a site-specific di-PEGylated protein. Antiviral activity of our di-PEGylated IFN was similar to that of unmodified IFN-α2b. The di-PEGylated IFN exhibited 3.0-fold greater antiviral activity than that of a commercial PEGylated IFN. Moreover, our di-PEGylated IFN showed higher in vitro and in vivo stability than those of unmodified IFN-α2b. Hence, we propose that highly bioactive Lys-deficient proteins solve the limitation of conventional PEGylation with respect to the reduction in bioactivity of PEGylated proteins.

Expedient synthesis of trifunctional oligoethyleneglycol-amine linkers and their use in the preparation of PEG-based branched platforms

We designed a convergent synthesis pathway that provides access to trifunctional oligoethyleneglycol-amine (OEG-amine) linkers. By applying the reductive coupling of a primary azide to bifunctional OEG-azide precursors, the corresponding symmetrical dialkylamine bearing two homo-functional end chain groups and a central nitrogen was obtained. These building blocks bear minimal structural perturbation compared to the native OEG backbone which makes them attractive for biomedical applications. The NMR investigations of the mechanism process reveal the formation of nitrile and imine intermediates which can react with the reduced free amine form. Additionally, these trifunctional OEG-amine linkers were employed in a coupling reaction to afford branched multifunctional PEG dendrons which are molecularly defined. These discrete PEG-based dendrons (n = 16, 18 and 36) could be useful for numerous applications where multivalency is required.

Pharmacokinetic and Pharmacodynamic Evaluation of Different PEGylated Human Interleukin-11 Preparations in Animal Models

Treating thrombocytopenia induced by chemotherapy remains an unmet-medical need. The use of recombinant human interleukin-11 (rhIL-11) requires repeated injections and induces significant fluid retention in some patients. Modification of human interleukin-11 with chemically inert polyethylene glycol polymer (PEG) may extend the peripheral circulation half-life leading to an improved pharmacokinetic and pharmadynamic profile. In this study, a number of rhIL-11 PEG conjugates were created to determine the optimal approach to prolong circulating half-life with the most robust pharmacological effect. The lead candidate was found to be a single 40-kDa Y-shaped PEG linked to the N-terminus, which produced a long-lasting circulating half-life, enhanced efficacy and alleviated side effect of dilutional anemia in healthy rat models. This candidate was also shown to be effective in myelosuppressive rats in preventing the occurrence of severe thrombocytopenia while ameliorating dilutional anemia, compared to rats receiving daily administration of unmodified rhIL-11 at the same dose. These data indicated that a single injection of the selected modified rhIL-11 for each cycle of chemotherapy regimen is potentially feasible. This approach may also be useful in treating patients of acute radiation syndrome when frequent administration is not feasible in a widespread event of a major radiation exposure.

Polymeric therapeutic delivery systems for the treatment of infectious diseases

Infectious diseases caused by germs, parasites, fungi, virus and bacteria are one of the leading causes of death worldwide. Polymeric therapeutics are nanomedicines that offer several advantages making them useful for the treatment of infectious diseases such as targeted drug release mechanism, ability to maintain the drug concentration within a therapeutic window for a desired duration, biocompatibility with low immunogenicity and reduced drug toxicity resulting in enhanced therapeutic efficacy of the incorporated drug. Although polymeric therapeutics have been evaluated for the treatment of infectious diseases in vitro and in vivo with improved therapeutic efficacy, most treatments for infectious disease have not been evaluated using polymeric therapeutics. This review will focus on the applications of polymeric therapeutics for the treatment of infectious diseases (preclinical studies and clinical trials), with particular focus on parasitic and viral infections.

Biodistribution, Clearance, and Long-Term Fate of Clinically Relevant Nanomaterials

Realization of the immense potential of nanomaterials for biomedical applications will require a thorough understanding of how they interact with cells, tissues, and organs. There is evidence that, depending on their physicochemical properties and subsequent interactions, nanomaterials are indeed taken up by cells. However, the subsequent release and/or intracellular degradation of the materials, transfer to other cells, and/or translocation across tissue barriers are still poorly understood. The involvement of these cellular clearance mechanisms strongly influences the long-term fate of used nanomaterials, especially if one also considers repeated exposure. Several nanomaterials, such as liposomes and iron oxide, gold, or silica nanoparticles, are already approved by the American Food and Drug Administration for clinical trials; however, there is still a huge gap of knowledge concerning their fate in the body. Herein, clinically relevant nanomaterials, their possible modes of exposure, as well as the biological barriers they must overcome to be effective are reviewed. Furthermore, the biodistribution and kinetics of nanomaterials and their modes of clearance are discussed, knowledge of the long-term fates of a selection of nanomaterials is summarized, and the critical points that must be considered for future research are addressed.

Characterization of the PEGylated Functional Upstream Domain Peptide (PEG-FUD): a Potent Fibronectin Assembly Inhibitor with Potential as an Anti-Fibrotic Therapeutic

PURPOSE

To develop PEGylated variants of pUR4/FUD (FUD), a fibronectin assembly inhibitor, using 10 kDa, 20 kDa, and 40 kDa PEGs to evaluate their binding affinity and inhibitory potency.

METHODS

The FUD peptide was recombinantly expressed, purified, and PEGylated at the N-terminus using 10 kDa, 20 kDa, and 40 kDa methoxy-PEG aldehyde. The PEGylates were purified and fractionated using ion-exchange chromatography. The molecular weight and degree of PEGylation of each conjugate was verified using MALDI-TOF. The binding affinity of each PEG-FUD conjugate was studied using isothermal titration colorimetry (ITC) and their inhibitory potency was characterized by a cell-based matrix assembly in vitro assay.

RESULTS

The 10 kDa, 20 kDa, and 40 kDa PEG-FUD conjugates were synthesized and isolated in good purity as determined by HPLC analysis. Their molecular weight was consistent with attachment of a single PEG molecule to one FUD peptide. The binding affinity (Kd) and the fibronectin fibrillogenesis inhibitory potency (IC50) of all PEG-FUD conjugates remained nanomolar and unaffected by the addition of PEG.

CONCLUSIONS

Retention of FUD fibronectin binding activity following PEGylation with three different PEG sizes suggest that PEG-FUD holds promise as an effective anti-fibrotic with therapeutic potential and a candidate for further pharmacokinetic and biodistribution studies.

Synthesis and Assembly of Laccase-Polymer Giant Amphiphiles by Self-Catalyzed CuAAC Click Chemistry

Covalent coupling of hydrophobic polymers to the exterior of hydrophilic proteins would mediate unique macroscopic assembly of bioconjugates to generate amphiphilic superstructures as novel nanoreactors or biocompatible drug delivery systems. The main objective of this study was to develop a novel strategy for the synthesis of protein-polymer giant amphiphiles by the combination of copper-mediated living radical polymerization and azide-alkyne cycloaddition reaction (CuAAC). Azide-functionalized succinimidyl ester was first synthesized for the facile introduction of azide groups to proteins such as albumin from bovine serum (BSA) and laccase from Trametes versicolor. Alkyne-terminal polymers with varied hydrophobicity were synthesized by using commercial copper wire as the activators from a trimethylsilyl protected alkyne-functionalized initiator in DMSO under ambient temperature. The conjugation of alkyne-functionalized polymers to the azide-functionalized laccase could be conducted even without additional copper catalyst, which indicated a successful self-catalyzed CuAAC reaction. The synthesized amphiphiles were found to aggregate into spherical nanoparticles in water and showed strong relevance to the hydrophobicity of coupled polymers. The giant amphiphiles showed decreased enzyme activity yet better stability during storage after chemical modification and self-assembly. These findings will deepen our understanding on protein folding, macroscopic self-assembly, and support potential applications in bionanoreactor, enzyme immobilization, and water purification.

The Locational Impact of Site-Specific PEGylation: Streamlined Screening with Cell-Free Protein Expression and Coarse-Grain Simulation

Although polyethylene glycol (PEG) is commonly used to improve protein stability and therapeutic efficacy, the optimal location for attaching PEG onto proteins is not well understood. Here, we present a cell-free protein synthesis-based screening platform that facilitates site-specific PEGylation and efficient evaluation of PEG attachment efficiency, thermal stability, and activity for different variants of PEGylated T4 lysozyme, including a di-PEGylated variant. We also report developing a computationally efficient coarse-grain simulation model as a potential tool to narrow experimental screening candidates. We use this simulation method as a novel tool to evaluate the locational impact of PEGylation. Using this screen, we also evaluated the predictive impact of PEGylation site solvent accessibility, conjugation site structure, PEG size, and double PEGylation. Our findings indicate that PEGylation efficiency, protein stability, and protein activity varied considerably with PEGylation site, variations that were not well predicted by common PEGylation guidelines. Overall our results suggest current guidelines are insufficiently predictive, highlighting the need for experimental and simulation screening systems such as the one presented here.

Bioorthogonal strategies for site-directed decoration of biomaterials with therapeutic proteins

Emerging strategies targeting site-specific protein modifications allow for unprecedented selectivity, fast kinetics and mild reaction conditions with high yield. These advances open exciting novel possibilities for the effective bioorthogonal decoration of biomaterials with therapeutic proteins. Site-specificity is particularly important to the therapeutics' end and translated by targeting specific functional groups or introducing new functional groups into the therapeutic at predefined positions. Biomimetic strategies are designed for modification of therapeutics emulating enzymatic strategies found in Nature. These strategies are suitable for a diverse range of applications - not only for protein-polymer conjugation, particle decoration and surface immobilization, but also for the decoration of complex biomaterials and the synthesis of bioresponsive drug delivery systems. This article reviews latest chemical and enzymatic strategies for the biorthogonal decoration of biomaterials with therapeutic proteins and inter-positioned linker structures. Finally, the numerous reports at the interface of biomaterials, linkers, and therapeutic protein decoration are integrated into practical advice for design considerations intended to support the selection of productive ligation strategies.

Reloadable multidrug capturing delivery system for targeted ischemic disease treatment

Human clinical trials of protein therapy for ischemic diseases have shown disappointing outcomes so far, mainly because of the poor circulatory half-life of growth factors in circulation and their low uptake and retention by the targeted injury site. The attachment of polyethylene glycol (PEG) extends the circulatory half-lives of protein drugs but reduces their extravasation and retention at the target site. To address this issue, we have developed a drug capture system using a mixture of hyaluronic acid (HA) hydrogel and anti-PEG immunoglobulin M antibodies, which, when injected at a target body site, can capture and retain a variety of systemically injected PEGylated therapeutics at that site. Furthermore, repeated systemic injections permit "reloading" of the capture depot, allowing the use of complex multistage therapies. This study demonstrates this capture system in both murine and porcine models of critical limb ischemia. The results show that the reloadable HA/anti-PEG system has the potential to be clinically applied to patients with ischemic diseases, who require sequential administration of protein drugs for optimal outcomes.

Impact of polymer geometry on the interactions of protein-PEG conjugates

The conjugation of high molecular weight polyethylene glycol (PEG) to an active pharmaceutical ingredient (API) is an attractive strategy for the modification of biophysical and biodistribution properties of the API. Indeed, several therapeutic proteins conjugated to PEG have been safely administered in the clinic. While there have been studies on the configuration of these conjugates in solution, investigations on the impact of PEG geometry on protein-PEG conjugate interactions is limited. In this study, we use dynamic light scattering (DLS), rheology, and small-angle neutron scattering (SANS) to investigate the biophysical solution and interaction behavior of a 50kDa Fab protein attached to either a linear or tetrameric (branched) 40kDa PEG molecule. The hydrodynamic radii, diffusivity, viscosity and pair distance distribution function (PDDF) were obtained for the protein-PEG conjugates in solution. An analysis revealed that interactions between unconjugated proteins were quite attractive, however linear PEG-protein conjugates exhibited net repulsive interactions, similar to that of the unconjugated polymer. Tetramer PEG-protein conjugates on the other hand, exhibited a net weak attractive interaction, indicating a more balanced distribution of repulsive and attractive interaction states. Further analysis of the SANS data using geometric models consistent with the PDDF elucidated the conjugates' equilibrium configuration in solution. Insights gained from measurements and analysis used here can also be useful in predicting how conjugate geometries affect viscosity and aggregation behavior, which are important in determining suitable protein-polymer drug formulations.

HM10660A, a long-acting hIFN-α-2b, is a potent candidate for the treatment of hepatitis C through an enhanced biological half-life

Interferon-α (IFN-α) has been widely used for the treatment of infections due to the hepatitis C virus (HCV). Because of the short half-life of IFN-α in serum, it must be administered three times per week. To increase the half-life of IFN-α, the immunoglobulin G4 (IgG4) Fc fragment (HMC001) was conjugated with human IFN-α-2b to develop a long-acting IFN-α-2b, HM10660A. An analysis of the antiviral efficacy of HM10660A in a human hepatocyte-engrafted mouse model found that HM10660A reduced serum HCV titers more effectively than a commercially available peginterferon α-2a (PEGASYS^®) and IFN-α-2b. Pharmacokinetic (PK) and pharmacodynamic (PD) studies of HM10660A using monkeys demonstrated that the half-life of HM10660A was approximately 2-fold longer than commercially available peginterferon α-2a, which is approved for a once-weekly regimen. Moreover, the IFN-mediated induction profiles of neopterin and 2', 5'-oligoadenylate synthase (OAS) in normal cynomolgus monkeys indicated that HM10660A had enhanced antiviral activity and a prolonged duration of action compared with peginterferon α-2a. Considering the improved PK and PD properties, HM10660A can most likely be dosed every two or four weeks, providing superior antiviral efficacy and convenience for patients with HCV.

Pharmacological interventions for acute hepatitis B infection: an attempted network meta-analysis

BACKGROUND

Infection with hepatitis B virus (HBV) can be symptomatic or asymptomatic. Apart from chronic HBV infection, the complications related to acute HBV infection are severe acute viral hepatitis and fulminant hepatitis characterised by liver failure. The optimal pharmacological treatment of acute HBV infection remains controversial.

OBJECTIVES

To assess the benefits and harms of pharmacological interventions in the treatment of acute HBV infection through a network meta-analysis and to generate rankings of the available treatments according to their safety and efficacy. As it was not possible to assess whether the potential effect modifiers were similar across different comparisons, we did not perform the network meta-analysis, and instead, assessed the benefits and harms of different interventions using standard Cochrane methodological procedures.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, Science Citation Index Expanded, WHO International Clinical Trials Registry Platform, and randomised clinical trials (RCTs) registers to August 2016 to identify RCTs on pharmacological interventions for acute HBV infection.

SELECTION CRITERIA

RCTs, irrespective of language, blinding, or publication status in participants with acute HBV infection. We excluded trials if participants had previously undergone liver transplantation and had other coexisting viral diseases such as hepatitis C virus and HIV. We considered any of the various pharmacological interventions compared with each other or with placebo, or no intervention.

DATA COLLECTION AND ANALYSIS

We calculated the odds ratio (OR) and rate ratio with 95% confidence intervals (CI) using both fixed-effect and random-effects models based on available-participant analysis with Review Manager 5. We assessed risk of bias, controlled risk of random errors with Trial Sequential Analysis, and assessed the quality of the evidence using GRADE.

MAIN RESULTS

Seven trials (597 participants) met our review inclusion criteria. All trials provided information for one or more outcomes; however, five participants were excluded from analysis by study authors. All the trials were at high risk of bias. Overall, all the evidence was low or very low quality evidence because of risk of bias (downgraded one level for risk of bias), small sample size (downgraded one level for imprecision), and wide CIs (downgraded one more level for imprecision in some comparisons). Of the seven trials, six were two-armed trials, while one trial was a three-armed trial. The comparisons included hepatitis B immunoglobulin (HBIG) versus placebo (one trial; 55 participants); interferon versus placebo (two trials; 200 participants); lamivudine versus placebo or no intervention (four trials; 316 participants); lamivudine versus entecavir (one trial; 90 participants); and entecavir versus no intervention (one trial; 131 participants). One trial included only people with acute HBV with hepatic encephalopathy (i.e. people with fulminant liver failure); one trial included only people with severe acute HBV, but it did not state whether any of the people also had fulminant HBV infection; three trials excluded fulminant HBV infection; and two trials did not report the severity of acute HBV infection. The mean or median follow-up period in the trials ranged from three to 12 months in the trials that provided this information.There was no evidence of any differences in short-term mortality (less than one year) in any of the comparisons: HBIG versus placebo (OR 1.13, 95% CI 0.36 to 3.54; participants = 55; 1 trial), lamivudine versus placebo or no intervention (OR 1.29, 95% CI 0.33 to 4.99; participants = 250; 2 trials); lamivudine versus entecavir (OR 1.23, 95% CI 0.13 to 11.65; participants = 90; 1 trial), or entecavir versus no intervention (OR 1.05, 95% CI 0.12 to 9.47; participants = 131; 1 trial). The proportion of people who progressed to chronic HBV infection was higher in the lamivudine group than the placebo or no intervention group (OR 1.99, 95% CI 1.05 to 3.77; participants = 285; 3 trials) and in the lamivudine group versus entecavir group (OR 3.64, 95% CI 1.31 to 10.13; participants = 90; 1 trial). There was no evidence of a difference in the proportion of people who progressed to chronic HBV infection between the entecavir and the no intervention groups (OR 0.58, 95% CI 0.23 to 1.49; participants = 131; 1 trial). None of the trials reported progression to fulminant HBV infection. Three trials with 371 participants reported serious adverse events. There were no serious adverse events in any of the groups (no intervention: 0/183 (0%), interferon: 0/67 (0%), lamivudine: 0/100 (0%), and entecavir: 0/21 (0%)). The proportion of people with adverse events was higher in the interferon group than the placebo group (OR 348.16, 95% CI 45.39 to 2670.26; participants = 200; 2 trials). There was no evidence of a difference in the proportion of people with adverse events between the lamivudine group and the placebo or no intervention group (OR 1.42, 95% CI 0.34 to 5.94; participants = 35; 1 trial) or number of adverse events between the lamivudine group and the placebo or no intervention group (rate ratio 1.72, 95% CI 1.01 to 2.91; participants = 35; 1 trial). One trial with 100 participants reported quality of life at one week. The scale used to report the health-related quality of life was not stated and lacked information on whether higher score meant better or worse, making it difficult to interpret the results. None of the trials reported quality of life beyond one week or other clinical outcomes such as mortality beyond one year, liver transplantation, cirrhosis, decompensated cirrhosis, or hepatocellular carcinoma.Two trials received funding from pharmaceutical companies; three trials were funded by parties without any vested interest in the results or did not receive any special funding; the source of funding was not available in the remaining two trials.

AUTHORS' CONCLUSIONS

Low or very low quality evidence suggests that progression to chronic HBV infection was higher in people receiving lamivudine compared with placebo, no intervention, or entecavir. Low quality evidence suggests that interferon may increase the adverse events after treatment for acute HBV infection. Based on a very low quality evidence, there is currently no evidence of benefit of any intervention in acute HBV infection. There is significant uncertainty in the results and further RCTs are required.

Pharmacological interventions for acute hepatitis C infection: an attempted network meta-analysis

BACKGROUND

Hepatitis C virus (HCV) is a single-stranded RNA (ribonucleic acid) virus that has the potential to cause inflammation of the liver. The traditional definition of acute HCV infection is the first six months following infection with the virus. Another commonly used definition of acute HCV infection is the absence of HCV antibody and subsequent seroconversion (presence of HCV antibody in a person who was previously negative for HCV antibody). Approximately 40% to 95% of people with acute HCV infection develop chronic HCV infection, that is, have persistent HCV RNA in their blood. In 2010, an estimated 160 million people worldwide (2% to 3% of the world's population) had chronic HCV infection. The optimal pharmacological treatment of acute HCV remains controversial. Chronic HCV infection can damage the liver.

OBJECTIVES

To assess the comparative benefits and harms of different pharmacological interventions in the treatment of acute HCV infection through a network meta-analysis and to generate rankings of the available pharmacological treatments according to their safety and efficacy. However, it was not possible to assess whether the potential effect modifiers were similar across different comparisons. Therefore, we did not perform the network meta-analysis, and instead, we assessed the comparative benefits and harms of different interventions versus each other or versus no intervention using standard Cochrane methodology.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Science Citation Index Expanded, World Health Organization International Clinical Trials Registry Platform, and randomised controlled trials registers to April 2016 to identify randomised clinical trials on pharmacological interventions for acute HCV infection.

SELECTION CRITERIA

We included only randomised clinical trials (irrespective of language, blinding, or publication status) in participants with acute HCV infection. We excluded trials which included previously liver transplanted participants and those with other coexisting viral diseases. We considered any of the various pharmacological interventions compared with placebo or each other.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We calculated the odds ratio (OR) and rate ratio with 95% confidence intervals (CI) using both fixed-effect and random-effects models based on the available-participant analysis with Review Manager 5. We assessed risk of bias according to Cochrane, controlled risk of random errors with Trial Sequential Analysis, and assessed the quality of the evidence using GRADE.

MAIN RESULTS

We identified 10 randomised clinical trials with 488 randomised participants that met our inclusion criteria. All the trials were at high risk of bias in one or more domains. Overall, the evidence for all the outcomes was very low quality evidence. Nine trials (467 participants) provided information for one or more outcomes. Three trials (99 participants) compared interferon-alpha versus no intervention. Three trials (90 participants) compared interferon-beta versus no intervention. One trial (21 participants) compared pegylated interferon-alpha versus no intervention, but it did not provide any data for analysis. One trial (41 participants) compared MTH-68/B vaccine versus no intervention. Two trials (237 participants) compared pegylated interferon-alpha versus pegylated interferon-alpha plus ribavirin. None of the trials compared direct-acting antivirals versus placebo or other interventions. The mean or median follow-up period in the trials ranged from six to 36 months.There was no short-term mortality (less than one year) in any group in any trial except for one trial where one participant died in the pegylated interferon-alpha plus ribavirin group (1/95: 1.1%). In the trials that reported follow-up beyond one year, there were no further deaths. The number of serious adverse events was higher with pegylated interferon-alpha plus ribavirin than with pegylated interferon-alpha (rate ratio 2.74, 95% CI 1.40 to 5.33; participants = 237; trials = 2; I2 = 0%). The proportion of people with any adverse events was higher with interferon-alpha and interferon-beta compared with no intervention (OR 203.00, 95% CI 9.01 to 4574.81; participants = 33; trials = 1 and OR 27.88, 95% CI 1.48 to 526.12; participants = 40; trials = 1). None of the trials reported health-related quality of life, liver transplantation, decompensated liver disease, cirrhosis, or hepatocellular carcinoma. The proportion of people with chronic HCV infection as indicated by the lack of sustained virological response was lower in the interferon-alpha group versus no intervention (OR 0.27, 95% CI 0.09 to 0.76; participants = 99; trials = 3; I2 = 0%). The differences between the groups were imprecise or not estimable (because neither group had any events) for all the remaining comparisons.Four of the 10 trials (40%) received financial or other assistance from pharmaceutical companies who would benefit from the findings of the research; the source of funding was not available in five trials (50%), and one trial (10%) was funded by a hospital.

AUTHORS' CONCLUSIONS

Very low quality evidence suggests that interferon-alpha may decrease the incidence of chronic HCV infection as measured by sustained virological response. However, the clinical impact such as improvement in health-related quality of life, reduction in cirrhosis, decompensated liver disease, and liver transplantation has not been reported. It is also not clear whether this finding is applicable in the current clinical setting dominated by the use of pegylated interferons and direct-acting antivirals, although we found no evidence to support that pegylated interferons or ribavirin or both are effective in people with acute HCV infection. We could find no randomised trials comparing direct-acting antivirals with placebo or other interventions for acute HCV infection. There is significant uncertainty in the benefits and harms of the interventions, and high-quality randomised clinical trials are required.

Polymer Structure and Conformation Alter the Antigenicity of Virus-like Particle-Polymer Conjugates

Covalent conjugation of water-soluble polymers to proteins is critical for evading immune surveillance in the field of biopharmaceuticals. The most common and long-standing polymer modification is the attachment of methoxypoly(ethylene glycol) (mPEG), termed PEGylation, which has led to several clinically approved pharmaceuticals. Recent data indicate that brush-type polymers significantly enhance in vitro and in vivo properties. Herein, the polymer conformation of poly(ethylene glycol) is detailed and compared with those of water-soluble polyacrylate and polynorbornene (PNB) when attached to icosahedral virus-like particles. Small-angle neutron scattering reveals vastly different polymer conformations of the multivalent conjugates. Immune recognition of conjugated particles was evaluated versus PEGylated particles, and PNB conjugation demonstrated the most effective shielding from antibody recognition.

Self-Assembly PEGylation Retaining Activity (SPRA) Technology via a Host-Guest Interaction Surpassing Conventional PEGylation Methods of Proteins

Polyethylene glycol (PEG) modification (PEGylation) is one of the best approaches to improve the stabilities and blood half-lives of protein drugs; however, PEGylation dramatically reduces the bioactivities of protein drugs. Here, we present "self-assembly PEGylation retaining activity" (SPRA) technology via a host-guest interaction between PEGylated β-cyclodextrin (PEG-β-CyD) and adamantane-appended (Ad) proteins. PEG-β-CyD formed stable complexes with Ad-insulin and Ad-lysozyme to yield SPRA-insulin and SPRA-lysozyme, respectively. Both SPRA-proteins showed high stability against heat and trypsin digest, comparable with that of covalently PEGylated protein equivalents. Importantly, the SPRA-lysozyme possessed ca. 100% lytic activity, whereas the activity of the covalently PEGylated lysozyme was ca. 23%. Additionally, SPRA-insulin provided a prolonged and peakless blood glucose profile when compared with insulin glargine. It also showed no loss of activity. In contrast, the covalently PEGylated insulin showed a negligible hypoglycemic effect. These findings indicate that SPRA technology has potential as a generic method, surpassing conventional PEGylation methods for proteins.

Prolonged Pharmacokinetic and Pharmacodynamic Actions of a Pegylated Parathyroid Hormone (1-34) Peptide Fragment

Polyethylene glycol (PEG) addition can prolong the pharmacokinetic and pharmacodynamic actions of a bioactive peptide in vivo, in part by impeding rates of glomerular filtration. For parathyroid hormone (PTH) peptides, pegylation could help in exploring the actions of the hormone in the kidney; e.g., in dissecting the relative roles that filtered versus blood-borne PTH play in regulating phosphate transport. It could also lead to potential alternate forms of treatment for hypoparathyroidism. We thus synthesized the fluorescent pegylated PTH derivative [Lys¹³ (tetramethylrhodamine {TMR}), Cys³⁵ (PEG-20,000 Da)]PTH(1-35) (PEG-PTH^TMR ) and its non-pegylated counterpart [Lys¹³ (TMR), Cys³⁵ ]PTH(1-35) (PTH^TMR ) and assessed their properties in cells and in mice. In PTHR1-expressing HEK-293 cells, PEG-PTH^TMR and PTH^TMR exhibited similar potencies for inducing cAMP signaling, whereas when injected into mice, the pegylated analog persisted much longer in the circulation (>24 hours versus ∼ 1 hour) and induced markedly more prolonged calcemic and phosphaturic responses than did the non-pegylated control. Fluorescence microscopy analysis of kidney sections obtained from the injected mice revealed much less PEG-PTH^TMR than PTH^TMR on the luminal brush-border surfaces of renal proximal tubule cells (PTCs), on which PTH regulates phosphate transporter function, whereas immunostained phosphorylated PKA substrate, a marker of cAMP signaling, was increased to similar extents for the two ligands and for each, was localized to the basolateral portion of the PTCs. Pegylation of a bioactive PTH peptide thus led to prolonged pharmacokinetic/pharmacodynamic properties in vivo, as well as to new in vivo data that support a prominent role for PTH action at basolateral surfaces of renal proximal tubule cells. © 2016 American Society for Bone and Mineral Research.

PEGylation of Biopharmaceuticals: A Review of Chemistry and Nonclinical Safety Information of Approved Drugs

Modification of biopharmaceutical molecules by covalent conjugation of polyethylene glycol (PEG) molecules is known to enhance pharmacologic and pharmaceutical properties of proteins and other large molecules and has been used successfully in 12 approved drugs. Both linear and branched-chain PEG reagents with molecular sizes of up to 40 kDa have been used with a variety of different PEG derivatives with different linker chemistries. This review describes the properties of PEG itself, the history and evolution of PEGylation chemistry, and provides examples of PEGylated drugs with an established medical history. A trend toward the use of complex PEG architectures and larger PEG polymers, but with very pure and well-characterized PEG reagents is described. Nonclinical toxicology findings related to PEG in approved PEGylated biopharmaceuticals are summarized. The effect attributed to the PEG part of the molecules as observed in 5 of the 12 marketed products was cellular vacuolation seen microscopically mainly in phagocytic cells which is likely related to their biological function to absorb and remove particles and macromolecules from blood and tissues. Experience with marketed PEGylated products indicates that adverse effects in toxicology studies are usually related to the active part of the drug but not to the PEG moiety.

Prediction model for sustained hepatitis B e antigen seroconversion to peginterferon alfa-2a in chronic hepatitis B

BACKGROUND AND AIM

Clinically applicable models to predict hepatitis B e antigen (HBeAg)-positive chronic hepatitis B (CHB) response to peginterferon (PEG-IFN) are scarce. This study aimed to develop simple scoring systems, based on multiple parameters, for predicting sustained HBeAg seroconversion to PEG-IFN.

METHODS

Eighty-five treatment-naïve patients with HBeAg-positive CHB underwent 52-week PEG-IFN treatment and 24-week follow-up. Logistic regression analysis assessed parameters at baseline and weeks 12, 24, and 52 to predict HBeAg seroconversion at week 24 off-treatment. The best three predictors at each time point were included in prediction models of PEG-IFN therapy efficacy.

RESULTS

The three most meaningful predictors were alanine aminotransferase (ALT) > 5 × ULN, HBeAg ≤ 500 S/CO, and antibody to hepatitis B core antigen (anti-HBc) > 10.7 S/CO at baseline; HBeAg ≤ 20 S/CO, anti-HBc > 11.7 S/CO, and HBeAg decline > 1 log10 S/CO at week 12; ALT > 2 × ULN, HBeAg ≤ 15 S/CO, and anti-HBc > 10.4 S/CO at week 24; HBeAg ≤ 5 S/CO, anti-HBc > 11.1 S/CO, and hepatitis B virus DNA decline > 2 log10 copies/mL at week 52. Parameters meeting optimal cutoff thresholds were scored 1 or otherwise scored 0. For total scores of 0 versus 3 at baseline and weeks 12, 24, and 52, response rates were 6.3%, 12.5%, 0%, and 0% versus 90.0%, 83.3%, 76.9%, and 86.4%, respectively.

CONCLUSIONS

We successfully established prediction models for PEG-IFN response in HBeAg-positive CHB.

Effects of localized interactions and surface properties on stability of protein-based therapeutics

OBJECTIVES

Protein-based therapeutics garner significant attention because of exquisite specificity and limited side effects and are now being used to accomplish targeted delivery of small-molecule drugs. This review identifies and highlights individual chemical attributes and categorizes how site-specific changes affect protein stability based on published high-resolution molecular analyses.

KEY FINDINGS

Because it is challenging to determine the mechanisms by which the stability of large, complex molecules is altered and data are sparse, smaller, therapeutic proteins (insulin, erythropoietin, interferons) are examined alongside antibody data. Integrating this large pool of information with the limited available studies on antibodies reveals common mechanisms by which specific alterations affect protein structure and stability.

SUMMARY

Physical and chemical stability of therapeutic proteins and antibody drug conjugates (ADCs) is of critical importance because insufficient stability prevents molecules from making it to market. Individual moieties on/near the surface of proteins have substantial influence on structure and stability. Seemingly small, superficial modification may have far-reaching consequences on structure, conformational dynamics, and solubility of the protein, and hence physical stability of the molecule. Chemical modifications, whether spontaneous (e.g. oxidation, deamidation) or intentional, as with ADCs, may adversely impact stability by disrupting local surface properties or higher order protein structure.

Towards the next generation of biomedicines by site-selective conjugation

Bioconjugates represent an emerging class of medicines, which offer therapeutic opportunities overtaking those of the individual components. Many novel bioconjugates have been explored in order to address various emerging medical needs. The last decade has witnessed the exponential growth of new site-selective bioconjugation techniques, however very few methods have made the way into human clinical trials. Here we discuss various applications of site-selective conjugation in biomedicines, including half-life extension, antibody-drug conjugates, conjugate vaccines, bispecific antibodies and cell therapy. The review is intended to highlight both the progress and challenges, and identify a potential roadmap to address the gap.

Site-Specific Transglutaminase-Mediated Conjugation of Interferon α-2b at Glutamine or Lysine Residues

Interferon α (IFN α) subtypes are important protein drugs that have been used to treat infectious diseases and cancers. Here, we studied the reactivity of IFN α-2b to microbial transglutaminase (TGase) with the aim of obtaining a site-specific conjugation of this protein drug. Interestingly, TGase allowed the production of two monoderivatized isomers of IFN with high yields. Characterization by mass spectrometry of the two conjugates indicated that they are exclusively modified at the level of Gln101 if the protein is reacted in the presence of an amino-containing ligand (i.e., dansylcadaverine) or at the level of Lys164 if a glutamine-containing molecule is used (i.e., carbobenzoxy-l-glutaminyl-glycine, ZQG). We explained the extraordinary specificity of the TGase-mediated reaction on the basis of the conformational features of IFN. Indeed, among the 10 Lys and 12 Gln residues of the protein, only Gln101 and Lys164 are located in highly flexible protein regions. The TGase-mediated derivatization of IFN was then applied to the production of IFN derivatives conjugated to a 20 kDa polyethylene glycol (PEG), using PEG-NH₂ for Gln101 derivatization and PEG modified with ZQG for Lys164 derivatization. The two mono-PEGylated isomers of IFN were obtained in good yields, purified, and characterized in terms of protein conformation, antiviral activity, and pharmacokinetics. Both conjugates maintained a native-like secondary structure, as indicated by far-UV circular dichroism spectra. Importantly, they disclosed good in vitro antiviral activity retention (about only 1.6- to 1.8-fold lower than that of IFN) and half-lives longer (about 5-fold) than that of IFN after intravenous administration to rats. Overall, these results provide evidence that TGase can be used for the development of site-specific derivatives of IFN α-2b possessing interesting antiviral and pharmacokinetic properties.

Measurement of Pre-Existing IgG and IgM Antibodies against Polyethylene Glycol in Healthy Individuals

Polyethylene glycol (PEG) is a biocompatible polymer that is often attached to therapeutic molecules to improve bioavailability and therapeutic efficacy. Although antibodies with specificity for PEG may compromise the safety and effectiveness of PEGylated medicines, the prevalence of pre-existing anti-PEG antibodies in healthy individuals is unclear. Chimeric human anti-PEG antibody standards were created to accurately measure anti-PEG IgM and IgG antibodies by direct ELISA with confirmation by a competition assay in the plasma of 1504 healthy Han Chinese donors residing in Taiwan. Anti-PEG antibodies were detected in 44.3% of healthy donors with a high prevalence of both anti-PEG IgM (27.1%) and anti-PEG IgG (25.7%). Anti-PEG IgM and IgG antibodies were significantly more common in females as compared to males (32.0% vs 22.2% for IgM, p < 0.0001 and 28.3% vs 23.0% for IgG, p = 0.018). The prevalence of anti-PEG IgG antibodies was higher in younger (up to 60% for 20 year olds) as opposed to older (20% for >50 years) male and female donors. Anti-PEG IgG concentrations were negatively associated with donor age in both females (p = 0.0073) and males (p = 0.026). Both anti-PEG IgM and IgG strongly bound PEGylated medicines. The described assay can assist in the elucidation of the impact of anti-PEG antibodies on the safety and therapeutic efficacy of PEGylated medicines.

Stability Enhancing N-Terminal PEGylation of Oxytocin Exploiting Different Polymer Architectures and Conjugation Approaches

Oxytocin, a cyclic nine amino acid neurohypophyseal hormone therapeutic, is effectively used in the control of postpartum hemorrhaging (PPH) and is on the WHO List of Essential Medicines. However, oxytocin has limited shelf life stability in aqueous solutions, particularly at temperatures in excess of 25 °C and injectable aqueous oxytocin formulations require refrigeration (<8 °C). This is particularly problematic in the hot climates often found in many developing countries where daytime temperatures can exceed 40 °C and where reliable cold-chain storage is not always achievable. The purpose of this study was to develop N-terminal amine targeted PEGylation strategies utilizing both linear PEG and polyPEG "comb" polymers as an effective method for stabilizing solution formulations of this peptide for prolonged storage in the absence of efficient cold-chain storage. The conjugation chemistries investigated herein include irreversible amine targeted conjugation methods utilizing NHS ester and aldehyde reductive amination chemistry. Additionally, one reversible conjugation method using a Schiff base approach was explored to allow for the release of the native peptide, thus, ensuring that biological activity remains unaffected. The reversibility of this approach was investigated for the different polymer architectures, alongside a nonpolymer oxytocin analogue to monitor how pH can tune native peptide release. Elevated temperature degradation studies of the polymer conjugates were evaluated to assess the stability of the PEGylated analogues in comparison to the native peptide in aqueous formulations to mimic storage conditions in developing nations and regions where storage under appropriate conditions is challenging.

Repeated Panniculitis Induced by Pegylated Interferon Alpha 2a in a Patient with Chronic Hepatitis C

Pegylated interferon alpha (PEG-IFN-α) is widely used to treat chronic hepatitis C in combination with ribavirin. Many adverse effects of PEG-IFN-α, such as hematologic, psychologic, dermatologic, immunologic, and other abnormalities, have been reported, and some serious adverse events lead to PEG-IFN-α treatment discontinuation. For very rare adverse events such as panniculitis, there are no established guidelines on whether to continue PEG-IFN-α treatment. Published reports on panniculitis induced by PEG-IFN-α 2a are sparse. Herein we report a case of repeated occurrences of panniculitis in a patient with chronic hepatitis C, leading to treatment cessation.