Comparative pharmacokinetics and pharmacodynamics of two recombinant human interferon beta-1a (IFN beta-1 a) products administered intramuscularly in healthy male and female volunteers

Pharmacokinetic considerations in the treatment of multiple sclerosis with interferon-β

INTRODUCTION

Interferon-β (IFNβ) is well established as a disease-modifying treatment for patients with multiple sclerosis. Several preparations of the biopharmaceutical are available differing in protein structure, formulation, dose as well as frequency and route of administration. Recently, a pegylated form of IFNβ has been marketed.

AREAS COVERED

Following a PubMed database search, we provide an overview of what is presently known about the pharmacokinetics (PK) of IFNβ including its absorption, distribution, metabolism and elimination. Also, we discuss the association with clinically relevant issues such as treatment efficacy, adverse events and anti-drug antibodies.

EXPERT OPINION

IFNβ has a bioavailability of ∼ 30% after subcutaneous or intramuscular administration, shows peak serum concentrations within several hours, has a half-life of < 1 day and is eliminated by a renal and hepatic pathway. PK parameters do not substantially differ between the types of IFNβ and routes of administration; only pegylation of IFNβ results in substantially increased and prolonged PK. Although no clinical dose-effect relationship could be established, there is an association of IFNβ dose with magnetic resonance imaging outcome parameters. Furthermore, there is an association of IFNβ serum levels with the occurrence of adverse events and anti-drug antibodies.

Development of oral immunomodulatory agents in the management of multiple sclerosis

The emergence of oral disease-modifying therapies in multiple sclerosis (MS) will have a significant impact on the evolving scenario of immunomodulatory treatments in MS where current therapies are all injectable. Reducing relapses in trials translates for individuals with MS into a therapeutic aim of stopping future events. Thus the possible absence of any perceived benefits to the individual together with the long disease course, variable outcome, and a younger age group affected in MS makes side effects the major issue. The use of disease-modifying therapies as a whole needs to be placed in the context of a widening therapeutic indication where the use of these therapies is being justified at an increasingly early stage and in pre-MS syndromes such as clinically isolated and radiologically isolated syndromes where no fixed disability is likely to have accumulated. The five oral therapies discussed (cladribine, fingolimod, laquinimod, BG-12, and teriflunomide) have just completed Phase III studies and some have just been licensed. New oral drugs for MS need to be placed within this evolving marketplace where ease of delivery together with efficacy and side effects needs to be balanced against the known issues but also the known long-term safety of standard injectables.

Biotherapeutic bioanalysis: a multi-indication case study review

A thorough understanding of the structure and biology of a biotherapeutic is crucial to defining a suitable strategy for pharmacokinetic characterization in proof-of-concept disease models, toxicology species as well as the healthy and disease indication patient populations. This manuscript summarizes parameters that impact bioanalytical strategy for over 50 biotherapeutics indicated for the treatment of oncology, rheumatoid arthritis, allergy, multiple sclerosis, hematology, metabolism and infectious disease. We have addressed numerous therapeutic modalities including chimeric, humanized and fully human monoclonal antibodies, replacement proteins, peptides and fusion proteins, including polyethylene glycol and Fc fusions, as well as antibody–drug conjugates. With the rapid evolution of biotherapeutics over the last 20 years and the contraction of the pharmaceutical and biotechnology labor force, efficient workflow management becomes a crucial bioanalytical component. Thus, we have also addressed new technologies that have demonstrated either increased throughput or enhanced characterization, including Meso Scale Discovery, Gyrolab and affinity MS.

Current and future disease-modifying therapies in multiple sclerosis

The development of disease-modifying therapies (DMT) in multiple sclerosis (MS) has rapidly evolved over the last few years and continues to do so. Prior to the United States Food and Drug Administration approval of the immunomodulatory agent, interferon-beta1b in 1993, no other drug had been shown to alter the course of the disease in a controlled study of MS. At present, there are five licenced disease-modifying agents in MS - interferon-beta1b, interferon-beta1a, glatiramer acetate, natalizumab and mitoxantrone. All have shown significant therapeutic efficacy in large controlled trials. However, current therapies are only partially effective and are not free from adverse effects. Moreover, available DMTs are overwhelmingly biased in favour of those with relapsing-remitting disease. Effective treatment for progressive MS is severely limited, with only interferon-beta1b and mitoxantrone having licenced use in secondary progressive, but not primary progressive disease. Monoclonal antibodies, such as natalizumab selectively target immune pathways involved in the pathogenic process of MS. Alemtuzumab, daclizumab and rituximab are other notable monoclonal antibodies currently undergoing phase II and III trials in MS. Alemtuzumab has so far shown promising therapeutic benefit in relapsing disease, although immunological adverse effects have been a problem. Oral therapies have the benefit of improved tolerability and patient compliance compared with current parenteral treatments. Cladribine and fingolimod (FTY720) have shown encouraging results in their phase III clinical trials. It is also worth noting the evidence for starting DMT in patients with clinically isolated syndrome, whereby early treatment has shown to delay the onset of clinically definite MS in separate phase III studies.

Pharmacogenomics of IFN-beta in multiple sclerosis: towards a personalized medicine approach

Multiple sclerosis (MS) is an inflammatory disease of the CNS. The clinical presentation of MS is heterogeneous. Interferons (IFNs) were the first agents to show clinical efficacy in the treatment of MS and prolonged treatment is still the best available therapy. Although IFN treatment ameliorates immune dysfunction, the response is partial. Clinical experience indicates that there are responders and nonresponders. This distinction suggests that a subset of patients are insensitive or resistant to the action of IFN. This implies that pharmacodynamic responses may differ between patients, leading to interindividual differences in clinical response. Understanding of the factors that underlie the therapeutic response is key to the identification of predictive markers. Here, we describe novel developments in pharmacogenomics research to improve the understanding of the pharmacological effects of IFN therapy, and the identification of biomarkers that allow stratification of MS patients for their response to IFN-beta. Ultimately, this information will lead to a personalized form of medicine, whereby a specific therapy will be applied that is best suited to an individual patient.

Interferon-beta treatment for relapsing multiple sclerosis

BACKGROUND

Recombinant forms of IFN-beta were the first therapeutic intervention found to be effective at interfering with the course of multiple sclerosis (MS), a chronic and debilitating disease affecting the CNS in young adults.

OBJECTIVE/METHODS

To examine the application of IFN-beta to MS treatment by a review of relevant literature.

RESULTS

The different IFN-beta products available are similar in their clinical effects. However, the response to IFN-beta therapy is only partial and the most efficient individual-specific dose, route and frequency of administration are not elucidated fully. The mechanism of action of IFN-beta in MS is also not understood fully but its immunomodulatory effects are probably more important than its anti-proliferative and antiviral activities.

CONCLUSIONS

Although new therapeutic approaches are being sought to better treat MS, IFN-beta remains one of the most recognized and approved worldwide therapeutic options for this disease.

Detection and characterization of altered conformations of protein pharmaceuticals using complementary mass spectrometry-based approaches

Unlike small-molecule drugs, the conformational properties of protein biopharmaceuticals in solution are influenced by a variety of factors that are not solely defined by their covalent chemical structure. Since the conformation (or higher order structure) of a protein is a major modulator of its biological activity, the ability to detect changes in both the higher order structure and conformational dynamics of a protein, induced by an array of extrinsic factors, is of central importance in producing, purifying, and formulating a commercial biopharmaceutical with consistent therapeutic properties. In this study we demonstrate that two complementary mass spectrometry-based approaches (analysis of ionic charge-state distribution and hydrogen/deuterium exchange) can be a potent tool in monitoring conformational changes in protein biopharmaceuticals. The utility of these approaches is demonstrated by detecting and characterizing conformational changes in the biopharmaceutical product interferon beta-1a (IFN-beta-1a). The protein degradation process was modeled by inducing a single chemical modification of IFN-beta1a (alkylation of its only free cysteine residue with N-ethylmaleimide), which causes significant reduction in its antiviral activity. Analysis of IFN-beta1a ionic charge-state distributions unequivocally reveals a significant decrease of conformational stability in the degraded protein, while hydrogen/deuterium exchange measurements provide a clear indication that the higher order structure is affected well beyond the covalent modification site. Importantly, neither technique required that the location or indeed the nature of the chemical modification be known prior to or elucidated in the process of the analysis. In contrast, application of the standard armamentarium of biophysical tools, which are commonly employed for quality control of protein pharmaceuticals, met with very limited success in detection and characterization of conformational changes in the modified IFN-beta1a. This work highlights the role mass spectrometry can and should play in the biopharmaceutical industry beyond the presently assigned task of primary structure analysis.

Pharmacogenomics of interferon-beta therapy in multiple sclerosis: baseline IFN signature determines pharmacological differences between patients

BACKGROUND

Multiple sclerosis (MS) is a heterogeneous disease. In order to understand the partial responsiveness to IFNbeta in Relapsing Remitting MS (RRMS) we studied the pharmacological effects of IFNbeta therapy.

METHODOLOGY

Large scale gene expression profiling was performed on peripheral blood of 16 RRMS patients at baseline and one month after the start of IFNbeta therapy. Differential gene expression was analyzed by Significance Analysis of Microarrays. Subsequent expression analyses on specific genes were performed after three and six months of treatment. Peripheral blood mononuclear cells (PBMC) were isolated and stimulated in vitro with IFNbeta. Genes of interest were measured and validated by quantitative realtime PCR. An independent group of 30 RRMS patients was used for validation.

PRINCIPAL FINDINGS

Pharmacogenomics revealed a marked variation in the pharmacological response to IFNbeta between patients. A total of 126 genes were upregulated in a subset of patients whereas in other patients these genes were downregulated or unchanged after one month of IFNbeta therapy. Most interestingly, we observed that the extent of the pharmacological response correlates negatively with the baseline expression of a specific set of 15 IFN response genes (R = -0.7208; p = 0.0016). The negative correlation was maintained after three (R = -0.7363; p = 0.0027) and six (R = -0.8154; p = 0.0004) months of treatment, as determined by gene expression levels of the most significant correlating gene. Similar results were obtained in an independent group of patients (n = 30; R = -0.4719; p = 0.0085). Moreover, the ex vivo results could be confirmed by in vitro stimulation of purified PBMCs at baseline with IFNbeta indicating that differential responsiveness to IFNbeta is an intrinsic feature of peripheral blood cells at baseline.

CONCLUSION

These data imply that the expression levels of IFN response genes in the peripheral blood of MS patients prior to treatment could serve a role as biomarker for the differential clinical response to IFNbeta.

Interferon-beta treatment for multiple sclerosis

Multiple sclerosis (MS) is the leading nontraumatic cause of neurologic disability in young adults. Interferon-beta, approved for use in 1993, was the first treatment to modify the course and prognosis of the disease and remains a mainstay of MS treatment. Numerous large-scale clinical trials in early, active patient populations have established the clinical efficacy of interferon-beta in reducing relapses and delaying disability progression. Although its mechanism of action remains incompletely understood, a reduction in active lesions seen on magnetic resonance imaging implies primary anti-inflammatory properties, a mechanism supported by basic immunologic research. Variation in individual patient responsiveness to interferon-beta may be due to disease variability or differential induction of interferon-stimulated genes. The magnitude of the therapeutic effect appears to be similar among products, but the optimal dose, route, and frequency of administration of the drug remain uncertain.

Interferon-beta1a treatment for multiple sclerosis

Although multiple sclerosis is probably the most common cause of neurologic disability in young adults, the cause is unknown, the prognosis uncertain and available treatments unsatisfactory. Multiple sclerosis is an inflammatory autoimmune disorder of the CNS and the result of both environmental factors and susceptibility genes. The prognosis is difficult or impossible to predict at the time of diagnosis. Treatments that modulate the course of the disease have only recently become available but the long-term aim to prevent disability and promote repair remains distant. Interferon-beta is the most widely used therapy. The efficacy of interferon-beta in the short term is well documented in many large treatment trials, but the treatment effects are only modest and many issues relating to efficacy in the long term are unresolved. These include uncertain benefit on conversion to secondary-progressive multiple sclerosis, the relevance of neutralizing antibodies and the controversial effect on multiple sclerosis-related brain atrophy.

Intramuscular interferon-beta-1a: in patients at high risk of developing clinically definite multiple sclerosis

Intramuscular interferon-beta-1a, a recombinant interferon-beta approved in the US for the treatment of relapsing forms of multiple sclerosis (MS), has also been evaluated in the treatment of patients with a first clinical demyelinating episode and brain lesions consistent with MS confirmed by magnetic resonance imaging (MRI). In a randomised, double-blind trial, patients at high risk of developing clinically definite MS who received intramuscular interferon-beta-1a 30 microg once weekly had a 44% reduction in the cumulative probability of developing MS, compared with placebo recipients (rate ratio 0.56; p = 0.002), over a 3-year period after a first, MRI-confirmed demyelinating event. These results were supported by MRI findings that showed significantly smaller increases in the volume of brain lesions and the number of new/enlarging and gadolinium-enhancing lesions in interferon-beta-1a recipients than in those receiving placebo. A nonblind extension of this trial demonstrated that early treatment with interferon-beta-1a significantly reduced the probability of developing MS by 35% (p = 0.03), compared with delayed treatment, over a 5-year period. Intramuscular interferon-beta-1a was generally well tolerated; however, influenza-like syndrome was documented in >50% of patients at high risk of developing clinically definite MS who received the drug.

An open-label safety and drug interaction study of natalizumab (Antegren) in combination with interferon-beta (Avonex) in patients with multiple sclerosis

In this open-label drug-interaction trial, we studied 38 patients with relapsing-remitting multiple sclerosis (MS) who received 3.0 or 6.0 mg/kg of natalizumab as a single intravenous (i.v.) infusion during stable treatment with intramuscular (i.m.) interferon beta-1a 30 microg (IFNbeta-1a; Avonex). To assess the pharmacokinetic (PK) interaction of natalizumab and IFNbeta-1a, serum concentration-time data for both agents were collected and analysed. Biologic response markers of IFNbeta-1a activity, beta2-microglobulin and neopterin, were also assessed to determine effects of natalizumab on IFNbeta-1a pharmacodynamics (PD). Further, safety and immunogenicity were evaluated. The combination of drug therapies was well tolerated. Although natalizumab serum concentrations (and corresponding PK exposure measures) appeared to be somewhat elevated in the presence of IFNbeta-1a, when compared to the same dose (6.0 mg/kg) administered alone in a concurrent comparator study, the differences were generally small and unlikely to be clinically relevant. In general, natalizumab had no apparent clinically relevant effects on the PK or PD properties of IFNbeta-1a. The presence of antibodies to IFNbeta-1a and natalizumab was relatively low. Overall, the study provided safety, immunogenicity, PK and PD data to support a combination strategy for the use of natalizumab and IFNbeta-1a in the treatment of patients with relapsing-remitting MS. A large clinical study is currently in progress to evaluate the efficacy and long-term safety of this combination drug therapy.

Comparative tolerance of IFN beta-1a regimens in patients with relapsing multiple sclerosis

The EVIDENCE study was a direct comparative study of two dose regimens of interferon (IFN) beta-1a used in the treatment of relapsing-remitting multiple sclerosis (RRMS): 30 mcg intramuscularly once weekly (qw; n=338) and 44 mcg subcutaneously three times weekly (tiw; n=339). The study continued for an average of 64 weeks. The safety population consisted of all patients receiving at least one dose of study drug. Clinical assessments occurred every 4 weeks for 24 weeks and then every 12 weeks. Blood tests for safety were taken at baseline and at weeks 4 and 12, and every 12 weeks thereafter. Overall adverse events were more common with the 44 mcg tiw regimen (p=0.007), and were due predominantly to differences in injection-site reactions. The majority of adverse events were rated mild by investigators. Hepatic and haematological adverse events and asymptomatic laboratory abnormalities were more common with 44 mcg tiw (p<0.001),with no difference seen for severe events. Flu-like symptoms were more common with 30 mcg qw (p=0.031), were more severe and persisted for longer. Serious adverse events were comparable for both groups, as were drug discontinuations. In conclusion, although adverse events were more common with high-dose, high-frequency IFN therapy, differences were primarily for mild events and did not affect treatment adherence. Based on superior clinical and magnetic resonance imaging outcomes over an average of 64 weeks, coupled with modest safety differences, the risk-benefit ratio for IFN therapy in RRMS favours the 44 mcg tiw regimen over this period of time.

High-dose, frequently administered interferon beta therapy for relapsing–remitting multiple sclerosis must be maintained over the long term: the interferon beta dose-reduction study

Long-term trials have demonstrated the continued efficacy of interferon (IFN) beta treatment in patients with relapsing-remitting (RR) multiple sclerosis (MS) during prolonged administration. The objective of the work was to evaluate the effects of reducing IFN beta administration frequency and total weekly dose in patients with RR MS who have achieved clinical and MRI disease activity stabilization during long-term IFN beta-1b treatment. Prospective 1-year follow-up of 27 RR MS patients on long-term 250 microg every other day (standard dose) IFN beta-1b treatment were randomized either to gradually reduce dose to 30 microg once-a-week IFN beta-1a (13 patients), or to continue on IFN beta-1b standard dose (14 patients). We found significant differences in the two group of patients. In the group of patients continuously treated with IFN beta-1b standard dose, 79% remained relapse free compared to 23% in the group receiving once-weekly IFN beta-1a (p=0.006). The number of patients without new PD/T2 lesions was higher in the group of patients continuously treated with IFN beta-1b standard dose (77%) compared to the once-weekly IFN beta-1a group (23%) (p=0.04). IFN beta is a long-term treatment for MS. The reduction of IFN beta-1b administration frequency and dose is not advisable even in patients free from clinical and MRI disease activity for many years.

Is serum neopterin level a marker of responsiveness to interferon beta-1a therapy in multiple sclerosis?

BACKGROUND

Interferon beta (INFbeta) may induce the expression of several proteins, including neopterin, considered a biological marker of INFbeta activity.

OBJECTIVES

The aim of this study was to determine the serum neopterin concentration at the beginning of, and during, IFNbeta-1a therapy in relapsing-remitting multiple sclerosis (r-r MS) patients, and to look for a possible correlation between protein synthesis and the clinical course of the disease.

METHODS

Thirteen r-r MS patients were treated with INFbeta-1a (i.m. 6 MIU/week) for 2 years. Blood samples for neopterin determinations were taken daily over a period of 1 week at the end of each 6 months of therapy, and tested for neutralizing antibodies (NABs).

RESULTS

Neopterin levels peaked 24-48 h post-injection and returned to baseline after 120 h. After 1 year of therapy, four patients dropped out of the study because of progression of the disease: in these subjects a significant decrement of neopterin was observed.

CONCLUSION

Neopterin baseline values were not found to decrease over the 2 years of therapy, and neopterin may be considered to be a useful marker of responsiveness to IFNbeta.

Interferon-β in the treatment of relapsing–remitting multiple sclerosis

The role of interferon-beta as a disease-modifying drug (DMD) for the treatment of relapsing-remitting multiple sclerosis (RRMS) is now well established, and its efficacy has been demonstrated unequivocally in large-scale clinical trials. However, current evidence suggests that in order to increase the benefit of therapy, use of an effective drug and dosing regimen should be commenced early in the course of the disease, a finding that places new emphasis on the need for early diagnosis. Indeed, it is now known that MS lesions often develop at a subclinical level and that axonal damage occurs even in the very early stages of the disease. Moreover, such damage may be irreversible, and there is strong evidence to suggest that efficacy lost as a consequence of delay in the onset of treatment or the use of a suboptimal drug regimen cannot be regained. At present, the choice of interferon-beta is complicated by the availability of 3 different products, each with a different dosing regimen. Although the optimal interferon-beta dosing regimen for RRMS has been the focus of much discussion, the issues of dose, and particularly dosing frequency, have not been satisfactorily addressed in clinical trials until recently. Over the last 2 years, however, 3 comparative studies of interferon-beta products have been conducted. The results obtained from these recent trials underline the importance of both dose and dosing frequency and indicate that for improved efficacy in RRMS, interferon-beta therapy should be administered frequently at the highest tolerable, and thus most effective, dose.

Pharmacological methods to overcome IFN-beta antibody formation in the treatment of multiple sclerosis

Diminished efficacy in terms of clinical relapses and lesion load on magnetic resonance images for patients developing neutralising antibodies (NAbs) to recombinant IFN-beta may be found in multiple sclerosis. NAbs become detectable over the first few years of therapy, disappearing during the treatment course in some patients and persisting longer in some others. Therefore, the administration of concomitant therapies to recombinant IFNbeta to prevent the formation of NAbs could be indicated mainly in the latter group of patients at the early stage of the treatment. Among those therapies, steroids meet the best criteria in terms of either safety or impact on the development of NAbs, at the present time.

Receptor-mediated pharmacokinetics and pharmacodynamics of interferon-beta1a in monkeys

A pharmacokinetic/pharmacodynamic (PK/PD) model was developed to simultaneously characterize interferon after i.v. and s.c. dosing at various dose levels. A sequential study in monkeys (n = 18) was conducted, where single doses of 1, 3, and 10 MIU/kg of recombinant-human interferon-beta (IFN-beta) 1a were given i.v. and then s.c. Plasma concentrations of IFN-beta were determined and biphasic neopterin concentrations were used as the pharmacodynamic (PD) endpoint. Multiple dosing also was evaluated by giving 1 MIU/kg s.c. doses once daily for 7 days (n = 3). The integrated model uses target-mediated drug disposition to describe drug elimination by receptor binding and internalization, and well characterizes the observed nonlinear pharmacokinetic (PK) profiles. The s.c. doses exhibited an absorption phase (Tmax = 3 h) and incomplete bioavailability (F = 0.3-0.7). An indirect response model for stimulation of neopterin triphosphate production by activated receptor complex followed by conversion to neopterin was used to jointly model the formation and loss of neopterin with a capacity factor Smax = 23.8. Greater relative neopterin response after s.c. dosing was accounted for by prolonged receptor activation relative to the SC50 value. Repeated daily s.c. dosing produced modestly elevated IFN-beta1a concentrations and neopterin concentrations that were lower than simulated from single-dose modeling. Although several mechanisms could be involved, these phenomena were simply remodeled as down-regulation of Smax and receptors. The PK/PD model for IFN-beta1a depicts receptor binding as a key feature controlling nonlinear elimination, nonstationary kinetics, and neopterin induction in a manner consistent with known processes controlling its disposition and pharmacological effects.

Persistent neutralizing antibodies abolish the interferon beta bioavailability in MS patients

BACKGROUND

MxA is an antiviral protein exclusively induced by type I interferons (IFN) and some viruses, and MxA gene expression is one of the most appropriate markers for measuring the biologic activity of exogenous IFNbeta.

METHODS

A new quantitative-competitive PCR method was used to quantify MxA mRNA in peripheral blood mononuclear cells of 99 treatment-naïve and 92 IFNbeta-treated patients with MS (22 Avonex, 17 Betaferon, and 53 Rebif-22). Every 3 months, IFNbeta-induced neutralizing antibodies (NAb) were evaluated in sera using a cytopathic effect assay. Three categories of patients were identified: NAb negative (NAb-), persistent NAb positive (NAb+, >or=2 consecutive positive samples), and isolated NAb+ (one positive sample).

RESULTS

Treatment-naïve patients expressed detectable MxA mRNA levels (mean = 36 +/- 32 fg MxA/pg glyceraldehyde-3-phosphate dehydrogenase (GAPDH); range 1 to 160) and an upper normal threshold was established (mean + 3 SD = 132 fg MxA/pg GAPDH). IFNbeta-treated patients exhibited more than 11-fold higher levels (mean = 412 +/- 282 fg MxA/pg GAPDH; range 16 to 1,172). However, 17 patients did not exhibit an increase in MxA mRNA level; 15 of these 17 patients showed a concurrent Nab+ titer. Moreover, 13 were persistent NAb+. Isolated NAb+ patients did not show a decrease in bioavailability of IFNbeta (n = 9; mean = 567 +/- 366 fg MxA/pg GAPDH; range 83 to 1,120). In NAb- patients, bioavailability was comparable among the three different IFNbeta preparations 12 hours after injection.

CONCLUSION

During IFNbeta therapy, the presence of NAb reduced or abolished bioavailability in a relevant percentage of patients. These data could be important for the early detection of patients with MS who are not responsive to IFNbeta therapy.

Receptor-mediated pharmacokinetic/pharmacodynamic model of interferon-beta 1a in humans

PURPOSE

An integrated receptor-based pharmacokinetic/pharmacodynamic (PK/PD) model of interferon-beta la (IFN-beta la) previously developed for monkeys was used to capture the time-course of drug and induced neopterin concentrations after intravenous (IV) and subcutaneous (SC) dosing in humans.

METHODS

Data were extracted from the literature by digitalization. Single-dose (3 IV doses and I SC dose) PK/PD profiles were simultaneously fitted using the basic model and the ADAPT II computer program. Additional submodels incorporating neutralizing antibody formation and negative feedback inhibition were applied to account for drug accumulation and lower than expected neopterin concentrations encountered after multiple-dosing (1 SC dose every 48 hs).

RESULTS

The basic model jointly-captured the nonlinear PK behavior of the drug and induced neopterin concentrations after all single doses. Slow and incomplete absorption (F = 0.33) of the SC dose resulted in prolonged drug concentrations reflective of flip-flop kinetics. Despite lower drug concentrations, SC dosing produced a similar neopterin profile as compared with the IV doses; however, with a longer time to peak effect and slightly higher neopterin concentrations at later time points. The PD component of the model represents a modified precursor-dependent indirect response model driven by the amount of internalized drug-receptor complex. The latter stimulated a 6-fold increase in the production of the neopterin precursor (Smax = 5.89). Drug accumulation and lower than expected neopterin concentrations after multiple dosing were also captured after the inclusion of the submodels.

CONCLUSIONS

The present integrated PK/PD model for IFN-beta 1a is mechanistic in nature with receptor-mediated disposition and dynamics and was successfully applied to human clinical data.

Interferon Beta-1a

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Mechanisms for regulation of cellular responsiveness to human IFN-beta1a

Interferons (IFNs) are potent, pleiotropic cytokines, and therefore it is likely that the cell has mechanisms to modulate IFN activity in response to excessive or prolonged IFN exposure. To investigate this question, Jurkat T cells were exposed to IFN-beta1a in vitro. The effect of dose and frequency of IFN treatment on receptor expression, the signal transduction pathway, and biologic activity was examined. Results demonstrate that at even modest doses of IFN (60 IU/ml), cell surface expression of the IFN receptor subunit, IFNAR-1, decreased significantly, and the cells were unresponsive to further IFN treatment. More interestingly, after an initial treatment with very low concentrations of IFN (<10 IU/ml), even when receptor levels remained normal and phosphorylation of signaling molecules occurred, cells were still refractory to further IFN treatment. After withdrawal of IFN, full cellular responsiveness was a progressive but surprisingly slow process. Cells retreated 2 days or 4 days after the initial IFN treatment were still refractory to even high doses (500 IU/ml) of IFN. Cells retreated 1 week after the initial IFN treatment were fully responsive. High levels of Stat1 and Stat2 correlated with the block in transcriptional activation of IFN-dependent genes and may be a mechanism by which cells can downmodulate an IFN response. Similar results were obtained when fresh peripheral blood mononuclear cells (PBMC) were treated with IFN and expression of the endogenous IFN-dependent gene, MxA, was examined. Cell surface levels of IFNAR-1 decreased and Stat1 levels increased after IFN-beta treatment, and retreatment with IFN resulted in an attenuated induction of Mx protein expression. In the context of using IFNs as therapeutic agents in the treatment of human disease, our data suggest that increasing the amount or frequency of IFN administration may not yield desired biologic effects. Thus, issues concerning the dosage and the frequency of IFN-beta administration deserve careful consideration.

Interferon-beta therapy in multiple sclerosis: evidence for a clinically relevant dose response

There have been considerable advances made recently in the treatment of multiple sclerosis (MS). In particular, interferon (IFN)beta has been demonstrated in several independent, multicentre clinical trials to lower unequivocally the biological activity of this illness. The results of these trials have been remarkably consistent, demonstrating a reduction in both disease activity and cumulative disability, using a combination of clinical and magnetic resonance imaging outcome measures. Nevertheless, the importance of the total weekly IFNbeta dose in the clinical management of individual patients has been controversial. However, there is considerable information available regarding the effect of IFNbeta dose on the various biochemical and clinical markers that are affected by IFNbeta, which is derived both from pre-clinical studies and multicentre clinical trials. On balance, convincing evidence is provided to support the notion that there is a clinically relevant dose-response in the use of IFNbeta to treat patients with relapsing/remitting MS. However, many of the clinical trials of IFNbeta in MS have confounded the potential effects of dose with the possible effects of frequency of IFNbeta administration. As a result, it is possible that the apparent dose-response observed in these clinical trials may be due, in part, to the more frequent dose administration schedule rather than the total weekly dose.

General pharmacokinetic model for drugs exhibiting target-mediated drug disposition

Drugs that bind with high affinity and to a significant extent (relative to dose) to a pharmacologic target such as an enzyme, receptor, or transporter may exhibit nonlinear pharmacokinetic (PK) behavior. Processes such as receptor-mediated endocytosis may result in drug elimination. A general PK model for characterizing such behavior is described and explored through computer simulations and applications to several therapeutic agents. Simulations show that model predicted plasma concentration vs. time profiles are expected to be polyexponential with steeper distribution phases for lower doses and similar terminal disposition phases. Noncompartmental parameters always show apparent Vss and CL(D) decreasing with dose, but apparent clearance decreases only when the binding process produces drug elimination. The proposed model well captured the time-course of drug concentrations for the aldose reductase inhibitor imirestat, the endothelin receptor antagonist bosentan, and recombinant human interferon-beta 1a. This type of model has a mechanistic basis and considerable utility for fully describing the kinetics for various doses of relevant drugs.

Impact of age and gender on the pharmacokinetics of gemtuzumab ozogamicin

STUDY OBJECTIVE

To determine the pharmacokinetic parameters of the components of gemtuzumab ozogamicin and to assess the possible influence of age and gender on the values.

DESIGN

Phase II, multicenter, open-label, nonrandomized, parallel study

SETTING

Hospitals and outpatient oncology clinics.

PATIENTS

Fifty-eight patients with acute myeloid leukemia in first relapse participated. Demographic data included 29 men and 29 women; 34 were younger than 60 years of age (mean age 53+/-16 yrs).

INTERVENTION

Patients received gemtuzumab ozogamicin as a single 2-hour infusion of 9 mg/m2. Serial plasma samples were collected over 10 days after the beginning of the infusion.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of components of gemtuzumab ozogamicin (hP67.6 antibody, total and unconjugated calicheamicin derivatives) were measured by validated enzyme-linked immunosorbent assays. Pharmacokinetic parameters were determined by noncompartmental methods and comparisons between groups were made by analysis of variance. No significant differences were seen between men and women or between those over 60 and those less than 60 years of age in maximum concentration, time to maximum concentration, area under the curve, clearance, or volume of distribution for components of gemtuzumab ozogamicin.

CONCLUSION

No differences occur in the pharmacokinetics of the components of gemtuzumab ozogamicin (hP67.6 or calicheamicin) based on gender or age.

Interferon-beta1a administration results in a transient increase of serum amyloid A protein and C-reactive protein: comparison with other markers of inflammation

Putative markers of inflammation such as serum beta2-microglobulin and neopterin have been shown to be transiently upregulated following interferon-beta (IFN-beta) administration to multiple sclerosis (MS) patients. However, to date the role of the important inflammatory mediators serum amyloid A protein (SAA) and C-reactive protein (CRP) have not been described. Here we show that SAA but not CRP is elevated in relapsing-remitting MS patients compared to normal healthy individuals, and furthermore that both are transiently upregulated following intramuscular injection with IFN-beta1a (Avonex). This pattern of expression was found to parallel that of beta2-microglobulin and neopterin following injection and was mirrored by a selective activation of peripheral monocytes with respect to upregulation of receptors known to be involved in the inflammatory response (HLA-DR, CD16 and CD86). Injection of saline solution intramuscularly to six healthy control individuals did not produce a similar upregulation of any of the inflammatory markers investigated. Following IFN-beta1a injection, all inflammatory responses were attenuated at week 12 of therapy in comparison to those following the initial injection in a group of follow-up patients. In addition, IFN-beta1a injected on a weekly basis did not produce a sustained modulation of any of the markers investigated in patients treated for 32 weeks.

Pharmacokinetics and pharmacodynamics of IFN-beta 1a in healthy volunteers

The pharmacokinetics of recombinant human interferon-beta1a (IFN-beta1a) (Rebif, Ares-Serono, Geneva, Switzerland) were investigated in healthy volunteers following intravenous (i.v.) administration of increasing single doses of the drug (22 microg/6 million international units [MIU], 44 microg/12 MIU, and 66 microg/18 MIU); i.v., intramuscular (i.m.), and subcutaneous (s.c.) administration of a 66-microg dose; and repeated s.c. administration of four 66-microg doses at 48-h intervals. The disposition of IFN-beta1a followed triexponential decay after i.v. administration (half-lives 3 min, 42 min, and 22 h, respectively). After s.c. and i. m. administration, absorption was the rate-limiting factor in the terminal phase. The median absolute bioavailabilities were 30% and 27%, respectively. The accumulation ratio after repeated s.c. injections was 2.4, and a terminal half-life of 66 h was observed. Intracellular 2-5A synthetase activity and serum neopterin and beta2-microglobulin concentrations increased after all IFN-beta1a injections and remained elevated following every-other-day administration. The local tolerance was good, and the systemic tolerance was satisfactory.

Therapeutic developments in multiple sclerosis

Recently there have been considerable advances made in the treatment of multiple sclerosis. For the first time since its initial clinical description in the 1800s, there are now available several medications which unequivocally exert favourable clinical effects through the lowering of the biological activity of the human illness. The therapeutic efficacy of IFN-beta preparations seems particularly well established in this regard on the basis of five large, independent, trials of this agent. These trials have demonstrated remarkably consistent reductions in both attack rates and disability levels using a combination of clinical and magnetic resonance imaging outcome measures. The therapeutic benefit of glatiramer acetate also has been well established, although there is less available data on this agent than there is for interferon. It is important to recognise, however, that, although these agents represent an important first step in the management of patients with multiple sclerosis, they are only partial therapies. In order to actually cure the illness or even to substantially improve patient outcome we need considerably better agents than we have currently. Nevertheless, it is likely that, with improved knowledge of the role that interferon beta plays in the pathogenesis of multiple sclerosis and with better understanding of the mechanism by which glatiramer acetate exerts its therapeutic effect, greatly improved therapeutic agents will be available in the future. In addition, it seems likely that, in the future (by analogy to the experience in oncology), we will begin utilising combinations of therapies in order to better control the biological activity of this debilitating disease. Such combination therapy will almost certainly include combinations of partially effective agents as well as combinations of these agents with other medications (e.g., the immunosuppressive drugs) which, by themselves, have only been demonstrated to exert marginal clinical benefits on the course of illness. Moreover, it also seems likely that, increasingly, therapeutic strategies that enhance or promote myelin repair will become a major focus of clinical research in this area.

Pharmacodynamic comparison of single doses of IFN-beta1a and IFN-beta1b in healthy volunteers

In a study in 75 volunteers, preparations of interferon-beta1b (IFN-beta1b) and IFN-beta1a were compared in terms of the resulting serum concentrations of three biologic markers, neopterin, human Mx protein, and 2',5' oligoadenylate synthetase. Each preparation was tested at five dose levels, the middle dose being that recommended for use in patients with multiple sclerosis on the basis of large clinical trials. Five randomly chosen volunteers each received a single subcutaneous dose of one of the IFN or of IFN-beta1a given intramuscularly. The amounts of each marker induced were dose related. There were no major differences between the results with the two IFN or in the duration of the changes in the markers after the two routes of injection. The data indicated that 8 million international units (MIU) of IFN-beta1b and 6 MIU of IFN-beta1a had very similar effects. Even after the highest single dose tested, the increase in the biologic markers were not sustained for a full week.

Changes in plasma cytokines induced by interferon-beta1a treatment in patients with multiple sclerosis

It has been postulated that the efficacy of interferon-beta1a in multiple sclerosis may be due to the induction of type 2 cytokines. In this report we demonstrate that after 3 months of therapy, there is no sustained alteration in the plasma levels of type 1 (IL-12, IL-1beta and TNF-alpha) or type 2 (IL-6, IL-10) cytokines, but rather repeated induction of both with each injection. Little alteration is seen in the profile of cytokines induced with time, despite a decline in side effects. This suggests that IFN-beta1a causes repeated transient modulation of cytokine expression, but no sustained deviation in the type 1/type 2 balance.

Influence of interferon beta-1a dose frequency on PBMC cytokine secretion and biological effect markers

Interferon-beta regimens for immune-mediated diseases, such as multiple sclerosis (MS), have not been compared regarding their biological effects. In this randomized, parallel-group, placebo-controlled study, cytokine secretion by mitogen-stimulated PBMCs and serum response markers were assessed in volunteers receiving subcutaneous recombinant IFN beta-1a (Rebif, Ares-Serono) 22 microg once a week (QW), 22 microg three times a week, 66 microg QW, or placebo. The production of IL-1beta, IL-6, IFN-gamma, TNF-alpha and TNF-beta markedly decreased during 24-48 h after each injection, with limited dose-dependency and no evidence of tolerance or effect augmentation over 1 month. IL-10 secretion remained unchanged. The increase in serum beta2-microglobulin, neopterin and 2-5A-synthetase was more sustained. Thus, IFN-beta-induced immunomodulation in vivo strongly depends on the administration schedule, the time-integrated effect being 2-3 times greater when a same weekly dose is divided in three injections.

Comparative study of the pharmacodynamic and pharmacologic effects of Betaseron and AVONEX

The aim of this 1 week study was to compare the biologic effects induced by Betaseron and AVONEX using their approved dose, route, and schedule. Sixteen healthy volunteers were randomly assigned to receive either a single i.m. dose of AVONEX (6 million International Units [MIU]) or, every other day s.c. doses of Betaseron (8 MIU). Common side effects associated with interferon-beta (IFN-beta) treatment and biologic response parameters (neopterin, beta2-microglobulin, interleukin-10 [IL-10], and MxA protein levels in blood) were measured. Ibuprofen was administered to all subjects throughout the study. Fever, chills, and myalgia occurred most frequently and with the greatest severity between 6 and 12 h after the first dose of either IFN-beta. Despite the additional dosing of subjects in the Betaseron group, the incidence, duration, and severity of the side effects were not significantly different from those in the AVONEX group. Biologic response parameters reached similar maximum concentrations in both treatment groups. In the Betaseron group, neopterin and beta2-microglobulin levels remained significantly greater than baseline throughout the 7 day study, whereas those in the AVONEX group were elevated only through day 5. Betaseron treatment significantly increased IL-10 levels above baseline, but AVONEX treatment did not. The overall induction of neopterin, beta2-microglobulin, and IL-10 (as measured by area under the concentration-time curve) was significantly greater in the Betaseron group than the AVONEX group (p = 0.031). The results of this study demonstrate that the approved Betaseron dosing regimen, in combination with ibuprofen use, provided a significantly greater and more consistently elevated biologic response compared with that of AVONEX and did so with a side effects profile comparable to that of once a week AVONEX dosing.

Structural and functional differences between glycosylated and non-glycosylated forms of human interferon-beta (IFN-beta)

PURPOSE

Two recombinant IFN-beta products have been approved for the treatment of multiple sclerosis, a glycosylated form with the predicted natural amino acid sequence (IFN-beta-1a) and a non-glycosylated form that has a Met-1 deletion and a Cys-17 to Ser mutation (IFN-beta-1b). The structural basis for activity differences between IFN-beta-1a and IFN-beta-1b, is determined.

METHODS

In vitro antiviral, antiproliferative and immunomodulatory assays were used to directly compare the two IFN-beta products. Size exclusion chromatography (SEC), SDS-PAGE, thermal denaturation, and X-ray crystallography were used to examine structural differences.

RESULTS

IFN-beta-1a was 10 times more active than IFN-beta-1b with specific activities in a standard antiviral assay of 20 x 10(7) IU/mg for IFN-beta-1a and 2 x 10(7) IU/mg for IFN-beta-1b. Of the known structural differences between IFN-beta-1a and IFN-beta-1b, only glycosylation affected in vitro activity. Deglycosylation of IFN-beta-1a produced a decrease in total activity that was primarily caused by the formation of an insoluble disulfide-linked IFN precipitate. Deglycosylation also resulted in an increased sensitivity to thermal denaturation. SEC data for IFN-beta-1b revealed large, soluble aggregates that had reduced antiviral activity (approximated at 0.7 x 10(7) IU/mg). Crystallographic data for IFN-beta-1a revealed that the glycan formed H-bonds with the peptide backbone and shielded an uncharged surface from solvent exposure.

CONCLUSIONS

Together these results suggest that the greater biological activity of IFN-beta-1a is due to a stabilizing effect of the carbohydrate on structure.

Comparative pharmacokinetics and pharmacodynamics of recombinant human interferon beta-1a after intramuscular and subcutaneous administration

The pharmacokinetics and pharmacodynamics of recombinant human interferon beta (IFN-beta-1a) were compared after intramuscular administration of two preparations (Rebif(R) and AvonexTM) and subcutaneous administration of Rebif(R). Healthy volunteers (n = 30) received a single dose (60 µg) of each of the three treatments in a randomised crossover study. Serum concentrations of IFN-beta were measured by enzyme-linked immunosorbent assay over 24 h after dosing. Pharmacodynamics were assessed by measurement of intracellular 2',5'-oligoadenylate synthetase activity, and serum neopterin and beta2-microglobulin concentrations, over 144 h after dosing. There was no significant difference between the three treatments in peak serum IFN-beta concentrations (Cmax) or area under the concentration-time curve (AUC). No significant differences in pharmacodynamic measures were observed between the three treatments. It is concluded that the bioavailability of IFN-beta-1a is equivalent after subcutaneous or intramuscular administration of Rebif(R), and intramuscular administration of AvonexTM. Copyright Rapid Science Ltd