Breakthrough disease during interferon-β therapy in MS

Altered Immune Phenotypes and HLA-DQB1 Gene Variation in Multiple Sclerosis Patients Failing Interferon β Treatment

Background

Interferon beta (IFNβ) has been prescribed as a first-line disease-modifying therapy for relapsing-remitting multiple sclerosis (RRMS) for nearly three decades. However, there is still a lack of treatment response markers that correlate with the clinical outcome of patients.

Aim

To determine a combination of cellular and molecular blood signatures associated with the efficacy of IFNβ treatment using an integrated approach.

Methods

The immune status of 40 RRMS patients, 15 of whom were untreated and 25 that received IFNβ1a treatment (15 responders, 10 non-responders), was investigated by phenotyping regulatory CD4⁺ T cells and naïve/memory T cell subsets, by measurement of circulating IFNα/β proteins with digital ELISA (Simoa) and analysis of ~600 immune related genes including 159 interferon-stimulated genes (ISGs) with the Nanostring technology. The potential impact of HLA class II gene variation in treatment responsiveness was investigated by genotyping HLA-DRB1, -DRB3,4,5, -DQA1, and -DQB1, using as a control population the Milieu Interieur cohort of 1,000 French healthy donors.

Results

Clinical responders and non-responders displayed similar plasma levels of IFNβ and similar ISG profiles. However, non-responders mainly differed from other subject groups with reduced circulating naïve regulatory T cells, enhanced terminally differentiated effector memory CD4⁺ T_EMRA cells, and altered expression of at least six genes with immunoregulatory function. Moreover, non-responders were enriched for HLA-DQB1 genotypes encoding DQ8 and DQ2 serotypes. Interestingly, these two serotypes are associated with type 1 diabetes and celiac disease. Overall, the immune signatures of non-responders suggest an active disease that is resistant to therapeutic IFNβ, and in which CD4⁺ T cells, likely restricted by DQ8 and/or DQ2, exert enhanced autoreactive and bystander inflammatory activities.

Efficacy of alemtuzumab over 6 years in relapsing-remitting multiple sclerosis patients who relapsed between courses 1 and 2: Post hoc analysis of the CARE-MS studies

BACKGROUND

Alemtuzumab is administered as two annual courses for relapsing-remitting multiple sclerosis (MS). Patients may relapse before completing the two-course regimen.

OBJECTIVE

The objective was to evaluate 6-year outcomes in patients who relapsed between alemtuzumab Courses 1 and 2 (early relapsers).

METHODS

Post hoc analysis of patients from the Comparison of Alemtuzumab and Rebif^® Efficacy in Multiple Sclerosis (CARE-MS) studies who enrolled in the extension.

RESULTS

Early relapsers (CARE-MS I: 15%; CARE-MS II: 24%) had more relapses in 1-2 years pre-alemtuzumab and higher mean baseline Expanded Disability Status Scale score than patients without relapse. Their annualized relapse rate declined from Year 1 (CARE-MS I: 1.3; CARE-MS II: 1.2) to Year 2 following Course 2 (0.3; 0.5) and remained low thereafter. Over 6 years, 60% remained free of 6-month confirmed disability worsening; 24% (CARE-MS I) and 34% (CARE-MS II) achieved 6-month confirmed disability improvement. During Year 6, 69% (CARE-MS I) and 68% (CARE-MS II) were free of magnetic resonance imaging (MRI) disease activity. Median percent yearly brain volume loss (Year 1: -0.67% (CARE-MS I); -0.47% (CARE-MS II)) declined after Course 2 (Year 6: -0.24%; -0.13%).

CONCLUSION

Early relapsers' outcomes improved after completing the second alemtuzumab course. These findings support administering the approved two-course regimen to maximize clinical benefit.

CLINICALTRIALS.GOV REGISTRATION NUMBERS

CARE-MS I, II, extension: NCT00530348, NCT00548405, NCT00930553.

A cell type-specific transcriptomic approach to map B cell and monocyte type I interferon-linked pathogenic signatures in Multiple Sclerosis

Alteration in endogenous Interferon (IFN) system may profoundly impact immune cell function in autoimmune diseases. Here, we provide evidence that dysregulation in IFN-regulated genes and pathways are involved in B cell- and monocyte-driven pathogenic contribution to Multiple Sclerosis (MS) development and maintenance. In particular, by using an Interferome-based cell type-specific approach, we characterized an increased susceptibility to an IFN-linked caspase-3 dependent apoptotic cell death in both B cells and monocytes of MS patients that may arise from their chronic activation and persistent stimulation by activated T cells. Ongoing caspase-3 activation functionally impacts on MS monocyte properties influencing the STAT-3/IL-16 axis, thus, driving increased expression and massive release of the bio-active IL-16 triggering and perpetuating CD4⁺ T cell migration. Importantly, our analysis also identified a previously unknown multi-component defect in type I IFN-mediated signaling and response to virus pathways specific of MS B cells, impacting on induction of anti-viral responses and Epstein-barr virus infection control in patients. Taking advantage of cell type-specific transcriptomics and in-depth functional validation, this study revealed pathogenic contribution of endogenous IFN signaling and IFN-regulated cell processes to MS pathogenesis with implications on fate and functions of B cells and monocytes that may hold therapeutic potential.

A gene expression study denies the ability of 25 candidate biomarkers to predict the interferon-beta treatment response in multiple sclerosis patients

We studied the baseline expression level of 25 interferon-regulated genes (MxA, GPR3, IL17RC, ISG15, TRAIL, OASL, IFIT1, IFIT2, RSAD2, OAS3, IFI44L, TRIM22, IL10, CXCL10, STAT1, OAS1, OAS2, IFNAR1, IFNAR2, IFNβ, ISG20, IFI6, PKR, IRF7, USP18), recurrently proposed in the literature as predictive biomarkers of interferon-beta treatment response, in whole blood of 10 "responders" and 10 "non-responders" multiple sclerosis relapsing-remitting patients, retrospectively selected on the basis of stringent clinical criteria after a five years follow-up. However, we cannot confirm the predictive value of these candidate biomarkers.

Endogenous interferon-β-inducible gene expression and interferon-β-treatment are associated with reduced T cell responses to myelin basic protein in multiple sclerosis

Autoreactive CD4⁺ T-cells are considered to play a major role in the pathogenesis of multiple sclerosis. In experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis, exogenous and endogenous type I interferons restrict disease severity. Recombinant interferon-β is used for treatment of multiple sclerosis, and some untreated multiple sclerosis patients have increased expression levels of type I interferon-inducible genes in immune cells. The role of endogenous type I interferons in multiple sclerosis is controversial: some studies found an association of high expression levels of interferon-β-inducible genes with an increased expression of interleukin-10 and a milder disease course in untreated multiple sclerosis patients, whereas other studies reported an association with a poor response to treatment with interferon-β. In the present study, we found that untreated multiple sclerosis patients with an increased expression of interferon-β-inducible genes in peripheral blood mononuclear cells and interferon-β-treated multiple sclerosis patients had decreased CD4⁺ T-cell reactivity to the autoantigen myelin basic protein ex vivo. Interferon-β-treated multiple sclerosis patients had increased IL10 and IL27 gene expression levels in monocytes in vivo. In vitro, neutralization of interleukin-10 and monocyte depletion increased CD4⁺ T-cell reactivity to myelin basic protein while interleukin-10, in the presence or absence of monocytes, inhibited CD4⁺ T-cell reactivity to myelin basic protein. Our findings suggest that spontaneous expression of interferon-β-inducible genes in peripheral blood mononuclear cells from untreated multiple sclerosis patients and treatment with interferon-β are associated with reduced myelin basic protein-induced T-cell responses. Reduced myelin basic protein-induced CD4⁺ T-cell autoreactivity in interferon-β-treated multiple sclerosis patients may be mediated by monocyte-derived interleukin-10.

Trichuris suis ova therapy in relapsing multiple sclerosis is safe but without signals of beneficial effect

Background:

An observational study has suggested that relapsing–remitting multiple sclerosis patients with helminth infections have lower disease activity and progression than uninfected multiple sclerosis patients.

Objective:

To evaluate the safety and efficacy on MRI activity of treatment with TSO in relapsing MS.

Methods:

The study was an open-label, magnetic resonance imaging assessor-blinded, baseline-to-treatment study including ten patients with relapsing forms of multiple sclerosis. Median (range) age was 41 (24–55) years, disease duration 9 (4–34) years, Expanded Disability Status Scale score 2.5 (1–5.0), and number of relapses within the last two years 3 (2–5). Four patients received no disease modifying therapy, while six patients received IFN-β. After an observational period of 8 weeks, patients received 2500 ova from the helminth Trichuris suis orally every second week for 12 weeks. Patients were followed with serial magnetic resonance imaging, neurological examinations, laboratory safety tests and expression of immunological biomarker genes.

Results:

Treatment with Trichuris suis orally was well-tolerated apart from some gastrointestinal symptoms. Magnetic resonance imaging revealed 6 new or enlarged T2 lesions in the run-in period, 7 lesions in the early period and 21 lesions in the late treatment period. Two patients suffered a relapse before treatment and two during treatment. Eight patients developed eosinophilia. The expression of cytokines and transcription factors did not change.

Conclusions:

In a small group of relapsing multiple sclerosis patients, Trichuris suis oral therapy was well tolerated but without beneficial effect.

Prediction of response to interferon therapy in multiple sclerosis

OBJECTIVE

Single nucleotide polymorphisms (SNPs) in the genes encoding interferon response factor (IRF)-5, IRF-8 and glypican-5 (GPC5) have been associated with disease activity in multiple sclerosis (MS) patients treated with interferon (IFN)-β. We analysed whether SNPs in the IRF5, IRF8 and GPC5 genes are associated with clinical disease activity in MS patients beginning de novo treatment with IFN-β.

METHODS

The SNPs rs2004640, rs3807306 and rs4728142 in IRF5, rs13333054 and rs17445836 in IRF8 and rs10492503 in GPC5 were genotyped in 575 patients with relapsing-remitting MS followed prospectively after the initiation of their first treatment with IFN-β.

RESULTS

62% of patients experienced relapses during the first 2 years of treatment, and 32% had disability progression during the first 5 years of treatment. Patients with a pretreatment annualized relapse rate >1 had an increased risk of relapse (hazard ratio 1.53, 95% confidence interval 1.24-1.90) and progression (hazard ratio 1.48, 95% confidence interval 1.10-1.99) on treatment and patients with breakthrough relapses in the form of relapses during the first 2 years of treatment had an increased risk of progression during the first 5 years of treatment (hazard ratio 2.04, 95% confidence interval 1.47-2.85).The gene variants in IRF5, IRF8 and GPC5 were not associated with risk of relapse or disease progression.

CONCLUSIONS

Pretreatment relapse rate and clinical disease activity during the first 2 years of treatment may be associated with disease progression in MS patients treated with IFN-β. Genetic analysis of the studied gene variants do not provide additional information.

Are randomized, blind clinical trials enough to guide individualized decisions for patients with neurologic diseases?

The practice of medicine relies on the patient-physician relationship, knowledge, and clinical judgment. Randomized controlled trials (RCTs) remain the least biased method for studying the effects of interventions in selected populations and are the only method to control adequately for unknown confounders. However, physicians face the limitations of RCTs on a daily basis as they treat relatively unselected populations and individual patients. We explore the benefits and limitations of RCTs for some neurologic disorders, and discuss the difficulties of predicting individualized outcomes and anticipating treatment responses in those heterogeneous conditions. Observational studies and advances in understanding neurologic diseases complement RCTs in decision-making. Considerable challenges remain for personalized medicine; for now, clinicians must rely on their ability to integrate evidence and clinical judgment.

A changing treatment landscape for multiple sclerosis: challenges and opportunities

Multiple sclerosis (MS) is primarily an autoimmune disease of the central nervous system, but also encompasses prominent neurodegenerative aspects. A significant proportion of MS patients will develop neurological disability over time and up until recently treatment options have been limited. However, MS treatment is now at a stage of rapid progress, with several new drugs that have reached the market or will be launched in the near future. This provides new opportunities for individualized treatment, but also creates new challenges regarding monitoring of disease activity, long-term safety issues and efficacy, not least in patients with progressive disease.

The chemokine receptor CCR5 Δ32 allele in natalizumab-treated multiple sclerosis

OBJECTIVE

The chemokine receptor CCR5 may be important for the recruitment of pathogenic T cells to the CNS in multiple sclerosis (MS). We hypothesized that this chemokine receptor might still be important for T-cell migration during treatment with anti-very late antigen (VLA)-4 antibody. We therefore analysed whether natalizumab-treated MS patients carrying the CCR5 Δ32 deletion allele, which results in reduced expression of CCR5 on the cell surface, had lower disease activity.

METHODS

CCR5 Δ32 was analysed in 212 natalizumab-treated MS patients.

RESULTS

CCR5 Δ32 status had no significant impact on the frequency of relapses 1 year prior to natalizumab treatment or during the first 48 weeks of treatment. The multiple sclerosis severity score (MSSS) was significantly lower at baseline in patients carrying CCR5 Δ32 (P = 0.031).

CONCLUSIONS

CCR5 Δ32 is not associated with lower disease activity in MS patients treated with natalizumab. We found lower MSSS scores in patients carrying CCR5 Δ32 compared with the remaining patients, which is consistent with previous studies reporting an association with a more favourable disease course. Further studies are, however, needed before the relationship between CCR5 Δ32 and disease activity in MS can be definitely established.

Guidelines on the clinical use for the detection of neutralizing antibodies (NAbs) to IFN beta in multiple sclerosis therapy: report from the Italian Multiple Sclerosis Study group

Interferon beta (IFNβ) was the first specific disease-modifying treatment licensed for relapsing-remitting multiple sclerosis, and is still one of the most commonly prescribed treatments. A strong body of evidence supports the effectiveness of IFNβ preparations in reducing the annual relapse rate, magnetic resonance (MRI) disease activity and disease progression. However, the development of binding/neutralizing antibodies (BAbs/NAbs) during treatment negatively affects clinical and MRI outcomes. Therefore, guidelines for the clinical use for the detection of NAbs in MS may result in better treatment of these patients. In October 2012, a panel of Italian neurologists from 17 MS clinics convened in Milan to review and discuss data on NAbs and their clinical relevance in the treatment of MS. In this paper, we report the panel's recommendations for the use of IFNβ Nabs detection in the early identification of IFNβ non-responsiveness and the management of patients on IFNβ treatment in Italy, according to a model of therapeutically appropriate care.

Differential microRNA expression in blood in multiple sclerosis

BACKGROUND

microRNAs (miRNAs) regulate the expression of the genome at the post-transcriptional level. They play a role in autoimmunity and inflammation, and show potential for use as therapeutic targets in many diseases. With the recent detection of miRNAs in body fluids, the possibility for using miRNAs as diagnostic biomarkers has emerged.

OBJECTIVE

We assessed whether miRNAs contribute to the altered immune activation state in relapsing-remitting multiple sclerosis (RRMS) patients and investigated the possible use of miRNAs as diagnostic biomarkers in multiple sclerosis (MS).

METHODS

We performed global miRNA expression profiling analysis in peripheral blood mononuclear cells (PBMCs) and selected miRNAs were measured in plasma. We detected expression of miRNAs by real-time qPCR and compared results with cytokines related to inflammation and disease activity. Selected miRNAs were analyzed in PBMC subpopulations, after isolating them by magnetic bead separation.

RESULTS

We found that among validated miRNAs, let-7d correlated with the pro-inflammatory cytokine interleukin-1B. The miR-145 was 3-fold up-regulated in MS patients; its possible use as a diagnostic biomarker in PBMCs, plasma and serum was confirmed by ROC-curve analysis (Area under the curve (AUC) 0.785, p = 0.0004; 0.785, p = 0.004; 0.981, P < 0.0001, respectively).

CONCLUSIONS

RRMS patients in remission had altered expression of miRNAs. We validated miR-145 as a potential diagnostic biomarker for the diagnosis of MS in blood, plasma and serum.

Serum levels of IL-17A in patients with relapsing–remitting multiple sclerosis treated with interferon-β

Background:

Interleukin-17 (IL-17), which is secreted by Th17 cells, is a proinflammatory cytokine that is implicated in the pathogenesis of multiple sclerosis (MS) and plays a role in nonresponse of MS patients to interferon-β (IFN-β) therapy.

Objectives:

The purpose of this study was to establish a correlation between nonresponders (NR) and IL-17A serum titers and binding antibodies (BAbs) to IFN-β, as well as to find a correlation between IL-17A serum levels and other features of MS patients.

Methods:

Our prospective study included 72 inactive relapsing–remitting multiple sclerosis (RRMS) patients that had been treated for at least 18 months with IFN-β and 15 healthy subjects. We determined the serum levels of IL-17A and of BAbs. IL-17A levels were considered elevated (IL-17A+) if the recorded value was greater than 1.6 pg/ml.

Results:

Twenty-seven patients (37.5%) were NR and had a significantly higher serum IL-17A level compared to the responders group. Nineteen patients (26.4%) were IL-17A+ and had had a significantly higher number of relapses in the previous year and a higher Expanded Disability Status Score. The majority of IL-17A+ patients were NR and had a shorter MS duration.

Conclusions:

RRMS patients with high serum IL-17A levels do not respond well to IFN-β therapy and have shorter MS duration compared to patients with low IL-17A levels. This response is not influenced by the presence of BAbs.

Endogenous and recombinant type I interferons and disease activity in multiple sclerosis

Although treatment of multiple sclerosis (MS) with the type I interferon (IFN) IFN-β lowers disease activity, the role of endogenous type I IFN in MS remains controversial. We studied CD4+ T cells and CD4+ T cell subsets, monocytes and dendritic cells by flow cytometry and analysed the relationship with endogenous type I IFN-like activity, the effect of IFN-β therapy, and clinical and magnetic resonance imaging (MRI) disease activity in MS patients. Endogenous type I IFN activity was associated with decreased expression of the integrin subunit CD49d (VLA-4) on CD4+CD26(high) T cells (Th1 helper cells), and this effect was associated with less MRI disease activity. IFN-β therapy reduced CD49d expression on CD4+CD26(high) T cells, and the percentage of CD4+CD26(high) T cells that were CD49d(high) correlated with clinical and MRI disease activity in patients treated with IFN-β. Treatment with IFN-β also increased the percentage of CD4+ T cells expressing CD71 and HLA-DR (activated T cells), and this was associated with an increased risk of clinical disease activity. In contrast, induction of CD71 and HLA-DR was not observed in untreated MS patients with evidence of endogenous type IFN I activity. In conclusion, the effects of IFN-β treatment and endogenous type I IFN activity on VLA-4 expression are similar and associated with control of disease activity. However, immune-activating effects of treatment with IFN-β may counteract the beneficial effects of treatment and cause an insufficient response to therapy.

Reassessment of blood gene expression markers for the prognosis of relapsing-remitting multiple sclerosis

Despite considerable advances in the treatment of multiple sclerosis, current drugs are only partially effective. Most patients show reduced disease activity with therapy, but still experience relapses, increasing disability, and new brain lesions. Since there are no reliable clinical or biological markers of disease progression, long-term prognosis is difficult to predict for individual patients. We identified 18 studies that suggested genes expressed in blood as predictive biomarkers. We validated the prognostic value of those genes with three different microarray data sets comprising 148 patients in total. Using these data, we tested whether the genes were significantly differentially expressed between patients with good and poor courses of the disease. Poor progression was defined by relapses and/or increase of disability during a two-year follow-up, independent of the administered therapy. Of 110 genes that have been proposed as predictive biomarkers, most could not be confirmed in our analysis. However, the G protein-coupled membrane receptor GPR3 was expressed at significantly lower levels in patients with poor disease progression in all data sets. GPR3 has therefore a high potential to be a biomarker for predicting future disease activity. In addition, we examined the IL17 cytokines and receptors in more detail and propose IL17RC as a new, promising, transcript-based biomarker candidate. Further studies are needed to better understand the roles of these receptors in multiple sclerosis and its treatment and to clarify the utility of GPR3 and IL17RC expression levels in the blood as markers of long-term prognosis.

Glatiramer acetate antibodies, gene expression and disease activity in multiple sclerosis

BACKGROUND

Glatiramer acetate (GA) treatment suppresses disease activity in multiple sclerosis (MS). The immunological response to treatment may differ in patients who are stable on GA therapy and patients with breakthrough disease activity, but the results of previous studies are inconsistent.

OBJECTIVES

We studied the immunological response to GA and its relationship with disease activity.

METHODS

Anti-GA antibodies in plasma and the expression of genes encoding cytokines and T-cell-polarizing transcription factors in blood cells were analysed by flow cytometric bead array and polymerase chain reaction (PCR) analysis in 39 untreated and 29 GA-treated relapsing-remitting MS patients. Definition of breakthrough disease was based on the occurrence of relapses, disability progression, or gadolinium (Gd)-enhanced MRI.

RESULTS

The expression of T helper type 1 (Th1) and Th17 cytokines and transcription factors was reduced during long-term treatment, but there was no relationship between the expression of cytokines and transcription factors and anti-GA antibodies. High expression of mRNA encoding GATA3 and lymphotoxin-β (LT-β) was associated with low disease activity in Gd-enhanced MRI studies. None of the variables studied were associated with clinical disease activity. GA treatment resulted in the development of IgG and IgG4 anti-GA antibodies during the first months of treatment, persisting during long-term treatment.

CONCLUSIONS

The observed relationship between the expression of mRNA encoding GATA3 and LT-β expression and MRI disease activity deserves further analysis in future studies. The development of anti-GA antibodies was observed in all patients treated with GA, but this was not related with measures of cellular immunity, clinical or MRI disease activity.

Sieving treatment biomarkers from blood gene-expression profiles: a pharmacogenomic update on two types of multiple sclerosis therapy

Interferon-β (IFN-β) and glatiramer acetate are routinely used to inhibit disease activity in multiple sclerosis, but their mechanisms of action are incompletely understood. Individual treatment responses vary and candidate molecular markers that predict them have yet to be established. Why some patients respond poorly to a certain treatment while others respond well is addressed by the pharmacogenomic approach, which postulates that the molecular response to treatment correlates with the clinical effects, and thus seeks biological markers to estimate prognosis, guide therapy, comprehend the drugs' mechanisms of action and offer insights into disease pathogenesis. A poor clinical response can be owing to genetic variants in drug receptors or signaling components, or the appearance of neutralizing antibodies that interfere with the drug's binding efficacy. Independently, such mechanisms could lead to inadequate, that is to say unchanged, molecular responses, or exceedingly increased or decreased changes. By means of DNA microarray studies, various research groups endeavour to establish a clinically relevant relationship between the biological response to these drugs and treatment effects. Molecular profiles obtained in this way differ in the pattern and number of modulated genes, suggesting the existence of an individual 'drug-response fingerprint'. To further unravel the underlying regulatory interaction structure of the genes responsive to these immunotherapies represents a daunting but inevitable task. In this article, we focus on longitudinal ex vivo transcriptomic studies in multiple sclerosis and its therapy. We will discuss recurrently reported biomarker candidates, emphasizing those of immunologically meaning, and review studies with network module outputs.

Alterations in KLRB1 gene expression and a Scandinavian multiple sclerosis association study of the KLRB1 SNP rs4763655

Multiple sclerosis (MS) is a complex autoimmune disease affecting genetically susceptible individuals. A genome-wide association study performed by the International MS Genetics Consortium identified several putative susceptibility genes; among these, the KLRB1 gene is represented by the single-nucleotide polymorphism rs4763655. We could confirm a marginally significant association between rs4763655 and MS (P=0.046, odds ratio=1.06 (1.00-1.13)) in a large Scandinavian case-control study of 5367 MS patients and 4485 controls. The expression of KLRB1 in blood from MS patients was higher compared with healthy controls (P<0.001), and the KLRB1 expression decreased significantly (P<0.001) after interferon (IFN)-β treatment. KLRB1 was expressed in T and natural killer (NK) cells, and expression mainly decreased in NK cells in patients treated with IFN-β. Collectively, our results indicate that KLRB1 gene expression is altered in MS and likely to be involved in the pathogenesis of the disease, whereas rs4763655 in KLRB1 seems to have a minimal role in MS susceptibility.

Population pharmacokinetic-pharmacodynamic modeling of biological agents: when modeling meets reality

The pharmacokinetics (PK) and pharmacodynamics (PD) of many biological agents (biologics) have inherent complexities requiring specialized approaches to develop reliable, unbiased models. Three cases are covered: preponderance of zero values, nonresponder subpopulations, and adaptive dosing. Engineered biologics exhibit high affinity for target receptors. Biologics can saturate receptors, abolishing free receptor levels for protracted periods. Consequently, the distribution of observations can be heavy at, and near, the boundary. A 2-part model (ie, a truncated δ log-normal distribution) may be appropriate. Mixture models identify subpopulations based on bimodal or multimodal distributions of η values. With biologics, PD may be compromised because of lack of receptors, or the PD may be affected because of other events resulting in erratic excursions. Nonresponders exhibit a random walk-around placebo trajectory, resulting in high residual variability. The distributions of etas are often badly skewed or polymodal. An indescribable mixture model separates subjects who are nonresponders, providing diagnostic pharmacologic information on the drug. Many biologics use PD-based adaptive dosing. During model development, data used for model development include adaptive dosing. For simulation, adaptive dosing must be implemented. Failure to account for dose adjustments results in biased or inflated prediction intervals because subjects in the simulated data undergo inappropriate dose adjustments.

Neuroimaging in multiple sclerosis: neurotherapeutic implications

Imaging techniques, in particular magnetic resonance imaging (MRI), play an important role in the diagnosis and management of multiple sclerosis (MS) and related demyelinating diseases. Findings on MRI studies of the brain and spinal cord are critical for MS diagnosis, are used to monitor treatment response and may aid in predicting disease progression in individual patients. In addition, results of imaging studies serve as essential biomarkers in clinical trials of putative MS therapies and have led to important insights into disease pathophysiology. Although they are useful tools and provide in vivo measures of disease-related activity, there are some important limitations of MRI findings in MS, including the non-specific nature of detectable white matter changes, the poor correlation with clinical disability, the limited sensitivity and ability of standard measures of gadolinium enhancing lesions and T2 lesions to predict future clinical course, and the lack of validated biomarkers of long term outcomes. Advancements that hold promise for the future include new techniques that are sensitive to diffuse changes, the increased use of higher field scanners, measures that capture disease related changes in gray matter, and the use of combined structural and functional imaging approaches to assess the complex and evolving disease process that occurs during the course of MS.