Daniel D. Mikol

Comparison of subcutaneous interferon beta-1a with glatiramer acetate in patients with relapsing multiple sclerosis (the REbif vs Glatiramer Acetate in Relapsing MS Disease (REGARD) study): a multicentre, randomised, parallel, open-label trial

BACKGROUND Interferon beta-1a and glatiramer acetate are commonly prescribed for relapsing-remitting multiple sclerosis (RRMS), but no published randomised trials have directly compared these two drugs. Our aim in the REGARD (REbif vs Glatiramer Acetate in Relapsing MS Disease) study was to compare interferon beta-1a with glatiramer acetate in patients with RRMS. METHODS In this multicentre, randomised, comparative, parallel-group, open-label study, patients with RRMS diagnosed with the McDonald criteria who had had at least one relapse within the previous 12 months were randomised to receive 44 mug subcutaneous interferon beta-1a three times per week or 20 mg subcutaneous glatiramer acetate once per day for 96 weeks to assess the time to first relapse. A subpopulation of 460 patients (230 from each group) also had serial MRI scans to assess T2-weighted and gadolinium-enhancing lesion number and volume. Treatments were assigned by a computer-generated randomisation list that was stratified by centre. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00078338. FINDINGS Between February and December, 2004, 764 patients were randomly assigned: 386 to interferon beta-1a and 378 to glatiramer acetate. After 96 weeks, there was no significant difference between groups in time to first relapse (hazard ratio 0.94, 95% CI 0.74 to 1.21; p=0.64). Relapse rates were lower than expected: 258 patients (126 in the interferon beta-1a group and 132 in the glatiramer acetate group) had one or more relapses (the expected number was 460). For secondary outcomes, there were no significant differences for the number and change in volume of T2 active lesions or for the change in the volume of gadolinium-enhancing lesions, although patients treated with interferon beta-1a had significantly fewer gadolinium-enhancing lesions (0.24 vs 0.41 lesions per patient per scan, 95% CI -0.4 to 0.1; p=0.0002). Safety and tolerability profiles were consistent with the known profiles for both compounds. The overall number and severity of adverse events were similar between the treatments and were not an important cause for discontinuation of the trial during the 96 weeks. INTERPRETATION There was no significant difference between interferon beta-1a and glatiramer acetate in the primary outcome. The ability to predict clinical superiority on the basis of results from previous studies might be limited by a trial population with low disease activity, which is an important consideration for ongoing and future trials in patients with RRMS.

Oligodendrocyte-myelin glycoprotein (OMgp) is an inhibitor of neurite outgrowth

A protein fraction purified from bovine brain myelin, previously called arretin because of its ability to inhibit neurite outgrowth, has been identified as consisting predominantly of oligodendrocyte‐myelin glycoprotein (OMgp). We show that it is a potent inhibitor of neurite outgrowth from rat cerebellar granule and hippocampal cells; from dorsal root ganglion explants in which growth cone collapse was observed; from rat retinal ganglion neurons; and from NG108 and PC12 cells. OMgp purified by a different procedure from both mouse and human myelin behaves identically in all bioassays tested.

Mitoxantrone treatment of multiple sclerosis Safety considerations

Treatment of patients with mitoxantrone for worsening multiple sclerosis (MS) requires careful monitoring for possible adverse events. Common side effects that are minor and easily managed include transient leukopenia and elevated liver enzymes, nausea, alopecia, bluish discoloration of urine, and urinary tract infections. Amenorrhea, severe infection, cardiac toxicity, and toxic leukemias are more serious adverse events associated with mitoxantrone treatment but occur infrequently. The potential for clinically significant heart failure is low and is dose-related. Subclinical reductions in left ventricular ejection fraction may occur with serial doses, underscoring the importance of careful monitoring before initiating and during treatment. The risk for chronic cardiomyopathy limits the approved cumulative dose of mitoxantrone for treatment of MS to 140 mg/m2. Dexrazoxane has a cardioprotective effect when used with anthracycline in the treatment of patients with neoplasms. Studies under way address whether concomitant administration of dexrazoxane with mitoxantrone might decrease the risk for cardiac toxicity in MS patients and perhaps increase the allowable cumulative dose of mitoxantrone. A phase IV clinical study of mitoxantrone (RENEW) is in progress to assess the long-term safety and tolerability of treatment. Careful laboratory and cardiac monitoring can reduce the possibility of adverse events and enhance patient safety.

Caveolin-1 Expression in Schwann Cells

Caveolae are non-clathrin-coated invaginations of the plasma membrane, which are present in most cell types. An integral component of caveolae is the caveolin family of related proteins, which not only forms the structural framework of caveolae, but also likely subserves its functional roles, including regulation of signal transduction and cellular transport, in particular, cholesterol trafficking. Although caveolae have been identified ultrastructurally in the peripheral nervous system (PNS), caveolin expression has not previously been studied. To date, three caveolin genes have been reported. Here, we show for the first time that caveolin-1 is expressed by Schwann cells (SC) as well as several SC-derived cell lines. Caveolin-1 is enriched in the buoyant, detergent-insoluble membranes of rat sciatic nerve (SN) and SC, a hallmark of the caveolar compartment. Caveolin-1 exists as both soluble and insoluble forms in rat SN and SC, and localizes to SC cytoplasm and abaxonal myelin. SC caveolin-1 decreases after axotomy, when SC revert to a premyelinating phenotype. We speculate that caveolin-1 may regulate signal transduction and/or cholesterol transport in myelinating SC.

Efficacy of disease-modifying therapies in relapsing remitting multiple sclerosis: a systematic comparison.

The treatment of relapsing-remitting multiple sclerosis (RRMS) has become more effective over the last decade with the advent of the currently available disease-modifying therapies (DMTs). Pivotal clinical studies differ in many characteristics, such that cross-comparisons of relative risk reductions are of limited value and can be misleading. Our objective was to compare the clinical efficacy of currently approved first-line DMTs in patients with RRMS, applying an evidence-based medicine approach. We reviewed all phase III pivotal trials of DMTs. Six clinical trials of Avonex®, Betaseron®, Copaxone®, Rebif® and Tysabri® in patients with RRMS were identified for analysis. Only randomized, placebo-controlled, double-blind studies were included. The clinical efficacy endpoints compared were: proportion of relapse-free patients at 1 and 2 years; annualized relapse rate at 2 years; proportion of progression-free patients at 2 years, and proportion of patients free of gadolinium-enhancing lesions at 1 year or 9 months. Based on these analyses, Betaseron, Rebif, and Tysabri show comparable effects, whereas for several endpoints Avonex or Copaxone did not significantly differ from placebo. In the absence of head-to-head studies for all products used to treat RRMS, it still may be possible to compare treatment effects by applying evidence-based medicine principles.

Schwann cell caveolin-1 expression increases during myelination and decreases after axotomy

The caveolins are a family of related proteins that form the structural framework of caveolae. They have been implicated in the regulation of signal transduction, cell cycle control, and cellular transport processes, particularly cholesterol trafficking. Caveolin‐1 is expressed by a variety of cell types, including Schwann cells, although its expression is greatest in differentiated cell types, such as endothelial cells and adipocytes. In the present work, we characterize caveolin‐1 expression both during rat sciatic nerve development and after axotomy. Schwann cells express little caveolin‐1 on postnatal days 1 and 6. By P30, myelinating Schwann cells express caveolin‐1, which is localized in the outer/abaxonal myelin membranes as well as intracellularly. After axotomy, Schwann cell caveolin‐1 expression in the distal nerve stump decreases as Schwann cells revert to a premyelinating (p75‐positive) phenotype; residual caveolin‐1 within the nerve largely localizes to myelin debris and infiltrating macrophages. We speculate that caveolin‐1 plays a role in the biology of myelinating Schwann cells. GLIA 38:191–199, 2002.

The changing face of multiple sclerosis clinical trial populations

Abstract Background: Since the commercial introduction of disease-modifying drugs (DMDs) for the treatment of multiple sclerosis (MS), there have been numerous randomized placebo-controlled and head-to-head clinical trials assessing the efficacy and safety of these agents in relapsing–remitting MS (RRMS). Scope: Recent trials in the past 10 years demonstrate that the characteristics and behavior of clinical trial populations in RRMS have changed. Here we review evidence from key published clinical trials of DMDs in RRMS that highlights the general shift in trial populations, and examine the implications of this shift for future trial design. Findings: Populations in recent studies are characterized by lower clinical disease activity. This difference is apparent with regards to baseline patient characteristics and on-study behavior in terms of outcomes (e.g., relapse rates). The reasons for this shift are probably multifactorial and include study design, current treatment options, patient selection, and a possible change in the natural history of MS. Conclusions: The variation among study designs makes it difficult to draw more extensive conclusions about changes in clinical trial populations. However, these recent changes undoubtedly will affect interpretation of recent study results, some of which based clinical and statistical assumptions on earlier trials. Furthermore, the shift in populations has major implications for the design of future studies: (1) assumptions regarding effect size and statistical powering must be based on comparable patient populations; (2) larger trials of longer duration may be needed, possibly with stopping criteria based on the number of actual events rather than a preset, fixed time point for the end of study; (3) the use of biomarkers to facilitate identification of subpopulations may be considered; and (4) enhanced measures of disease activity (e.g., composite outcomes) may help to identify effects in multiple relevant MS outcomes. Furthermore, trial design may need to be modified to study the effects of a medication in patients who are representative of the anticipated patient population. To ensure that the clinical trial experience of a drug is reflected in its eventual clinical use, ‘real-life’ observation study programmers should be conducted to continuously monitor its effects in relevant populations and in comparison with available therapies.

Suppression of mitoxantrone cardiotoxicity in multiple sclerosis patients by dexrazoxane.

To explore the potential of dexrazoxane to suppress subclinical cardiotoxicity in MS patients receiving mitoxantrone.

High-Throughput Profiling of Ion Channel Activity in Primary Human Lymphocytes

We present a high-throughput method to quantify the functional activity of potassium (K (+)) ion channels in primary human lymphocytes. This method is rapid, automated, specific (here for the voltage-gated Kv1.3 ion channel), and capable of measuring, in parallel, the electrical currents of over 200 individual lymphocytes isolated from freshly drawn blood. The statistics afforded by high-throughput measurements allowed direct comparison of Kv1.3 activity in different subsets of lymphocytes, including CD4 (+) and CD8 (+) T cells, gammadelta T cells, and B cells. High-throughput measurements made it possible to quantify the heterogeneous, functional response of Kv1.3 ion channel activity upon stimulation of CD4 (+) and CD8 (+) T cells with mitogen. These experiments enabled elucidation of time-courses of functional Kv1.3 activity upon stimulation as well as studies of the effects of the concentration of mitogenic antibodies on Kv1.3 levels. The results presented here suggest that Kv1.3 ion channel activity can be used as a functional activation marker in T cells and that it correlates to cell size and levels of a surface antigen, CD25. Moreover, this work presents an enabling methodology that can be applied widely, allowing high-throughput screening of specific voltage-gated ion channels in a variety of primary cells.

Oligodendrocyte-Myelin Glycoprotein Is Present in Lipid Rafts and Caveolin-1-Enriched Membranes

The oligodendrocyte‐myelin glycoprotein is a ligand of the neuronal Nogo receptor and a potent inhibitor of neurite outgrowth, but its physiological function remains to be elucidated. The oligodendrocyte‐myelin glycoprotein is anchored solely in the outer leaflet of the plasma membrane via its glycosylphosphatidylinositol anchor, and through its leucine‐rich repeat domain, it likely interacts with other proteins. In the present study, we compare its buoyancy and detergent solubility characteristics with those of other myelin proteins. Based on its detergent solubility profile and membrane fractionation using established ultracentrifugation procedures, we conclude that the oligodendrocyte‐myelin glycoprotein is a lipid raft component that is closely associated with the axolemma. Moreover, it associates with caveolin‐1 and caveolin‐1‐enriched membranes. We postulate that, by virtue of its concentration in lipid rafts and perhaps through interactions with caveolin‐1, the oligodendrocyte‐myelin glycoprotein may influence signaling pathways.