Self-tolerance in multiple sclerosis.

During the last decade, several defects in self-tolerance have been identified in multiple sclerosis. Dysfunction in central tolerance leads to the thymic output of antigen-specific T cells with T cell receptor alterations favouring autoimmune reactions. In addition, premature thymic involution results in a reduced export of naïve regulatory T cells, the fully suppressive clone. Alterations in peripheral tolerance concern costimulatory molecules as well as transcriptional and epigenetic mechanisms. Recent data underline the key role of regulatory T cells that suppress Th1 and Th17 effector cell responses and whose immunosuppressive activity is impaired in patients with multiple sclerosis. Those recent observations suggest that a defect in self-tolerance homeostasis might be the primary mover of multiple sclerosis leading to subsequent immune attacks, inflammation and neurodegeneration. The concept of multiple sclerosis as a consequence of the failure of central and peripheral tolerance mechanisms to maintain a self-tolerance state, particularly of regulatory T cells, may have therapeutic implications. Restoring normal thymic output and suppressive functions of regulatory T cells appears an appealing approach. Regulatory T cells suppress the general local immune response via bystander effects rather than through individual antigen-specific responses. Interestingly, the beneficial effects of currently approved immunomodulators (interferons ß and glatiramer acetate) are associated with a restored regulatory T cell homeostasis. However, the feedback regulation between Th1 and Th17 effector cells and regulatory T cells is not so simple and tolerogenic mechanisms also involve other regulatory cells such as B cells, dendritic cells and CD56(bright) natural killer cells.

Endogenous neuroprotection in multiple sclerosis.

Endogenous neuroprotection was mostly investigated in stroke, trauma and neurodegenerative diseases. However, several endogenous neuroprotective mechanisms have been identified recently in multiple sclerosis: protective autoimmunity, direct low molecular weight antioxidants, indirect antioxidants inducing cytoprotective proteins, kynurenine pathways, ischemic preconditioning, integrated cell response, cannabinoids and complement system. Numerous endogenous neuroprotective strategies are investigated in animal models but the translation into the clinic of positive results obtained in the laboratory has been disappointing so far Endogenous neuroprotection is the net result of complex and interconnected mechanisms and modulating an individual neuroprotective pathway will likely yield a partial benefit, if any. Another concern, consistently observed in multiple sclerosis and its animal models, is that the same cells and the same chemical mediators can initiate degenerative cascades and/or neuroprotective pathways. The final outcome depends on the local microenvironment but most of the regulatory mechanisms that control the balancing of protective versus detrimental responses are unknown at present. Before experimental strategies are to become approved treatments further studies are necessary to understand the precise molecular mechanisms underlying neuroprotective pathways and their complex interconnections.

Neurodegeneration in multiple sclerosis: the role of oxidative stress and excitotoxicity.

In multiple sclerosis (MS) disability results from neuronal and axonal loss, the hallmark of neurodegenerative diseases (ND). Neurodegeneration is initiated by microglia activation and mediated by oxidative stress and excitotoxicity. The same sequence of events has been consistently observed in MS. However, microglia activation correlates with a marked cell infiltration in MS but not in ND. In both pathological states, peroxynitrite is the common initiating factor of oxidative stress and excitotoxicity and is thus a potential interesting therapeutic target. Oxidative stress leads to multiple lipid and protein damages via peroxidation and nitration processes. The pathomechanisms of excitotoxicity are complex involving glutamate overload, ionic channel dysfunction, calcium overload, mitochondriopathy, proteolytic enzyme production and activation of apoptotic pathways. The inflammatory component in MS is important for the design of therapeutic strategies. Inflammation not only causes axonal and neuronal loss but it also initiates the degenerative cascade in the early stage of MS. Potent anti-inflammatory agents are now available and it is not unreasonable to think that an early blockade of inflammatory processes might also block associated degenerative mechanisms and delay disability progression. The development of neuroprotective drugs is more problematic. Indeed, given the multiple and parallel mechanisms involved in neurodegeneration, modulation of a single specific pathway will likely yield a partial benefit if any.

Oxidative stress and excitotoxicity: a therapeutic issue in multiple sclerosis?

There is increasing evidence that multiple sclerosis (MS) is not only characterized by immune mediated inflammatory reactions but also by neurodegenerative processes. In neurodegenerative diseases, neuronal and axonal loss is mediated by oxidative stress and excitotoxicity which constitute a final common toxic pathway. Importantly, peroxynitrite is the key mediator of those two intertwined pathomechanisms. In MS, peroxynitrite is consistently associated with active lesions and produces highly toxic nitrating and oxidizing radical species that alter lipid, protein, DNA and mitochondrial structures and functions. During the remitting phase, peroxynitrite participates to neuron and oligodendrocyte damage in association with inflammatory processes. During the chronic phase, peroxynitrite contributes to self-perpetuating mechanisms responsible for disease progression. Neutralization of oxidative stress and excitotoxicity, and in particular of peroxynitrite derived free radicals, might represent a therapeutic approach to provide neuroprotection in MS.

Effect of mitoxantrone on MRI in progressive MS: results of the MIMS trial.

OBJECTIVE: To evaluate the effects of mitoxantrone (Mx) in progressive multiple sclerosis (MS) on MRI. METHODS: A total of 194 patients with worsening relapsing-remitting or secondary progressive MS were treated with Mx 12 mg/m2 (n = 34), Mx 5 mg/m2 (n = 40), or placebo (n = 36) at 3-month intervals IV over a 2-year period. In preselected MRI centers unenhanced and Gd-enhanced MRI scans were performed at month (M) 0, 12, and 24 in a non-randomized subset of 110 patients and non-selected for MRI criteria. The primary MRI outcome measure was the total number of MRI scans with positive Gd enhancement per group. RESULTS: Twelve mg/m2 Mx failed to reach a significant difference from placebo as measured by the primary MRI outcome at month 12 (p = 0.431) and 24 (p = 0.065). Secondary MRI outcome measures: 5 mg/m2 Mx influenced favorably the number of Gd-enhancing lesions only at month 24 (p = 0.004), but not at month 12 (p = 0.095). Twelve mg/m2 Mx reduced the number of T2-weighted lesions at month 24 (p = 0.027) and showed a positive trend at month 12 (p = 0.069), but not 5 mg/m2 Mx. The number of active MR lesions showed a strong trend toward reduction in the 12 mg/m2 Mx group only at month 24 (p = 0.054). All comparisons are vs placebo, and unadjusted for baseline incidence. CONCLUSIONS: In the MIMS trial 12 mg/m2 Mx does not reduce the number of MRI scans with positive Gd enhancement at month 12 and 24 vs placebo. Results of secondary MRI outcome measures are suggestive of a positive impact of 12 and 5 mg/m2 Mx on some of the Gd enhanced and unenhanced MRI measures as expected from other Mx MRI studies in the past.

Pixantrone (BBR2778): a new immunosuppressant in multiple sclerosis with a low cardiotoxicity.

Mitoxantrone (MX) has been approved by the Food and Drug Administration for the treatment of rapidly progressive multiple sclerosis (MS). Unfortunately, its long-term administration is prevented by the cardiotoxicity. Pixantrone (PIX) is an analogue of MX devoid of toxic effects on cardiac tissue and was developed as a replacement for other anthracenediones in cancer patients. With a view to an application in MS patients, experimental data demonstrated that PIX is as potent as MX in preventing acute experimental allergic encephalomyelitis development as well as the occurrence of relapses in the chronic model. Safety data from animal studies and from phase II trials in cancer patients confirm a very weak cardiotoxicity, if any. A phase I trial with PIX in patients with a rapidly progressive MS seems thus warranted.

New immunosuppressants with potential implication in multiple sclerosis.

New immunosuppressants are consistently developed to treat autoimmune diseases and some of them might have implications in multiple sclerosis (MS). A new antiproliferative agent, pixantrone, an analogue of mitoxantrone (MX), has a much lower cardiotoxicity and exerts the same potent immunosuppressive effects in experimental allergic encephalomyelitis (EAE). A phase I trial in MS patients is planned in the next future. New monoclonal antibodies (mAb) and other biological constructs containing foreign proteins are developed but their potential immunogenicity is a considerable drawback to their long-term administration. In addition, their beneficial effects in MS are not evident so far. Small molecules targeting the voltage-gated Kv1.3K+ channel regulating CA2+ signaling in T lymphocytes, specifically target activated, pathogenic T cells. Already found effective in EAE, those agents would be easier to handle than T-cell vaccination. Two new immunosuppressants with a unique mechanism of action (FTY720 and Epomycine M) selectively impair autoreactive T-cell homing, without affecting the other components of the immune response. The potent protective effect of TRY720 has been demonstrated in EAE and a phase I trial in MS appears warranted. Finally, a new concept about immunosuppressive treatments in organ transplantation, "tolerogenic immunosuppression", may have potential in MS.

Combination therapy for multiple sclerosis.

To improve the partial benefit of approved monotherapies in multiple sclerosis (MS), over 25 combined therapies have been tested in recent years, either as fixed-dose or sequential combination regimes. The main therapeutic targets for combination therapy in MS are the same as for monotherapy: the immune-mediated inflammatory cascade, oxidative toxicity and excitotoxicity. There are numerous reasons to consider combination therapy in MS, including to improve the benefit and/or tolerance in patients responding to approved treatments, stop frequent disabling relapses and/or rapid progression in patients who do not respond to approved therapies, and maintain the benefit of immunosuppressive treatments. Preliminary clinical trials suggest that combination therapy in MS does not increase the side-effects of approved monotherapy; its efficacy over monotherapy should therefore be tested. Statistically robust trials would need to involve many patients for each combination, so the first step in determining the efficacy of combination therapy should be to perform safety studies, followed by proof-of-concept efficacy studies.

Mitoxantrone in progressive multiple sclerosis: when and how to treat?

Mitoxantrone (MX) has been approved by the Food and Drug Administration (FDA) for the treatment of patients with worsening relapsing-remitting (RR) or secondary progressive (SP) multiple sclerosis (MS). However, indications should be refined and mitoxantrone reserved as a rescue therapy to: (1) patients in the relapsing-remitting phase with frequent and disabling exacerbations likely leading to permanent severe disability and (2) to patients in the secondary progressive phase whose disability progression rate increases by one EDSS point or more per year and who do not respond to other current therapies. An induction phase with the monthly intravenous administration of 12 mg/m(2) followed by a maintenance phase with 12 mg/m(2) every 3 months for 2 years seems the most effective and safe treatment regimen, not exceeding the maximum cumulative dose of 140 mg/m(2). Given the potent myelosuppressive activity of mitoxantrone, dosage should be carefully adapted to the body surface and hematological changes. Long-term toxicities (amenorrhoea and therapy-related leukemia) seem acceptable but a valid evaluation will need a longer follow-up in more patients. Cardiotoxicity, the major long-term toxicity, is clearly dose-dependent and is a strict treatment duration limiting factor. To reduce the risk of cardiac events, the drug should be administered by slow infusion (over 30 min). Analogs of mitoxantrone with a much lower cardiotoxicity are currently investigated in animal experimental models.

A study of therapy-related acute leukaemia after mitoxantrone therapy for multiple sclerosis.

To evaluate the incidence of therapy-related acute leukaemia (t-AL) after single-agent mitoxantrone (MITO) treatment, we reviewed medical records of patients in three studies of single-agent MITO therapy for multiple sclerosis (MS) and existing literature on MITO therapy in MS, leukaemia, and solid tumors. Of 1378 MITO recipients in the three MS studies (mean cumulative dose of 60 mg/m2 and mean follow-up of 36 months), one patient had t-AL, an observed incidence proportion of 0.07% [95% confidence interval (CI) = 0.00-0.40%]. There were no cases of t-AL in published reports of nine additional studies of single-agent MITO therapy for MS. There was one published case report of acute promyelocytic leukoemia detected five years after initiating MITO therapy for MS. The observed incidence proportion of t-AL is very low in patients who received MITO as single-agent therapy for MS. Although these observations provide preliminary reassurance, extended follow-up of these patients and those who receive higher cumulative doses of MITO is required to define the long-term risk of t-AL after MITO therapy for MS.

Cardiac adverse effects associated with mitoxantrone (Novantrone) therapy in patients with MS.

BACKGROUND: Mitoxantrone (MITO) is associated with dose-related cardiotoxicity when administered concomitantly with other cytotoxic agents with or without radiotherapy for leukemia and solid tumors. OBJECTIVE: To review observed cardiotoxicity of single-agent MITO therapy for MS. METHODS: Records of 1,378 patients from three clinical trials of MITO treatment for MS were reviewed for signs and symptoms of cardiac dysfunction and left ventricular ejection fraction (LVEF) results. Duration of follow-up was a median of 29 months (4,084 patient-years). RESULTS: No patients experienced congestive heart failure (CHF) before treatment. Cumulative MITO doses ranged from 2 to 183 mg/m(2) (mean 60.5 mg/m(2), median 62.5 mg/m(2)), and 141 patients received >100 mg/m(2). Two of 1,378 patients experienced CHF after initiating MITO therapy. Of 1,378 patients, 779 completed baseline and scheduled follow-up LVEF testing. Baseline LVEF was >50% in all 779 patients. Seventeen of 779 patients had asymptomatic LVEF of <50% (incidence proportion = 2.18%, 95% CI = 1.28 to 3.47%). Although the incidence of asymptomatic LVEF of <50% was not significantly related to monthly versus 3-monthly therapy, duration of therapy, age, or gender, asymptomatic LVEF of <50% trended higher with a cumulative dose of >/=100 mg/m(2) (5.0%) than with <100 mg/m(2) (1.8%) (p = 0.06). CONCLUSIONS: The observed incidence of CHF in patients with MS who received a mean cumulative dose of 60.5 mg/m(2) MITO was <0.20%. Continued monitoring of patients with MS who are receiving MITO is needed to determine whether the incidence of CHF increases with higher cumulative MITO doses and prolonged follow-up.

Bladder cancer in patients with multiple sclerosis treated with cyclophosphamide.

PURPOSE: We define the risk of bladder cancer in multiple sclerosis related to the use of indwelling catheters and cyclophosphamide administered as an immunomodulating agent. MATERIALS AND METHODS: We retrospectively reviewed the records of 2,351 patients with multiple sclerosis referred to the National Center for Multiple Sclerosis. RESULTS: Of the 2,351 patients 2 women and 5 men (0.29%) had bladder cancer. Of the 850 chronically catheterized patients the incidence was 0.7%. One patient with cancer performed intermittent catheterization for a rate of 0.23% in this group. In a subgroup of 70 patients treated with cyclophosphamide 5 chronically catheterized patients (5.7%) had bladder cancer. Hematuria was the most common presenting symptom. These data were compared with those in the literature on bladder cancer in spinal cord injury. CONCLUSIONS: These data suggest a possible synergistic role of cyclophosphamide and chronic catheterization in the induction of secondary bladder cancer. Regular cystoscopy is warranted in these patients to allow early detection of bladder tumors. Nitric oxide metabolism may be an important factor in the carcinogenesis of this type of bladder cancer.

Introductory remarks: immunosuppressive and immunomodulating drugs, where and how do they act?

Immunotherapies used in multiple sclerosis are reviewed. The mechanisms of action supporting their clinical application are described according to our current understanding. Immune treatments can be divided into three groups: (1) cytostatic and cytotoxic immunosuppressants which block the cell cycle of immunocompetent cells and/or provoke their deletion; (2) immunomodulators which specifically interfere in cellular or humoral immune mechanisms; (3) immunoregulators which restore immunodeficient states but have also immunosuppressive properties at the same time. Numerous attempts have been made to correct almost all abnormal immune mechanisms underlying disease progression. The results of those clinical trials are reviewed. Recent studies have demonstrated that a severe, unspecific and sustained immunosuppression markedly downregulates the clinical and pathological activity of the disease. Unfortunately, serious delayed adverse effects prevent a long-term administration. Recent specific immunomodulators with an acceptable toxicity have provided modest but unquestionable benefit on the attack rate and MRI lesion burden. No clear effect on progression has been demonstrated to date. There is still much work to be done to improve the efficacy of our current therapies on the attack rate and particularly on the progression. Several promising new compounds are already under evaluation. Another approach is combination therapies which will certainly become critical in MS like in other autoimmune diseases.

Mitoxantrone immunotherapy in multiple sclerosis.

Mitoxantrone, a cytotoxic agent recently developed, was subsequently found a very potent immunosuppressor. Experimental data in experimental allergic encephaloymyelitis demonstrated a dramatic suppression of both active and passive forms. Immune effects concern cellular and humoral components and are particularly persistent. B cell subset is preferentially deleted. Suppressor cells are relatively spared and suppression becomes dominant. In cancer therapy, the main advantages of mitoxantrone are a definitely better immediate tolerance and very low delayed adverse reactions (carcinogenicity, teratogenicity, impact on reproductive organs). Given its major immunosuppressive activity and its better tolerance, mitoxantrone was a potential candidate for multiple sclerosis therapy. Several clinical trials have confirmed the remarkable efficacy of mitoxantrone to reduce both attack and progression rates. Unfortunately the cardiotoxicity was found more frequent than expected and limits the maximum cumulative dose to 120 mg/m2. Mitoxantrone, when employed properly, may be useful in patients with frequent and disabling excerbations and/or rapidly progressing disability. It must be kept in mind that multiple sclerosis is a chronic disease, and that the benefit is limited to the period of administration of any treatment.

Homolateral disappearance of essential tremor after cerebellar stroke.

The case of a patient with essential tremor in whom tremor disappeared on the right side after a homolateral cerebellar infarct is reported. The pathophysiology of essential tremor remains unknown. Vascular and surgical lesions of dentorubrothalamic pathway have been reported to improve various kinds of tremor including essential tremor. In this patient, a lesion of this pathway related to the cerebellar infarct probably explains the homolateral cessation of essential tremor.