Chapter 23

Immunosuppressive treatments in multiple sclerosis

DARIN T. OKUDA*

Clinical Center for Multiple Sclerosis, Department of Neurology and Neurotherapeutics,UT Southwestern Medical Center, Dallas, TX, USA

INTRODUCTION

Multiple sclerosis (MS) is a heterogeneous disorder ofthe central nervous system (CNS) that is enigmatic,relapsing, and in some instances progressive. Initially,the disease course is punctuated by acute neurologicrelapses, with associated changes observed within thebrain or spinal cord on magnetic resonance imaging(MRI). This may be followed by a period of neurodegen-eration characterized by progressive physical impair-ment in the absence of exacerbations. The underlyingpathogenic mechanism behind the development ofdemyelinating plaques provides a sound rationale forthe use of immunosuppressive medications in MS withoutcomes aimed at reducing the frequency of clinicalattacks, suppressing further progression on structuralneuroimaging of the brain and spinal cord, and prevent-ing physical and mental disability.

Prior to the discovery, study, and utilization of the USFood andDrugAdministration (FDA)-approved disease-modifying therapies (i.e., interferon (IFN-b) class ofmedications or glatiramer acetate), and even beforethe advent of MRI technology as a diagnostic or clinicalsurveillance tool, immunosuppressive treatments servedas essential medical therapy for patients with MS. Cur-rently, immunosuppressive agents are being utilized asmonotherapy or in combination with parenterally admin-istered immunomodulators as treatment for those whoare suboptimal responders, are intolerant or experienceadverse reactions to disease-modifying treatments, orfor patients who exhibit an aggressive disease course.

This chapter focuses on themost widely used immuno-suppressive treatments inMS: cyclophosphamide, metho-trexate, azathioprine, mycophenolate mofetil, and theonly FDA-approved chemotherapeutic agent for the

treatment of MS, mitoxandrone. Seminal data regardingits use inMS, the knownmechanism(s) of action, and con-temporary studies focusing on efficacy and safety datawill be reviewed. The role of these chemotherapeuticagents in the management of MS and implications fortherapeutic intervention are also discussed.

CYCLOPHOSPHAMIDE

Cyclophosphamide is an immunosuppressive agent thatwas commonly used in the treatment of MS prior to theapproval of platform disease-modifying therapies. Usedin the treatment of cancer, this chemotherapeutic hasbeen regarded within the field of neuroimmunology aspossessing the greatest potential for impacting the dis-ease course in MS when compared to the other non-FDA-approved treatments.

Cyclophosphamide is an alkylating agent related tonitrogen mustard that binds to DNA and disrupts cellreplication. This immunosuppressant is converted toactive metabolites in the liver (main active metabolite,4-hydroxycyclophosphamide) and targets rapidly prolif-erating malignant cells. It has been used in the treatmentof cancer, immune-mediated disorders (i.e., Wegener’sgranulomatosis, nephrotic syndrome, multiple mye-loma), including disorders of the peripheral nervous sys-tem, in addition to MS (Weiner, 2004).

The mechanism of action of cyclophosphamide isextensive. In general, the treatment serves as a generalimmune suppressant, impacting both cell-mediatedand humoral immunity, has been shown to suppressinterleukin-12 (IL-12) and Th1-type responses (Balashovet al., 1997), and enhances Th2 and Th3 activity, potenti-ating less inflammatorymediators, including IL-4, IL-10,and transforming growth factor-b and eosinophilia

*Correspondence to: Darin T. Okuda, MD, Associate Professor of Neurology, Clinical Center for Multiple Sclerosis,Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, 5959 Harry Hines Blvd, Dallas, TX 75390-

8829, USA. E-mail: darin.okuda@utsouthwestern.edu

Handbook of Clinical Neurology, Vol. 122 (3rd series)Multiple Sclerosis and Related DisordersD.S. Goodin, Editor© 2014 Elsevier B.V. All rights reserved

(Smith et al., 1997; Weiner, 2004). Specifically, cyclo-phosphamide has also been shown to upregulate the per-centage of anti-inflammatory CCR4þ IL-4-producingT cells while normalizing CCR5þ and CXCR3þ T cellsin secondary progressive MS patients (SPMS) (Karniet al., 2004), favoring a Th2-type response and sugges-ting that it may possess a more selective immune thera-peutic effect rather than serving solely as a generalimmune suppressant.

Varied dosing protocols exist for cyclophosphamidewith regimens dependent on the medical condition it isaimed to address. The therapy may be administeredorally or intravenously. The most widely used regimenis monthly pulsed therapy with 800 mg/m2 administeredmonthly for 1 year, followed by bimonthly treatmentsin those who are responders, although numerous otherregimens have been proposed, including the use of com-bined treatment with methylprednisolone. Dose adjust-ments are made based on the peripheral white bloodcell (WBC) nadir acquired on the 14th day following treat-ment (Oger, 2007). The rationale of this adjustment is toattenuate the peripheral WBC counts with levels between1500 and 2000 WBC/mm3.

Cyclophosphamide was first used in an MS patient in1966 (Aimard et al., 1966). Following this case report,landmark work was performed by Hommes, who ini-tially reported on 32 patients with chronic progressiveMS treated, in an open-label fashion, with 400 mg ofintravenous cyclophosphamide combined with predni-sone 100 mg daily (Hommes et al., 1975). Clinicalimprovements were observed in neurologic signs, func-tional systems, and disabilitymeasures inmore than 50%of treated patients. In addition, sustained improvementswere observed in the 0.5–3 years following treatment.

Studies involving larger cohorts followed. Gonsetteet al. (1977) reported on a cohort of 110 patients treatedwith intravenous cyclophosphamide over a 1–2-weekperiod (1–2 g exposure) in an effort to maintain a leuko-penia of 2000 and lymphopenia of 1000 for 2–3 weeks.These patients were followed over a time period of 2–4years. Improvements in clinical measures were observedin most cases and 62% of patients were found to havestabilization of disease over 2–4 years, suggesting thatintensive immunosuppressionmay interferewith diseasepathogenesis.

It has been suggested that cyclophosphamide may bemore impactful earlier in the disease course and in youn-ger patients with MS given the theoretic framework ofits overarching mechanism of action. Pediatric MS isunique, in comparison to adult forms, as the temporalprofile of disease appears to be different, with moreclinical relapses observed (Gorman et al., 2009), inaddition to notable differences on structural neuroimag-ing of the brain (Waubant et al., 2009). A unique CSF

inflammatory profile in young children withMS has alsobeen recently proposed, highlighting the existence ofpotential biological differences depending on age(Chabas et al., 2010).

Recently, the promise of cyclophosphamide was eval-uated in pediatric MS. The initial study involved a multi-center retrospective evaluation of 17 children, initiallydiagnosed with relapsing-remitting MS (RRMS), andtreatedwith a variety of employed regimens of cyclophos-phamide with doses ranging from 600 to 1000 mg/m2

administered (Makhani et al., 2009). In the majority ofpatients 1 year following treatment, a reduction in therelapse rate and stability of expanded disability statusscale (EDSS) scoreswas observed. The treatmentwaswelltolerated; however, bladder carcinoma was identified,and successfully treated, in a single patient. Overall, theseretrospective data provided evidence that cyclophospha-mide may be an appropriate therapeutic for childrenwho are refractory to treatment with routinely prescribedimmunomodulatory treatments, although further stratifi-cation beyond this is unclear.

The safety profile for cyclophosphamide is wellestablished. Aside from the anticipated side-effects ofnausea, vomiting, alopecia, transient immunosuppres-sion, and amenorrhea that are commonly observed in thistherapeutic class, the most common general cause forconcern over its use involves the development of hemor-rhagic cystitis, gonadal toxicity (in both men andwomen), bladder cancer, and future risk for malignan-cies. The risk of bladder carcinoma appears to be asso-ciated with cumulative exposures of >100 g andpossibly related to duration of exposure (2.7 years)(Talar-Williams et al., 1996). In the clinical setting, urinecytology and in some cases cystoscopy are recom-mended for clinical surveillance depending on theduration and cumulative exposure in a given patient.Aggressive hydration is also performed prior to and fol-lowing treatment in an effort to reduce risk. The effectof cyclophosphamide on the development of futuremalignancies even after discontinuation of the medica-tion was evaluated in a cohort of refractory rheumatoidarthritis patients treated with oral cyclophosphamide(Radis et al., 1995). After reviewing follow-up dataextending 20 years, a relative risk of 1.5 (95% confidenceinterval (CI) 0.93–5.5) for the development of cancerwas identified when comparing treated patients(n¼ 119) to an equal number of age, sex, disease durationand functional class-matched controls, suggesting thatthe risk for malignancy still persists even after treatmentcessation.

The current scientific data suggest that cyclophospha-mide is well tolerated and has a beneficial effect in MSpatients who exhibit an active inflammatory componentto their clinical case. In addition, this widely used and

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studied immunosuppressant may be an important thera-peutic consideration in treatment-nonresponsive oraggressive pediatric MS. At present, the literature sug-gests that it has a limited role in altering the course ofprogressive MS (Goodin et al., 2002) and its true impactonMRImeasures of disease is incompletely understood,yet future prospective studies, if designed, will help todetermine better if early intervention can be beneficialin suppressing long-term clinical disability. This uniqueimmunosuppressant may have a role as an inductionform of treatment in aggressive MS cases wherebyhigh-dose cyclophosphamide is administered monthlyfor a few years followed by long-term immunomodula-tory treatment. Given the unique biologic effects ofcyclophosphamide, it may be useful in low doses, incombination with an immunomodulatory agent or as aform of intervention when fulminant demyelinating dis-ease is present.

METHOTREXATE

Methotrexate is an antimetabolite principally used in thetreatment of neoplastic diseases, severe psoriasis, andadult rheumatoid arthritis. However, this relativelypotent oral immunosuppressant has been commonlyused as an off-label treatment for MS. Methotrexateinhibits dihydrofolate reductase, an enzyme responsiblefor the conversion of dihydrofolate into tetrahydrofo-late. Tetrahydrofolate and its derivatives are essentialfor purine and thymidylate synthesis and cell prolifera-tion and growth. Other beneficial anti-inflammatoryeffects within the immune system are theorized; how-ever the exact mechanism by which this is accomplishedis currently unknown. Overall, the mechanism of actionprovides a rationale for its use in cancer and autoim-mune disease.

At present, there are limited scientific data on well-designed, large clinical trials exploring the efficacy ofmethotrexate as an effective treatment in MS. In oneof the earliest randomized trials for methotrexate, 45patients with RRMS, chronic progressive MS, and pro-gressive MS were evaluated over a study period of 18months, with 44 included in the final data analysis(Currier et al., 1993). The aim of the trial was to studythe efficacy of low-dose methotrexate inMS, principallyby assessing differences in relapse rate and EDSS.Patients were randomized to receive either methotrexate2.5 mg every 12 hours for three consecutive doses once aweek (7.5 mg/week) versus placebo. No significant dif-ference in suppressing exacerbations was observedbetween groups; however, when evaluating the subgroupof RRMS patients there was a suggestion of benefit withfewer relapses observed in the treated versus nontreatedgroup (8/22 (36%) versus 9/22 (41%); p¼0.05). Overall,

the medication was well tolerated. In treated patients,nausea, elevation in liver function tests, and hair thin-ning were identified.

Further studies on the impact of methotrexate onchronic progressiveMS ensued. In a study of 60 patientswith clinically definite chronic progressive MS, partici-pants were stratified by EDSS score (3.0–5.5, 6.0–6.5)and randomized to receive either methotrexate (7.5 mgweekly) or placebo for 2 years, followed by an observa-tion period of 1 year (Goodkin et al., 1995). Clinical out-comes included the EDSS, ambulation index, box andblock test, and the 9-hole peg test. The principal findingof this investigation was the identification of less pro-gression of impairment in the 9-hole peg test(p¼0.017) and box and block test (p¼0.037) in patientswith EDSS>6.0. Adverse experiences were found to besimilar between methotrexate and placebo-treatedgroups. Although the number of patients evaluatedwas modest, this study provided data that methotrexatemay have promise in MS patients with chronic progres-siveMS who have more disability. The mechanisms as towhy this may occur are unclear but may be related to animmunosuppressive, anti-inflammatory, or immunoreg-ulatory effect.

The MRI effects of methotrexate within this cohortwere also published in a later paper (Goodkin et al.,1996). Thirty-one chronic progressive MS patients (16treated with methotrexate (7.5 mg/weekly), 15 placebo)with no clinical exacerbations during the 8 months pre-ceding study entry underwent contrast-enhanced MRIscans performed every 6 weeks for 6 months. An abso-lute change in the T2-weighted total lesion area was iden-tified in themethotrexate group after adjusting for studyweek and baseline T2-weighted total lesion area(p¼0.036). A modest relationship between T2-weightedtotal lesion area and 9-hole peg test performance wasalso observed (odds ratio¼ 1.4; p¼0.025). No significantdifferences in the presence of contrast-enhancing lesionwere observed between groups.

Recently, the effects of intrathecal methotrexate inMS patients with refractory disease were evaluated ina retrospective study (Sadiq et al., 2010). The rationalefor this delivery was based on the hypothesis that orallyadministered therapy may be suboptimal in impactingspinal cord disease, the area of the CNS believed to beprincipally responsible for clinical impairment in pro-gressive MS patients. Data were provided on 121patients (87 SPMS, 34 primary progressive MS (PPMS))who were exposed to eight methotrexate treatments(12.5 mg dose) administered every 8–11 weeks via lumbarpuncture or access port from a previously implantedpump. Follow-up data extending to a period of 1 year fol-lowing the time period of last treatment were evaluated.Outcomes were based on changes in EDSS scores.

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Results from the SPMS subgroup revealed improvedmean posttreatment EDSS scores when comparedwith baseline data (p¼0.014). This significant benefitwas not identified in the PPMS subgroup, although sta-ble EDSS scores were identified in 82% of subjectsevaluated. Overall, the intrathecal treatment was welltolerated and no serious adverse effects were identified,suggesting that intrathecal methotrexate may be benefi-cial in progressive patients with treatment-unresponsiveMS. A potential explanation for these findings maybe the impact of methotrexate on suppressing glialscarring or its effects on follicular structures that mayserve as reservoirs housing a wealth of lymphocytesand dendritic cells within the meninges and Virchow–Robin spaces. These structures may be more responsiveto intrathecal-delivered therapy (Serafini et al., 2004;Franciotta et al., 2008), supporting the rationale forthis mode of delivery.

The Therapeutics and Technology Assessment Sub-committee of the American Academy of Neurologyand theMS Council for Clinical Practice Guidelines con-cluded in 2002 that methotrexate possibly alters the dis-ease course in progressive MS patients (Goodin et al.,2002). A similar observation was identified followinga systematic review of oral methotrexate in MS, citinglimited data on the effect of the medication on relapseprevention, along with trends towards benefit on sus-tained EDSS progression scores (Gray et al., 2006).

This was followed by an industry-sponsored investiga-tion to evaluate the safety, tolerability, and efficacy oforal methotrexate combined with IFN-b1a (30 mg intra-muscularly (IM) weekly) on an MRI outcome measure(new or enlarged T2 lesion number at month 12 versusbaseline) (Cohen et al., 2009). A total of 313 participantswithRRMScontinuingon IFN-b1a,withmild tomoderatedisease (EDSS 0.0–5.5), were randomized to receive: (1)placebo; (2) methotrexate (20 mg weekly); (3) placeboplus intravenous methylprednisolone (1 g/day for 3 con-secutive days bimonthly); or (4) methotrexate plus intra-venous methylprednisolone. Interestingly, no significantdifferences were observed between treatment groupson the primary outcome measure.

The scientific data surrounding methotrexate as aneffective form of treatment in MS suggest that it hasa limited role. The evidence of its use as an adjuvantimmunosuppressant is also lacking. The current use ofthis treatment, aside from the scientific rationale, isone of convenience given that it is orally administeredand administered weekly. The emergence of oralimmunomodulatory therapeutics in MS (fingolimod(Gilenya)), along with exciting therapies at the precipiceof being approved within the United States and beyond,will likely reduce the future use and investigation ofmethotrexate in the field of neuroimmunology.

AZATHIOPRINE

Azathioprine is currently approved for use in Germanyas an MS treatment. Although not FDA-approved in theUnited States for the treatment of MS, this immunosup-pressive agent is used principally as an adjunctive formof therapy, and in some instances, as a first-line treat-ment for those unwilling to use IFN-b or glatiramer ace-tate, despite somewhat conflicting data from severalstudies regarding its ability to reduce relapses and theuncertainty of its effect on disability progression(Goodin et al., 2002).

Discovered in the 1950s and used to prevent the rejec-tion of transplanted tissues and organs, azathioprine is asteroid-sparing purine analog that is rapidly metabolizedin vivo into cytotoxic and immunosuppressant deriva-tives, 6-mercaptopurine and 6-thioinosinic acid. Themedication targets activation, proliferation, and differ-entiation of fast-growing cells, including T and B cells,through inhibition of purine synthesis. This purine ana-log also inhibits T-cell-dependent antibody-mediatedresponses by interfering with CD28 costimulation ofautoreactive T lymphocytes (Tiede et al., 2003).

The largest randomized controlled trial of azathioprinein MS was published in 1988 (British and Dutch MultipleSclerosis Azathioprine Trial Group, 1988). A total of 354patients with MS were randomized to receive azathioprine(2.5 mg/kg daily) or placebo. After evaluating study partic-ipants for 3 years, there were no significant differences inrelapses between groups. A trend towards benefit wasobserved in the azathioprine-treated groupwhen outcomessuch as deterioration in the Kurtzke disability score andchanges in the ambulation index were evaluated. Basedon these data, the authors concluded that the treatmenteffect was somodest that azathioprine cannot be generallyrecommended for most patients with MS.

In 2007, the Cochrane Collaboration performed a sys-tematic review of its efficacy inMS, focusing on studiesthat were randomized, placebo-controlled trials of atleast 1 year (Casetta et al., 2007). Five such trials wereidentified. Adverse events related to exposure werederived from these studies in addition to cohort, case-control, case series, and case reports. A combined totalof 698 randomized patients were identified, with 1-yeardata available from 499 patients, 2-year data in 488, and415 patients containing 3 years of follow-up data toassess relapse frequency. The data suggested that azathi-oprine reduced the number of clinical relapses at year 1to 3, with an approximate 20% relative risk reduction(RRR) observed during each of the 3 years. A reductionin disease progression at 2–3 years (RRR¼42%; 95%CI¼7–64%) was observed in a modest number ofazathioprine-treated patients (n¼87). These data sug-gest that a treatment effect in reducing relapse

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frequencymay be present and that the ultimate effects inpreventing disease progression, although robust in thisreview, are still uncertain given the low number of sub-jects included within the analysis.

In general, azathioprine is well tolerated. Commonside-effects include gastrointestinal disturbances, bonemarrow suppression, and hepatic toxicity. Based on datafrom a large series of azathioprine-treated patients(n¼207) who were exposed to a dose of 2.0 mg/kg overamean treatment time of 4.2 years and follow-up time of5.9 years, compared to 247 azathioprine-untreatedpatients (mean follow-up time of 6.7 years), no increasedrisk inmalignancies was observed in the treatment group(Amato et al., 1993). Data from larger studies suggest atrend towards an increased risk of malignancy withhigher cumulative doses. In the evaluation of 1191 MSpatients, a possible long-term risk of cancer from azathi-oprinemay be related to duration of exposure (>10 yearsor a cumulative dose of 600 g) (Casetta et al., 2007).Concerns for non-Hodgkin lymphoma as well as otherconditions (i.e., squamous cell carcinoma, in situ cervicalcarcinoma) associated with long-term immune suppres-sion may exist with the long-term use of azathioprine.

More recently, the effect of azathioprine in compar-ison to IFN-b products in RRMS was evaluated(Etemadifar et al., 2007). A total of 94 MS patients, witha clinical history of>2 relapses within the 2-year periodof treatment initiation, were randomly assigned to twotherapeutic groups: (1) IFN-b products (Avonex, Beta-seron, or Rebif) or (2) azathioprine (initial dose of25 mg daily with titration up to 3 mg/kg, with dose titra-tion based on the WBC and liver function panel counts).Participants were treated for a period of 12 months, withresponse to the medical treatments assessed at months 3,6, and 12. A significant benefit in the mean number ofrelapses was observed in the azathioprine treatmentgroup when compared to those treated with IFN-b prod-ucts (0.28 versus 0.64, p<0.05). In addition, a higherpercentage of patients treated with azathioprineremained relapse-free (77% versus 57%) and demon-strated a greater reduction in EDSS scores comparedwith the IFN-b group. Overall, larger studies with higherpatient numbers are required to determine better its clin-ical effect of reducing relapses and disease progression.In addition, prospective trials with longer follow-updurations are needed, along with the incorporation ofradiologic outcome measures, for a more comprehen-sive understanding of its true potential as an appropriateMS treatment.

Our current understanding of the impact of azathio-prine on suppressing progression on conventional MRImetrics of disease (i.e., contrast enhancement, new T2lesions, T2 lesion volume) commonly used in MS is lim-ited. This is likely due to many studies occurring in the

era when MRI technology was not universally available.An investigation of a modest cohort of patients (n¼ 14)with active MRI disease prior to study entry was per-formed and the efficacy of azathioprine in suppressingnew brain lesions evaluated (Massacesi et al., 2005). Themain outcome measures were the presence of contrast-enhancing and new T2 lesions. Following a median aza-thioprine dose of 2.6–2.8 mg/kg daily within the studygroup, a >50% suppression of new contrast-enhancinglesions or new T2 lesions was observed in 12/14 (p<0.01)and 9/14 (p<0.02) subjects, respectively. In addition, areduction in new T2 lesion volumes was observed whencomparing the baseline burden of disease to the evalua-tion period (p<0.05). During the treatment period, 7/14subjects developed an adverse event: 3 had lymphopenia(<900 cells/mm3), 2 had gastric pain, 1 had hyperbiliru-binemia, and 1 had benign peripheral toxoplasmosis. Nosignificant changes in neurologic disability scores wereobserved during the study period.

Further MRI data were available from a randomizedstudy of 181 patients with RRMS. Patients were random-ized to one of three treatment arms: (1) IFN-b1a 30 mg IMonce weekly; (2) IFN-b1a 30 mg IM once weekly plusazathioprine 50 mg orally daily; or (3) IFN-b1a 30 mgIM once weekly plus azathioprine 50 mg orally dailyand prednisone 10 mg orally every other day. A signifi-cant reduction in T2 lesion volumes was observed at2 years in the combination (14.5%) versus IFN-b1aalone (þ30.3%) treatment arm (p<0.05) (Havrdovaet al., 2009).

Based on these scientific data, it is understandablewhy a trial designed to assess the promise of azathio-prine as an adjuvant agent was pursued. In 2009, a ran-domized study of IFN-b1a, low-dose azathioprine, andlow-dose glucocorticosteroid treatment in relapsingforms of MS was performed (Havrdova et al., 2009).A total of 181 RRMS patients were randomized toreceive: (1) IFN-b1a (30 mg once weekly); (2) IFN-b1a(30 mg once weekly) plus azathioprine (50 mg daily);or (3) IFN-b1a (30 mg once weekly) plus azathioprine(50 mg daily) plus prednisone (10 mg every other day).The primary outcome measure was the annualizedrelapse rate after 2 years. Unfortunately, no statisticallysignificant clinical difference was observed between thetreatment arms; however the combination group demon-strated a significant decline in percentage T2 lesion vol-ume change at 2 years (p<0.05).

Azathioprine is still a widely used medication, notonly in the field of MS but in other medical disciplines(i.e., rheumatology, other fields of neurology, e.g., neu-romuscular disease, internal medicine). The immuno-suppressant and steroid-sparing qualities make it anattractive form of treatment for those with autoimmunedisease. Its placement within the treatment algorithm for

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MS patients is still heavily debated; however, given theexisting scientific literature, duration of exposureneeded to see a treatment effect, and lack of FDAapproval in the United States it may be viable as athird-line agent or recommended earlier depending onthe individual patient.

MITOXANDRONE

Mitoxandrone was FDA-approved for the treatment ofMS in 2000 and represents the only currently approvedchemotherapeutic treatment for MS. This immunosup-pressant is specifically indicated for reducing neurologicdisability and/or the frequency of clinical relapses inpatients with: (1) SPMS; (2) progressive relapsing formsof MS; or (3) worsening RRMS. Classically, the treat-ment is given intravenously at a dose of 12 mg/m2 every3 months until a cumulative lifetime maximum dose of140 mg/m2 is achieved; however, modified treatmentregimens utilizing an induction form of treatment havebeen proposed.

The Report of the Therapeutics and TechnologyAssessment Subcommittee of the American Academyof Neurology and the MS Council for Clinical PracticeGuidelines concluded that mitoxandrone probablyreduces the attack rate in patients with relapsing formsof MS, and possibly has a beneficial effect on diseaseprogression; however, in the early course of the disease,the potential toxicity of mitoxandrone may outweigh theclinical benefits (Goodin et al., 2002).

Originating from a class of alkylating agents, thisanthracenedione derivative is a medication that inhibitstopoisomerase II and intercalates with DNA, causingsingle- and double-strand breaks (Smith, 1983). Themechanism of action of mitoxandrone extends beyondits immunosuppressive activity on proliferating immunecells, as it also contains immunomodulatory properties,by inhibiting the proliferation of macrophages, B and Tlymphocytes, alters antigen-presenting cells, andenhances suppressor T-cell functions, along with reduc-ing the secretion of IL-2, a proinflammatory cytokine,IFN-g, and tumor necrosis factor alpha (Fidler et al.,1986; Neuhaus et al., 2005; Kopadze et al., 2006).Through these actions, mitoxandrone may suppressinflammatory activity both clinically and radiologically.

The results from a pivotal phase III trial ultimatelypublished in 2002 (European Mitoxandrone in MultipleSclerosis Group) led to the support of its use for the treat-ment of aggressive RRMS, SPMS, and progressive-relapsing MS (Hartung et al., 2002). In this incompletelyblinded, placebo-controlled trial, 194 patients with anEDSS between 3.0 and 6.0 were randomized to receive:(1) mitoxandrone 12 mg/m2; (2) mitoxandrone 5 mg/m2;or (3) placebo (methylene blue). Treatments were

administered every 3 months for a period of 2 years.The study endpoints were outcomes from a multivariateanalysis of five clinical measures (change from three neu-rologic baseline scores after 24 months, time to first trea-ted relapse, and the number of relapses treated withsteroids). At the end of the study, 188 patients remained.The mitoxandrone treatment group experienced benefitscompared with the placebo group when evaluating thechange in expanded disability status scale (p¼0.02),change in ambulation index (p¼0.03), adjusted totalnumber of treated relapses (p<0.01), time to first treatedrelapse (p<0.01), and change in the standardized neuro-logic status (p¼0.03). The authors concluded that mitox-androne at 12 mg/m2 was generally well tolerated giventhe absence of serious adverse events or evidence ofclinically significant cardiac dysfunction and that the ther-apy reduced clinical exacerbations and progression ofdisability.

A modified treatment regimen involving inductiontherapy, whereby a patient is exposed to 12 mg/m2 eachmonth for 3–6 months, followed by glatiramer acetate,IFN-b, azathioprine, or methotrexate, was previouslyinvestigated (Le Page et al., 2008; Vollmer et al.,2008). The rationale behind this approach is to “reset”the immune mechanisms thought to be responsible forinjury in MS, thereby reducing the overall inflammatorypotential. The proposed therapeutic effect is believed tobe further enhanced by providing the patient with subse-quent immune-modulating therapy. The overall out-comes of these studies suggest a potential positiveeffect on disease control by reducing relapse rates andbrain lesions followed by MRI. Further studies areneeded to conclude accurately if this treatment regimenis superior to monotherapy with conventional MStherapies.

In recent years, our understanding of the safety pro-file of mitoxandrone has improved greatly. Treatment-related acute leukemia and cardiotoxicity are twodefinable negative outcomes associated with prolongedexposure. Prior to 2005, evaluation of the left ventricularejection fraction (LVEF) was recommended prior to ini-tiating treatment and following each infusion after acumulative dose of>100 mg/m2 was reached. In March2005, after the FDA’s “black box” warning of cardio-toxicity, LVEF evaluation prior to initiating therapyand before each subsequent administered dose wasadvised. To extend the surveillance for cardiac injury,an additional recommendation of annual cardiac func-tion testing following exposure was made in July 2008.

The efficacy and safety of mitoxandrone wererecently re-evaluated by the Therapeutics and Tech-nology Assessment Subcommittee of the AmericanAcademy of Neurology (Marriott et al., 2010). Acomprehensive review of the literature revealed an

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estimated decreased LVEF rate of 12% (83/716) and 0.4%(3/716) risk of congestive heart failure after comprehen-sively reviewing the published literature and consolidat-ing nonuniform mitoxandrone dosing regimens andcardiac assessments from class III and IV studies. Inaddition, based on the observed data, 1 patient wouldexperience left ventricular dysfunction out of 8 patientsexposed to mitoxandrone (number needed to harm(NNH)¼8) (Marriott et al., 2010).

The incidence of treatment-related acute leukemiarelated to mitoxandrone, following a comprehensivereview of the literature, is estimated to be 0.81% (33/4076), with the calculated NNH being 123. These data,in addition to the cardiac data, are approximations asthe dosing regimens, follow-up visits, and duration oflongitudinal follow-up are heterogeneous.

The risk of developing cardiotoxicity and therapy-related acute leukemia appears higher than previous esti-mates. In the era when numerous injectable therapies areavailable (i.e., glatiramer acetate, IFN-b), along withnewer treatments that are perceived to be more potentbased on their mechanism of action (natalizumab(Tysabri) and fingolimod (Gilenya)), and the excitingpipeline of emerging therapies, the future use ofmitoxan-drone as a therapeutic option may be limited. Althoughthe indications for its use are relatively liberal, individualtreatment decisions are advised given a refreshed under-standing of the potential high risk for adverse events toMS patients in the longterm and the rigorous clinical sur-veillance required, even after exposure.

MYCOPHENOLATEMOFETIL

Mycophenolate mofetil is an inhibitor of inosine 5’-monophosphate dehydrogenase type II, resulting in aninterruption in purine biosynthesis within activated Tand B lymphocytes and macrophages. Commonly usedto prevent organ transplant rejection, this immunosup-pressant has been used in the treatment ofMS.Mycophe-nolic acid, a metabolite of mycophenolate mofetil, hasbeen shown to inhibit IFN-g and lipopolysaccharide-induced IL-6 and nitric oxide (Miljkovic et al., 2002),chemical mediators known to induce a proinflammatoryimmune response. Despite being non-FDA-approved forthe treatment ofMS, alongwith a paucity of scientific evi-dence that speaks to its efficacy and safety in MS, thistherapy has been prescribed as monotherapy in thosewho are nonresponsive to conventional treatments or incombination with an immunomodulatory agent. In addi-tion, the medication is well tolerated, demonstrates rapidreversibility, and is easily administered, making it anattractive treatment option.

One of the first publications of mycophenolate mofe-til in MS involved an observational study of its use in 7

patients with chronic progressive or relapsing MS(Ahrens et al., 2001). Clinical benefits were observedin 5 of 7 cases. This seminal publication was followedby larger studies.

A recent randomized, blinded, parallel-group trial ofmycophenolate mofetil (500 mg twice daily with dosetitration up to 1000 mg twice daily after 2 weeks) com-pared with IFN-b1a (30 mg IMweekly) in RRMSwas per-formed (Frohman et al., 2010). In this study, 35previously untreated patients with active MRI scans atbaseline (presence of contrast enhancement) were fol-lowed. The primary outcome measure was the reductionin the cumulative mean number of combined activelesions, new contrast-enhancing lesions, and new T2lesions. Mycophenolate mofetil was well tolerated. Atrend towards benefit in MRI outcomes was observedwithin this group when compared to those treated withIFN-b1a. The short study time of 6 months may be partlyresponsible for lack of statistical differences betweentreatment groups; however, these data suggest that fur-ther studies are warranted.

A recent combination study was also performed in 24treatment-naı̈ve RRMS patients in a 1-year study(Remington et al., 2010). All study subjects receivedIFN-b1a prior to being randomized to receive mycophe-nolate mofetil (250 mg twice daily for 1 week with doseescalation by 250 mg twice daily per week until a finaldose of 1000 mg twice daily was achieved) or placebo.Results demonstrated a trend towards benefit on MRImetrics in the mycophenolate mofetil plus IFN-b1agroup. Similar findings were also observed in a pre-vious combination investigation of shorter duration(6 months) (Vermersch et al., 2007). Collectively, thesedata provide evidence thatmycophenolatemofetil is welltolerated and that it may be an agent for inclusion in themedications used to suppress disease activity in MS.

Of all the immunosuppressive agents discussed thusfar, mycophenolate mofetil has been studied the least inMS. A comprehensive understanding of its effect on sup-pressing clinical and radiologic relapses and disability out-comes is currently unclear. Future prospectivelongitudinal investigations over the next few years mayassist us in evaluating its value in the treatment of MS.For now, other treatment options may be more suitable.

SUMMARY

A challenge encountered by MS specialists and neurolo-gists is the therapeutic management of patients with pro-gressive disease, aggressive forms of MS, or those whoare intolerant, nonresponsive, or refuse to receive ourcurrent FDA-approved treatments. Immunosuppressivetreatments in MS, based on their mechanism of action,are used to attenuate the immune system and the cascade

IMMUNOSUPPRESSIVE TREATMENTS IN MULTIPLE SCLEROSIS 509

of inflammatory events that lead to injury to the myelinsheath and axonal injury. Where these oral and intrave-nously administered immunosuppressants fall in thetreatment paradigm for MS patients is highly variable.Future investigations may provide data that will allowtreatment recommendations to be enhanced and bettertargeted for the individual patient afflicted with MS,although such investigations may be usurped by studiesfocused on newmechanistic pathways for contemporaryMS therapeutics. Even through these efforts of acquir-ing a better understanding of the efficacy of immuno-suppressive treatments in MS, exposure to theseagents may subsequently place patients at risk for futuremalignancies and opportunistic infections if other ther-apies that suppress the immune system are introduced.The contemporary treatments in MS that possess moreselective mechanisms of action may also significantlyimpair the recommendation of classical treatments.Although invaluable in the management of MS priorto the year 1993 and beyond, the ultimate role of thesetreatments is still uncertain given the dynamic natureand ever-changing landscape of investigated immuno-modulators and immunosuppressants in MS.

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