Editorial

Annette Langer-Gould, MD, Department of Neurology/Multiple Sclerosis Clinic, Stanford University School of Medicine, Stanford, California

Offered in this Multiple Sclerosis Forum Report are select clinical studies presented at the 55th Annual Meeting of the American Academy of Neurology in Honolulu, Hawaii—one which sheds light on the etiology and pathogenesis of multiple sclerosis (MS); and others which provide guidance on how to manage non-responders to beta-interferons.

Insights into the Elusive Etiology and Pathogenesis of Multiple Sclerosis

Both genetic and environmental factors are important, yet whether MS is an autoimmune disease or chronic viral infection is still hotly debated. Unlike in the autoimmune animal model of MS, CD4+ T cells may not be the principal drivers of MS pathology; with other lymphocytes and macrophages probably playing equally important roles. The importance of the CD4+ and CD8+ T cell-driven immune response in the pathogenesis of MS were highlighted in the Campath-1H study.¹

In this open label study, treatment with Campath-1H (an antibody that depletes T cells and to a lesser extent, B cells and macrophages) produced dramatic immunologic quiescence in both patients with aggressive relapsing-remitting MS and secondary-progressive MS. However, only patients with relapsing-remitting MS had a striking clinical benefit. These findings demonstrate that once the progressive phase of MS begins, even potent immunosuppressants such as Campath-1H are not enough to halt the ensuing neurodegeneration. Yet—if highly effective immunomodulation is achieved early in the disease—clinical deterioration is dramatically altered and relapse-related disability may be reversible. This underscores the importance of early initiation of immunomodulatory treatments in relapsing-remitting MS.

The Campath-1H experience also highlights the link between Graves' disease and MS. Several studies have suggested that the prevalence of Graves' disease may be higher in MS cohorts. Campath-1H is widely used to treat graft-versus-host disease in allogeneic bone marrow transplantation and lymphoid malignancies; in neither of these study populations has Graves' disease been reported as an adverse event. In this Campath-1H study, astonishingly, one third of the MS patients developed Graves' disease. This finding strongly indicates that susceptibility to MS and Graves' disease are mediated by common genetic traits, environmental agents or both.

Identifying and Treating Non-Responders to Therapy

How should we treat patients who have not responded to interferon beta or glatiramer acetate? How can we identify such non-responders? Is there any way we could predict who will respond to interferon beta before initiating therapy? What do we do when our patient has received their lifetime maximum dose of mitoxantrone? What if our patients cannot tolerate or afford mitoxantrone? These are questions that confront all physicians of MS patients. Up until recently, very little reliable safety data of the most commonly used rescue therapies has been available and even less convincing efficacy data.

This Multiple Sclerosis Forum Report describes the results for two rescue therapies—encouraging safety and efficacy data from a blinded, randomized study of intravenous cyclophosphamide plus methylprednisolone,² and short-term safety data from an open-label study of high dose intravenous methotrexate in combination with Avonex.³

An exciting, potential prognostic marker of interferon beta responsiveness, tumor necrosis factor (TNF)-related apoptosis inducing ligand (TRAIL) is also discussed in this report. This pilot study, using very stringent criteria for treatment response, shows that in relapsing-remitting MS patients with high pre-treatment serum levels of TRAIL, 90% responded to interferon beta therapy; whereas of those with low levels, 71% did not.⁴

Preliminary data demonstrating the existence of neutralizing antibodies to glatiramer acetate in a small subset of MS patients is also offered.⁵ This study confirms the high seroprevalence of binding antibodies to glatiramer acetate observed in previous studies and shows that in 6 of 42 patients treated with glatiramer acetate for at least one year, the binding antibodies were able to neutralize the in vitro effect of glatiramer on Th1-to-Th2 cytokine shifts. It raises the question of whether neutralizing antibodies to glatiramer acetate could explain why some patients don't respond to glatiramer acetate treatment. Certainly, further investigation is needed to address this question.

Perhaps the most promising new MS treatment on the horizon is natalizumab. A monoclonal antibody that blocks activated T cells from entering the CNS, this treatment showed remarkable efficacy in a phase II study and was very well tolerated. Described in this report is the outstanding design of two ongoing phase III studies; natalizumab as monotherapy for relapsing-remitting MS (AFFIRM study) and natalizumab in combination with Avonex as a rescue therapy (SENTINEL study).⁶

I hope you will find the information in this Multiple Sclerosis Forum Report useful and enlightening. Enjoy!

Complications of Immunogenicity: Binding and Neutralizing Antibodies

Blocking Effects of Serum-Reactive Antibodies Induced by Glatiramer Acetate Treatment in Patients with Multiple Sclerosis

Ying C.Q. Zang, MD, PhD, Baylor Multiple Sclerosis Center and Baylor College of Medicine, Houston, Texas

High titers of serum antibodies produced by glatiramer acetate (Copaxone) block the immunomodulatory effects of Copaxone in vitro and can neutralize the in vivo effect of Copaxone on serum cytokine concentrations, according to the results of a recent study from Baylor College of Medicine, Houston, Texas.⁵ The study is considered to be the first to show that serum antibodies produced in response to treatment with Copaxone diminish the in vitro biological activity of the agent. While long-term Copaxone treatment is known to induce an antibody response, the biological effect and therapeutic implications of these antibodies had not been previously established, according to Principal Investigator Ying C. Q. Zang, MD, PhD.

The study tested serum specimens from 42 patients with MS, taken prior to and following treatment (1 to 5 years) with Copaxone, for antibody reactivity to Copaxone. Samples from 6 of the patients who had high antibody titers (antibody binding index [ABI] of ≥16 to 64) were further evaluated for their ability to block Copaxone-stimulated immunoregulatory effects in vitro. Specifically, the proliferation of peripheral blood mononuclear cells (PBMC) and Copaxone-specific T cells was determined using ³H thymidine assays. Levels of interleukin (IL)-10, IL-4, IL-12, and tumor necrosis factor (TNF)-α were measured by enzyme-linked immunosorbent assay (ELISA). A preliminary assessment of the clinical relevance of these antibodies was made by correlating serum cytokine levels with changes in Expanded Disability Scale Scores (EDSS) and relapses.

High Titers of Antibodies Block Immunomodulatory Effects of Copaxone In Vitro

Copaxone-induced antibodies were demonstrated in samples from 48% of the patients; of those patients high antibody titers (ABI ≥16 to 64) occurred in 33% and low antibody titers (ABI ≤4) in 14% of these patients. The high antibody titers induced by Copaxone not only blocked the agent's normal stimulatory effects on the proliferation of PBMC and Copaxone-specific T cells in vitro but may have reduced clinical efficacy as well, Dr. Zang reported.

The increase in IL-10 and IL-4 levels and the decrease in IL-12 and TNF-α levels, which normally result from Copaxone stimulation, were reversed in the presence of the Copaxone antibodies. Patients with low antibody titers, however, had a post-treatment increase in IL-10 and a reduction in TNF-α and IL-12.

"These results suggest that the in vivo effects of glatiramer acetate on serum cytokine levels are blocked by high titers of glatiramer acetate molecules," Dr. Zang noted.

Immunoblot analysis of the serum specimens from the 6 high-antibody patients confirmed the specific reactivity of serum antibodies to Copaxone.

Potential Effects of High Antibody Titers Induced by Copaxone on Clinical Efficacy

By comparing EDSS pre- and post-treatment, investigators suggested a possible association between high titers of Copaxone-induced antibodies and reduction in clinical efficacy with Copaxone. However, the number of patients was small and the changes in EDSS scores were not robust.

With Copaxone treatment, mean EDSS generally improved from pre-treatment levels in patients with low antibody titers (Table 1). But for the 14 patients with high antibody titers, mean EDSS worsened in all categories during the duration of treatment (1 to 5 years). For example, in the 3 patients with high antibody titers treated for 4 years with Copaxone, EDSS worsened from 4.3 to 4.8 post-treatment; for the 8 patients treated for 5 years with Copaxone, EDSS worsened from 3.9 to 4.1. Relapse rates, however, were generally reduced with continued treatment, though more so in patients with low antibody titers.

In an interview with Jeffrey Greenstein, MD, founder of the Multiple Sclerosis Institute of Philadelphia, Pennsylvania, Dr. Greenstein noted, "Apparently 15% of the patients treated with glatiramer acetate in this study had antibodies that one could categorize as neutralizing. This was shown by preparing glatiramer acetate-specific T cell lines and then determining whether the sera inhibited the proliferation of those T cell lines. For patients with high antibody titers, there was indeed inhibition of proliferation. The investigators then extended the study to see if there was inhibition of cytokine production across a broad range of cytokines, and they found a decrease in cytokine production in both Th1 and Th2 cytokines."

"This is an important study that gives new insights into why glatiramer acetate may not be that different from the interferons in the potential to develop antibodies. It is a synthetic biological protein therapy that with the right assays can be shown to produce neutralizing antibodies and/or other forms of inhibition," Dr. Greenstein continued. "This leaves us with the suggestion that we should re-examine glatiramer acetate to see if we have the same problem of neutralization of effect that we see with the interferons."

The Significant Influence of Binding Antibodies on Outcome Measures in Interferon Beta-Treated Multiple Sclerosis Patients

Ebrima Gibbs, MSc, Doctoral Candidate, University of British Columbia, Vancouver, Canada

Binding antibodies are excellent predictors of the development of neutralizing antibodies in response to interferon beta treatment. Binding antibodies are less likely produced with interferon beta-1a (Rebif) than beta-1b (Betaseron), significantly affect interferon beta bioavailability, and are associated with treatment failure, according to investigators from the University of British Columbia.⁷

[Ed. A binding antibody is a descriptive term for any antibody that is capable of binding to interferon beta. Neutralizing antibodies are a subset of binding antibodies that prevent productive signaling of interferon beta to its receptor and thus block interferon receptor activation and its biologic effects including the release of cytokines.]

There is mounting evidence of the biological and clinical significance of both binding and neutralizing antibodies. In general, only samples that are positive for binding antibodies are assayed for neutralizing antibodies, but binding antibodies and neutralizing antibodies develop in different patterns. Patients who develop neutralizing antibodies benefit less from interferon beta therapy and have higher relapse rates, more disease progression, and more new or enlarging magnetic resonance imaging (MRI) lesions, as compared to patients who are neutralizing antibody-negative, according to the study investigators. This was also evident in the Prevention of Relapses and Disability by Interferon-beta-1a Subcutaneously in Multiple Sclerosis (PRISMS)-4 (Rebif)⁸ and Betaseron 3-year results.⁹ The 6-year data of PRISMS,¹⁰ reported here, reconfirms the 4-year data concerning neutralizing antibodies. Clinical efficacy of interferon beta also appears to be significantly affected by the development of binding antibodies.¹¹

The detection systems for neutralizing antibodies are cell-culture-based and measure only those antibodies that neutralize the anti-viral activity of interferon beta. Only test sera that demonstrate binding antibodies are assayed for neutralizing antibodies, based on the premise that neutralizing antibodies are a subset of binding antibodies.

The interferon beta products differ in formulation, dosing and routes of administration. They have been shown to differ, as well, in their propensity to induce neutralizing and binding antibodies in response to treatment. Interferon beta-1a (Avonex) has consistently demonstrated the lowest incidence of neutralizing antibody formation.^12-14

Laboratory Analysis Reveals Differences in Induction of Binding Antibodies

The objective of the current study was to evaluate the effect of binding antibodies on the interferon beta-induced surrogate bioavailability marker, lymphocyte MxA, and on the clinical outcomes of the patients treated with interferon beta. Patients were evaluated serially for binding antibodies by ELISA; 49 randomly chosen patients were further analyzed for neutralizing antibodies by a neutralization assay based on inhibition of MxA induction; and 29 patients were assayed for interferon beta bioavailability by measuring lymphocyte MxA levels. A total of 221 patients with clinically-definite MS (Betaseron, n = 133; Rebif, n = 90) were evaluated. Clinical information was only available for 125 patients on Betaseron, and they were stratified by a blinded neurologist into treatment successes (no relapse and no change in EDSS) and non-success for the first 2 years of therapy.

Differences emerged in the frequency, timing, and persistence of anti-interferon beta antibodies between Betaseron and Rebif. Binding antibodies were detected in 69% (92/133) of the Betaseron-treated patients, as compared to 30% (26/88) of the Rebif-treated patients. Not only were binding antibodies more frequent with Betaseron administration, but also the time course to antibody formation peaked earlier with Betaseron (at month 5 versus months 9-12 with Rebif) though the binding antibodies persisted longer in Rebif-treated patients.

The incidence of binding antibodies peaked an average of 11 months before neutralizing antibodies (peak) and predicted the positivity of neutralizing antibody formation (Table 2).

"Binding antibodies are an excellent predictor of the future development of neutralizing antibodies," Mr. Gibbs noted, adding that patients who became neutralizing antibody-positive tended to have higher binding antibody levels.

Lymphocyte MxA levels were significantly increased during treatment with Betaseron (no data were available for Rebif-treated patients). Patients who developed binding antibodies had significantly lower MxA levels at Months 4 to 5 after initiation of therapy, and tended to have lower levels at other time points up to 2 years, compared to patients without binding antibodies, though the differences were not significant. Peak binding antibody levels coincided with a reduction in lymphocyte MxA.

Clinical efficacy also appeared to be affected by the presence of binding antibodies, since patients with binding antibodies tended towards treatment failure (Pearson χ² = 4.19, P = 0.006) (Table 3).

Effect of Neutralizing Antibodies on the Clinical Efficacy of Interferon Beta-1a: Results from the European Dose-Comparison Study

Ludwig Kappos, MD, Professor of Neurology, University Hospitals, Basel, Switzerland

The incidence of neutralizing antibodies during therapy with Avonex continues to be low after 4 years, in patients enrolled in the European Interferon Beta-1a Dose-Comparison Study.¹⁵ The results are consistent with previous findings showing the lower immunogenicity of Avonex compared with other interferon beta formulations.^12-14

The double-blind, parallel-group, 38-center European Interferon Beta-1a Dose-Comparison Study is the largest long-term study ever conducted in MS without patient re-randomization. In the main analysis of 802 patients,¹⁶ there was no difference between the 30 mcg (n = 402) and the 60 mcg (n = 400) once-weekly doses of Avonex in the rate of accumulation of physical disability over the 3 years of treatment. An extension phase of the study involved 491 patients who continued double-blind treatment for one additional year.¹⁷ Strong maintenance of benefit was shown with the 30 mcg once-weekly dose with no additional benefit from increasing the dose to 60 mcg.

Sustained efficacy with Avonex was demonstrated in multiple outcomes including cumulative rate of sustained disability progression, extent of change in EDSS, relapse rate, percentage of relapse-free patients, and intravenous steroid use.

At the end of 3 years, the cumulative rate of sustained disability progression was comparable between the 2 dosage groups. The percentage of subjects progression-free at 3 years was 63% in both dosage groups (hazard ratio 0.96, 95% Confidence Interval (CI), 0.77-1.20; P = 0.73), and at 4 years was 52% with the 30 mcg group and 57% with the 60 mcg group. Further, there were no differences in progression-free patients observed between the 30 mcg and 60 mcg doses for subjects with baseline EDSS scores &$8804;3.5 (mean EDSS score 2.8; hazard ratio 0.88; 95% CI, 0.64-1.22; P = 0.45) or baseline EDSS scores ≥4.0 (mean EDSS score 4.5; hazard ratio 1.05; 95% CI, 0.76-1.43; P = 0.80).¹⁶ Avonex therapy maintained its effect on relapse rate at 4 years. Reduction in relapse was 43% with 30 mcg and 42% with 60 mcg Avonex.¹⁷

A significantly lower proportion of patients receiving 30 mcg weekly compared with 60 mcg had at least one neutralizing antibody titer ≥20 LU/mL (2.3% versus 5.8%, respectively; P = 0.011). The number of these patients who remained persistently positive at their last visit was 7 of 9 in the 30 mcg group and 13 of 21 in the 60 mcg group. In general, patients did not begin to become neutralizing antibody-positive until 6 months after treatment initiation, and the mean time to development of neutralizing antibodies was 15 months.

The proportion of patients from the total cohort who tested negative at baseline and had two or more post-baseline titers ≥20 LU/mL was 3.8%, or 2.3% with 30 mcg Avonex and 5.3% with 60 mcg Avonex.

Relationship of Neutralizing Antibody Positivity to Clinical Outcome

The incidence of neutralizing antibodies has varied among interferon beta products. In PRISMS-4,⁸ neutralizing antibodies impacted the therapeutic efficacy of interferon beta, and the same results were confirmed in this study. Patients who developed neutralizing antibodies had an annual relapse rate that was 34% higher during months 12 to 48 of treatment than patients who did not develop neutralizing antibodies. Relapses occurred, over years 2 to 4, at a rate of 0.74 to 0.62 in the antibody-negative patients compared to 1.06 to 0.90 for patients who developed neutralizing antibodies.

There was, however, no difference in sustained disability (increase of 1.0 points on EDSS sustained for 6 months), though the mean change in EDSS from baseline to 48 months indicated a slight tendency toward higher scores in patients with neutralizing antibodies. The percentage change from baseline EDSS scores increased faster in neutralizing antibody-positive patients versus neutralizing antibody-negative patients over 48 months of treatment (P = 0.043). On a statistical note, Dr. Kappos added, "All P-values are only indicative, because they are derived from a post hoc analysis and are not corrected for multiple comparisons."

Gadolinium-enhanced lesions were significantly more numerous at baseline in the patients without neutralizing antibodies (P = 0.012). To compensate for this difference at baseline, the effect of neutralizing antibodies on mean and median change from baseline in number of gadolinium-positive lesions was analyzed. Differences were observed between neutralizing antibody-positive and neutralizing antibody-negative patients in the change from baseline for gadolinium-enhancing lesions at Month 24 (P = 0.03) and Month 36 (P = 0.05) (Table 4).

The low incidence of neutralizing antibodies is consistent with previous reports of Avonex, Dr. Kappos said. Though there were only a small number of neutralizing antibody-positive patients in this population, efficacy was reduced, as measured by higher annualized relapse rate, less change from baseline in gadolinium-enhancing lesions, higher relapse rates from months 12 to 48 (P = 0.037), and a more rapid increase from baseline to EDSS changes over 48 months. The effect on clinical efficacy was not apparent until 18 to 24 months after treatment, Dr. Kappos summarized.

"This study provides additional information about the development of neutralizing antibodies. There continues to be a low incidence—about 4% in the combined groups—with Avonex, and they seem to develop after 15 months, which is later than with the other interferon beta preparations," Dr. Kappos said. "Although there were a small number of patients with neutralizing antibodies, we seemed to find some differences in efficacy compared to antibody-negative patients, especially in the third and fourth year of observation. This indicates that neutralizing antibodies have clinical importance, and this should be taken into consideration even at initiation of therapy."

The PRISMS Study: Report on Neutralizing Antibodies Up To Year 6 of Treatment

Magnhild Sandberg-Wollheim, MD, Department of Neurology, University Hospitals, Lund, Sweden

In follow-up that now extends to 6 years of treatment, 24.8% of patients in the PRISMS study developed neutralizing antibodies at some point during the 6 years of the study, according to results reported by Dr. Sandberg-Wollheim, Department of Neurology, University Hospitals, Lund, Sweden.¹⁰

"Although the long-term impact of neutralizing antibody development on the efficacy of interferon beta treatment in patients with relapsing-remitting multiple sclerosis has not yet been fully studied, it does appear that, in the minority of patients who do develop them, neutralizing antibodies will at least partially negate the benefits of high and frequent Rebif dosing," noted Dr. Sandberg-Wollheim.

Antibodies that neutralize interferon beta have been the focus of much attention. Concerns have been expressed about their potential impact on treatment efficacy, and questions have been raised as to the relationship between dose regimen and the development of neutralizing antibodies.

Analysis of the time at which the neutralizing antibodies developed showed that 22% of patients developed these molecules within the first 6 months, 64% within 12 months, and 90% within 18 months of treatment initiation of Rebif. No new incidence of neutralizing antibody formation was observed later than 4 years after treatment initiation.

At their final 6-year assessment, however, up to one third of patients had reverted to antibody-negative status. Of the 90 patients who received 44 mcg or 22 mcg three times weekly and were classified neutralizing antibody-positive, 33 patients (36.7%) had reverted to neutralizing antibody-negative status by the time of their final assessment. Among patients who received active treatment for the full study period (rather than switching from placebo), neutralizing antibodies persisted in 12.1% (22/182) patients receiving the 44 mcg dose and in 18.8% (35/186) patients receiving the 22 mcg dose, reported Dr. Sandberg-Wollheim. This still leaves almost two-thirds of patients neutralizing antibody-positive. Patients that were neutralizing antibody-positive received less efficacy from Years 2 to 6.

During the original PRISMS study,¹⁸ 560 patients with MS were randomized to receive Rebif 22 mcg, 44 mcg, or placebo subcutaneously three times weekly. At the end of the first 2 years, patients in the placebo group were re-randomized to active treatment with either dose for the remainder of the trial, while those initially on active treatment continued at their previous dose level and remained blinded to their original treatment. Efficacy and safety data have been analyzed for Years 1 to 4,⁸ but the study on Years 5 and 6 provide data only on safety and the incidence of neutralizing antibodies rather than efficacy. Of the original 560 patients, 74% remained on study for 4 years, 57% entered Year 5, and 48% completed Year 6 on dose-blinded Rebif treatment.

Managing Breakthrough Disease with Combination Therapy

Blinded, Randomized Trial of Pulse Cyclophosphamide in Interferon Beta-Resistant Active MS

Derek R. Smith, MD, Assistant Professor of Neurology, Harvard Medical School, Boston, Massachusetts

Although the currently available immunomodulatory agents are relatively effective in reducing relapse rates, and some in slowing disability progression, many patients still progress with their disease. Switching between immunomodulatory agents has been an approach used to try to manage these patients—with little or no benefit. Emerging data suggest that the use of adjunctive agents, along with initial immunomodulatory platform therapy, may be a beneficial strategy in patients with treatment-resistant MS disease.

In a multicenter study presented by Derek R. Smith, MD, Assistant Professor of Neurology, Harvard Medical School, Boston, Massachusetts the addition of 6 monthly intravenous infusions of cyclophosphamide plus methylprednisolone to a regimen of Avonex was effective in reducing the signs of MS disease activity and preventing treatment failure.²

The study included 58 patients who were considered to have active MS despite therapy with Avonex. After receiving a 3-day course of methylprednisolone, patients were randomized to either 6 monthly intravenous doses of cyclophosphamide (800 mg/m²) plus intravenous methylprednisolone (1000 mg) or methylprednisolone alone. Patients continued Avonex therapy (30 mcg intramuscularly once weekly) during the 6-month infusion phase and the 18-month follow-up phase. The primary outcome measure was change in number of gadolinium-enhancing lesions with a secondary outcome measure of time to treatment failure (defined as the occurrence of two or more confirmed relapses in a 9-month period).

One month after the initial 3-day course of methylprednisolone, the baseline mean number of gadolinium-enhancing lesions was 0.87, with no differences seen between the 2 treatment arms (P = 0.71). Treatment with cyclophosphamide plus methylprednisolone successfully reduced the number of gadolinium-enhancing lesions and resulted in fewer treatment failures, reported Dr. Smith.

The differences between the treatment arms emerged at Month 3, when gadolinium-enhancing lesions decreased in the cyclophosphamide treatment arm by -0.7 over baseline levels, but increased in the methylprednisolone treatment arm by +0.57 (P = 0.01). At Month 6, gadolinium-enhancing lesions were again diminished in the cyclophosphamide treatment arm by -0.77 (P = 0.04) but increased by +0.19 over baseline in the methylprednisolone treatment arm.

Six months after completion of the infusion phase (at Month 12), patients receiving methylprednisolone plus Avonex had an increase of +0.58 gadolinium-enhancing lesions compared to a decrease of -0.53 in patients treated with the combination of Avonex and cyclophosphamide plus methylprednisolone (P = 0.02).

The addition of cyclophosphamide to methylprednisolone also resulted in fewer total scans that contained at least one gadolinium-enhancing lesion during the infusion phase, and a much lower mean number of gadolinium-enhancing lesions: 0.2 for cyclophosphamide plus methylprednisolone-treated patients compared to 1.18 in patients receiving methylprednisolone (P = 0.001).

Protocol-defined treatment failures were also twice as great in the methylprednisolone treatment arm as the cyclophosphamide plus methylprednisolone treatment arm: 25% versus 50% (P = 0.03). The time to treatment failure was also significantly shorter in the methylprednisolone treatment arm (13 months versus 16 months; P = 0.04). Final analysis of this subset of data is pending.

"The analysis of treatment failures favored the cyclophosphamide plus methylprednisolone treatment arm, both in patients with gadolinium-positive and gadolinium-negative scans. Overall, however, patients with gadolinium-positive scans had much more disease activity, compared to those with negative scans at the time of baseline MRI," advised Dr. Smith.

Dr. Smith commented on the promise of this therapy by comparing it to the pivotal study by Edan et al¹⁹ that led to FDA approval of mitoxantrone. "The 63% decrease (P = 0.02) in the percentage of patients with gadolinium-enhancing lesions with cyclophosphamide plus methylprednisolone was a larger reduction than was seen with mitoxantrone versus methylprednisolone at 3 months, which was less than 50%," noted Dr. Smith.

[Ed. Differences in patient populations make such comparisons problematic.]

Rescue Therapy with High-Dose Intravenous Methotrexate in MS Patients Worsening Despite Avonex Therapy

Vernon D. Rowe, MD, MidAmerica Neuroscience Institute, Kansas City, Missouri

High doses of intravenous methotrexate combined with Avonex therapy appears to stop the progression of disease activity in patients who are worsening on Avonex treatment, according to Vernon D. Rowe, MD, from the MidAmerica Neuroscience Institute, Kansas City, Missouri.³

The open-label study enrolled 15 patients with relapsing MS worsening while on Avonex therapy. Patients were eligible if they experienced a decrease in the MS Functional Composite (MSFC) score over a minimum of 3 months while being treated with Avonex for at least 6 months. The MSFC is comprised of 3 tests: the Paced Auditory Serial Addition Test (PASAT), 9-Hole Peg Test, and the 25-foot Timed Walk. Remaining on Avonex, patients received high-dose intravenous methotrexate (2 g/m²) followed by leucovorin rescue, every 2 months for a total of 6 treatments.

Dr. Rowe and colleagues had previously reported the use of bimonthly high-dose intravenous methotrexate with leucovorin rescue in 10 worsening MS patients, demonstrating that clinical progression was arrested or reversed after 1 year of treatment.²⁰ The present study evaluated this strategy in combination with Avonex.

Methotrexate is an S-phase chemotherapeutic antimetabolite used to treat lymphoma of the central nervous system and other inflammatory conditions. Given intravenously in high enough doses, methotrexate crosses the blood-brain barrier and enters the central nervous system. By giving repeated treatments at regular intervals, significant repopulation of the central nervous system by immune elements from the periphery might be prevented, explained Dr. Rowe.

In this regimen, patients received intravenous methotrexate (2 g/m²) at an outpatient infusion center. This was followed 8 hours later by intravenous leucovorin 80 mg, then leucovorin 50 mg orally every 6 hours for a total of 12 doses. In such high doses, methotrexate would be lethal unless leucovorin was administered as rescue therapy. Leucovorin is a reduced form of folic acid and is usually used 24 hours after methotrexate to selectively "rescue" normal cells from the adverse effects of methotrexate caused by inhibition of production of reduced folates. It is not used simultaneously with methotrexate, as it might then nullify the therapeutic effect of the methotrexate. Two days after treatment, methotrexate levels were obtained, and if they were greater than 0.05 micromolar, additional oral doses of leucovorin were administered. Leucovorin does not penetrate the blood-brain barrier, Dr. Rowe pointed out.

In the first 8 patients to complete the treatment, there was a significant improvement in the composite MSFC of 0.39 points (mean MSFC score at baseline 0.137, range, -2.03 to 1.23; P = 0.016). Significant improvements were also noted for the subsets of the PASAT (P = 0.031) and 9-Hole Peg Test (P = 0.008).

"The statistically significant improvement in the MSFC composite represents a clinically important improvement in patient functioning," advised Dr. Rowe. "No patient significantly worsened during treatment and each improved in one or more subsets during the 1-year treatment period. All the patients were worsening prior to the first infusion," reported Dr. Rowe.

In addition, MRI evaluations before and after leucovorin rescue therapy showed no increase in enhancement for 7 of the 8 patients; one patient missed multiple Avonex treatments and had minimal enhancement at the end of the study.

Immunological Analysis

Changes occurred and persisted in several immunological parameters, in particular, chemokine receptors and cytokine secretion. Chemokines and their receptors are important mediators for selective recruiting of leukocytes into tissues during inflammation. The immune response in the brain is mainly mediated by proinflammatory cytokines, and cytokine secretion has been widely used to monitor MS therapy, Dr. Rowe pointed out.

Treatment for one year decreased chemokine receptor expression on both Th1 and Th2 cells. The percentage of T cells expressing CXCR3 and CCR4 were all decreased significantly; CCR5 expression was also down-regulated, though not significantly. In addition, the percentage of T cells producing TNF-α was also significantly reduced after in vitro stimulation.

The decrease of CXCR3 and CCR4 on T cells indicates that the treatment has a general, rather than a specific, action on activated T cells. The decrease in TNF-α secretion after in vitro stimulation suggests an immunomodulatory effect of therapy on Th1 cells, Dr. Rowe explained.

"The underlying molecular mechanisms of down-regulation of both chemokine receptor expression and cytokine secretion are not clear, and we do not know if the two observations are related," Dr. Rowe added. "It is not known how Avonex and methotrexate contributed to the immunological changes. Avonex has been reported to decrease the expression of CCR5 and CXCR3 by blood T cells in multiple sclerosis patients as well as interferon-gamma-producing T cells. The effect of methotrexate on chemokine receptor expression has not been previously reported."

"These immunological changes, in addition to the clinical improvement, may reflect lasting decreases in multiple sclerosis inflammatory responses in the central nervous system brought about by this combination therapy. When you give an intravenous dose of methotrexate that is high enough to cross the blood-brain barrier, you may affect the primary biology of this disease. Furthermore, this is a very safe drug when given with leucovorin rescue," advised Dr. Rowe.

In Dr. Rowe's opinion, "The real promise of [this therapy] is in the early modification of the biology of multiple sclerosis, because it addresses multiple sclerosis as what it is—a disease of the central nervous system. Combination therapy is the direction in which multiple sclerosis therapy is going in managing breakthrough disease."

Future Treatment Options for Multiple Sclerosis

Safety and Efficacy of Natalizumab (Antegren) Alone and When Added to Interferon Beta 1-a (Avonex) in Patients with Relapsing-Remitting MS: Design of Two Phase III Trials

Richard A. Rudick, MD, Director, The Mellen Center for Multiple Sclerosis, Cleveland Clinic Foundation, Cleveland, Ohio

Future therapy for MS will undoubtedly be directed toward new molecular targets. One promising approach involves a molecule that is designed to interfere with the movement of potentially damaging T cells across the blood-brain barrier. The first of these selective adhesion molecule inhibitors to be studied in MS is natalizumab (Antegren©), a humanized monoclonal antibody that antagonizes glycoprotein α-4 integrin which is expressed on the surfaces of activated lymphocytes and monocytes and plays a critical part in their adhesion to the vascular endothelium and migration into the parenchyma. The parameters and design of two phase III trials evaluating natalizumab were presented by Richard A. Rudick, MD, Director of The Mellen Center for Multiple Sclerosis, Cleveland Clinic Foundation, Cleveland, Ohio.⁶

Trafficking of leukocytes across the blood-brain barrier is a potentially crucial step in the initiation of a cascade of events that lead to inflammation and demyelination within the central nervous system. It is believed that preventing their entry in the parenchyma might preclude many of the disastrous neurological consequences of MS. The interaction of α-4 integrin with its endothelial counter receptor, vascular cell adhesion molecule (VCAM-1), appears to be important for autoreactive T-cell migration across the blood brain barrier into MS lesions. Natalizumab is able to block crucial interactions necessary for the migration of T cells and consequently decrease leukocyte infiltration.

"Antegren is targeted at a specific molecule that is involved in the trafficking of lymphocytes into the central nervous system," Dr. Rudick explained. "It is likely the mechanism of action of Antegren is different from that of Avonex, which has very broad activity."

A phase II study of 213 patients with relapsing-remitting or secondary progressive MS, recently reported in the New England Journal of Medicine,²¹ showed that natalizumab significantly reduced clinical relapses and the formation of new gadolinium-enhancing lesions. At 6 months, placebo-treated patients demonstrated a steady increase in new lesions (mean of 9.6 new lesions per patient), while patients administered natalizumab 3 mg/kg and 6 mg/kg demonstrated 90% fewer lesions (mean of 0.7 and 1.1 new lesions per patient, respectively; P<0.001). Twenty-seven patients in the placebo group had relapses, as compared with 13 and 14 natalizumab-treated patients receiving 3 mg/kg and 6 mg/kg, respectively (P = 0.02).

"There is a lot of excitement and enthusiasm about Antegren because it looked so promising in the phase II trials," Dr. Rudick said. "There is a great deal of interest to see, in a study of about 1000 patients, whether there will be an effect against placebo. If the phase II trial is correct, Antegren should show efficacy and then we will have another treatment option."

Based on the results from earlier phase II studies, two large randomized, double-blind, placebo-controlled, multicenter phase III efficacy studies have been designed to further evaluate the potential of natalizumab as MS therapy. Both studies have completed enrollment.

The phase III AFFIRM study (Safety and efficacy of natalizumab in the treatment of multiple sclerosis) will evaluate the efficacy and safety of single-agent natalizumab in over 900 patients with relapsing-remitting MS.^6,22 Natalizumab 300 mg or placebo will be administered intravenously monthly for a treatment period of 2 years.

The phase III SENTINEL study (Safety and efficacy of natalizumab in combination with Avonex in the treatment of multiple sclerosis) will evaluate the therapeutic potential of natalizumab in combination with Avonex in about 1200 patients with relapsing-remitting MS who have experienced a clinical relapse while on single-agent Avonex.^6,23 Patients will be randomized to natalizumab 300 mg or placebo administered intravenously monthly while continuing to receive Avonex 30 mcg weekly.

The 2-year studies will evaluate the ability of natalizumab to reduce the number of clinical relapses and slow the progression of disease disability as measured by EDSS. Secondary endpoints will be the treatments' effect on number of gadolinium-enhancing lesions and new or enlarging T2 hyperintense lesions, rate of disability progression as determined by changes in the MSFC, proportion of relapse-free subjects at 1 year, rate of clinical relapses at 2 years, and T1 hypointense lesion number and T2 hyperintense lesion volume at 2 years. Tertiary objectives include safety and tolerability, global impression of change in well-being, brain atrophy, quality of life, incidence of antibody development, and pharmacokinetics and saturation of α-4 integrin on PBMC.

Dr. Rudick noted that the SENTINEL study should answer a very important question concerning treatment options in MS—the true benefit of combination therapy. "SENTINEL is the largest randomized placebo-controlled trial conducted thus far to explore the use of combination therapy as a potential therapeutic approach to the treatment of multiple sclerosis. With this study, we are very interested in seeing whether patients who do not fully respond to interferon will fully respond if we add Antegren. We are asking whether you can better control a patient with multiple sclerosis by adding a second drug initial therapy. This combination could offer an alternative to switching from one single agent therapy to another. My reading of the current situation is that the single-agent therapies are much more similar than they are different, in terms of their effectiveness. The future is with combination therapy, and this study puts that to the test," advised Dr. Rudick, the principal investigator for SENTINEL.

Campath-1H Treatment in Multiple Sclerosis

Alasdair Coles, MD, University of Cambridge, Cambridge, United Kingdom.

Campath-1H, a humanized monoclonal antibody that depletes T cells, significantly reduced relapse rates and improved the disability status in a small series of worsening MS patients treated in a study from the United Kingdom.¹

In previous studies of patients with secondary progressive MS,²⁴ Campath-1H appeared to powerfully suppress inflammatory activity, as demonstrated by the sustained reduction in lymphocytes, especially CD4- and CD8-positive cells. "This effect lasted for months, in fact, for years," Dr. Coles said.

Campath-1H reduced relapse rates and reduced gadolinium-enhancing lesions but did not slow the progression of disability. The investigators believed, therefore, that Campath-1H may not influence the mechanisms underlying established disease progression—axonal degeneration and cerebral atrophy. Thus, the current study was designed to evaluate this novel agent earlier in the disease course, in an effort to prevent axonal degeneration.

The study was an open-label experience in a group of "aggressive" MS patients who received Campath-1H in a pulsed weekly dose, including 36 secondary progressive- and 22 relapsing-remitting MS patients. Patients were evaluated clinically every 3 to 6 months. Approximately half the patients are now in their second year of treatment.

The initial results of the study have confirmed the hypothesis of the investigators—that Campath-1H has greater efficacy when administered during the earlier phases of MS, when clinical disease activity is attributed to inflammation. "Campath-1H inhibits and prevents clinical episodes in early relapsing-remitting multiple sclerosis," Dr. Coles stated.

At treatment, the relapsing-remitting MS patients who entered the study were mostly treatment-naпve, had less than 5 years of disease (mean duration 2.7 years), their mean relapse rate was 3/year and their EDSS increased by 2.4 points. After treatment, relapse rate in the first year was 0.1/year; in subsequent follow-up (mean 13 months, range 1 to 69 months) only one patient has relapsed. Their mean EDSS is now 0.5 points less disabled than before Campth-1H treatment. Furthermore, progression of disability was also impacted by treatment with Campath-1H. There has been no disease progression among the relapsing-remitting patients, reported Dr. Coles.

"In fact, most of these patients show recovery of their previous abilities, and the nine patients now in their second year continue to shed disability as demonstrated by reductions in EDSS. Immunologic quiescence was achieved. We believe it is possible that repair of myelination may have a clinical impact," noted Dr. Coles.

The study also included 36 patients with secondary-progressive MS whose disease duration was 12 years and 4 years from onset of disease progression. In these patients, relapse rates remained suppressed during a mean of 7 years of follow-up but their disability continued to progress.

Campath-1H therapy was not without its adverse events. All patients experienced a "cytokine release" syndrome after the first dose, which produced urticaria and fever that was difficult to control. This syndrome was associated with a dramatic increase in neurological symptoms that fully reversed spontaneously, reported Dr. Coles.

In addition, approximately one third of the study population developed autoimmune thyroid disease (Graves' disease) 5 to 21 months after their first treatment, with varying levels of seriousness. In 10 of the 15 affected patients, this was detected pre-symptomatically through thyroid screening tests. Dr. Coles believes this represents a "generality of immune suppression in multiple sclerosis" and may not be specific to this treatment.

Dr. Cole offered, "Campath-1H may represent a new approach to treatment that will alter the early biology of multiple sclerosis. We have learned that there is a narrow window of opportunity, if inflammation is prolonged. But in an immunologically quiet environment, there is the possibility of structural and functional repair." Based on increases in CD4-positive cells and MRI activity, patients appear to need re-treatment at 18 months to 24 months.

TNF-Related Apoptosis Inducing Ligand (TRAIL) as a Potential Response Marker for Interferon Beta Therapy in Multiple Sclerosis

Wandinger KP, Lunemann JD, Wengert O, et al., Berlin, Germany

Early and sustained expression of TNF-related apoptosis-inducing ligand, or TRAIL, appears to be correlated with clinical response to interferon beta therapy and therefore may prove to be a prognostic marker for treatment success, according to German investigators who presented their results at the meeting.⁴

Jan D. Lunemann, MD, Charite, Humbolt University, Berlin, Germany described an experiment aimed at examining the function and role of TRAIL gene induction by interferon beta. In the study, total ribonucleic acid (RNA) was extracted from the peripheral immune cells of several cohorts of MS patients, either non-treated or participating in clinical trials of Rebif. Samples were obtained from all patients prior to treatment as well as longitudinally within the first year of therapy. The patients were classified as either first-year responders (n = 42) or first year non-responders (n = 31) due to lack of relapses and in a subgroup stable MRI. Gene expression was quantified by realtime-polymerase chain reaction (PCR). Protein levels were determined in 252 corresponding serum samples by ELISA.TRAIL gene and protein expression was correlated with clinical activity markers.

"TRAIL was evaluated because it is one of the genes that was consistently up-regulated in our in vitro studies...and has been shown to exert potent anti-inflammatory properties at the T-cell level," Dr. Lunneman explained.

The first cohort included 62 patients with relapsing-remitting MS and EDSS 0-5.5 who experienced at least two relapses during the previous 2 years. The patients had received no treatment 6 months prior to the study and were given Rebif once weekly [Ed. FDA-approved for 3 times weekly]. Blood was sampled at baseline and at 4, 26, and 52 weeks.

A significant induction of spontaneous gene expression was noted in peripheral blood mononuclear cells for both the biological response marker MxA and TRAIL at each time point, indicating an immediate and long-term effect of interferon beta. Other closely related TNF family members were increased, though not significantly. Clinical responders, compared to non-responders, had even higher MxA gene expression as well as early and sustained up-regulation of TRAIL expression, Dr. Lunneman reported.

Another study evaluated 23 patients who developed neutralizing antibodies after 1 year of Rebif treatment. In these patients, the gene expression and up-regulation of TRAIL was significantly abrogated, indicating a direct effect of interferon beta on TRAIL transcription. Responders had significantly higher pre-treatment TRAIL levels than non-responders.

"At this point, we concluded that early and sustained TRIAL gene induction corresponded to interferon beta response, and that up-regulation of TRAIL expression was abrogated in the presence of neutralizing antibodies," commented Dr. Lunemann. "Responders could be differentiated from non-responders by their soluble TRAIL protein expression and they revealed higher soluble TRIAL pretreatment levels."

To further test TRAIL as a response marker, the investigators evaluated an additional cohort of patients treated over 9 months with Rebif 22 mcg 3 times weekly. By MRI findings, responders had no progression of gadolinium-enhancing, T2 or T1 lesions. Responders were clearly differentiated from non-responders by TRAIL expression during therapy, Dr. Lunneman reported.

"Compared with previous patients given a lower dose of interferon, the impact of interferon beta in this study [using a standard dose] was a five-fold higher gene expression. This shows a dose-dependent effect of interferon beta on the gene. MxA expression was also increased, compared with healthy controls and untreated patients, which shows specificity of TRAIL expression in patients who respond," stated Dr. Lunemann.

Further refining soluble TRAIL as a prognostic marker for treatment response, the investigators found that pre-treatment levels of 584 pg/mL correctly predicted the clinical outcomes in 49 relapsing-remitting patients in 90.5% of the responders (n = 29), and in 71.4% of the non-responders (n = 20).

The overall conclusion of the presented studies was that TRAIL induction correlated with the response to interferon beta treatment, and that elevated soluble TRAIL protein pre-treatment predicted response status after one year of treatment. "TRAIL is a potential immune biological marker for clinical response to interferon beta," Dr. Lunneman suggested. "Moreover, the immunoregulatory potential of TRIAL suggests that it might represent a novel and promising target for future therapeutic strategies."

In the MS Therapy Highlights session during the 2003 AAN meeting, Richard M. Ransohoff, MD, of the Mellen Center, Cleveland Clinic, Cleveland, Ohio commented on the importance of this study. "This is an exciting finding that may lead to ways of differentiating responders from those who will not respond adequately to interferon beta treatment," stated Dr. Ransohoff. "Increased soluble TRAIL protein levels predicted which patients at baseline would respond to interferon beta later. This is essentially a blood test that is a potential marker for a clinical therapeutic response."

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