Disease-Modifying Therapies for Multiple Sclerosis
Since the approval of interferon beta-1b in 1993, the treatment landscape for relapsing multiple sclerosis (MS) has expanded dramatically to include more than 20 FDA-approved disease-modifying therapies (DMTs) across 10 distinct mechanisms of action. These agents reduce relapse frequency, delay disability accumulation, and have fundamentally improved the lives of people with MS. Treatment strategy, agent selection, monitoring, and when to switch or discontinue therapy are critical decisions that should involve shared decision making between patient and provider.
Bottom Line
- Two prevailing strategies: Escalation (start lower efficacy, escalate for breakthrough) vs early high-efficacy (potent agents from diagnosis)
- NEDA-3: "No evidence of disease activity" — absence of relapses, disability progression, and MRI activity; only ~8% maintain NEDA-3 at 7 years
- Highest efficacy agents: Natalizumab (67% ARR reduction), anti-CD20 antibodies (46–59%), alemtuzumab (49–55%), oral cladribine (58%)
- Ocrelizumab is the only DMT approved for primary progressive MS (24% reduction in disability progression)
- Fingolimod is the only DMT approved for pediatric MS (ages ≥10)
- Vaccine responses are reduced with S1P receptor modulators and anti-CD20 therapies; timing of vaccination is critical
- Immunosenescence: Age-related immune decline may increase DMT risks while reducing MS inflammatory activity, prompting consideration of discontinuation in older stable patients
Treatment Strategies
Escalation Approach
Initiate therapy with a modest-to-moderate efficacy agent (interferons, glatiramer acetate, teriflunomide, fumarates) after diagnosis. Monitor carefully with MRI (baseline at ~6 months, then at least annually) and clinical assessments for breakthrough disease activity. Escalate to higher-efficacy therapy if breakthrough is identified. This approach prioritizes safety while using MRI to assess radiographic efficacy.
Early High-Efficacy Approach
Initiate high-efficacy agents (natalizumab, anti-CD20 antibodies, alemtuzumab, cladribine, or S1P modulators) at the time of diagnosis to rapidly gain control of inflammatory activity. Retrospective studies and registry data suggest that patients treated with high-efficacy therapy within 2 years of diagnosis have better disability outcomes, and earlier treatment age predicts better treatment response. However, randomized controlled trials (TREAT-MS, DELIVER-MS) are needed to definitively compare these approaches.
Shared Decision Making
- Patients prioritize: disability progression reduction, risk of adverse events, relapse rate reduction, bothersome side effects
- Providers tend to prioritize: relapse rate, MRI outcomes, and may deprioritize serious adverse event risk compared to patients
- A dedicated treatment visit (separate from the diagnostic visit) is recommended by AAN practice guidelines
- No proven method exists to choose the best DMT for an individual patient; decisions balance efficacy, safety, disease aggressiveness, comorbidities, and patient preference
DMT Classes
Modest-to-Moderate Efficacy (Injectable Immunomodulators)
| Agent | Route | ARR Reduction (vs Placebo) | Disability Reduction | Key Safety/Monitoring |
|---|---|---|---|---|
| Interferon beta-1a (30 μg/wk IM) | IM | 18% | 37% | CBC, LFTs, TSH; flulike symptoms; depression; neutralizing antibodies; safe in pregnancy |
| Interferon beta-1a (44 μg 3×/wk SC) | SC | 32% | 30% | Same as above; MRI activity reduced 81% |
| Interferon beta-1b (250 μg QOD SC) | SC | 31% | 20–30% (active SPMS) | Same class monitoring; 83% reduction in active lesions |
| Glatiramer acetate | SC | 29% | 28% | No lab monitoring required; postinjection reaction; lipoatrophy; safe in pregnancy/breastfeeding |
Interferons and glatiramer acetate are immunomodulatory (not immunosuppressive), have no association with opportunistic infections or cancer, and preserve normal vaccine responses. They have the longest safety track record (>30 years).
Moderate Efficacy (Oral Agents)
| Agent | ARR Reduction | Disability Reduction | Key Safety/Monitoring |
|---|---|---|---|
| Teriflunomide (14 mg/d) | 31–36% vs placebo | 30–31% | LFTs monthly ×6 months; TB screening; blood pressure; peripheral neuropathy; teratogenic (pregnancy category X); accelerated elimination procedure available |
| Dimethyl fumarate | 44–53% vs placebo | 21–38% | CBC with differential, LFTs; GI side effects; flushing; lymphopenia monitoring; rare PML risk with prolonged lymphopenia |
| Diroximel fumarate | Same active metabolite as dimethyl fumarate | Expected equivalent | Same monitoring; improved GI tolerability profile |
High Efficacy: S1P Receptor Modulators
S1P receptor modulators prevent lymphocyte egress from lymphoid tissue, resulting in peripheral lymphopenia while potentially having direct CNS effects. All require first-dose cardiac monitoring.
| Agent | S1P Receptors | ARR Reduction | Key Notes |
|---|---|---|---|
| Fingolimod | 1, 3, 4, 5 | 50% vs placebo; 52% vs IFNβ-1a | Only DMT approved for pediatric MS (≥10 years); first-dose bradycardia; macular edema; CBC, LFTs, ophthalmology, dermatology, BP |
| Siponimod | 1, 5 | 55% vs placebo (SPMS trial) | 21% disability progression reduction in SPMS; CYP2C9 genotyping required before initiation |
| Ozanimod | 1, 5 | 38–48% vs IFNβ-1a | Gradual dose titration; same class monitoring |
| Ponesimod | 1 | 30.5% vs teriflunomide | Most S1P1-selective; same class monitoring |
S1P Modulator Vaccine Considerations
- Delay starting S1P modulators for 4 weeks after vaccination
- COVID-19 mRNA vaccine humoral response: only 3.8% of fingolimod-treated patients mounted a protective response (vs 100% of untreated MS patients)
- Avoid live/live-attenuated vaccines during and for 2–3 months after discontinuation
- Vaccinations may be less effective during treatment and for weeks after discontinuation (varies by agent)
High Efficacy: Oral Cladribine
Oral cladribine is a purine nucleoside analog that is cytotoxic to T and B lymphocytes by impairing DNA synthesis. It is given as short oral courses (cumulative dosing over 2 years), with no treatment needed in years 3–4 in many patients.
- ARR reduction: 58% vs placebo
- Approved for RRMS and active SPMS after suboptimal response to ≥1 other DMT
- Monitoring: CBC with differential, LFTs
- COVID-19 mRNA vaccine response preserved (unlike S1P modulators and anti-CD20)
High Efficacy: Natalizumab
Natalizumab is a monoclonal antibody targeting α4-integrin (VLA-4), blocking lymphocyte trafficking across the blood-brain barrier.
- ARR reduction: 67% vs placebo — among the highest of any single DMT
- Disability reduction: 42% in 12-week confirmed disability progression
- MRI: 92% reduction in gadolinium-enhancing lesions
- Major risk: Progressive multifocal leukoencephalopathy (PML) — risk stratified by JC virus antibody status, antibody index level, and prior immunosuppressant use
- Monitoring: LFTs, JC virus antibody testing every 6 months
- Extended interval dosing (every 6–8 weeks instead of 4) may reduce PML risk while maintaining efficacy
High Efficacy: Anti-CD20 Monoclonal Antibodies
| Agent | Route | ARR Reduction | Disability Reduction | Special Notes |
|---|---|---|---|---|
| Ocrelizumab | IV infusion q6 months | 46–47% vs IFNβ-1a SC | 40% vs IFNβ-1a (relapsing); 24% vs placebo (PPMS) | Only DMT approved for PPMS; 94–95% reduction in enhancing lesions |
| Ofatumumab | SC injection monthly | 51–59% vs teriflunomide | 34.4% vs teriflunomide | Self-administered at home; fully human anti-CD20 antibody |
| Rituximab | IV infusion (off-label) | Widely used off-label | Extensive real-world evidence | Not FDA-approved for MS but extensively used; lower cost |
Anti-CD20 antibodies deplete B cells expressing the CD20 surface molecule. Monitoring includes CBC with differential, lymphocyte subsets, quantitative immunoglobulins, and LFTs. Key concerns include:
- Hypogammaglobulinemia: Cumulative risk with prolonged treatment; monitor IgG levels
- Infection risk: Increased risk of respiratory and urinary tract infections
- Vaccine responses: Significantly reduced humoral response (22.7% response to COVID-19 mRNA vaccine vs 100% in untreated MS); delay starting anti-CD20 for 2–4 weeks after vaccination
- Rare PML risk: Reported cases, particularly in patients previously treated with natalizumab
High Efficacy: Alemtuzumab (Anti-CD52)
Alemtuzumab is a monoclonal antibody that lyses cells expressing CD52 (broadly expressed on T cells, B cells, monocytes, and NK cells). It is given as IV infusions in two annual courses and can produce durable remission.
- ARR reduction: 49–55% vs IFNβ-1a SC
- Approved for RRMS and active SPMS after suboptimal response to ≥2 other agents
- Major risks: Secondary autoimmunity (thyroid disease 30–40%, ITP ~2%, anti-GBM disease rare but life-threatening)
- Monitoring: CBC with differential, lymphocyte subsets, LFTs, TSH, creatinine, urinalysis — monthly for 48 months after each course
Mitoxantrone
An anthracenedione chemotherapeutic agent that was the first approved treatment for worsening RRMS and SPMS. Rarely used now due to cardiotoxicity (lifetime dose limit) and risk of therapy-related acute leukemia. Monitoring requires cardiac ejection fraction assessment.
Switching DMT
The most common reason for switching is lack of efficacy, followed by tolerability concerns. Key principles:
- Lateral switches (between agents of similar efficacy) are less likely to improve disease control than escalation to higher-efficacy agents
- MRI surveillance provides high-sensitivity assessment of DMT efficacy and should be done at least annually
- Washout periods vary by agent and must be considered to avoid both disease rebound and compounded immunosuppression
- Consider natalizumab rebound risk: disease reactivation can occur 3–6 months after discontinuation, particularly severe in some patients
DMT Discontinuation
With immunosenescence (age-related immune decline), both the inflammatory activity of MS and the efficacy of DMTs may wane in older patients, while risks of immunosuppression increase. Key considerations:
- Patients ≥45 years who discontinue DMT after a period of stability may be more likely to have a stable course
- Patients <45 at discontinuation are more likely to experience new attacks or radiographic activity
- The decision to discontinue should weigh disease stability duration, age, current DMT risk profile, and patient preferences
NEDA: Treatment Target
No Evidence of Disease Activity (NEDA)
- NEDA-3: Absence of relapses + no disability progression + no MRI activity (new/enlarging T2, gadolinium-enhancing lesions)
- NEDA-4: NEDA-3 plus no accelerated brain volume loss
- At 1 year: ~46% of patients achieve NEDA-3
- At 7 years: only ~8% maintain NEDA-3
- NEDA-3 at 2 years is predictive of a lack of disability at 7 years
- Failure to achieve NEDA does not always predict poor outcome
References
- Cross A, Riley C. Treatment of multiple sclerosis. Continuum (Minneap Minn). 2022;28(4):1025-1051.
- Hauser SL, Bar-Or A, Comi G, et al. Ocrelizumab versus interferon beta-1a in relapsing multiple sclerosis. N Engl J Med. 2017;376(3):221-234.
- Montalban X, Hauser SL, Kappos L, et al. Ocrelizumab versus placebo in primary progressive multiple sclerosis. N Engl J Med. 2017;376(3):209-220.
- Hauser SL, Bar-Or A, Cohen JA, et al. Ofatumumab versus teriflunomide in multiple sclerosis. N Engl J Med. 2020;383(6):546-557.
- Polman CH, O'Connor PW, Havrdova E, et al. A randomized, placebo-controlled trial of natalizumab for relapsing multiple sclerosis. N Engl J Med. 2006;354(9):899-910.