Has anyone discussed a treatment target with you, including the need to rebaseline your disease activity? Have the concepts of preventing end-organ damage to the central nervous system (the ‘end-organ’ in MS) and brain volume loss or atrophy been broached?

Key points

• Achieving long-term remission is a well-established treatment target in MS and several other autoimmune diseases.
• Key measures of MS disease activity are used to define composite treatment targets; they provide objective means for monitoring and decision-making.
• To demonstrate a target of no evident disease activity (NEDA) requires a minimum of three criteria to be met: no relapses, no MRI activity and no disability progression.
• More stringent definitions of NEDA targets have evolved and will continue to do so as new predictors of treatment response are developed.

If you are on a disease-modifying therapy (DMT), what is the objective or treatment target for your MS? This is another question to be answered before committing yourself to a specific treatment strategy.

Treat-2-target

Relapses and ongoing focal inflammatory activity on MRI (new or enlarging T2 lesions and T1 gadolinium-enhancing lesions [Gd-enhancing]) are associated with poor outcomes. This has led to the adoption of ‘no evident disease activity’ (NEDA) as a treatment target in MS. NEDA, or NEDA-3, is a composite of three related measures of MS disease activity: (i) no relapses, (ii) no MRI activity (new or enlarging T2 lesions or Gd-enhancing lesions) and (iii) no disability progression. NEDA is an important goal for treating individuals with MS.

When to rebaseline

To use NEDA as a treatment target in day-to-day clinical practice, it is advisable to be ‘rebaselined’ after the onset of action of the DMT you have been started on. The timing of the MRI to provide a new baseline depends on the DMT concerned. The recommendations for immune reconstitution therapies (IRTs) are very different from those for maintenance therapies. In the case of an IRT (for example alemtuzumab or cladribine, which are given as short courses), breakthrough disease activity can be used as an indicator to retreat rather than necessarily to switch therapy. Therefore, a rebaselining MRI should be delayed until after the final course of therapy, e.g. 2 years, or close enough to the time when a third, or subsequent course, can be administered.

Determining treatment failure: IRTs

Questions remain of how many treatment cycles need to be given before considering that a specific IRT has not been effective.

• For alemtuzumab, the threshold is three cycles under NHS England’s treatment algorithm (based on their cost-effectiveness analysis). Alemtuzumab is a biological or protein-based treatment, so the risk of developing neutralising anti-drug antibodies increases with each infusion.
• Cladribine on the other hand is a small molecule, so neutralising antibodies are not a problem and there is no real limit on the number of courses that can be given.
• Although HSCT tends to be a one-off treatment, there are rare reports of people with MS receiving more than one cycle.

Please note there are potentially cumulative risks associated with multiple cycles of an IRT: secondary malignancies in the case of HSCT and persistent lymphopaenia with cladribine. 

Determining treatment failure: maintenance therapies

In comparison to IRTs, if you have disease activity on a particular maintenance DMT, and provided you have been adherent to your treatment, this is usually interpreted as a suboptimal response or non-response and it should trigger a switch to another class of DMT. 

A criticism of NEDA is the omission of so-called ‘non-relapse-associated disease worsening’ as a component of the treatment target (in addition to evidence of incomplete recovery from relapses). I refer to this disease worsening as smouldering MS. Worsening disability in the absence of relapses may have little to do with ongoing focal inflammatory activity. It may simply represent a delayed dying-off of axons and nerve fibres following earlier focal inflammatory lesions. As a result, many neurologists feel uncomfortable switching, or stopping a DMT, based simply on non-relapse-associated worsening disability. For more information, please see Getting worse – smouldering MS.

Beyond NEDA-3

The definition of NEDA is evolving with clinical practice. Some centres are now testing for brain volume loss (that is, brain atrophy) and/or increased neurofilament light chain (NFL) in cerebrospinal fluid (CSF) as part of the NEDA-3 treatment target. NEDA-4 builds on NEDA-3, by including the target of normalising brain atrophy rates to within the normal range. The problem we have found with this is that the measurement of brain atrophy in an individual with MS level is very unreliable. For example, dehydration, excessive alcohol consumption and some symptomatic medications can cause the brain to shrink temporarily. We, therefore, think that CSF NFL levels are a better treatment target, less prone to misinterpretation. Neurofilaments are proteins that are found in nerves and axons (nerve fibres) and are released in proportion to the amount of nerve fibre damage that occurs in MS. Normalising CSF NFL levels, which would indicate that nerve damage is stopped, is referred to as NEDA-5. From a scientific perspective, including a more objective end-organ biomarker makes sense and will almost certainly be incorporated into our treatment target in the future.  

The components of NEDA-recommended targets are expanding as our ability to measure predictors of treatment response grows.
CSF, cerebrospinal fluid; MRI, Magnetic resonance imaging; NEDA, no evident disease activity; NEIDA, no evident inflammatory disease activity; NFL, neurofilament light; PROMS, patient-related outcome measures.

End-organ damage

The combination of relapses, the development of new MRI lesions and brain volume loss over 2 years in clinical trials predicts quite accurately who will become disabled over the same time period. From a treatment perspective, it is important to stop relapses, new MRI lesions and brain volume loss if we are to prevent or slow down worsening disability. Therefore, we must go beyond NEIDA (no evident inflammatory activity), which refers to relapses and focal MRI activity, and normalise brain volume loss if we can. 

Alternatives to NEDA?

Many neurologists are critical of using NEDA as a treatment target in clinical practice, fearing that it encourages people with MS to take highly effective DMTs that they consider may be ‘more risky’ (see short summaries of the available DMTs for information about individual drugs). Such neurologists, therefore, promote a less proactive approach and allow for some residual MS disease activity, but at a lower level. This treatment target is referred to as minimal evidence of disease activity, or MEDA.

In my opinion, MEDA flies in the face of the science of focal inflammatory lesions being ‘bad’ and it is associated with poor short-term, intermediate and long-term outcomes. If most people with MS end up receiving so-called high-efficacy therapies because of breakthrough disease activity, then this is what they probably need, that is, to have their MS treated adequately. Compelling evidence has emerged from trials, large registries and real-world data that people with MS treated early with highly effective DMTs (flipping the pyramid) do better than those who have delayed access to more effective DMTs.^1,2,3 You can find a short summary of some key findings on the MS Brain Health website.

Implementing NEDA in clinical practice

Please note that achieving long-term remission, or NEDA, is a well-established treatment target in other autoimmune diseases, such as rheumatoid arthritis, autoimmune kidney disease and inflammatory bowel disease. People with MS treated to a target of NEDA do better than those with breakthrough disease activity. I would therefore strongly encourage you to discuss this treatment target with your own MS neurologist. 

The flowchart below illustrates how we implement a treat-2-target of NEDA strategy. The important take-home message is that the treatment targets in MS have moved; goal-setting and the active monitoring of outcomes is now required to achieve these goals. 

Recommended approaches to implementing a treat-2-target of NEDA strategy, using maintenance ̶ escalation or immune reconstitution therapy (IRT). The dotted lines indicate that if treatment fails you can either switch within the class (maintenance or IRT) or reassess the strategy. From Giovannoni, Curr Opin Neurol.⁴
Alem, alemtuzumab; Clad, cladribine; DMF, dimethyl fumarate; Fingo, fingolimod; GA, glatiramer acetate; HSCT, haematopoietic stem cell transplantation; IFNβ, interferon-beta; Mitox, mitoxantrone; NEDA, no evident disease activity; Nz, natalizumab; Ocre, ocrelizumab; Ofat, ofatumumab; Teri, teriflunomide.

There is also a clear need to update the definition of NEDA regularly as new technologies become available and are validated as predictors of treatment response. I therefore envisage the definition of NEDA changing still further in future to include more objective measures, particularly ones measuring end-organ damage and the inclusion of patient-related outcome measures.

References

• Harding K et al. Clinical outcomes of escalation vs early intensive disease-modifying therapy in patients with multiple sclerosis. JAMA Neurol 2019;76:536-41.
• Merkel B et al. Timing of high-efficacy therapy in relapsing-remitting multiple sclerosis: A systematic review. Autoimmun Rev 2017;16:658-65.
• Simpson A et al. Early aggressive treatment approaches for multiple sclerosis. Curr Treat Options Neurol 2021;23:19.
• Giovannoni G. Disease-modifying treatments for early and advanced multiple sclerosis: a new treatment paradigm. Curr Opin Neurol 2018;31:233 ̶ 43.