The Promise and Perils of Alemtuzumab in MS Treatment
For people living with multiple sclerosis (MS), treatment options have steadily improved over the last few decades—thanks, in part, to our growing understanding of the immune system’s role in the disease. One treatment that stands out for its promise—and controversy—is alemtuzumab, a monoclonal antibody that offers a powerful and long-lasting effect by hitting the immune system’s "reset button."
A 2014 editorial in Neurology by Drs. Neil Robertson and Neil Scolding dives into the complex interplay between alemtuzumab, immune reconstitution, and disease activity in MS. Let’s unpack their key insights and why they still matter today.
What is Alemtuzumab?
Alemtuzumab is an antibody that targets CD52, a protein found on the surface of certain immune cells. When administered, it causes a rapid and profound depletion of circulating lymphocytes—T cells and B cells—without affecting stem cells. This opens the door to an immune “rebuild” that may shift the immune system into a less inflammatory mode, beneficial for controlling MS.
Originally developed and licensed to treat leukemia, alemtuzumab later found a second life as a potent therapy for relapsing forms of MS. Clinical trials have shown over 70% reduction in relapse rates and disability accumulation over 3 to 5 years compared to traditional therapies like interferon beta-1a.
A Mixed Blessing: Durable, but Risky
Alemtuzumab’s biggest selling point is its durability. Unlike most MS treatments that require regular dosing, alemtuzumab is typically given in two yearly cycles, and many patients enjoy years of disease control without needing further treatment.
But this powerful reset doesn’t come without risks. About 30% of patients develop autoimmune complications, including thyroid disease and, more rarely, kidney disorders and other issues. Some patients also show no meaningful improvement, raising questions about how to identify who will benefit—and who won’t—early on.
Can We Predict Who Will Respond?
Researchers have tried to find a biomarker—something measurable in the blood—that could predict how a patient will respond to alemtuzumab. One hopeful idea came from earlier studies suggesting that faster recovery of CD4+ T cells (a key immune cell type) might signal a return of disease activity.
However, in a more rigorous and longer-term study published by Kousin-Ezewu et al. and reviewed in this editorial, those earlier findings didn’t hold up. The researchers found no reliable correlation between CD4+ recovery and MS relapse or MRI activity. That means absolute CD4+ counts can’t currently guide treatment decisions.
Why the Conflicting Results?
The editorial offers a few reasons for these discrepancies:
Different study sizes and follow-up durations
Varying patient characteristics, including prior treatment exposure and disease aggressiveness
Differences in how and when MRI scans and clinical assessments were conducted
Potential flaws in statistical methods, such as assuming immune recovery behaves the same across all treatment cycles
In short, measuring CD4+ cells alone may be too simplistic to capture the complex immune reconstitution that alemtuzumab triggers.
The Bigger Problem: U.S. Patients Left Behind
At the time of the editorial’s publication, alemtuzumab had been approved in Europe, Australia, Canada, and elsewhere—but not in the United States. The FDA had raised concerns about study designs and side effects, despite mounting international evidence of the drug’s efficacy. This led the authors to express concern—and frustration—about the treatment being inaccessible to American patients.
What’s Next?
Robertson and Scolding emphasize that while alemtuzumab remains one of the most powerful tools in the MS treatment toolbox, it’s also among the most complex. Identifying which patients need retreatment—or are at risk of adverse events—remains an open question. The search for better biomarkers continues, potentially in more advanced immune profiling techniques that go beyond traditional cell counts.
Takeaway
Alemtuzumab is a fascinating example of precision immunotherapy—a drug that doesn’t just suppress the immune system, but reshapes it. Its potential in MS is undeniable, but so are its risks. We need more refined tools to personalize its use, especially given the unpredictable nature of MS itself.
As we wait for those tools to mature, alemtuzumab reminds us that in medicine, the line between breakthrough and backlash can be razor-thin.
Disclaimer: This blog post is based on the provided research article and is intended for informational purposes only. It is not intended to provide medical advice. Please consult with a healthcare professional for any health concerns.
References:
Robertson NP, Scolding NJ. Immune reconstitution and treatment response in multiple sclerosis following alemtuzumab. Neurology. 2014;82(24):2150-2151.
