Cladribine is a medication used to treat multiple sclerosis (MS), particularly the relapsing forms of the disease. Its effectiveness lies in its ability to reduce the frequency of MS relapses (flare-ups) and slow the progression of disability over time. Cladribine works by selectively targeting and reducing certain immune cells, especially lymphocytes, which play a key role in the autoimmune attack on the nervous system seen in MS.
When patients take cladribine, there is a dose-dependent reduction in lymphocyte count, with the lowest levels occurring about two to three months after starting treatment. This reduction helps to calm the immune system’s attack on the nervous system. Typically, lymphocyte levels recover around 28 weeks after treatment. Clinical trials involving over a thousand patients have shown that cladribine significantly decreases the number of relapses compared to placebo. For example, after about two years, approximately 81% of patients on cladribine remained relapse-free, compared to 63% on placebo. It also reduces the progression of disability and the number of lesions visible on MRI scans, which are markers of disease activity in MS.
One of the notable features of cladribine is its long-lasting effect despite the drug itself not remaining in the body for more than a week after administration. This means patients can receive short courses of treatment and still experience benefits that last for years. Real-world data suggest that many patients continue on cladribine treatment for several years, with treatment persistence rates around 70% at four years. This durability is important because it offers a treatment option that does not require continuous immunosuppression, potentially reducing long-term risks associated with ongoing immune system suppression.
However, cladribine is not without downsides. Because it lowers lymphocyte counts, it can increase the risk of infections and other immune-related side effects. Patients need monitoring during and after treatment to manage these risks. Additionally, cladribine contains an ingredient that can interact with other medications, so timing of administration with other drugs or supplements is important.
Comparatively, some studies have shown that other treatments like rituximab may provide superior disease control and better disability outcomes than cladribine in relapsing-remitting MS. Rituximab showed a lower rate of new MRI disease activity and fewer relapses over several years compared to cladribine. Disability improvement was also more common with rituximab. Despite this, cladribine remains a valuable option, especially for patients seeking a high-efficacy oral treatment with a convenient dosing schedule.
Recent long-term data reinforce cladribine’s role in managing relapsing MS, showing that nearly 9 out of 10 patients remain free from disability progression independent of relapse activity over four years. This highlights its potential to provide durable disease control beyond just reducing relapses.
Mechanistically, cladribine’s effectiveness is linked to its ability to deplete memory B cells, a subset of immune cells thought to be crucial in driving MS disease activity. By targeting these cells, cladribine helps to halt the autoimmune process that damages the nervous system.
In clinical practice, cladribine is often considered for patients who have active relapsing MS and may not have responded well to other treatments or prefer an oral therapy with intermittent dosing. Its use requires careful patient selection and monitoring, especially regarding immune status and infection risk.
Overall, cladribine offers a potent, long-acting treatment option for relapsing MS that reduces relapses, slows disability progression, and decreases MRI lesion activity. While other therapies may outperform it in some measures, cladribine’s unique dosing and durable effects make it an important part of the MS treatment landscape.
