Relapsing-remitting multiple sclerosis (MS) can alternate between periods of stability and attacks that bring new or worsening neurological symptoms. While clinical trials establish whether a medicine is effective under controlled conditions, monitoring patients in routine care shows how well it performs in the real world.

A new study co-authored by Dr. Maya Zeineddine, clinical associate professor and chair of the Department of Pharmacy Practice at the School of Pharmacy, helps fill the gap for long-term use of oral cladribine, an approved drug for relapsing-remitting multiple sclerosis, in the UAE. 

The study, “Long-term Real-world Safety and Efficacy of Cladribine Tablets in Patients with Relapsing-Remitting Multiple Sclerosis: The UAE Experience,” published in Multiple Sclerosis and Related Disorders, examined the effectiveness, safety, and early predictors of response in four tertiary multiple sclerosis centers in the United Arab Emirates.

According to Dr. Zeineddine, the study provides the first dedicated real-world evidence on cladribine from the UAE, addressing a gap in research that had largely come from Europe and North America. “The UAE also has a highly diverse population comprising patients of different nationalities and ethnic backgrounds, many of whom remain underrepresented in clinical trials,” she said.

Lebanon is another valuable setting for such research, she added. Her team had already collected real-world data on patients treated with cladribine in Lebanon, but those findings were published alongside data from European centers as part of a larger international cohort.

In the study, the researchers reviewed records for 163 patients treated with cladribine tablets, a therapy delivered in short courses that temporarily reduces certain immune cells that risk damaging the nervous system. The median follow-up was two years; around three in four participants were women and had previously used another disease-modifying treatment. The team tracked relapses, disability, new or enlarging MRI lesions, blood cell counts, infections, and malignancies.

At the end of follow-up, around 92 percent of patients had not experienced a progression in disability, and 74 percent showed no new or worsening lesions on the MRI. Overall, 70 percent achieved NEDA-3, meaning no relapses, no confirmed disability worsening, and no new MRI activity, and the average number of relapses per patient-year fell by 84.4 percent after treatment. Among the baseline characteristics tested, only the number of relapses before cladribine predicted whether a patient reached NEDA-3. The other assessed characteristics were not significant predictors, suggesting that recent disease activity may be more informative than a wider set of starting features when estimating response.

The link between pretreatment relapses and NEDA-3 was clinically plausible and partly expected, said Dr. Zeineddine. She explained that frequent recent relapses reflect greater inflammatory disease activity and may indicate more aggressive disease, making the combined requirements of NEDA-3 harder to meet. “However, this should not be interpreted as meaning that cladribine is ineffective in patients with highly active disease,” she cautioned. Rather, relapse activity before treatment may remain an indicator of likely outcomes even after an effective therapy begins.

The absence of other independent predictors could suggest that cladribine’s effectiveness is relatively consistent across different patient profiles, she added.  As the sample size and the number of NEDA-3 events may have limited the researchers’ ability to identify additional predictors, she said, “this finding should be considered hypothesis-generating and confirmed in larger prospective cohorts.”

The safety findings were also generally reassuring. Grade 3 lymphopenia—a substantial reduction in a type of white blood cell that supports the immune system—occurred in only 7 percent of patients, whereas no Grade 4 cases were recorded. The study reported seven adverse events, though none required hospitalization. One patient developed an astrocytoma, a type of brain tumor, more than a year after starting treatment, though it was not established whether it was a result of the treatment.

Taken together, these findings indicate that cladribine is an effective short-course treatment option in routine UAE clinical practice, and reinforce the importance of appropriate hematological monitoring and continued follow-up of long-term effectiveness and safety outcomes.

Larger prospective studies directly comparing cladribine with other high-efficacy therapies, particularly monoclonal antibodies, are needed to better inform treatment selection. Furthermore, identifying reliable clinical, imaging, and biological biomarkers may support a more individualized approach and help clinicians select the most appropriate therapy for each patient.

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