Multiple sclerosis is a chronic, immune-mediated disease of the central nervous system that remains a leading cause of neurological disability in young adults worldwide. While disease-modifying therapies have transformed long-term outcomes for many patients, most of the evidence guiding their use still comes from clinical trials conducted in North America and Europe. This raises a persistent and important question for clinicians and researchers alike. Do these therapies perform the same way in everyday clinical practice and in populations that have historically been underrepresented in trials?
A new study, led by Adolfo del Canto as part of his Neurimmunology Fellowship project under the guidance of Ethel Ciampi, provides one of the most comprehensive answers to date for Latin America. Published in the Multiple Sclerosis Journal, the article titled “Real-world evidence of ocrelizumab in Chilean patients with multiple sclerosis” presents four years of prospective observational data from a large cohort of Chilean patients treated at a specialised multiple sclerosis unit at the Pontificia Universidad Católica de Chile.
The findings are striking. Across nearly 300 patients and more than 700 patient-years of exposure, ocrelizumab was associated with extremely low relapse rates, sustained suppression of MRI disease activity, and a safety profile consistent with that observed in pivotal clinical trials. Importantly, these outcomes were observed in a real-world healthcare setting shaped by public funding policies, pandemic disruptions, and diverse disease phenotypes.
Why real-world data matters in multiple sclerosis research
Randomised controlled trials remain the gold standard for demonstrating the efficacy and safety of new therapies. However, they are designed around strict inclusion criteria, controlled environments, and limited follow-up periods. As a result, many patients encountered in daily clinical practice are underrepresented. This includes older individuals, those with progressive forms of multiple sclerosis, patients with prior treatment exposure, and populations outside Europe and North America.
Real-world evidence fills this gap by capturing how therapies perform in real-world care settings. It reflects clinical complexity, long-term adherence, comorbidities, and health system constraints. In multiple sclerosis, where treatment decisions often span decades and involve balancing efficacy against cumulative risks, such evidence has become increasingly influential.
The study directly addresses this need. Latin American populations have been notably underrepresented in multiple sclerosis research, despite growing recognition that disease course, disability progression, and treatment response may vary by ethnicity, socioeconomic factors, and access to care. By focusing on a Chilean cohort followed prospectively over four years, the study adds depth and geographic diversity to the global evidence base surrounding ocrelizumab.
Inside the Chilean cohort and study design
The research team conducted a prospective longitudinal observational study involving 305 people with multiple sclerosis who received at least one dose of ocrelizumab between June 2018 and October 2023. Patients were diagnosed according to the 2017 McDonald criteria and were followed within the Programa de Esclerosis Múltiple UC, a specialised multiple sclerosis programme based at the Pontificia Universidad Católica de Chile.
The cohort included a broad spectrum of disease phenotypes. Approximately three-quarters of participants had relapsing-remitting multiple sclerosis, while the remainder had secondary progressive or primary progressive disease. The mean age at treatment initiation was just under 39 years, with a median Expanded Disability Status Scale score of 2.0, reflecting relatively early disease for many patients but also including those with more advanced disability.
Unlike many clinical trials, most patients were not treated naively. More than half of those with relapsing disease had switched to ocrelizumab because of treatment failure or adverse effects with prior disease-modifying therapies. In contrast, most patients with primary progressive multiple sclerosis were initiating their first disease-modifying treatment, reflecting national reimbursement policies in Chile.
Near elimination of relapses in routine clinical care
One of the most attention-grabbing findings from the study is the extremely low relapse rate observed during follow-up. Over a four-year period, only one clinical relapse was recorded across the entire cohort. This occurred in a patient with active secondary progressive multiple sclerosis shortly after switching from fingolimod.
For clinicians accustomed to managing relapsing disease, this result stands out even when viewed alongside existing trial data. In the pivotal OPERA I and II trials, ocrelizumab significantly reduced annualised relapse rates compared with interferon beta, but relapses were not eliminated. The Chilean cohort showed an even greater reduction, likely influenced by a lower baseline relapse rate and the prompt suppression of MRI activity after treatment initiation.
From a real-world perspective, this finding reinforces the effectiveness of high-efficacy disease-modifying therapies when used in patients with active inflammatory disease. It also supports the growing clinical emphasis on early intervention and timely treatment escalation to prevent irreversible neurological damage.
–Ethel Ciampi
Safety outcomes under real-world conditions
Safety is a critical concern for long-term immunotherapy, particularly with B-cell-depleting agents. The Chilean study provides reassuring data in this regard. Infusion-related reactions were most common during the first administration and decreased steadily with subsequent doses. Most reactions were mild and manageable, and no patient discontinued treatment due to infusion reactions.
Malignancies were rare, occurring in approximately 1% of patients. Two deaths were reported during follow-up, one related to severe COVID-19 and the other to metastatic cancer. While any such events warrant careful monitoring, the overall safety profile observed aligns with established pharmacovigilance data for ocrelizumab.
Implications beyond Chile and Latin America
While the study focuses on a Chilean population, its implications extend well beyond national borders. It demonstrates that high-efficacy multiple sclerosis therapies can deliver consistent outcomes across diverse healthcare systems and patient populations when access is appropriately structured.
The research also underscores the importance of including underrepresented groups in long-term observational studies. Ethnicity, socioeconomic context, and health system design all influence disease outcomes; however, these factors are often underexplored in neurological research. By contributing robust real-world evidence from Latin America, the study helps close a critical knowledge gap and strengthens the global relevance of multiple sclerosis research.
Reference
del Canto, A., Cárcamo, C., Garcia, L., Aylwin, E., Jürgensen-Heinrich, L., Guzman-Carcamo, I., de la Barra, J., Gutierrez-Calquin, L., Barrera-Hormazabal, A., Cruz, J. P., Bravo, S., Pelayo, C., Soler, B., Uribe-San-Martin, R., & Ciampi, E. (2025). Real-world evidence of ocrelizumab in Chilean patients with multiple sclerosis. Multiple Sclerosis Journal, 31(4), 444–454. https://doi.org/10.1177/13524585241309835
Dr. Adolfo del Canto is a member of the Neuroimmunology Unit at both the Catholic University of Chile and Hospital del Salvador in Santiago, Chile. His current research projects focus on MOGAD, NMOSD, and Real-World Evidence of Ocrelizumab. His work combines clinical care, real-world evidence research and academic publishing, with active participation in international conferences and collaborative research projects across Latin America and Europe.
