Does Ocrevus reduce brain lesions? Understanding its impact on multiple sclerosis

October 10, 2025 •

2 min read

In clinical trials for relapsing-remitting MS, Ocrevus was shown to reduce the number of T1 gadolinium-enhancing lesions by over 90% compared to interferon beta-1a. This powerful evidence directly addresses the question: Does Ocrevus reduce brain lesions? The answer, supported by extensive research, is a resounding yes, making it a pivotal treatment for multiple sclerosis.

Quick Summary

Ocrevus, an anti-CD20 B-cell depleter, is proven to significantly reduce the formation and volume of inflammatory brain lesions seen on MRI scans in patients with relapsing and primary progressive MS.

Key Points

Significant Lesion Suppression: Clinical trials (OPERA, ORATORIO) have shown Ocrevus significantly reduces the number and volume of brain lesions detected on MRI scans.
Active Inflammation Reduction: The drug is highly effective at suppressing T1 gadolinium-enhancing lesions, which indicate active inflammation in the CNS.
Mechanism of Action: Ocrevus works by targeting and depleting CD20-positive B-cells, which are key drivers of inflammation and lesion formation in MS.
Impact on Brain Volume: Studies indicate that Ocrevus can slow the rate of brain atrophy, or volume loss, potentially to levels observed in healthy aging.
New Subcutaneous Formulation: The newer subcutaneous injection of Ocrevus provides comparable, near-complete suppression of brain lesions to the established intravenous infusion.
Long-term Efficacy: Extended-phase studies show that the benefits of Ocrevus in lesion control are maintained over several years of continuous treatment.
Benefit for PPMS: Ocrevus was the first therapy approved for primary progressive MS (PPMS) and has been shown to reduce both brain lesion volume and cortical lesion activity in these patients.

Ocrevus's mechanism of action in tackling brain lesions

Ocrevus (ocrelizumab) is a monoclonal antibody that targets and depletes CD20-positive B cells, which are believed to contribute to the inflammation in multiple sclerosis (MS). By removing these B cells, Ocrevus helps prevent damage to the myelin sheath, the protective covering of nerve fibers, within the central nervous system (CNS). This action ultimately leads to a reduction in the formation of new brain lesions.

Clinical trial evidence for lesion reduction

Clinical trials have demonstrated Ocrevus's effectiveness in reducing brain lesions, a key measure of treatment success in both relapsing-remitting MS (RRMS) and primary progressive MS (PPMS).

Relapsing-remitting MS (RRMS)

Studies such as OPERA I and OPERA II showed that Ocrevus significantly reduced new lesions compared to interferon beta-1a. This included a superior reduction in T1 gadolinium-enhancing lesions (indicating active inflammation) and new/enlarging T2 lesions (representing total disease activity). Long-term extension studies also indicated sustained lesion suppression with continued Ocrevus use.

Primary progressive MS (PPMS)

The ORATORIO trial was the first to show a positive effect of a disease-modifying therapy in PPMS, with Ocrevus-treated patients showing a reduction in T2 lesion volume compared to an increase in the placebo group. Analysis also indicated a reduction in cortical lesions.

Impact on brain volume and atrophy

Ocrevus has also been shown to impact brain volume loss, or atrophy, which is linked to neurodegeneration in MS. Clinical data suggests Ocrevus can slow the rate of brain atrophy.

The new subcutaneous formulation and lesion activity

A subcutaneous (SC) injection of Ocrevus has been developed and approved. Clinical trials indicate that this new formulation provides similar efficacy in suppressing brain lesions as the intravenous version.

Ocrevus vs. Other MS Treatments: An MRI Perspective

Comparing Ocrevus to interferon beta-1a highlights its efficacy in lesion reduction.


Feature	Ocrevus (Ocrelizumab)	Interferon Beta-1a (Rebif)	Placebo (Pre-Switch)
Mechanism	Targets and depletes CD20+ B-cells.	Modulates immune system response.	No active treatment.
Effect on T1 Gd+ Lesions	Near-complete suppression observed in clinical trials.	Associated with a higher rate of new lesions compared to Ocrevus.	High lesion activity observed.
Effect on T2 Lesion Volume	Significantly reduced.	Volume increased in a long-term study.	Volume increased significantly.
Rate of Brain Atrophy	Slowed to levels similar to healthy aging.	Higher rate of atrophy compared to Ocrevus.	High rate of brain volume loss.

Conclusion: The definitive role of Ocrevus in lesion management

Clinical trial evidence confirms Ocrevus significantly reduces brain lesions in both relapsing and primary progressive multiple sclerosis by targeting CD20-positive B cells. It suppresses T1 gadolinium-enhancing and T2 lesion activity and slows brain atrophy. The subcutaneous option offers comparable efficacy. Ocrevus provides a powerful approach to controlling disease activity and reducing lesion accumulation in MS.

For more detailed information on multiple sclerosis and its treatments, visit the National Multiple Sclerosis Society website: https://www.nationalmssociety.org (this link is an example and should be updated with a specific, authoritative source if possible).

Frequently Asked Questions

Ocrevus reduces brain lesions by targeting and destroying CD20-positive B-cells, which are immune cells that contribute to the inflammation and damage of nerve fibers in multiple sclerosis. By removing these cells from circulation, Ocrevus prevents them from entering the brain and spinal cord, thereby reducing lesion formation.

Ocrevus demonstrates a rapid onset of action. Clinical studies have shown significant suppression of MRI lesion activity, particularly T1 gadolinium-enhancing lesions, within weeks of initiating treatment.

While its primary effect is preventing new lesion formation, Ocrevus can also influence existing lesions. Studies show it can reduce the volume of T2 lesions and limit the accumulation of T1 hypointense lesions, suggesting it mitigates ongoing injury within chronic areas of damage.

In comparative clinical trials (OPERA I & II), Ocrevus was shown to be superior at reducing inflammatory T1 gadolinium-enhancing lesions and new/enlarging T2 lesion volume compared to the older disease-modifying therapy interferon beta-1a (Rebif).

Reducing lesions is a crucial step in slowing disease progression, as lesions contribute to nerve damage and subsequent disability. Clinical trials for Ocrevus also demonstrated a reduction in the risk of confirmed disability progression, indicating a positive correlation between lesion reduction and clinical outcomes.

The effect is primarily measured using Magnetic Resonance Imaging (MRI). Neurologists monitor different lesion types, including T1 gadolinium-enhancing lesions (indicating active inflammation) and T2 lesions (reflecting total disease burden), to track treatment efficacy.

Yes, recent Phase III data confirms that the subcutaneous (SC) formulation of Ocrevus provides a comparable and near-complete suppression of brain lesions to the established intravenous (IV) infusion.

T1 Gd+ lesions are active inflammatory lesions that enhance with a contrast dye (gadolinium), while T2 lesions represent the total cumulative burden of disease and include older, chronic lesions.