A major analysis shows that more drug exposure does not always mean better disease control, as high-dose ocrelizumab cleared more circulating B cells without improving disability outcomes in MS.
Efficacy and safety of a bodyweight–adjusted higher dose of ocrelizumab in relapsing (MUSETTE) and primary progressive (GAVOTTE) multiple sclerosis: two multicentre, randomised, double-blind, parallel-group phase 3b trials. Image Credit: Camptoloma / Shutterstock
In a recent study published in The Lancet, researchers investigated whether bodyweight-adjusted high doses of ocrelizumab could better control disability progression in multiple sclerosis (MS). The study used data from two parallel phase 3b clinical trials, MUSETTE and GAVOTTE, both of which compared elevated doses against the approved 600 milligram regimen in patients with relapsing or primary progressive forms of the disease.
Study findings revealed that higher doses were associated with greater depletion of target immune cells in blood tests but did not provide added clinical benefit in delaying disability accumulation, indicating that the currently prescribed standard dose of 600 mg remains the supported standard regimen.
Background
Multiple sclerosis (MS) is a chronic, inflammatory, demyelinating, and progressive condition in which the body’s immune system mistakenly damages the myelin sheaths covering nerve fibers in the central nervous system (CNS). The disease phenotypically manifests as vision issues, sensory changes, motor difficulties, cognitive/mood alterations, or severe fatigue, depending on the specific nerve damage and the extent of disease progression.
Clinically, studies have shown that MS is traditionally classified into relapsing-remitting, secondary progressive, and primary progressive phenotypes, while the present trials focused on two clinically important populations: relapsing MS and PPMS. Reviews on the topic highlight that while modern disease-modifying therapies excel at suppressing acute inflammation and relapses, delaying long-term disability progression independent of relapses remains a major unmet, urgent medical need.
Ocrelizumab is a humanized anti-CD20 monoclonal antibody designed to target and deplete CD20-expressing B cells (white blood cells central to the autoimmune disease). The drug has previously been approved for both relapsing multiple sclerosis (RMS) and PPMS at a standard 600 milligram (mg) dose administered every six months.
Retrospective analyses of patients regularly administered ocrelizumab suggest that individuals with higher drug exposure experienced slower disability progression, but these observations and the resultant hypothetical link between dosage and MS outcomes remained unverified.
About the study
The present study aimed to elucidate this knowledge gap and inform future MS interventions by using data from two international, randomized, double-blind phase 3b clinical trials, MUSETTE and GAVOTTE. The MUSETTE trial was RMS-specific and comprised 860 RMS patients. The GAVOTTE trial focused on PPMS patients (n = 753). Both cohorts comprised participants aged 18 to 56.
Participants were assigned in a 2:1 ratio to receive either bodyweight-adjusted high-dose ocrelizumab or the standard 600 mg dose via intravenous infusion every 24 weeks. To account for differences in participants’ body mass, high-dose (experimental) cohort patients weighing under 75 kilograms received 1200 mg, while those weighing 75 kilograms or more received 1800 mg.
The study’s primary endpoint was the time to onset of 12-week composite confirmed disability progression (CCDP). CCDP was tracked using the expanded disability status scale (EDSS) to measure physical impairment, the timed 25-foot walk test (T25FWT) to evaluate participants’ walking speed, and the 9-hole peg test (9HPT) as a proxy for manual dexterity.
The study’s secondary outcomes included monitoring participants’ structural brain volume using high-resolution magnetic resonance imaging (MRI) and estimating neuroaxonal damage using blood concentrations of neurofilament light chain (NfL).
Study findings
Results revealed that while higher ocrelizumab dosages were associated with greater CD20-expressing B cell clearance (as expected), higher dosing did not provide superior disease control compared to the standard 600 mg dose.
In the MUSETTE (RMS) trial, 34% (198 of 577) of high-dose patients experienced 12-week disability progression, compared with 37% (104 of 283) in the standard group (hazard ratio [HR] 0.93; p = 0.53). The results from the GAVOTTE trial (PPMS) corroborated these patterns: 47% (235 of 500) of high-dose participants progressed, compared with 49% (124 of 253) in the standard arm (HR 0.95; p = 0.64).
Blood-associated B-cell count data revealed that at week 120, the proportion of patients with counts below 0.441 cells per microliter (µL) was notably higher in the high-dose arms (38% vs. 15% in MUSETTE; 31% vs. 20% in GAVOTTE). However, this did not translate into better clinical function. Both groups experienced substantial reductions in nerve damage markers, with blood NfL dropping by 37% at week 48 in both MUSETTE treatment arms (p < 0.0001).
Encouragingly, safety profiles and serious infection rates remained broadly similar across treatment arms, with no new safety concerns identified in either trial.
Conclusions
The present study demonstrates that increasing ocrelizumab doses produced greater peripheral B-cell depletion, but this did not translate into improved MS outcomes or reduced disability progression.
These findings suggest that the benefits of higher intervention dosages might have reached a therapeutic ceiling in MS management and further indicate that, because improved peripheral clearance does not equate to better protection against brain tissue loss, measuring circulating B-cell concentrations may be an insufficient basis for clinical decisions. The results also suggest that further progress may require targeting CNS-compartmentalized B cells or non-B-cell-mediated neurodegenerative mechanisms that contribute to disease progression.
This research supports the standard 600 mg dose as the current approved regimen with a favorable benefit-risk profile based on current MS knowledge.
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