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All Quizzes > Crossing the Blood-Brain Barrier: Lymphocyte Trafficking Blockade in MS

Deepen your understanding of lymphocyte trafficking blockade in RRMS. Challenge your knowledge on alpha-4-integrin biology, PML risk stratification, extended interval dosing strategies, and 2025 multicenter real-world evidence.

Crossing the Blood-Brain Barrier: Lymphocyte Trafficking Blockade in MS

Q1.
How does natalizumab prevent CNS inflammation in relapsing-remitting multiple sclerosis?

A. Reduces systemic TNF-alpha to lower neuroinflammatory cytokine levels in the CSF

B. Depletes CD20+ B cells by complement-mediated lysis, preventing antibody-mediated CNS demyelination

C. Directly inhibits CNS microglial activation through TLR4 antagonism

D. Blocks alpha-4-beta-1 integrin on lymphocytes, preventing VCAM-1 interaction on CNS vascular endothelium — blocking lymphocyte trafficking across the blood-brain barrier

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Correct Answer: D

Natalizumab binds the alpha-4 subunit of alpha-4-beta-1 integrin (VLA-4) on lymphocytes. By blocking the interaction of alpha-4-beta-1 with its endothelial ligand VCAM-1, it prevents activated autoreactive lymphocytes from transmigrating across the blood-brain barrier into the CNS — providing highly effective disease control in RRMS.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9580073/
Crossing the Blood-Brain Barrier: Lymphocyte Trafficking Blockade in MS

Q2.
2025 multicenter analysis (7 MS clinics): What was the primary finding comparing EID (every 6 weeks) vs SID (every 4 weeks) of natalizumab?

A. EID maintained comparable clinical and radiologic efficacy vs SID — no significant difference in relapse rates or MRI activity — while reducing treatment burden and potentially lowering PML risk

B. EID required dose escalation to every 5 weeks to maintain equivalent efficacy to every 4 weeks

C. EID showed significantly higher MRI lesion rates and clinical relapses vs SID

D. EID safe only in JCV-antibody-negative patients; antibody-positive patients showed increased disease activity

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Correct Answer: A

The 2025 multicenter retrospective analysis (CNS Neurosci Ther 2025) confirmed EID (every 6 weeks) maintained clinical and radiologic efficacy comparable to standard 4-week dosing, without increasing disease activity — while reducing infusion frequency, treatment burden, and potentially lowering PML risk.

https://onlinelibrary.wiley.com/doi/10.1111/cns.70445
Crossing the Blood-Brain Barrier: Lymphocyte Trafficking Blockade in MS

Q3.
What is the primary determinant of PML risk stratification in clinical practice with natalizumab?

A. Duration of MS disease prior to starting natalizumab

B. Anti-JCV antibody serostatus and index value — seropositive patients with high index (above 0.9), more than 24 months of treatment, and prior immunosuppressant use face highest PML risk

C. Age at treatment initiation — patients over 50 have disproportionately higher PML risk

D. Gender — males are significantly more susceptible to JCV reactivation on natalizumab

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Correct Answer: B

PML risk is stratified primarily by anti-JCV antibody serostatus and index value. JCV-seropositive patients with high index (above 0.9), treatment duration beyond 24 months, and prior immunosuppressant use face the highest cumulative PML risk. EID has been associated with significantly lower PML rates vs standard dosing in seropositive patients.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9580073/
Crossing the Blood-Brain Barrier: Lymphocyte Trafficking Blockade in MS

Q4.
NEXT-MS trial: What was the clinical conclusion regarding TDM-guided extended interval dosing of natalizumab?

A. TDM was useful only to detect neutralizing antibodies, not to guide dosing intervals

B. TDM-guided dosing was inferior to fixed 4-week dosing in controlling MRI disease activity

C. Personalized dosing based on trough concentrations (10 mcg/mL or higher) maintained efficacy equivalent to SID — supporting TDM as a tool to further individualize dosing intervals and optimize the benefit-risk balance

D. TDM showed no advantage over empirical 6-week dosing in any patient subgroup

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Correct Answer: C

NEXT-MS demonstrated that natalizumab trough concentrations of at least 10 mcg/mL maintained equivalent disease control to standard 4-week dosing. This supports TDM as a means to further individualize dosing intervals beyond the empirical 6-week approach, potentially allowing longer intervals in selected patients.

https://onlinelibrary.wiley.com/doi/10.1111/cns.70445
Crossing the Blood-Brain Barrier: Lymphocyte Trafficking Blockade in MS

Q5.
TOUCH registry data (15,000–24,000 patients): What is the primary rationale for widespread adoption of EID in JCV-seropositive RRMS patients?

A. EID adopted due to supply chain constraints during the COVID-19 pandemic

B. EID primarily reduces infusion-related reactions and anti-drug antibody formation

C. EID reduces total drug exposure per year — cost savings only, no risk-benefit consideration

D. TOUCH registry data demonstrate significantly lower PML rates with EID vs SID, while clinical and MRI efficacy is maintained — a meaningful risk-reduction strategy for long-term natalizumab users

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Correct Answer: D

TOUCH program registry data from 15,000–24,000 patients demonstrated that modest increases in dosing interval from every-4-weeks to approximately every-6-weeks produced meaningful PML risk reductions. Combined with maintained efficacy confirmed in NOVA, NEXT-MS, and real-world cohorts, EID has become a widely adopted PML risk-mitigation strategy for appropriately selected patients.

https://pmc.ncbi.nlm.nih.gov/articles/PMC10973016/

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Crossing the Blood-Brain Barrier: Lymphocyte Trafficking Blockade in MS

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