Blood lymphocyte rise may signal natalizumab response in multiple sclerosis

An analysis of data from the AFFIRM trial and the Cardiff MS register found that absent or limited lymphocyte increases during natalizumab treatment were associated with anti-drug antibodies. The authors suggest this measure could prompt antibody testing before disease activity indicates reduced efficacy.

Natalizumab increased lymphocyte counts by week 12.
Persistent antibody responses were associated with absent increases.
A threshold showed high sensitivity and specificity in the analyses.
Prospective clinical utility remains unestablished.

Natalizumab inhibits lymphocyte migration into the central nervous system and increases peripheral blood lymphocyte counts. Researchers assessed whether the lack of this relative lymphocytosis could indicate anti-drug antibody responses, using data from the AFFIRM trial (627 natalizumab-treated and 315 placebo participants) and the Cardiff MS register (185 patients). Analyses examined lymphocyte counts alongside antibody status, drug levels and disease activity.

By week 12, mean lymphocyte counts had increased by 1.40 ± 0.92 × 10⁹ cells/L with natalizumab, compared with a change of −0.05 ± 0.62 × 10⁹ cells/L with placebo (p<0.0001). The persistent anti-drug antibody group showed no comparable increase (−0.12 ± 0.60 × 10⁹ cells/L). An increase of at least 0.8 × 10⁹ cells/L from baseline discriminated patients without antibody responses, with reported sensitivity of at least 84% and specificity of at least 91%.

The findings suggest lymphocyte counts might help identify patients for antibody testing before clinical evidence of reduced efficacy emerges. The abstract does not establish a prospective testing strategy or show that count-guided testing improves outcomes; further validation would be needed before changing monitoring practice.

In practice

For people with multiple sclerosis receiving natalizumab, the findings suggest that a smaller-than-expected rise in peripheral lymphocyte counts may be associated with anti-drug antibodies and could help identify patients for antibody testing. The analysis included AFFIRM trial data and a real-world register, and a rise of at least 0.8 × 10⁹ cells/L discriminated patients without antibody responses with reported sensitivity of at least 84% and specificity of at least 91%. However, the evidence does not establish that count-guided testing improves outcomes or supports changing monitoring practice.

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Source

Multiple Sclerosis Journal: Lymphocytosis as a biomarker for natalizumab treatment response in multiple sclerosis: The link with anti-drug antibodies ↗

This is an automated AI-condensed summary that has not yet been reviewed by an editor. Always consult the full item at the original source.