Effect of Rituximab on Neurofilament Levels in CIDP: Results From the CIDPRIT Randomized Trial.

BACKGROUND AND AIMS: Rituximab has been proposed as a potential treatment in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), but formal evidence regarding its clinical effectiveness is weak. The CIDPRIT trial found no clinical benefit in comparison with placebo, but secondary analyses suggested some beneficial effect. Analysis of serum neurofilament light chain (sNfL) may provide evidence to support rituximab's effect on CIDP patients.

METHODS

We performed a post hoc analysis of sNfL levels from the CIDPRIT trial participants. Blood samples were collected at baseline, month 6, and 12. sNfL was measured using Simoa technology. Geometric means and z-scores were compared across groups. Linear mixed-effects models and survival analyses were used to evaluate treatment effects and clinical correlations.

RESULTS

33 participants were included (18 rituximab, 15 placebo). Baseline sNfL was significantly higher in the rituximab group (11.51 vs. 6.67 pg/mL, p = 0.019). While between-group differences over time were not statistically significant, rituximab-treated patients showed stable sNfL levels at month 6 and a slight decrease at month 12, contrasting with modest increases in the placebo group. Among rituximab-treated patients who remained clinically stable at month 12, sNfL showed a non-significant decline by 31%. No significant associations were found between baseline sNfL and clinical worsening. NfL levels correlated with neurophysiological parameters of axonal damage.

INTERPRETATION: The analysis did not demonstrate biomarker-based evidence of rituximab efficacy in CIDP. However, observed trends suggest a possible biological effect in reducing axonal injury in a subset of patients. Further studies are needed to clarify the role of sNfL in treatment monitoring and patient stratification.