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P0201 - Disability improvement in relapsing-remitting multiple sclerosis patients receiving cladribine tablets, evaluated by expanded disability status scale (ID 416)
In CLARITY, treatment with cladribine tablets 10 mg (cumulative dose 3.5 mg/kg over 2 years [CT3.5]) significantly reduced relapse rates and slowed disability progression versus placebo in RRMS patients. A key question is to evaluate whether and for how long cladribine tablets can improve EDSS scores.
To evaluate post hoc long-term prevalence of disability improvement assessed by Expanded Disability Status Scale (EDSS) score in relapsing-remitting multiple sclerosis (RRMS) patients treated with cladribine tablets enrolled into CLARITY Extension.
Patients enrolled into CLARITY Extension were included and pooled by early (CT3.5 in CLARITY then CT3.5 or placebo in CLARITY Extension; n = 284), versus delayed (placebo in CLARITY then CT3.5 in CLARITY Extension; n = 244) treatment. Disability improvement was defined as a decrease in EDSS from baseline of ≥ 1 point for baseline EDSS < 5.5, or ≥ 0.5 points for baseline EDSS ≥ 5.5, confirmed at 6 months. Improvement was considered lost when EDSS returned to ≥ baseline (regression of improvement confirmed at 6 months). Prevalence of improved EDSS was estimated by a new statistical approach, accounting for not only the onset of improvement but also the duration. Prevalence was estimated as the difference between the Kaplan-Meier (KM) estimators for the probability of having an improvement before time t and the probability of returning to baseline before time t. P values were estimated using a bootstrap technique on the area under the modified KM curve.
The prevalence of disability improvement (KM estimate) for the early versus delayed treatment groups at 2-years post-CLARITY baseline was 15.6% (95% confidence interval [CI]: 11.9–19.3) versus 9.3% (95% CI: 6.1–12.4), respectively and at 5-years was 12.7% (95% CI: 8.8–16.6) versus 8.6% (95% CI: 4.8–12.4), respectively (early versus delayed treatment group: P = 0.048 for 5-years difference).
Patients receiving early treatment with cladribine tablets had a greater prevalence of disability improvement over 5 years versus those with delayed treatment.