Fingerprick blood samples to measure serum natalizumab concentrations

BACKGROUND: Natalizumab via subcutaneous administration was recently approved for patients with multiple sclerosis. OBJECTIVE: In light of personalized extended dosing, in which treatment intervals are prolonged to a concentration cut-off, it would be preferable to measure natalizumab drug concentrations in capillary blood. METHODS: In this cross-sectional study in patients treated with intravenous (IV) natalizumab, capillary blood samples by fingerprick and venous blood samples were collected in 30 participants prior to IV administration of natalizumab. RESULTS: Natalizumab concentrations were similar with a mean bias of −0.36 μg/mL (95% CI: 1.3 to −2 μg/mL). CONCLUSIONS: This study shows that physicians can monitor natalizumab drug concentrations by a fingerprick, which could be used for personalized extended dosing.