Evaluation of natalizumab pharmacokinetics and pharmacodynamics with standard and extended interval dosing.

•Natalizumab blood levels vary considerably among patients receiving standard dosing.•Body weight, age, and treatment duration impact blood levels at nadir.•Extended interval dosing lowers blood levels and occupancy of α4-integrin receptors.•Extended interval dosing alters the impact of body weight on these parameters.•α4-integrin cell surface expression is increased with extended interval dosing.