Estimation of nadir serum concentration in extended dosing therapy using the present formula of natalizumab

In 2017, a pharmaceutical company revised the pharmacokinetics data of natalizumab (NTZ) formula E, in which the maximum serum concentration (Cmax) and elimination half‐time (t1/2) of American Caucasian patients (ACP) were higher than that of the original formula. We re‐evaluated the mean nadir serum concentrations (Ctrough) in ACP and compared with those using formula E in Japanese patients (JP). If the effects of the 6‐week NTZ administration in JP are anticipated to be similar to that in ACP, the administration interval in JP should be extended to ≥8 weeks.