The initial values for kin, kout, kdeep_br_in, and kdeep_br_out were 1, 1, 0.1, and 0.1, respectively. Through this fitting process, we obtained simulated compound brain concentration-time profiles, designated scenario I as a positive control experiment; this scenario had full plasma and brain PK profiles. It should be noted that due to the limited number of time points, we could not set any criteria for CV in parameter optimization; however, this was inevitable considering the practical drug discovery process, because it is too costly to obtain a sufficient number of brain samples for accurate kinetic parameter estimation.