TABLE 2.

Population PD parameters and bootstrap CIs for the final PK/PD model for Amyloid PET SUVr

Parameter	NONMEM		Bootstrap
	Estimate	%RSE	Median (95% CI)
PD parameters
Baseline SUVr	1.34	0.873	1.34 (1.31–1.38)
K in (1/year)	0.232	11.1	0.232 (0.174–0.277)
E max	1.54	11.8	1.56 (1.10–2.01)
EC50 (μg/ml)	75.0	19.6	77.1 (38.5–121)
Covariate
APOE4 carrier ~ baseline	1.04	1.04	1.04 (1.02–1.07)
Age ~ E max (exponent)	1.58	20.9	1.60 (0.972–2.07)
Interindividual variability (CV%)
Baseline	10.9	8.12	11.0 (9.79–11.9)
Correlation baseline ~ E max (R)	0.669	11.5	0.674 (0.556–0.713)
E max	50.3	12.0	50.8 (42.1–59.7)
Residual variability (CV%)
Proportional	5.01	2.75	5.02 (4.48–5.59)

Abbreviations: %RSE, percent relative standard error of the estimate = SE/parameter estimate × 100; CI, confidence interval; CV%, square root of variance × 100; EC₅₀, lecanemab concentration at which 50% of maximum drug effect is achieved; E _max, maximum drug effect; K _in, rate of production; PD, pharmacodynamic; PET, positron emission tomography; PK, pharmacokinetic; SUVr, standard uptake ratio.

$\text{Baseline}=1.34\bullet {1.04}^{\text{APOE}}$.

$E_{\max }=1.54\bullet {\left(\frac{\mathrm{AGE}}{72}\right)}^{1.58}.$

AGE = age; APOE = 0 (APOE4 carrier) or 1 (non‐carrier).

Eta shrinkage (%): ETA_Baseline = 6.94%, ETA_E _max = 27.7%.