Table 2.

Overview of final model parameter differences for [⁶⁸Ga]Ga-HA-DOTATATE and [¹⁷⁷Lu]Lu-HA-DOTATATE, where compartments represent blood (1), spleen (2), kidney (3), tumor (4), a SSTR-expressing (5) and rest (6) compartment

	Parameter values (RSE% provided for estimated values*)
	[68Ga]Ga-HA-DOTATATE	[177Lu]Lu-HA-DOTATATE
Structural parameters
k10 (h−1)	0.25	0.575
k12 (h−1)	0.21	0.0607 (0.29-fold difference (15%))
k20 (h−1)	0.01	0.01
k13 (h−1)	0.22	0.107 (0.49-fold difference (15%))
k30 (h−1)	0.01	0.01
k14 (h−1)	0.11	0.157 (1.43-fold difference (14%))
k40 (h−1)	0.01	0.00375 (0.38-fold difference (35%))
k15 (h−1)	2.5	2.5
k50 (h−1)	0.01	0.01
k16 (h−1)	1	1
k60 (h−1)	0.01	0.01
V1 (L)	4	4
V2 (L)	0.21	0.21
V3 (L)	0.3	0.3
V5 (L)	4	4
V6 (L)	50	50
Fraction unbound in plasma	0.69	0.57
BMAX compartment 2 (nmol/L)	16.7	16.7
BMAX compartment 3 (nmol/L)	6.7	6.7
BMAX compartment 4 (nmol/L)	30	30
BMAX compartment 5 (nmol/L)	2.4	2.4
IIV (CV%)
k10	31.6%	31.6%
k12 or BMAX compartment 2**	50%	50%
k13 or BMAX compartment 3**	50%	50%
k14 or BMAX compartment 4**	50%	50%
k15 or BMAX compartment 5**	31.6%	31.6%
Structural effect
Tumor volume on k14	1	0.67 (17%)
RUV
Proportional error (CV%)	31.6%	31.6%

RSEs were obtained from the NONMEM covariance step. The tumor compartment volume parameter (V4) was based on individually measured tumor volumes

B_MAX, maximum binding capacity; V, compartment volume; CV%, coefficient of variation; IIV, inter-individual variability; RSE, relative standard error; RUV, residual unexplained variability

*PK parameters for [¹⁷⁷Lu]Lu-HA-DOTATATE were estimated as a fold difference compared to the parameter for [⁶⁸Ga]Ga-HA-DOTATATE

**IIV was added to k parameters for [⁶⁸Ga]Ga-HA-DOTATATE, while for [¹⁷⁷Lu]Lu-HA-DOTATATE IIV was added to B_MAX