Table 1.

Biodistribution data for in vivo pretargeting (n = 5) using two different tetrazine radiotracers — [⁶⁴Cu]Cu-SarAr-Tz and [¹⁷⁷Lu]Lu-DOTA-PEG₇-Tz — in athymic nude mice bearing subcutaneous SW1222 xenografts. The mice were first administered huA33-TCO (100 μg, 0.67 nmol, 2.4 TCO/mAb) via tail vein, followed 24 hours later by the i.v. administration of [⁶⁴Cu]Cu-SarAr-Tz (10.4–11.3 MBq, 0.64–0.69 nmol) and 24 h thereafter by the i.v. injection of [¹⁷⁷Lu]Lu-DOTA-PEG₇-Tz (5.9–6.4 MBq, 0.69–0.74 nmol). The time values represent the number of hours following the administration of each Tz radiotracer (i.e. the 28 h column under [⁶⁴Cu]Cu-SarAr-Tz denotes 28 h after the injection of [⁶⁴Cu]Cu-SarAr-Tz, whereas the 4 h column under [¹⁷⁷Lu]Lu-DOTA-PEG₇-Tz denotes 4 h after the injection of [¹⁷⁷Lu]Lu-DOTA-PEG₇-Tz). The values for the stomach and small intestines include contents.

	[64Cu]Cu-SarAr-Tz			[177Lu]Lu-DOTA-PEG7-Tz
	28 h	48 h	72 h	4 h	24 h	48 h	120 h
Blood	3.5 ± 0.9	3.0 ± 9	2.3 ± 0.3	4.7 ± 0.8	3.4 ± 1.0	2.4 ± 0.4	1.1 ± 0.4
Tumor	11.0 ± 1.6	16.4 ± 2.7	18.3 ± 3.2	4.9 ± 0.4	11.3 ± 1.6	13.1 ± 2.7	18.1 ± 2.1
Heart	0.9 ± 0.2	1.0 ± 0.1	0.8 ± 0.2	1.2 ± 0.2	0.9 ± 0.2	0.6 ± 0.2	0.2 ± 0.1
Lungs	1.9 ± 0.5	1.9 ± 0.3	1.5 ± 0.3	2.4 ± 0.4	1.9 ± 0.5	1.2 ± 0.4	0.7 ± 0.3
Liver	2.0 ± 0.3	2.3 ± 0.2	1.6 ± 0.2	1.45 ± 0.2	1.2 ± 0.1	0.8 ± 0.2	0.5 ± 0.1
Spleen	1.4 ± 0.3	1.8 ± 0.6	1.1 ± 0.3	1.0 ± 0.2	1.0 ± 0.3	0.5 ± 0.1	0.4 ± 0.1
Stomach	0.3 ± 0.1	0.3 ± 0.1	0.2 ± 0.1	0.3 ± 0.1	0.3 ± 0.1	0.2 ± 0.1	0.2 ± 0.1
S. Intestine	0.4 ± 0.1	0.5 ± 0.2	0.4 ± 0.1	0.4 ± 0.1	0.3 ± 0.1	0.3 ± 0.1	0.2 ± 0.03
L. Intestine	0.3 ± 0.04	0.5 ± 0.1	0.3 ± 0.1	0.7 ± 0.2	0.4 ± 0.1	0.2 ± 0.1	0.1 ± 0.03
Kidneys	1.9 ± 0.4	2.3 ± 0.3	1.8 ± 0.2	1.6 ± 0.3	1.5 ± 0.3	0.9 ± 0.2	0.6 ± 0.2
Muscle	0.4 ± 0.2	0.5 ± 0.1	0.4 ± 0.1	0.4 ± 0.1	0.4 ± 0.1	0.2 ± 0.1	0.1 ± 0.03
Bone	0.5 ± 0.1	0.5 ± 0.1	0.4 ± 0.1	0.5 ± 0.1	0.4 ± 0.1	0.2 ± 0.04	0.2 ± 0.1