Comparative Evaluation of Anti-HER2 Affibody Molecules Labeled with ⁶⁴Cu Using NOTA and NODAGA

Table 1

Labeling of NOTA-ZHER2:S1 and NODAGA-ZHER2:S1 with ⁶⁴Cu and conjugates stability under 2-hour challenge with a 500-fold excess of Na₄EDTA.

	Overall yield (%)	Purity (%)	Stability (% of affibody-associated activity)
			Challenge	Control
	Protocol A
^64Cu-NOTA-ZHER2:S1	96.2	96.2	90.1 ± 1.2	96 ± 0.2
^64Cu-NODAGA-ZHER2:S1	96.9	96.9	90.3 ± 0.7	96.1 ± 0.0
	Protocol B
^64Cu-NOTA-ZHER2:S1	86.1 ± 0.6	98.4 ± 0.5	99.1 ± 0.0	98.8 ± 0.1
^64Cu-NODAGA-ZHER2:S1	86.6 ± 1.1	98.6 ± 0.7	98.5 ± 0.0	98.7 ± 0.4

Overall yield is defined as percentage of radionuclide incorporated into affibody molecules at the end of synthesis (Protocol A) or percentage of radionuclide incorporated in affibody molecules at the end of separation (Protocol B) (decay corrected).