In a study performed by Lee and colleagues, the tumor accumulation of an anti-HER2 affibody conjugated to Alexa Fluor® 750 was evaluated. The results showed its potential as a probe for in vivo imaging of HER2-positive breast cancer . In a previous study, Sexton et al. showed that the accumulation of an anti-EGFR affibody, conjugated to IRDye® 800CW, was higher in rodent glioma tumors than the anti-EGFR antibody cetuximab conjugated to IRDye® 680RD. The anti-EGFR affibody molecule was present in the tumor periphery whereas the anti-EGFR antibody was primarily localized in the central portion of the tumor . In the present study, the tumor uptake of pre-GMP ABY-029 was evaluated for the contrast in tumor-to-normal brain, as a function of time and administered dose.