Fig. 5.

Pharmacokinetics of new anti-PSMA mAbs compared with J591 and ex vivo NIRF imaging showing tumor specificity. Panel A: Representative mice, each bearing a PSMA-positive and PSMA-negative (not depicted in views shown) xenograft, was co-injected with the indicated IRDye680RD-labeled mAb (designated in the top row) and J591-IRDye800CW. Images collected at various times post-injection at the 710 nm peak emission (except for J591, asterisk) were normalized to the same exposure time. All mAbs were bound to the PSMA-positive tumor, as detectable 12 hr post-injection, and were cleared from non-target sites by 72 hr. 3F11 displayed particularly low uptake overall while 5D3 and 5B1 both showed high tumor uptake with 5D3 displaying the highest tumor signal as well as extensive non-target tissue clearance by 48 hr, similar to J591. Autofluorescence due to dietary chlorophyll was observed across the gastrointestinal (GI) tract. As J591 was imaged at 800 nm autofluorescence was not detected in this case. Panel B: Each mouse shown is from panel A after the 72 hr data point. The ventral skin was removed to reduce attenuation and reveal both tumors. J591-IRDye800CW is displayed in green; hence, yellow denotes co-localization of J591 uptake (green) with the indicated mAb (red) tested in each mouse. Panels at the lower right show an enlargement of the PSMA-positive tumor. Notably, all antibodies tested except 3F11 displayed specificity for the PSMA-positive PC-3 PIP tumor versus the antigen-negative tumor. 5D3 and 5B1 both showed mostly yellow/orange co-localization with J591 while 1A11 showed more heterogeneous tumor uptake. The mAb GCPII-04, which binds to a cytoplasmic epitope of PSMA, also displayed a more heterogeneous binding pattern compared with J591.