FAP and neoplasm: Coinjection with an excess of unlabeled FAPI-46 successfully blocked tumor uptake at 1 h after injection (SUVmean without blocking, 1.87 ± 0.08, vs. SUVmean with blocking, 0.16 ± 0.03; 92% reduction in tumor uptake), demonstrating that the uptake of the major fraction of 68Ga-DOTA-4P(FAPI)4 in tumors was FAP-mediated (Supplemental Fig. 6).