Table 1.
Characteristics of the most significant 99mTc-FAPI labeled compounds
| Author | Compound | Labelling strategy | Cell lines tested | Animal model | Pro | Cons |
|---|---|---|---|---|---|---|
| Roy et al. (2020) | [99mTc]Tc-FL-L3 | [99mTc][TcO]3+ | Embryonic kidney HEK 293 | MDA-MB231 breast tumors | Minimal uptake in non-target tissues | Relatively low tumor uptake |
| Lindner et al. (2020b) | [99mTc]Tc-FAPI-34 | [99mTc][Tc(CO)3]+ | HT-1080-FAP; HEK-muFAP; HEKCD26 | HT-1080-FAP–xenotransplanted mice | Stability in terms of reaction kinetics; low liver uptake | Formation of various complex isomers; need for precise pH adjustments during the radiolabeling process significantly limits clinical suitability |
| Ruan et al. (2022) | [99mTc][Tc-(CN-PEG4-FAPI)6]+ | [99mTc]Tc-isonitrile | HT-1080-FAP | U87 xenografted BALB/c nude mice | High tumor uptake | Limited water solubility; relatively high uptake in nontarget tissues, such as the kidney and liver |
| Trujillo-Benítez et al. (2022) | [99mTc]Tc-iFAP | [99mTc]Tc-HYNIC | N30 (FAP +) | Mice bearing induced liver cancer tumors (Hep-G2 cells) | Very rapid blood clearance; high sensitivity | Formation complex isomers; labeling with 188Re is not feasible |
| Yang et al. (2023) | [99mTc]Tc-TE-FAPT | [99mTc]Tc-HYNIC | A549-FAP | U87 xenografted BALB/c nude mice | Tumor/renal ratio > 10 | Formation complex isomers; labeling with 188Re is not feasible |
| Ruan et al. (2023a) | [99mTc]Tc-L1 | [99mTc]Tc-HYNIC | HT-1080-FAP | Mice bearing U87MG-derived FAP-positive | Favorable target-to-background ratios; robust in vitro stability and water solubility | Formation complex isomers; labeling with 188Re is not feasible |
| Luo et al. (2023) | [99mTc]Tc-HYNIC-FAPI-04 | [99mTc]Tc-HYNIC | U87MG cells (FAPI +) | Mice bearing U87MG-derived FAP-positive | Sensitive to tumor progression | Formation complex isomers; labeling with 188Re is not feasible |