Table 5.
Data on metabolism of F-18 labeled tryptophan derivative tracers by IDO and TDO enzymes.
| Author | Year | Tracer name | Study type | Result |
|---|---|---|---|---|
| Chiotellis, et al. | 2016 | 6-(2-[18F]fluoroethoxy)-DL-tryptophan 2-(3-[18F]fluoropropyl)-DL-tryptophan 5-hydroxy-2-(3-[18F]fluoropropyl)-DL-tryptophan 5-hydroxy-2-(2-[18F]fluoroethyl)-DL-tryptophan |
in vitro enzyme assays with rhIDO | not substrate for IDO (no oxygenation was found) |
| Tang, et al. | 2017 | 5-[18F] fluoro-L-tryptophan 5-[18F]fluoro-D-tryptophan |
in vitro enzyme assays with hIDO1 and hTDO2 in vitro cell uptake studies of cells with diverse IDO1 and TDO2 expression |
substrate for IDO1 and TDO2 not substrate for IDO1 and TDO2 |
| Zlatopolskiy, et al. | 2018 | 4-[18F]fluorotryptophan 5-[18F]fluorotryptophan 6-[18F]fluorotryptophan 7-[18F]fluorotryptophan |
in vitro cell uptake studies using IFN-γ treated and non-treated cells in vivo dynamic uptake studies |
substrate for IDO substrate for IDO substrate for IDO not substrate for TDO and IDO, inhibitor of both enzymes |
| Giglio, et al. | 2017 | 5-[18F] fluoro-α-methyl-tryptophan |
in vitro enzyme assays in vitro uptake study using IFN-γ treated cells |
substrate for IDO1 |
| Henrottin, et al. | 2016 | 1-(2-[18F]fluoroethyl)-L-tryptophan |
in vitro enzyme assays with rhIDO in vitro cell uptake studies of cells with diverse IDO expression |
good and specific substrate for IDO |
| Xin, et al. | 2017 | 1-(2-[18F]fluoroethyl)-L-tryptophan | in vitro cell uptake studies using IFN-γ treated and non-treated cells | substrate for IDO |
| Xin, et al. | 2019 | 1-(2-[18F] fluoroethyl)-L-tryptophan | radio-HPLC of tumor extracts | 30% of the tracer was converted to a radioactive kynurenine metabolite |
Abbreviations: rhIDO: recombinant human indoleamine 2,3-dioxygenase; hTDO: human tryptophan 2,3-dioxygenase; IFNγ: interferon-γ; HPLC: high-performance liquid chromatography.