Evaluation of [18F]-ATRi as PET tracer for in vivo imaging of ATR in mouse models of brain cancer.
BACKGROUND
Ataxia telangiectasia and Rad3-related (ATR) threonine serine kinase is one of the key elements in orchestrating the DNA damage response (DDR). As such, inhibition of ATR can amplify the effects of chemo- and radiation-therapy, and several ATR inhibitors (ATRi) have already undergone clinical testing in cancer. For more accurate patient selection, monitoring and staging, real-time in vivo imaging of ATR could be invaluable; the development of appropriate imaging agents has remained a major challenge.


METHODS
3-amino-N-(4-[18F]phenyl)-6-(4-(methylsulfonyl)phenyl)pyrazine-2-carboxamide ([18F]-ATRi), a close analogue of Ve-821, (a clinical ATRi candidate), was readily accomplished similarly to already established synthetic procedures. Structurally,18F was introduced at the 4-position of the aromatic ring of Ve-821 for generating a labeled ATR inhibitor. In vitro experiments were conducted in U251 MG glioblastoma cell lines and ex vivo biodistribution were performed in subcutaneous U251 MG xenograft bearing athymic nude mice following microPET imaging.


RESULTS
[18F]-ATRi has a similar pharmacokinetic profile to that of Ve-821. Using an U251 MG glioblastoma mouse model, we evaluated the in vivo binding efficiency of [18F]-ATRi. Blood and tumor showed a statistically significant difference between mice injected with only the probe or following blocking experiment with Ve-821 (1.48±0.40%ID/g vs. 0.46±0.12%ID/g in tumor and 1.85±0.47%ID/g vs. 0.84±0.3%ID/g in blood respectively).


CONCLUSIONS
[18F]-ATRi represents the first18F positron emission tomography (PET) ATR imaging agent, and is designed on a low nanomolar and clinically relevant ATR inhibitor.
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA.
Giuseppe
G
Carlucci
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA; Department of Chemistry, Hunter College and PhD Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10018, USA.
Brandon
B
Carney
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA.
Ahmad
A
Sadique
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA.
Axel
A
Vansteene
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA.
Jun
J
Tang
Department of Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, 10065, USA; Weill Cornell Medical College, New York, NY, 10065, USA. Electronic address: reinert@mskcc.org.
Thomas
T
Reiner
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D005462:Fluorine Radioisotopes; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D051379:Mice; D049268:Positron-Emission Tomography / Q000379:methods*; D047428:Protein Kinase Inhibitors / Q000737:chemistry* / Q000378:metabolism / Q000493:pharmacokinetics; D011719:Pyrazines / Q000737:chemistry* / Q000378:metabolism / Q000493:pharmacokinetics; D011849:Radioactive Tracers; D011854:Radiochemistry; D013450:Sulfones / Q000737:chemistry* / Q000378:metabolism / Q000493:pharmacokinetics; D014018:Tissue Distribution
C560580:3-amino-6-(4-(methylsulfonyl)phenyl)-N-phenylpyrazine-2-carboxamide; D005462:Fluorine Radioisotopes; D047428:Protein Kinase Inhibitors; D011719:Pyrazines; D011849:Radioactive Tracers; D013450:Sulfones; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins
(18)F; ATR; Cell cycle; PET imaging; U251 mg; Ve-821