Improved purification of cyclotron [68Ga]GaCl3 for the production of 68Ga radiopharmaceuticals

Evaluation of [18F]AlF NOTA-5G, an Aluminum [18F]fluoride Labeled Peptide Targeting the Cell Surface Receptor Integrin Alpha(v)beta(6) for PET Imaging

PURPOSE

Peptide-based probes targeting integrin αvβ6 have shown promise in clinical trials for cancer imaging based on the high over-expression of this epithelial-specific cell surface receptor in many cancerous tissues. Recently, the αvβ6-targeting gallium-68 labeled DOTA-5G peptide, [68Ga]Ga DOTA-5G, demonstrated diagnostic value in patients with metastatic pancreatic cancer. To facilitate adoption at sites without access to gallium-68 and take advantage of the characteristics of fluorine-18 through convenient [18F]fluoride chelation chemistry, this study evaluated the fluorine-18 labeled analog, [18F]AlF NOTA-5G, in vitro and in vivo in a tumor mouse model, and compared it to [68Ga]Ga DOTA-5G.

PROCEDURES

NOTA-5G was synthesized on solid phase and radiolabeled with aluminum [18F]fluoride to generate [18F]AlF NOTA-5G. Cell binding and internalization of [18F]AlF NOTA-5G were evaluated in paired DX3puroβ6 (αvβ6 +) and DX3puro (αvβ6 -), and pancreatic BxPC-3 (αvβ6 +) cells. Imaging (1-6 h) and biodistribution were performed in BxPC-3 tumor-bearing mice.

RESULTS

[18F]AlF NOTA-5G was obtained in > 93% radiochemical purity. Cell binding was αvβ6-targeted (1 h: 66% bound to DX3puroβ6, vs 2% to DX3puro), and ≥ 50% of bound activity was internalized; analogous to [68Ga]Ga DOTA-5G, PET imaging showed clearly delineated tumors. Excretion remained primarily renal (1 to 4 h: 18.6 to 12.5% ID/g). Tumor uptake remained relatively steady (1 to 4 h: 2.3 ± 0.4 to 1.8 ± 0.6% ID/g - closely matching [68Ga]Ga DOTA-5G with 2.6 ± 0.8 and 2.0 ± 0.6% ID/g at 1 and 2 h), resulting in tumor/pancreas, tumor/liver, and tumor/blood ratios of 18/1, 24/1, and 162/1, respectively (4 h); by comparison, for [68Ga]Ga DOTA-5G the values were 21/1, 20/1, and 22/1 (2 h).

CONCLUSIONS

[18F]AlF NOTA-5G demonstrated selective αvβ6-targeting and tumor uptake similar to [68Ga]Ga DOTA-5G. The tumor-to-background ratio resulted high-contrast PET images, with an extended imaging window compared to [68Ga]Ga DOTA-5G. The synthesis of [18F]AlF NOTA-5G is currently being optimized for clinical production.

[68Ga]PSMA-11 for positron emission tomography (PET) imaging of prostate-specific membrane antigen (PSMA)-positive lesions in men with prostate cancer

INTRODUCTION

Theranostics targeting prostate-specific membrane antigen (PSMA) represent a new targeted approach for prostate cancer care that combines diagnostic and therapeutic radiopharmaceuticals to diagnose and treat the disease. Positron emission tomography (PET) is the imaging method of choice and several diagnostic radiopharmaceuticals for quantifying PSMA have received FDA approval and are in clinical use. [68Ga]Ga-PSMA-11 is one such imaging agent and the focus of this article. One beta-emitting radioligand therapy ([177Lu]Lu-PSMA-617) has also received FDA approval for prostate cancer treatment, and several other alpha- and beta-emitting radioligand therapies are in clinical trials.

AREAS COVERED

Theranostics targeting PSMA in men with prostate cancer are discussed with a focus on use of [68Ga]Ga-PSMA-11 for imaging PSMA-positive lesions in men with prostate cancer. The review covers [68Ga]Ga-PSMA-11 manufacture, current regulatory status, comparison of [68Ga]Ga-PSMA-11 to other imaging techniques, clinical updates, and emerging applications of artificial intelligence for [68Ga]Ga-PSMA-11 PET.

EXPERT OPINION

[68Ga]Ga-PSMA-11 is used in conjunction with a PET/CT scan to image PSMA positive lesions in men with prostate cancer. It is manufactured by chelating precursor with68Ga, either from a generator or cyclotron, and has regulatory approval around the world. It is widely used clinically in conjunction with radioligand therapies like [177Lu]Lu-PSMA-617.