Synthesis of 68Ga-radiopharmaceuticals using both generator-derived and cyclotron-produced 68Ga as exemplified by [68Ga]Ga-PSMA-11 for prostate cancer PET imaging

[Ga-68]Ga-PSMA-11 has recently been approved by the US Food and Drug Administration as a radiopharmaceutical for PET imaging of prostate cancer. To meet higher demand for this tracer, procedures for its synthesis using both generator-eluted and cyclotron-produced Ga-68 are described. [Ga-68]Ga-PSMA-11, a urea-based peptidomimetic, is a diagnostic radiopharmaceutical for positron emission tomography (PET) imaging that targets the prostate-specific membrane antigen (PSMA). The recent Food and Drug Administration approval of [Ga-68]Ga-PSMA-11 for PET imaging of patients with prostate cancer, expected follow-up approval of companion radiotherapeutics (e.g., [Lu-177]Lu-PSMA-617, [Ac-225]Ac-PSMA-617) and large prostate cancer patient volumes requiring access are poised to create an unprecedented demand for [Ga-68]Ga-PSMA-11 in nuclear medicine clinics around the world. Meeting this global demand is going to require a variety of synthesis methods compatible with Ga-68 eluted from a generator or produced on a cyclotron. To address this urgent need in the PET radiochemistry community, herein we report detailed protocols for the synthesis of [Ga-68]Ga-PSMA-11, (also known as HBED-CC, Glu-urea-Lys(Ahx)-HBED-CC and PSMA-HBED-CC) using both generator-eluted and cyclotron-produced Ga-68 and contrast the pros and cons of each method. The radiosyntheses are automated and have been validated for human use at two sites (University of Michigan (UM), United States; Royal Prince Alfred Hospital (RPA), Australia) and used to produce [Ga-68]Ga-PSMA-11 for patient use in good activity yields (single generator, 0.52 GBq (14 mCi); dual generators, 1.04-1.57 GBq (28-42 mCi); cyclotron method (single target), 1.47-1.89 GBq (40-51 mCi); cyclotron method (dual target), 3.63 GBq (98 mCi)) and high radiochemical purity (99%) (UM, n = 645; RPA, n > 600). Both methods are appropriate for clinical production but, in the long term, the method employing cyclotron-produced Ga-68 is the most promising for meeting high patient volumes. Quality control testing (visual inspection, pH, radiochemical purity and identity, radionuclidic purity and identity, sterile filter integrity, bacterial endotoxin content, sterility, stability) confirmed doses are suitable for clinical use, and there is no difference in clinical prostate cancer PET imaging using [Ga-68]Ga-PSMA-11 prepared using the two production methods.

Automated summary

[Ga-68]Ga-PSMA-11, a radiopharmaceutical approved for prostate cancer PET imaging, is in high demand. This study presents synthesis methods for [Ga-68]Ga-PSMA-11 using generator-eluted and cyclotron-produced Ga-68. Both methods are suitable for clinical production, but the cyclotron method is more promising for meeting high patient volumes in the long term.