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MR Molecular Imaging of Prostate Cancer with a Small Molecular CLT1 Peptide Targeted Contrast Agent
Published on: September 3, 2013
PSMA-1-DOTA Potentially for Effective Targeted Radioligand Therapy of Prostate Cancer
Xinning Wang1, Olga Sergeeva2, Maxim Sergeev3
1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.
Purpose:
While PSMA-targeted radioligand therapy (RLT) has shown remarkable efficacy for treating end-stage prostate cancer, the α-emitting RLT often results in severe salivary gland toxicity, limiting its use. Various strategies to mitigate this side effect have been attempted with limited success. Accordingly, this study introduced a new PSMA-targeting ligand with more favorable binding characteristics than the existing ligands.
Procedures:
The binding affinity of PSMA-1-DOTA to PSMA was compared with that of PSMA-11 and PSMA I&T. Comparison of uptake in the salivary glands, kidneys and PC3pip tumor cells in the xenograft mouse models between [68 Ga]Ga-PSMA-1-DOTA, [68 Ga]Ga-PSMA-11 and [68 Ga]Ga-PSMA I&T was conducted with microPET/CT within the same week. The same mouse models were treated with [177Lu]Lu-PSMA-1-DOTA or [177Lu]Lu-PSMA-617. A compassionate use PET imaging study on a patient with metastatic castration-resistant prostate cancer was performed using [68 Ga]Ga-PSMA-1-DOTA.
Results:
The binding affinity of PSMA-1-DOTA to PSMA was found to be approximately four times greater than other PSMA-targeted ligands. Imaging with microPET/CT revealed significantly lower kidney, uptake and little salivary and lacrimal gland uptake with [68 Ga]Ga-PSMA-1-DOTA compared to other PSMA-radioligands. Preclinical efficacy studies demonstrated that [177Lu]Lu-PSMA-1-DOTA inhibited tumor growth comparable to that with [177Lu]Lu-PSMA-617, suggesting its potential to enhance the therapeutic window of targeted RLT by avoiding damage to the salivary glands. The compassionate use PET imaging confirmed the reduced salivary gland uptake of [68 Ga]Ga-PSMA-1-DOTA in the patient, indicating its potential utility as a targeting agent for RLT with α- or β-emitting radionuclides in patients with PSMA-positive prostate cancer.
Conclusion:
PSMA-1-DOTA shows reduced uptake in salivary glands while effectively targeting PSMA-expressing tumors, thus potentially avoiding the side effects of xerostomia, and possibly moving PSMA-targeted RLT to a more frontline therapy for prostate cancer rather than the current use as a last resort.
Insights
A novel PSMA-targeting ligand, PSMA-1-DOTA, demonstrates significantly reduced salivary gland uptake in prostate cancer radioligand therapy (RLT). This improved safety profile may enhance RLT efficacy and expand its use in treating prostate cancer.
Area of Science:
- Nuclear Medicine
- Oncology
- Radiopharmaceutical Chemistry
Background:
- Prostate-specific membrane antigen (PSMA)-targeted radioligand therapy (RLT) is effective for advanced prostate cancer.
- Salivary gland toxicity is a major limitation of current α-emitting RLT.
- Existing PSMA-targeting ligands have suboptimal binding characteristics and toxicity profiles.
Purpose of the Study:
- To introduce and evaluate a novel PSMA-targeting ligand, PSMA-1-DOTA, with enhanced binding affinity and reduced salivary gland uptake.
- To compare the efficacy and toxicity of PSMA-1-DOTA with established PSMA-targeted agents.
- To assess the potential of PSMA-1-DOTA to improve the therapeutic window of PSMA-targeted RLT.
Main Methods:
- Binding affinity of PSMA-1-DOTA was compared to PSMA-11 and PSMA I&T.
- MicroPET/CT imaging in xenograft mouse models assessed uptake of [⁶⁸Ga]Ga-PSMA-1-DOTA, [⁶⁸Ga]Ga-PSMA-11, and [⁶⁸Ga]Ga-PSMA I&T in salivary glands, kidneys, and tumors.
- Therapeutic efficacy of [¹⁷⁷Lu]Lu-PSMA-1-DOTA was compared to [¹⁷⁷Lu]Lu-PSMA-617 in mouse models.
- A compassionate use PET imaging study in a prostate cancer patient was conducted using [⁶⁸Ga]Ga-PSMA-1-DOTA.
Main Results:
- PSMA-1-DOTA exhibited approximately four times greater binding affinity to PSMA than other ligands.
- [⁶⁸Ga]Ga-PSMA-1-DOTA showed significantly lower kidney uptake and minimal salivary/lacrimal gland uptake compared to controls.
- [¹⁷⁷Lu]Lu-PSMA-1-DOTA demonstrated comparable tumor growth inhibition to [¹⁷⁷Lu]Lu-PSMA-617.
- PET imaging in a patient confirmed reduced salivary gland uptake of [⁶⁸Ga]Ga-PSMA-1-DOTA.
Conclusions:
- PSMA-1-DOTA effectively targets PSMA-expressing tumors with reduced salivary gland uptake, potentially mitigating xerostomia.
- This novel ligand may enhance the therapeutic window for PSMA-targeted RLT.
- PSMA-1-DOTA holds promise for advancing PSMA-targeted RLT from a last-resort treatment to a more frontline therapy for prostate cancer.
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