Radioligands are at the forefront of innovation in prostate cancer care. These molecules, or ligands, have the remarkable ability to bind to specific receptors, exerting an effect on the cells where these receptors reside. The radioactive labelling of these ligands allows medical researchers to track their destination and monitor their behaviour within the body.
Positron emission tomography (PET) is revolutionized by the application of radioligands, with their ability to specifically bind to cells in different stages of disease progression. This specialized binding allows researchers and clinicians to visualize the distribution of these cells within the body, turning the potential for early disease detection from a vague horizon into a tangible reality.
Radioactive therapeutic radioligands can bind to specific disease-targeting cells, delivering a lethal dose of radiation that would result in the therapeutic destruction of these cells. Thus, bearing the potential to target and eliminate devastating diseases such as cancer with unprecedented precision.
Key Components of Radioligands:
- Radioisotope: This is the radioactive element integrated into the radioligand. Commonly used isotopes include Lutetium-177 and Gallium-68, known for their therapeutic and imaging properties, respectively.
- Ligand: The ligand is designed to bind specifically to PSMA, a protein highly expressed on the surface of prostate cancer cells. This specificity ensures that the radioligand targets cancerous tissue while sparing healthy cells.
Diagnostic Applications: Radioligands play a pivotal role in diagnostic imaging, especially with Positron Emission Tomography (PET) scans. The PSMA ligand, when combined with a radioisotope like Gallium-68, allows for the precise visualization of prostate cancer lesions. This aids in early detection, accurate staging, and monitoring treatment response.
Therapeutic Applications: In addition to their diagnostic utility, radioligands are employed in targeted therapy for prostate cancer. Lutetium-177-labeled PSMA ligands, such as Pluvicto, deliver therapeutic radiation directly to prostate cancer cells. This targeted approach enhances the effectiveness of treatment while minimizing damage to surrounding healthy tissues.
Advantages of Radioligand Therapy:
- Precision: Radioligands target cancer cells specifically, minimizing collateral damage to healthy tissues.
- Effectiveness: The localized delivery of radiation enhances the therapeutic impact on cancerous cells.
- Personalized Treatment: Radioligand therapy can be tailored to individual patients based on the expression of PSMA in their tumors.
Challenges and Considerations: While radioligands show tremendous promise, there are challenges and considerations to be aware of:
- Logistics: Due to the short half-life of some radioisotopes, radioligand therapy requires careful coordination and quick administration after production.
- Availability: Access to radioligand therapy may be limited in certain regions, and efforts are ongoing to expand availability.
Ongoing Research and Future Directions: The field of radioligands for prostate cancer is dynamic, with ongoing research exploring new isotopes, ligands, and combination therapies. Investigational studies are focusing on improving treatment outcomes and expanding the application of radioligands in various stages of prostate cancer.
As technology advances and more clinical data become available, radioligands continue to evolve, offering hope for enhanced precision and efficacy in the diagnosis and treatment of prostate cancer.
Novartis’ Pluvicto
Novartis produces two different radioligand therapies: Lutathera, which treats neuroendocrine tumors, a rare form of cancer in the digestive tract, and Pluvicto, for patients with a specific type of prostate cancer. Pluvicto was approved by Health Canada in September 2022 as the “first targeted radioligand therapy for progressive PSMA positive metastatic castration-resistant prostate cancer” (Novartis).
Is Pluvicto for me?
Pluvicto (lutetium (177Lu) vipivotide tetraxetan injection) is indicated for the treatment of adult patients with prostate-specific membrane antigen (PSMA)-positive metastatic castration-resistant prostate cancer (mCRPC) who have received at least one androgen receptor pathway inhibitor (ARPI) and taxane-based chemotherapy (Government of Canada).
Warnings
Bone marrow suppression that may be severe, life-threatening or that may lead to death. Tell your healthcare provider right away if you get any of the following signs and symptoms at anytime during treatment:
- Tiredness, weakness, and pale skin
- Shortness of breath
- Bleeding or bruising more easily than normal or difficulty to stop bleeding
- Frequent infections with signs such as fever, chills, sore throat or mouth ulcers
Kidney impairment can occur in patients treated with Pluvicto. Tell your physician about any kidney condition prior to receiving Pluvicto.
To minimize radiation exposure to others following administration of Pluvicto, limit close contact (less than 3 feet) with household contacts for 2 days or with children and pregnant women for 7 days, refrain from sexual activity for 7 days, and sleep in a separate bedroom from household contacts for 3 days, from children for 7 days, or from pregnant women for 15 days.
Clinical studies of Pluvicto have consistently indicated a highly favourable safety profile. Adverse reactions remain few, chiefly mild to moderate in severity, substantiating its favorable tolerability. Typical side effects include fatigue, nausea, and dry mouth, although these are generally transient and manageable. Severe side effects were sporadic in the studied population, further indicating the broad safety margin of Pluvicto.
Coverage Status
CADTH – Pluvicto should be reimbursed by public drug plans for the treatment of patients with mCRPC.
INESSS – Pluvicto should be reimbursed by public drug plans for the treatment of patients with mCRPC.
Despite Health Canada approval, Pluvicto, which is sold for as much as $27,000 a dose for a six-dose treatment cycle, is limited due to national and provincial drug reviews and funding processes. Francois Lamoureux, president of the Canadian Association of Nuclear Medicine, estimates that the average number of treatments will be 4.5, meaning that the average cost in Quebec will be $120,000 (HealthyDebate). This is comparable to the estimated $135,000 to $270,000 range that regular cancer chemotherapy costs.