Locametz (Gozetotide)
Radioactive Diagnostic Agent for PSMA-PET Imaging in Prostate Cancer
Quick Facts About Locametz
Key Takeaways About Locametz
- Diagnostic use only: Locametz is a radioactive tracer used exclusively for PET imaging of prostate cancer – it is not a treatment
- Targets PSMA: After radiolabelling with gallium-68, gozetotide binds to prostate-specific membrane antigen (PSMA) on cancer cells, making them visible on PET scans
- Three key indications: Used for initial staging before curative treatment, detection of suspected recurrence, and assessment of eligibility for PSMA-targeted therapy
- Hospital-administered only: Locametz is prepared, handled, and injected solely by trained nuclear medicine professionals in controlled clinical settings
- Low side effect profile: The most common side effect is fatigue; the procedure involves a small amount of ionising radiation with very low associated risk
What Is Locametz and What Is It Used For?
Locametz (gozetotide) is a radioactive diagnostic agent used in combination with gallium-68 for PET (positron emission tomography) imaging. It is designed to detect prostate cancer cells that express prostate-specific membrane antigen (PSMA), helping doctors stage, monitor, and plan treatment for prostate cancer in adult patients.
Locametz contains the active substance gozetotide, a synthetic peptide-based ligand that has a high affinity for prostate-specific membrane antigen (PSMA). PSMA is a protein found on the surface of most prostate cancer cells, and its expression tends to increase as the disease becomes more aggressive or progresses to metastatic stages. Before use, gozetotide (supplied as a freeze-dried powder in a vial) is combined with the radioactive isotope gallium-68 through a process called radiolabelling, forming gallium(68Ga)gozetotide injection solution.
Once injected intravenously, the radiolabelled compound travels through the bloodstream and binds to PSMA on the surface of prostate cancer cells. The gallium-68 isotope emits positrons, which are detected by a PET scanner, producing detailed images that reveal the location and extent of PSMA-positive tumours throughout the body. This technique, known as PSMA-PET imaging, has become a cornerstone of modern prostate cancer management due to its superior sensitivity and specificity compared to conventional imaging methods such as CT scans and bone scintigraphy.
Approved Indications
Locametz is approved for use in adult male patients with prostate cancer in the following clinical scenarios:
- Initial staging before curative treatment: To determine whether prostate cancer has spread to lymph nodes or other tissues beyond the prostate gland before primary treatment such as radical prostatectomy (surgical removal of the prostate) or radiotherapy. PSMA-PET can detect metastases that may be missed by conventional imaging, potentially changing the treatment plan in a significant proportion of patients.
- Detection of suspected recurrence: To identify the location of recurrent prostate cancer in patients who have already undergone primary curative treatment and in whom biochemical recurrence (rising prostate-specific antigen, or PSA, levels) is suspected. PSMA-PET is particularly valuable in this setting because it can detect recurrent disease at much lower PSA levels than conventional imaging.
- Assessment for PSMA-targeted therapy: To determine whether patients with progressive metastatic castration-resistant prostate cancer (mCRPC) have PSMA-positive disease and may therefore be suitable candidates for PSMA-targeted radioligand therapy, such as lutetium-177 vipivotide tetraxetan (Pluvicto).
PSMA-PET imaging using agents like Locametz represents a significant advancement in prostate cancer diagnostics. The VISION trial (2021) and the proPSMA trial (2020) demonstrated that PSMA-PET has substantially higher accuracy than conventional imaging for detecting metastatic prostate cancer, leading to international guideline updates recommending PSMA-PET as a preferred imaging modality. Locametz was approved by the European Medicines Agency (EMA) in 2022 and by the U.S. Food and Drug Administration (FDA) in 2022.
How Locametz Works
The mechanism of action of Locametz is fundamentally based on the interaction between gozetotide and PSMA. PSMA is a type II transmembrane glycoprotein that is overexpressed on the surface of approximately 90–95% of prostate cancer cells. Expression levels of PSMA are typically 100 to 1,000 times higher on prostate cancer cells compared to normal prostate tissue, and expression increases further in high-grade, metastatic, and castration-resistant disease.
After intravenous injection, gallium(68Ga)gozetotide distributes throughout the body via the bloodstream. The gozetotide component binds with high affinity and specificity to the extracellular domain of PSMA on cancer cells. The gallium-68 radionuclide has a physical half-life of approximately 68 minutes and decays by positron emission. When the emitted positrons encounter electrons in the surrounding tissue, annihilation radiation is produced in the form of two 511 keV gamma photons travelling in opposite directions. These photons are simultaneously detected by the PET scanner, enabling precise three-dimensional localisation of the radiotracer and, by extension, the PSMA-positive cancer cells.
It is important to understand that exposure to the small amount of radioactivity delivered by Locametz carries a very low associated risk. Your doctor will have determined that the clinical benefit of the diagnostic information gained from the PET scan outweighs the very small risk associated with the radiation exposure.
What Should You Know Before Receiving Locametz?
Before receiving Locametz, inform your doctor about any allergies, other types of cancer you may have, and whether you are taking any medications. Locametz must not be used if you are allergic to gozetotide or any of its other ingredients. It is administered only in specialist nuclear medicine departments.
Contraindications
Locametz must not be used if you have a known allergy (hypersensitivity) to gozetotide or to any of the other ingredients in the medicine. The inactive ingredients include gentisic acid, sodium acetate trihydrate, and sodium chloride. If you have previously experienced an allergic reaction to any of these components, inform your doctor before the procedure.
Warnings and Precautions
Talk to your doctor or nuclear medicine specialist before receiving Locametz if any of the following apply to you:
- Other types of cancer: If you have or have previously had cancer other than prostate cancer, inform your doctor. PSMA is not exclusively expressed on prostate cancer cells; it can also be found at low levels on certain other tumour types (such as renal cell carcinoma, some neuroendocrine tumours, and certain brain tumours) as well as in some normal tissues (kidneys, salivary glands, small intestine, liver). This means that PSMA-PET imaging may occasionally show areas of uptake that are not related to prostate cancer, which could affect the interpretation of the scan results.
- Kidney problems: Because the radioactive tracer is partly excreted through the kidneys, patients with significant kidney impairment should discuss this with their doctor, although no specific dose adjustment is typically required.
- Previous radiation exposure: If you have undergone multiple diagnostic procedures involving ionising radiation, your doctor will weigh the cumulative radiation exposure against the expected diagnostic benefit of the PSMA-PET scan.
Hydration Before and After the Scan
Adequate hydration is essential both before and after the procedure. Before receiving Locametz, you should:
- Drink plenty of water to ensure you are well hydrated
- Urinate immediately before the PET scan to empty your bladder
- Continue drinking fluids and urinate as frequently as possible during the first several hours after the injection to help eliminate the radioactive substance from your body more quickly
Pregnancy, Breastfeeding and Fertility
Locametz is not intended for use in women. It is a diagnostic agent specifically designed for adult male patients with prostate cancer. All radioactive medicinal products, including Locametz, have the potential to cause harm to a developing foetus. If a female partner of a male patient is pregnant or suspected of being pregnant, the nuclear medicine physician should be informed.
Children and Adolescents
Locametz should not be given to children or adolescents under 18 years of age. There are no clinical data available on the safety or efficacy of Locametz in this age group, and prostate cancer is an extremely rare condition in paediatric populations.
Driving and Operating Machinery
It is considered unlikely that Locametz affects the ability to drive or use machines. However, as with any medical procedure, if you feel unwell or fatigued after receiving the injection, you should avoid driving until you feel well enough to do so safely.
Sodium Content
Locametz contains 28.97 mg of sodium per injection, equivalent to approximately 1.5% of the WHO-recommended maximum daily dietary sodium intake for adults (2 g sodium per day). This should be taken into consideration by patients on a controlled sodium diet.
How Does Locametz Interact with Other Drugs?
No formal drug interaction studies have been conducted with Locametz. However, certain medications – particularly androgen deprivation therapy and some other prostate cancer treatments – may influence PSMA expression on cancer cells and potentially affect scan interpretation. Always inform your nuclear medicine specialist about all medications you are taking.
While no systematic drug-drug interaction studies have been performed with Locametz, the scientific literature suggests that certain medications used in the management of prostate cancer may affect PSMA expression levels on cancer cells, which could theoretically influence the results of PSMA-PET imaging. Understanding these potential interactions is important for accurate scan interpretation.
Medications That May Affect PSMA Expression
Several classes of prostate cancer treatments have been studied for their potential effects on PSMA expression:
| Medication / Class | Potential Effect on PSMA | Clinical Significance |
|---|---|---|
| Androgen deprivation therapy (ADT) | May upregulate PSMA expression | Could increase scan sensitivity; timing relative to ADT initiation may matter |
| Enzalutamide / Abiraterone | May increase PSMA expression through androgen receptor pathway suppression | Some studies suggest enhanced tumour detection under these treatments |
| Taxane chemotherapy (docetaxel, cabazitaxel) | Effect on PSMA expression varies | Discuss timing of PSMA-PET relative to chemotherapy cycles with your doctor |
| Corticosteroids | Theoretical downregulation of PSMA at high doses | Limited clinical evidence; inform your doctor if taking high-dose steroids |
It is essential to tell your nuclear medicine specialist about all medications you are currently taking, including prescription medicines, over-the-counter drugs, vitamins, and herbal supplements. This information helps ensure the most accurate interpretation of your PSMA-PET scan results.
Because Locametz is a diagnostic imaging agent administered as a single dose in a hospital setting (rather than a medication taken regularly at home), the risk of traditional pharmacokinetic drug interactions is minimal. The primary concern is not about drug-drug interactions in the conventional sense, but rather about how concurrent medications may influence the expression of PSMA on cancer cells and thus affect image interpretation.
What Is the Correct Dosage of Locametz?
Locametz is administered as a single intravenous injection at a dose of 1.8–2.2 MBq per kilogram of body weight, with a minimum of 111 MBq and a maximum of 259 MBq. It is prepared and injected exclusively by trained nuclear medicine professionals. PET imaging is performed 50 to 100 minutes after injection.
The use, handling, and disposal of radioactive medicinal products are governed by strict regulations. Locametz is only used in specially designated controlled areas within nuclear medicine departments. The medicine is handled and administered exclusively by healthcare professionals who are trained and qualified in the safe use of radioactive substances. These professionals will take special care to ensure that the medicine is used safely and will keep you informed throughout the process.
Adults
The doctor supervising the procedure will determine the appropriate dose of Locametz for you. The goal is always to use the lowest amount of radioactivity necessary to obtain the required diagnostic information. The standard recommended dosing is as follows:
Standard Adult Dosing
- Dose per kilogram: 1.8–2.2 MBq/kg body weight
- Minimum dose: 111 MBq (3 mCi)
- Maximum dose: 259 MBq (7 mCi)
- Administration route: Slow intravenous injection
- Imaging time: PET scan performed 50–100 minutes after injection
The unit MBq (megabecquerel) is the standard unit of measurement for radioactivity. Your doctor will calculate the precise dose based on your body weight to ensure optimal image quality while minimising unnecessary radiation exposure.
Children and Adolescents
Locametz must not be used in children or adolescents under 18 years of age. No dosing information is available for this population as no clinical studies have been conducted in paediatric patients.
Elderly Patients
No dose adjustment is required for elderly patients. The standard weight-based dosing applies to all adult patients regardless of age. However, as prostate cancer predominantly affects older men, the majority of patients receiving Locametz will be in the older age groups. The doctor will take into account the patient's overall health status and kidney function when planning the procedure.
Administration Procedure
After preparation and radiolabelling, Locametz is given through a slow intravenous injection into a vein, typically in the arm. The entire injection process takes only a few minutes. After the injection, you will be asked to wait for approximately 50 to 100 minutes before the PET scan begins. During this time, the radiolabelled compound distributes throughout your body and binds to any PSMA-positive cells. You should continue drinking water and urinate as often as possible during this waiting period.
Duration of the Scan
Your doctor will inform you about how long the PET scan typically takes. A full-body PSMA-PET/CT scan usually takes approximately 20 to 30 minutes, during which you will need to lie still on the scanning table. The entire visit, including preparation, injection, waiting time, and the scan itself, typically takes 2 to 3 hours.
Overdose
An overdose of Locametz is unlikely to occur because you receive only a single dose that is carefully calculated and controlled by the doctor supervising the procedure. In the unlikely event that an overdose does occur, you will receive appropriate supportive treatment. You may be asked to drink plenty of fluids and urinate frequently to help eliminate the radioactive substance from your body as quickly as possible. There is no specific antidote for gallium(68Ga)gozetotide overdose.
| Patient Group | Recommended Dose | Notes |
|---|---|---|
| Adults (all ages) | 1.8–2.2 MBq/kg (min 111 MBq, max 259 MBq) | Weight-based dosing; single IV injection |
| Elderly | No dose adjustment required | Standard adult dosing applies |
| Renal impairment | No dose adjustment required | Adequate hydration recommended |
| Hepatic impairment | No dose adjustment required | No specific studies conducted |
| Children (<18 years) | Not recommended | No data available; not indicated in this population |
What Are the Side Effects of Locametz?
Like all medicines, Locametz can cause side effects, although not everybody gets them. The most common side effect is fatigue. Less common side effects include nausea, constipation, vomiting, diarrhoea, dry mouth, injection site reactions, and chills. The radioactive component delivers a small amount of ionising radiation with a very low associated risk.
The side effect profile of Locametz is generally mild, reflecting the fact that it is a diagnostic agent administered as a single dose rather than a medication taken on an ongoing basis. The majority of reported adverse reactions are transient and resolve without specific treatment. Below is a comprehensive overview of the known side effects, categorised by frequency according to standard medical conventions.
Common
- Fatigue (tiredness)
Uncommon
- Nausea (feeling sick)
- Constipation
- Vomiting
- Diarrhoea
- Dry mouth
- Injection site reactions (bruising, itching, warmth at the injection site)
- Chills
Radiation-Related Effects
As a radioactive medicinal product, Locametz delivers a small amount of ionising radiation to your body. The total effective radiation dose from a typical gallium(68Ga)gozetotide PET/CT examination is relatively low compared to many other nuclear medicine procedures. The European Association of Nuclear Medicine (EANM) has noted that the radiation exposure from PSMA-PET is generally comparable to or lower than that from a standard CT scan of the chest, abdomen, and pelvis.
Ionising radiation at any dose carries a theoretical risk, however small, of inducing cancer or causing hereditary genetic changes. Your doctor will have carefully weighed the diagnostic benefit of the PSMA-PET scan against this very small radiation risk before recommending the procedure. For the vast majority of patients, the clinical value of accurate prostate cancer staging and detection far outweighs the minimal radiation risk.
When to Report Side Effects
If any side effects become severe, persistent, or bothersome, you should inform your doctor or the nuclear medicine department. It is also important to report side effects that are not listed above, as ongoing pharmacovigilance helps ensure the continued safety monitoring of Locametz.
You can report suspected side effects to your national medicines regulatory authority. In the European Union, the reporting system is coordinated through the EudraVigilance database operated by the European Medicines Agency (EMA). In the United States, adverse reactions can be reported to the FDA MedWatch programme. In the United Kingdom, reports can be made through the Yellow Card Scheme operated by the Medicines and Healthcare products Regulatory Agency (MHRA).
After your Locametz PET scan, continue drinking plenty of water and urinate frequently to help flush the radioactive tracer from your body. The gallium-68 radionuclide has a short physical half-life of approximately 68 minutes, meaning that the radioactivity decreases rapidly. Within a few hours of the injection, the radiation level in your body will be negligible. Your doctor will advise you on any specific precautions, although for most patients no special measures beyond adequate hydration are needed.
How Should Locametz Be Stored?
You do not need to store Locametz yourself. It is stored under the supervision of specialist medical staff in the nuclear medicine department, in accordance with strict national regulations for radioactive materials. The freeze-dried powder is stored below 25°C before preparation, and the prepared solution must be used within 6 hours.
Locametz is a hospital-only medicinal product. All aspects of its storage, preparation, and disposal are managed by trained nuclear medicine professionals. You will never need to handle, transport, or store this medicine yourself. The following storage information is provided for completeness and transparency:
- Before preparation: The freeze-dried gozetotide powder in the vial is stored at temperatures not exceeding 25°C
- After preparation and radiolabelling: The vials containing the prepared gallium(68Ga)gozetotide solution must be stored upright at temperatures not exceeding 30°C
- Shelf life after preparation: The prepared solution must be used within 6 hours of radiolabelling
- Expiry date: Locametz must not be used after the expiry date printed on the carton and label. The expiry date refers to the last day of the stated month
- Radioactive waste: All radioactive materials and contaminated items are disposed of in accordance with national regulations for radioactive waste management
Radioactive medicinal products such as Locametz are stored in specially designed, shielded containers within secure areas of the nuclear medicine department. Access to these areas is restricted to authorised personnel with appropriate training in radiation protection.
What Does Locametz Contain?
Each vial of Locametz contains 25 micrograms of gozetotide as the active substance, along with gentisic acid, sodium acetate trihydrate, and sodium chloride as inactive ingredients. Gallium-68 is not included in the kit and must be obtained separately from a gallium-68 generator.
Active Ingredient
The active substance is gozetotide. Each vial contains 25 micrograms (µg) of gozetotide as a white freeze-dried (lyophilised) powder. Gozetotide is a PSMA-binding ligand that, upon radiolabelling with gallium-68, forms the radioactive diagnostic compound gallium(68Ga)gozetotide.
Inactive Ingredients (Excipients)
- Gentisic acid – acts as a stabiliser to protect the radiolabelled compound from radiolytic degradation
- Sodium acetate trihydrate – serves as a buffer to maintain an appropriate pH for the radiolabelling reaction
- Sodium chloride – used for tonicity adjustment
Gallium-68
The radioactive component, gallium-68, is not included in the Locametz kit. It must be obtained separately from a germanium-68/gallium-68 (68Ge/68Ga) generator, which is a device that produces gallium-68 through the radioactive decay of its parent isotope, germanium-68. The radiolabelling process combines the generator eluate containing gallium-68 with the gozetotide powder to produce the final injectable solution.
Appearance and Packaging
Locametz is supplied as a multi-dose kit containing one vial of white freeze-dried powder. After preparation and radiolabelling, the final product is a sterile, clear injection solution containing gallium(68Ga)gozetotide with a radioactivity of up to 1,369 MBq. The prepared solution also contains hydrochloric acid. Each pack contains 1 vial.
The marketing authorisation holder is Novartis Europharm Limited (Dublin, Ireland), and the manufacturer is Advanced Accelerator Applications (Italy) S.R.L. (Saluggia, Italy).
Frequently Asked Questions About Locametz
A PSMA-PET scan with Locametz produces detailed images of your entire body, highlighting areas where PSMA-positive prostate cancer cells are present. The scan can detect primary tumours in the prostate, as well as cancer that has spread to lymph nodes, bones, or other organs. It is significantly more sensitive than conventional imaging methods such as CT scans and bone scintigraphy, meaning it can detect smaller lesions and find cancer at earlier stages. The results help your doctor make more informed decisions about your treatment plan.
The entire procedure typically takes 2 to 3 hours from arrival to departure. This includes the intravenous injection (a few minutes), a waiting period of 50 to 100 minutes (during which the tracer distributes through your body), and the PET/CT scan itself (approximately 20 to 30 minutes). During the waiting period, you will be encouraged to drink water and use the bathroom. You can usually resume normal activities after the scan.
No, Locametz is not a treatment. It is a diagnostic agent used exclusively for imaging purposes. While it targets the same protein (PSMA) as certain therapeutic agents like lutetium-177 vipivotide tetraxetan (Pluvicto), Locametz is used with gallium-68 for diagnostic PET imaging, not for delivering therapeutic radiation. However, a positive Locametz PET scan can help determine whether you are a suitable candidate for PSMA-targeted therapy.
The radiation dose from a Locametz PET scan is relatively low and comparable to many routine medical imaging procedures. Gallium-68 has a short half-life of approximately 68 minutes, meaning the radioactivity in your body decreases rapidly after the scan. The radiation dose is generally similar to or lower than that from a standard CT scan. Your doctor will have determined that the diagnostic benefit of the scan outweighs the minimal radiation risk. Drinking plenty of water and urinating frequently after the procedure helps flush the tracer from your body more quickly.
Locametz detects prostate cancer cells that express PSMA on their surface. Approximately 90–95% of prostate cancers express PSMA, so the vast majority will be detected. However, a small percentage of prostate cancers (particularly certain neuroendocrine subtypes and some very aggressive variants) may have low or absent PSMA expression and could potentially be missed by a PSMA-PET scan. Additionally, false-positive results can occasionally occur in non-cancerous conditions such as benign prostatic hyperplasia, inflammatory changes, or Paget's disease of bone. Your doctor will interpret the scan results in conjunction with your full clinical picture.
In general, you do not need to stop your current medications before a Locametz PET scan. However, it is very important to tell your nuclear medicine specialist about all medications you are taking, including prescription drugs, over-the-counter medicines, and supplements. Certain prostate cancer treatments, such as androgen deprivation therapy or enzalutamide, may influence PSMA expression and potentially affect scan interpretation. Your doctor will advise you on any specific precautions.
References
- European Medicines Agency (EMA). Locametz – Summary of Product Characteristics (SmPC). European Medicines Agency. 2022. Available at: ema.europa.eu/locametz
- Hofman MS, Lawrentschuk N, Francis RJ, et al. Prostate-specific membrane antigen PET-CT in patients with high-risk prostate cancer before curative-intent surgery or radiotherapy (proPSMA): a prospective, randomised, multicentre study. The Lancet. 2020;395(10231):1208–1216. doi:10.1016/S0140-6736(20)30314-7
- Sartor O, de Bono J, Chi KN, et al. Lutetium-177-PSMA-617 for metastatic castration-resistant prostate cancer (VISION trial). New England Journal of Medicine. 2021;385(12):1091–1103. doi:10.1056/NEJMoa2107322
- U.S. Food and Drug Administration (FDA). Locametz (kit for the preparation of gallium Ga 68 gozetotide injection) – Prescribing Information. FDA Approved Drug Products. 2022.
- Fendler WP, Eiber M, Beheshti M, et al. EANM/SNMMI Joint Practice Guideline for PSMA-PET/CT. European Journal of Nuclear Medicine and Molecular Imaging. 2023;50(5):1466–1486. doi:10.1007/s00259-022-06089-w
- National Comprehensive Cancer Network (NCCN). Prostate Cancer Clinical Practice Guidelines in Oncology (Version 4.2024). NCCN.org.
- Mottet N, van den Bergh RCN, Briers E, et al. EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer. European Association of Urology. 2024.
- World Health Organization (WHO). WHO Model List of Essential Medicines – 23rd List. Geneva: World Health Organization; 2023.
Editorial Team
Medical Review
iMedic Medical Review Board
Independent panel of medical specialists in nuclear medicine, oncology, and urology. All content follows international guidelines (EMA, FDA, NCCN, EAU, EANM).
Evidence Standard
Level 1A Evidence
Based on systematic reviews, randomised controlled trials (proPSMA, VISION), and international clinical guidelines. GRADE evidence framework applied.
Conflict of Interest: None declared. iMedic receives no pharmaceutical company funding or sponsorship. All editorial content is produced independently.