What it is
Gozetotide is the targeting part of a radioactive tracer used in PET scans for prostate cancer. It is also known by its research name, PSMA-11. On its own it is not radioactive. A radiopharmacy adds a gallium-68 atom shortly before the scan, and the finished tracer is called gallium Ga 68 gozetotide. In the United States it is prepared from one of three kits: Illuccix, Locametz or Gozellix.
Is it a peptide? Only just. The Illuccix label calls gozetotide a "ligand peptide" and writes its sequence as Glu-NH-CO-NH-Lys(Ahx). That is two amino acids, glutamate and lysine, with a six-carbon spacer (Ahx, aminohexanoic acid). The two amino acids are joined by a urea group, not by the peptide bond that links amino acids in a normal chain. The Locametz label uses the word "peptidomimetic" for the same molecule. The library's peptide vs. protein entry explains where these lines are usually drawn.
The rest of the molecule is a chelator called HBED-CC, a claw-shaped group that holds the gallium atom. The complete tracer has a molecular weight of 1011.9.
How it works
The label's mechanism section is short. Gallium Ga 68 gozetotide binds to PSMA (prostate-specific membrane antigen), a protein that prostate cancer cells usually carry in large amounts. Gallium-68 gives off positrons, which a PET scanner detects. The scan shows where the tracer has collected.
The same glutamate-urea-lysine piece is the part that grips PSMA in vipivotide tetraxetan (Pluvicto), a drug that carries a treating dose of radiation instead of an imaging one. That link is why the Illuccix and Locametz labels include a third use: choosing men for PSMA-directed therapy. The Gozellix label read for this entry (version dated April 2025) lists only the first two uses.
What the two imaging studies found
The Illuccix label states that its effectiveness "has been established based on a study of another formulation" of the same tracer, and then reports two studies run at two centers.
| Study | Men scanned | Checked against | Outcome |
|---|---|---|---|
| PSMA-PreRP (NCT03368547, NCT02919111) | 325 men before prostate surgery; 123 (38%) had enough pathology to evaluate | Pelvic lymph-node cancer vs. surgical pathology | Sensitivity 47%, specificity 90%, PPV 61%, NPV 84% (majority read) |
| PSMA-BCR (NCT02940262, NCT02918357) | 635 men with rising PSA after treatment | Whether positive regions matched a reference standard | 469 (74%) scans positive; 192 of 210 checkable patients (91%) confirmed in at least one region |
Reading the first row. In the pre-surgery study, 30 of the 123 evaluable men had cancer in their pelvic lymph nodes. The scan found 14 of them and missed 16. When it was negative, it was right in 84 of 100 men. Single readers varied widely: sensitivity ran from 36% to 60%.
In the second study the 91% figure counts only men whose positive findings could be checked. The label also gives an exploratory estimate that covers every man scanned, positive or negative: 340 of 635 (54%) were counted as true positives after the unchecked scans were filled in statistically. The prostate bed was the weakest region, with 76% of positive results confirmed against 96% elsewhere.
Side effects in the label
Every patient in these studies had a single injection. In the 960 patients of the two imaging studies, the most common reactions were nausea, diarrhea and dizziness, each in fewer than 1%. In a third study of 1,003 men with advanced prostate cancer, the label lists fatigue in 12 (1.2%) and nausea in 8 (0.8%). Two warnings follow in the label: images can be misread, and the dose adds to lifetime radiation exposure.
What is not established
- A scan is not proof either way. The label says a negative image does not rule cancer out, a positive one does not confirm it, and the tracer is also taken up by other cancers and by non-cancerous conditions.
- Only 38% of the men enrolled in the pre-surgery study could be evaluated. The label's exploratory estimate for all scanned men puts specificity lower, at 74%.
- In the recurrence study, negative scans were not systematically checked, so the study cannot say how many cancers the scan missed.
- This entry does not compare the three kits with each other or with other PSMA tracers such as piflufolastat F 18 or flotufolastat F 18. The library records compounds; it does not rank them.
Where it stands
| Question | Answer as of 2026-11-11 |
|---|---|
| Is it a peptide? | Two amino acids joined by a urea link; "ligand peptide" (Illuccix label), "peptidomimetic" (Locametz label) |
| US status | Illuccix 2021-12-17, Locametz 2022-03-23, Gozellix 2025-03-20 (Drugs@FDA) |
| Preparation | Kit plus gallium-68, mixed by a radiopharmacy on the day |
| PubMed | 2,088 records, 111 of them tagged as trials |
| Advice | None. The ordering team answers questions about a scan. |
Related reading
Outside prostate cancer, the library records a peptide tracer aimed at somatostatin receptors. The drug that uses the same PSMA-binding piece to deliver treatment is vipivotide tetraxetan.