NeoB
A receptor-seeking peptide that carries a radioactive label to prostate, breast and stromal tumours
NeoB, first called NeoBOMB1, is a synthetic peptide built to latch onto the gastrin-releasing peptide receptor, which many prostate and breast cancers and some gastrointestinal stromal tumours carry in large numbers. With gallium-68 attached it lights up those tumours on a PET scan; with lutetium-177 attached it delivers radiation to them. Small imaging studies in people are encouraging, and a first-in-human treatment study set a recommended activity of 9.25 GBq per cycle. It is an investigational hospital radiopharmaceutical, not approved anywhere.
Used in human trials: 9.25 GBq, Per cycle, at least 6 weeks apart, Intravenous (Lutetium-177 NeoB, advanced solid tumours: recommended phase 2 acti...) Details ↓
Recommended Dosing
Used in human trials
No manufacturer dose exists for this use: these are amounts given in published trials, not recommendations.
What is it?
The gastrin-releasing peptide receptor, GRPR, is a hormone receptor found in the pancreas and a few other normal tissues, and in much larger amounts on many prostate cancers, oestrogen-receptor-positive breast cancers and gastrointestinal stromal tumours (GIST). NeoB is a short synthetic peptide that binds this receptor, with a DOTA cage at one end to hold a radioactive metal. It was made by changing the tail of an earlier antagonist, SB3, and was described in 2017 as NeoBOMB1. Like RM2, the other widely studied GRPR tracer, it is an antagonist: it sits on the receptor without switching it on, and it stays mostly on the cell surface rather than being drawn inside.
In mice with human prostate, breast and GIST tumours, radiolabelled NeoB stuck to the tumours strongly and stayed there; its half-life inside GIST tumours was about 40 hours. Because the pancreas carries the same receptor, it also took up a lot of tracer, and two studies found that injecting more unlabelled peptide alongside the label cut pancreatic uptake sharply while leaving tumour uptake unchanged. Repeated lutetium-177 doses shrank tumours and lengthened survival in mice; at the higher doses the kidneys, the organ that clears it, showed the main damage.
In people, the first data came from small imaging studies. A European phase 1/2a study in six patients with GIST found gallium-68 NeoBOMB1 well tolerated over four weeks of follow-up, with a mean effective radiation dose of 0.029 mSv per MBq and the pancreas receiving the highest organ dose. In 27 men whose prostate cancer had returned on blood tests but not on standard scans, gallium-68 NeoB PET found disease in 18 and was more sensitive than a PSMA tracer given to the same men, picking up 14 lesions that the PSMA scan missed. In 20 women with oestrogen-receptor-positive breast cancer it was positive in 15, compared with 13 on the standard FDG scan.
The therapy version is earlier in testing. NeoRay, the first-in-human study of lutetium-177 NeoB in 17 people with advanced cancers, escalated the activity per cycle and found dose-limiting side effects, including anaemia and serious neurological problems, only at 11.1 GBq. It set 9.25 GBq as both the maximum tolerated and the recommended phase 2 activity. The kidneys received about 0.10 Gy per GBq, which the authors judged a wide margin below the limits used for external radiotherapy. The preliminary report gives safety and radiation-dose data, not whether tumours shrank.
All of this rests on studies of a few dozen patients, and a 2026 review notes that long-term efficacy and safety data in people are still missing. NeoB is made fresh in hospital radiopharmacies and injected in nuclear-medicine departments within trials. It has no FDA or EMA approval, and it is not a peptide anyone can buy or use at home.
Mechanism of Action
NeoB does nothing to the tumour by itself. It is a homing device: the peptide finds the gastrin-releasing peptide receptor, and the radioactive metal it carries is either seen by a scanner or irradiates the cells around it.
Gallium-68 for PET
With gallium-68 it showed GIST, prostate and breast cancer lesions on PET; tracer left the blood with a half-life of 27 minutes and was cleared through the kidneys (2020 study).
Lutetium-177 for therapy
The same peptide carrying lutetium-177 gave beta radiation to tumours in mice and was tested in people at 1.85 to 11.1 GBq per cycle (2026 study).
Normal uptake
The pancreas, which carries GRPR, took up the most among normal organs in 12 patients, with the liver and spleen next (2025 study); more unlabelled peptide lowered pancreatic uptake in mice (2017 studies).
Published Research
These are the studies of NeoB read from their PubMed abstracts on October 29, 2026: seven in patients, eight in mice (one of which also shows the first patient images), one on human tumour tissue and one review. The human studies are small. Two studies titled only for the receptor are carded because their abstracts name NeoB as the tracer used.
NeoRay: first lutetium-177 NeoB treatment study
Seventeen people with advanced GIST, prostate cancer, glioblastoma or breast cancer received at least one cycle, starting at 1.85 GBq and escalating to 5.55, 9.25 or 11.1 GBq. Four dose-limiting effects occurred in three patients on 11.1 GBq: two grade 3 anaemias, a grade 4 neurological decline and a grade 3 encephalopathy. Kidneys received 0.10 Gy per GBq on average; 9.25 GBq became the recommended dose.
Recurrent prostate cancer: NeoB vs PSMA-R2
In a phase 2 imaging study, 27 men with rising PSA and unhelpful standard scans had both PET/MRI scans. NeoB found 31 lesions in 18 men and the PSMA-R2 tracer 20 lesions in 15. Sensitivity was 85.7% against 71.4% and accuracy 88.9% against 77.8%, with specificity 100% for both. No adverse events were reported in the 72 hours after either scan.
Oestrogen-receptor-positive breast cancer
Twenty women with ER- and PR-positive, HER2-negative breast cancer had NeoB and FDG PET/CT. NeoB was positive in 15 and FDG in 13; at first staging NeoB was positive in 6 of 8 against 4 of 8. Uptake was higher with NeoB (median SUVmax 20.5 against 7.4). Some NeoB-negative, FDG-positive cases at restaging had lost oestrogen-receptor expression.
MITIGATE: safety and dosimetry in GIST
Six patients with advanced, previously treated GIST received about 174 MBq (3 MBq per kg). The tracer was well tolerated over four weeks. The mean effective dose was 0.029 mSv per MBq, the pancreas got the highest organ dose, the plasma half-life was 27.3 minutes and metabolites appeared only in urine. Three patients had clear tumour uptake.
MITIGATE: tumour targeting in nine patients
In the full group of nine GIST patients, six showed uptake in at least one lesion and 17 of 37 lesions took up the tracer. Five lesions were seen only on NeoBOMB1 PET. Uptake was higher in men, in people with higher body-mass index and in lesions that were not necrotic.
SDH-deficient GIST: 12 patients
In 12 people with metastatic succinate dehydrogenase-deficient wild-type GIST, a rare form with few treatment options, gallium-68 NeoB lesions were intensely but unevenly positive in 8 and showed little or no uptake in 4. Normal uptake was highest in the pancreas, liver and spleen.
Kit production for clinical use
Six batches made with a kit and a licensed gallium generator met quality and sterility criteria, yielding about 712 MBq at over 95% radiochemical purity in 20 minutes. Three GIST patients were scanned before and after local treatments, and the tracer showed their abdominal tumour deposits.
Design, mouse studies and first patient images
NeoBOMB1, made by changing the C-terminus of the antagonist SB3, bound GRPR at about 1-2 nM whether it carried gallium, indium or lutetium, stayed over 95% intact in mouse blood at 5 minutes, and reached about 30% of the injected dose per gram in prostate tumours in mice. Gallium-68 NeoBOMB1 PET showed lesions in men with prostate cancer.
Imaging and therapy versions in mice
In mice with PC-3 prostate tumours, both gallium-68 and lutetium-177 forms imaged the tumours well. A larger peptide amount with the lutetium label raised tumour uptake and cut pancreatic uptake from 105 to about 20% of the injected dose per gram. Extrapolated human doses were 0.10, 0.65 and 0.06 mGy per MBq for kidney, pancreas and liver.
Breast cancer model
NeoBOMB1 bound GRPR on T-47D breast cancer cells with an IC50 of about 2.2 nM and localised specifically in xenografts in mice. Raising the peptide amount from 10 to 200 pmol cut very high pancreatic uptake by about four fifths without lowering tumour uptake.
GIST tumours in mice
In 82 mice with human GIST tumours, lutetium-177 NeoB uptake was high and receptor-specific, with a tumour half-life of 40.2 hours and low pancreatic uptake. Three weekly doses significantly shrank tumours, with complete regression at the 400 pmol dose.
Toxicity in healthy mice
Healthy mice received three weekly injections of up to 120 MBq lutetium-177 NeoB and were followed for up to 43 weeks. The pancreas, liver and kidneys absorbed the most radiation; the pancreas and liver showed no clear microscopic damage, but the two higher doses caused kidney damage and raised blood urea.
Dose versus benefit in prostate cancer mice
Three weekly cycles at 30, 40 or 60 MBq all extended median survival of PC-3 tumour-bearing mice (82, 89 and 99 days against 19 untreated), with no significant difference between the doses. Kidney atrophy, fibrosis or inflammation appeared in some animals at 24 weeks.
Side by side with RM2
In cells and mice, lutetium-177 NeoB and RM2 both bound GRPR strongly and reached tumours equally well. NeoB was taken up more by the pancreas and stayed there longer; RM2 had a lower tumour-to-kidney ratio. NeoB bound more strongly to sections of several human tumour types.
Compared with ProBOMB1
Lutetium-labelled NeoBOMB1 bound GRPR more tightly than the related ProBOMB1 (Ki 2.26 against 30.2 nM) and gave higher tumour uptake in prostate cancer mice at every time point, with a better therapeutic index for the organs receiving the highest doses.
GRPR and PSMA across prostate disease
On 53 frozen human prostate tissue samples, lutetium-177 NeoB bound most to primary prostate cancer, while the PSMA ligand bound most to castration-resistant cancer. Three castration-resistant samples bound NeoB strongly, one with no PSMA binding, suggesting the two targets can complement each other.
Where NeoB stands
A narrative review of studies to January 2025 finds high detection of primary tumours and distant spread with gallium-68 NeoB but only moderate accuracy for lymph nodes, strong antitumour effects of the lutetium form in animals, and no long-term efficacy or safety data in people yet.
Dosing Data
NeoB has no approved label. It is dosed by radioactivity, not by weight of peptide. The rows below are the activities given in the published human studies carded above, injected into a vein in a nuclear-medicine department.
Educational information, not medical advice. Each dose above is tagged with its source: an approved label, a published human study, animal data, or amounts reported by users. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose. Full medical disclaimer.
What a Buyer Needs to Know
What is sold, how it is mixed, stored and taken, and what is known about its safety, quality and legal status. Each part names its source. Where we have none, it says unknown.
What is sold
Unknown: we hold no regulator's label that says in what form NeoB is supplied. It is a radioactive drug: the next part says where it is prepared and given.
Mixing a vial: a worked example
Nothing to mix at home, and no syringe units to work out: NeoB is a radioactive drug, prepared and given in nuclear-medicine departments, and its dose is an amount of radioactivity (MBq or GBq), not a weight.
This page's dosing note: “NeoB is labelled in a hospital radiopharmacy shortly before use and given by radioactivity; no reconstitution maths applies to it.”
Source: this page's own note in Dosing Data below; the amount of each dose row in Dosing Data below.
Storage before and after mixing
Unknown: no label on file says how NeoB is stored. It is a radioactive drug held by the nuclear-medicine department that prepares and gives it (see the part above); the home rules for a mixed vial in the mixing guide do not apply to it.
How it is taken
As it was given in human studies: Intravenous (Per cycle, at least 6 weeks apart; Lutetium-177 NeoB, advanced solid tumours: recommended phase 2 activity).
Source: Used in human trials: the route and frequency of each row in Dosing Data below.
What to expect, and when
How long it stays in the body: a half-life of 27.3 minutes, mean plasma half-life of gallium-68 NeoBOMB1 in 6 patients (PMID 32332143). After about five half-lives almost none is left.
How long the doses were given: Lutetium-177 NeoB, advanced solid tumours: recommended phase 2 activity: At least 3 cycles planned; Lutetium-177 NeoB, NeoRay dose escalation (17 patients): At least 3 cycles planned; Gallium-68 NeoBOMB1 PET, GIST (6 patients): Imaging up to 3-4 hours later.
When effects appear: unknown; no source on this page gives a time to effect for NeoB. Results reported in the studies are under Published Research.
Source: half-life: PMID 32332143; Used in human trials, the duration of each row in Dosing Data below.
Side effects, and when to stop or get help
From the Side Effects section: Imaging doses: no adverse events in the 72 hours after scanning in 27 men, and good tolerance over four weeks in GIST patients; Radiation from a gallium-68 scan: about 0.029 mSv per MBq, highest to the pancreas; Therapy at 11.1 GBq per cycle: grade 3 anaemia, grade 4 neurological decline and grade 3 encephalopathy; 4 of 17 patients had grade 3 or worse treatment-related effects; In mice, the kidneys showed the main radiation damage at higher therapy doses. Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping NeoB. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“From the human studies above”).
Interactions
Unknown: a PubMed search for human interaction studies of NeoB (reviewed 2026-10-28) found none. Unknown is not the same as safe to combine.
Every peptide's record, with its source: the interaction matrix.
Checking what you bought
Unknown: no published independent test of NeoB products is in our lab-results database yet, so how products sold under this name measure up is not known.
To read a certificate of analysis, paste it into the COA decoder. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: In Clinical Trials (Not approved: Drugs@FDA and the EMA medicines list hold no record (searched October 28, 2026)). Sport: Prohibited (S0 catch-all).
Country by country ↓ · Regulatory tracker
Source: this entry's approval status and the WADA Prohibited List, as in Legal Status below.
Side Effects & Contraindications
Reported Side Effects
From the human studies above.
Contraindications & Cautions
No approved label exists, so there are no official contraindications. Points from the studies:
Legal Status
NeoB is investigational in every jurisdiction checked.
Frequently Asked Questions
?What is NeoB?
A synthetic peptide that binds the gastrin-releasing peptide receptor without activating it, with a DOTA chelator that holds a radioactive metal. It was first called NeoBOMB1.
?What is it used for?
In trials, gallium-68 NeoB is used for PET scans of prostate cancer, oestrogen-receptor-positive breast cancer and GIST, and lutetium-177 NeoB is being tested as a radioligand treatment for tumours that carry the receptor.
?How does it compare with PSMA scans?
In one study of 27 men with recurrent prostate cancer it was more sensitive than a PSMA tracer and found 14 lesions the PSMA scan missed. The two targets are expressed differently, so they may complement each other.
?What dose is given?
It is dosed by radioactivity: about 3 MBq per kg for gallium-68 imaging, and a recommended 9.25 GBq per cycle of lutetium-177 in the first treatment study.
?Is NeoB approved?
No. It is investigational and given only in nuclear-medicine departments within studies.
References
- [other] PubChem CID 73438549, NeoBOMB1: formula C77H110N18O18, molecular weight 1575.8. Read October 28, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/73438549
- [clinical-trial] Mittra ES, et al. "Phase 1 Study of [(177)Lu]Lu-NeoB in Patients with Advanced Solid Tumors Overexpressing Gastrin-Releasing Peptide Receptor: Preliminary Safety and Dosimetry Results." J Nucl Med, 2026;67(2):262-268. PMID: 41344852.
- [clinical-trial] Duan H, et al. "Prospective Comparison of (68)Ga-NeoB and (68)Ga-PSMA-R2 PET/MRI in Patients with Biochemically Recurrent Prostate Cancer." J Nucl Med, 2024;65(6):897-903. PMID: 38664016.
- [pubmed] Sabahi Z, et al. "Diagnostic Potential of (68)Ga-NeoB PET/CT with Estrogen Receptor- and Progesterone Receptor-Positive Breast Cancer Undergoing Staging or Restaging for Metastatic Disease." J Nucl Med, 2025;66(5):700-706. PMID: 40147847.
- [clinical-trial] Gruber L, et al. "MITIGATE-NeoBOMB1, a Phase I/IIa Study to Evaluate Safety, Pharmacokinetics, and Preliminary Imaging of (68)Ga-NeoBOMB1, a Gastrin-Releasing Peptide Receptor Antagonist, in GIST Patients." J Nucl Med, 2020;61(12):1749-1755. PMID: 32332143.
- [clinical-trial] Gruber L, et al. "Imaging Properties and Tumor Targeting of (68)Ga-NeoBOMB1, a Gastrin-Releasing Peptide Receptor Antagonist, in GIST Patients." Biomedicines, 2022;10(11). PMID: 36428467.
- [pubmed] Hulse DGE, et al. "In vivo gastrin releasing peptide receptor expression in SDH deficient wild-type gastrointestinal stromal tumours (GIST): potential for theranostic applications." EJNMMI Res, 2025;15(1):132. PMID: 41118055.
- [pubmed] Pretze M, et al. "GMP-compliant production of [(68)Ga]Ga-NeoB for positron emission tomography imaging of patients with gastrointestinal stromal tumor." EJNMMI Radiopharm Chem, 2021;6(1):22. PMID: 34228236.
- [pubmed] Nock BA, et al. "Theranostic Perspectives in Prostate Cancer with the Gastrin-Releasing Peptide Receptor Antagonist NeoBOMB1: Preclinical and First Clinical Results." J Nucl Med, 2017;58(1):75-80. PMID: 27493272.
- [pubmed] Dalm SU, et al. "68Ga/177Lu-NeoBOMB1, a Novel Radiolabeled GRPR Antagonist for Theranostic Use in Oncology." J Nucl Med, 2017;58(2):293-299. PMID: 27609789.
- [pubmed] Kaloudi A, et al. "NeoBOMB1, a GRPR-Antagonist for Breast Cancer Theragnostics: First Results of a Preclinical Study with [(67)Ga]NeoBOMB1 in T-47D Cells and Tumor-Bearing Mice." Molecules, 2017;22(11). PMID: 29137110.
- [pubmed] Montemagno C, et al. "In Vivo Biodistribution and Efficacy Evaluation of NeoB, a Radiotracer Targeted to GRPR, in Mice Bearing Gastrointestinal Stromal Tumor." Cancers (Basel), 2021;13(5). PMID: 33801382.
- [pubmed] Ruigrok EAM, et al. "Safety of [(177)Lu]Lu-NeoB treatment: a preclinical study characterizing absorbed dose and acute, early, and late organ toxicity." Eur J Nucl Med Mol Imaging, 2022;49(13):4440-4451. PMID: 35951084.
- [pubmed] Verhoeven M, et al. "The Balance Between the Therapeutic Efficacy and Safety of [(177)Lu]Lu-NeoB in a Preclinical Prostate Cancer Model." Mol Imaging Biol, 2024;26(1):114-123. PMID: 37640941.
- [pubmed] Damiana TST, et al. "Side-by-side comparison of the two widely studied GRPR radiotracers, radiolabeled NeoB and RM2, in a preclinical setting." Eur J Nucl Med Mol Imaging, 2023;50(13):3851-3861. PMID: 37584725.
- [pubmed] Rousseau E, et al. "Comparison of biological properties of [(177) Lu]Lu-ProBOMB1 and [(177) Lu]Lu-NeoBOMB1 for GRPR targeting." J Labelled Comp Radiopharm, 2020;63(2):56-64. PMID: 31715025.
- [pubmed] Verhoeven M, et al. "GRPR versus PSMA: expression profiles during prostate cancer progression demonstrate the added value of GRPR-targeting theranostic approaches." Front Oncol, 2023;13:1199432. PMID: 37719014.
- [review] Rahmati H, et al. "Radiolabeled-NeoB: A Dual-Action Diagnostic and Therapeutic Agent Targeting Gastrin-Releasing Peptide Receptors in Cancer." Curr Protein Pept Sci, 2026. PMID: 42152655.
- [registry] ClinicalTrials.gov API v2, read October 28, 2026: NCT03872778 (phase 1/2, lutetium-177 NeoB, completed); NCT05889728 (phase 2, gallium-68 NeoB breast cancer staging, completed); NCT05870579 (phase 1, with ribociclib and fulvestrant).
Sources & Citations
Studies were read from their PubMed records on October 29, 2026. Regulatory status comes from Drugs@FDA and the EMA medicines list (searched October 28, 2026) and trial listings from ClinicalTrials.gov. Grey Peptides sells nothing and links to no vendor.
Medical Disclaimer: This content is for educational and informational purposes only. It is not medical advice, and nothing here is an instruction to obtain or use any compound. Talk to a licensed clinician about your own situation.