RM2
A gallium-68 scan agent that finds prostate and breast cancers through the gastrin-releasing peptide receptor
RM2 is a short synthetic peptide built to stick to the gastrin-releasing peptide receptor, which many prostate cancers and oestrogen-receptor-positive breast cancers carry. With radioactive gallium-68 attached it shows those cancers on a PET scan, sometimes ones that the more common PSMA scan misses. It has reached a phase 2/3 trial but is not approved anywhere. It is a hospital imaging agent, not something anyone can buy.
Used in human trials: 138 MBq (mean), Single injection, Intravenous (Gallium-68 RM2, healthy volunteers (5 men)) 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?
A radioligand is a targeting molecule with a radioactive atom attached. Injected into a vein, it travels to cells that carry its target, and a positron emission tomography (PET) camera picks up the radiation and shows where it has gathered. The amount of drug is tiny; what matters is where the radiation ends up. RM2 is such a tracer for the gastrin-releasing peptide receptor (GRPR), a receptor for the frog-skin peptide bombesin and its human relative, gastrin-releasing peptide.
RM2 is a modified fragment of bombesin. Its sequence was altered near the end, where a statine residue replaces part of the natural chain, so that it binds the receptor without switching it on; that makes it an antagonist. A DOTA cage at the front holds the gallium-68. The gallium-68 form also carries the development code BAY 86-7548, and the first five healthy men to receive it in 2013 tolerated it well; the tracer was broken down quickly in blood, with only about a fifth still intact after an hour, and most of the radiation dose went to the bladder wall and pancreas.
Prostate cancer is where it has been studied most. Low-grade prostate cancers often carry plenty of GRPR, while PSMA, the target of today's standard prostate PET scans, rises with grade. In men having surgery for newly found cancer, RM2 PET found 93% of the tumours later seen under the microscope and performed about as well as PSMA-11 PET; in a 22-man phase 2 study it detected more of the lower-grade lesions than PSMA-617 PET, while PSMA picked out the aggressive ones better. Several groups therefore see the two scans as complementary rather than rivals.
In men whose PSA has risen after treatment with nothing seen on CT, MRI or bone scan, Stanford's single-arm phase 2/3 trial of 100 men found RM2 PET-MRI positive in 69% against 40% for MRI alone. When both scans were done in the same patients, though, PSMA PET usually found more: in 50 men it picked up 36 lesions that RM2 missed, against 7 the other way, a 2024 Italian phase 2 trial found RM2 PET less sensitive than PSMA-11 PET (61% against 84%), and a German group found no PSMA-negative man in whom RM2 showed disease. It is a second option for PSMA-negative disease, not a replacement.
Breast cancer is the second use. GRPR is common in oestrogen-receptor-positive breast cancers, and in 15 women the tumours that lit up on RM2 PET were all oestrogen-receptor-positive; a 2024 meta-analysis found it detected 93% of ER-positive lesions. The same peptide has also been labelled with lutetium-177 as a treatment, with tumour doses judged worthwhile in four men, but the pancreas, which normally takes up the tracer strongly, receives the highest normal-organ dose.
RM2 is not approved by FDA or any other regulator checked, and the European Medicines Agency has no record of it. It is made in hospital radiopharmacies for scans within studies. There is no reason or way for anyone to obtain it outside that setting.
Mechanism of Action
RM2 binds the gastrin-releasing peptide receptor without activating it, and carries gallium-68 so that receptor-rich cancers show on PET.
GRPR antagonism
A bombesin-like peptide altered at its end so it occupies the receptor without switching it on (2016 pilot study).
Positron imaging
Its DOTA chelator holds gallium-68, whose positrons a PET scanner detects about 40 to 70 minutes after injection.
A different target from PSMA
GRPR expression in prostate cancer was independent of PSMA expression, so RM2 can show lesions a PSMA scan does not (2019 study).
Normal uptake and clearance
The pancreas, which carries GRPR, takes up the most; the tracer leaves through the kidneys into the bladder (atlas of 95 patients).
Published Research
Studies that gave gallium-68 RM2 (also called BAY 86-7548) or lutetium-177 RM2 to people, read from their PubMed abstracts. Modified successors such as AMTG and NeoB are different molecules and are not carded here.
First-in-human safety and dosimetry
Five healthy men received about 138 MBq. The tracer was well tolerated and broke down fast (92% intact at 1 minute, 19% at 65 minutes); the bladder wall and pancreas received the most radiation and the effective dose was 0.051 mSv per MBq, about 7.7 mSv for 150 MBq, less with frequent voiding.
First prostate cancer patients
In 14 men, 11 before prostatectomy, PET with BAY 86-7548 found primary prostate cancer with 88% sensitivity and 81% specificity against histology and 70% sensitivity for lymph node metastases; it missed bone metastases in one man with hormone-refractory disease.
Pilot comparison with PSMA-11
Seven men with rising PSA had both scans. RM2 collected mostly in the pancreas while PSMA-11 collected in salivary glands and bowel; abnormal uptake did not differ overall, PSMA-11 found a node and seminal vesicle lesion RM2 missed, and RM2 showed abdominal nodes more clearly because of less bowel activity.
Recurrence with negative standard scans
In 32 men with rising PSA and negative CT, MRI and bone scans, RM2 PET/MRI (mean 141 MBq) found recurrent cancer in 23 (72%), against 11 on the simultaneous MRI. PET-positive men had faster-rising PSA.
Phase 2/3 trial against MRI
Stanford's single-arm trial in 100 men with biochemical recurrence and negative conventional imaging met its primary endpoint: RM2 PET-MRI was positive in 69% against 40% for MRI alone, with 143 against 96 lesions found. No adverse events of grade 1 or worse were reported.
PSMA-positive and PSMA-negative men
Sixteen men had RM2 PET after a recent PSMA-11 PET. None of the eight PSMA-negative men showed abnormal RM2 uptake; in the eight PSMA-positive men RM2 found fewer bone and node metastases, missed liver metastases in one, and its two extra bone lesions changed nothing. The authors saw no added clinical benefit.
Phase 2 PET/MRI in recurrence
In 44 men followed for a median 23 months, RM2 PET alone was less sensitive than PSMA-11 PET and MRI (61% against 84% and 87%), with similar specificity; combined with MRI, RM2 reached 94% sensitivity.
Newly diagnosed prostate cancer
In 16 men before prostatectomy, RM2 PET/CT and multiparametric MRI performed similarly against whole-mount pathology, and fusing them gave the best sensitivity (85%) and accuracy (84%). GRPR expression did not correlate with PSMA expression or Gleason score.
Against post-surgery pathology
In 41 men with intermediate- or high-risk cancer given 118 to 248 MBq, RM2 PET found 50 of 54 tumours confirmed at surgery (93%), with sensitivity and accuracy similar to PSMA-11 PET and better than MRI; specificity was lower than MRI's.
Phase 2 comparison with PSMA-617 PET
In 22 men before prostatectomy, RM2 detected 78% of lesions and PSMA-617 74%; 19% of lesions were seen by only one tracer. PSMA uptake rose with tumour grade, RM2 uptake did not, and RM2 uptake was higher in grade group 2 tumours.
Atlas of normal uptake
Across 95 men, the bladder (from excretion) and pancreas (average SUVmax about 65) showed the most uptake; brain, salivary glands, lungs, heart, bone and muscle showed almost none, which helps readers tell normal from abnormal uptake.
Breast cancer staging
In 15 women with primary breast cancer, 13 of 18 tumours took up RM2 strongly; all of them were oestrogen- and progesterone-receptor-positive, and only oestrogen receptor status predicted uptake. The scan also found internal mammary nodes and an unsuspected bone metastasis.
Meta-analysis in ER-positive breast cancer
Four eligible studies were pooled: RM2 PET/CT detected 93% of oestrogen-receptor-positive breast cancer lesions, and their uptake values were well above those of ER-negative lesions (weighted mean difference 10.6) and of normal breast.
Lutetium-177 RM2 as treatment
Four men with castration-resistant prostate cancer and too little PSMA received a mean 4.5 GBq of lutetium-177 RM2 with no side effects observed. Tumours received about 6.2 Gy per GBq; the pancreas (1.08 Gy per GBq) was the organ most exposed.
Dosing Data
RM2 has no approved label. The rows below are the activities of radioactivity injected in the published human studies carded above, given once before a scan (gallium-68) or as a treatment cycle (lutetium-177).
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 RM2 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: RM2 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: “RM2 is dosed by radioactivity and labelled in a hospital radiopharmacy shortly before the scan; no reconstitution maths applies.”
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 RM2 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 (Single injection; Gallium-68 RM2, healthy volunteers (5 men)).
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: not established by a measurement cited on this entry.
How long the doses were given: Gallium-68 RM2, healthy volunteers (5 men): PET over about 2 hours; Gallium-68 RM2, recurrent prostate cancer (32 men): Imaging 40-69 minutes later; Gallium-68 RM2, before prostatectomy (41 men): Imaging 42-72 minutes later.
When effects appear: unknown; no source on this page gives a time to effect for RM2. Results reported in the studies are under Published Research.
Source: 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: Radiation exposure: about 7.7 mSv for a 150 MBq scan, less with frequent bladder emptying; No adverse events of grade 1 or worse in the 100-man phase 2/3 trial; No side effects observed in four men given lutetium-177 RM2, though the pancreas received the highest organ dose. Full list and cautions ↓
When to stop or get help: unknown; no label or trial on file sets rules for stopping RM2. Treat a severe or unexpected reaction as a reason to stop and see a doctor.
Source: the Side Effects section below (“From the studies above, which report few effects from the tracer itself”).
Interactions
Unknown: a PubMed search for human interaction studies of RM2 (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 RM2 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; it checks the measured mass against RM2's expected mass, 1,704.8 Da, from this entry's molecular data. Trust & Verification explains what independent testing can and cannot show.
Legal status
US: In Clinical Trials (Not approved: no Drugs@FDA record (openFDA, searched October 29, 2026) and none in the EMA medicines list). 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 studies above, which report few effects from the tracer itself.
Contraindications & Cautions
No approved label exists, so there are no official contraindications. Points from the studies above:
Legal Status
RM2 is investigational in every jurisdiction checked.
Frequently Asked Questions
?What is an RM2 PET scan?
A scan after an injection of RM2 carrying radioactive gallium-68. RM2 binds the gastrin-releasing peptide receptor, which many prostate and ER-positive breast cancers carry, and the PET camera shows where it has collected.
?Is it better than a PSMA scan?
Usually not on its own. In studies where men had both, PSMA PET found more recurrent disease. RM2 tends to do better on low-grade prostate tumours, which carry less PSMA, so the two can complement each other.
?Is RM2 approved?
No. It has been through phase 2 and phase 2/3 studies, but no regulator has approved it.
?Does it help when a PSMA scan is negative?
Sometimes. In 32 men with rising PSA and negative standard scans it found recurrence in 23, but a German group that scanned eight PSMA-negative men with RM2 found disease in none of them.
?Can I buy it?
No. It is a radioactive tracer made in hospital radiopharmacies for scans within studies, and it has no use outside imaging or experimental therapy.
References
- [other] PubChem CID 72722205 (synonyms 68Ga-RM2, BAY-86-7548): formula C78H115GaN20O19, molecular weight 1704.8 (the gallium-68 complex). Read October 28, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/72722205
- [registry] ClinicalTrials.gov API v2, read October 28, 2026: NCT02624518 (phase 2/3, biochemical recurrence, complete); NCT03606837 (phase 2, against gallium-68 PSMA-617, completed); NCT03831711 (phase 1/2, ER-positive breast cancer, completed).
- [other] US FDA, Drugs@FDA (openFDA): no application for RM2. European Medicines Agency medicines list: no record. Searched October 29, 2026.
- [clinical-trial] Roivainen A, et al. "Plasma pharmacokinetics, whole-body distribution, metabolism, and radiation dosimetry of 68Ga bombesin antagonist BAY 86-7548 in healthy men." J Nucl Med, 2013;54(6):867-72. PMID: 23564761.
- [pubmed] Kähkönen E, et al. "In vivo imaging of prostate cancer using [68Ga]-labeled bombesin analog BAY86-7548." Clin Cancer Res, 2013;19(19):5434-43. PMID: 23935037.
- [clinical-trial] Minamimoto R, et al. "Pilot Comparison of ⁶⁸Ga-RM2 PET and ⁶⁸Ga-PSMA-11 PET in Patients with Biochemically Recurrent Prostate Cancer." J Nucl Med, 2016;57(4):557-62. PMID: 26659347.
- [pubmed] Minamimoto R, et al. "Prospective Evaluation of (68)Ga-RM2 PET/MRI in Patients with Biochemical Recurrence of Prostate Cancer and Negative Findings on Conventional Imaging." J Nucl Med, 2018;59(5):803-808. PMID: 29084827.
- [clinical-trial] Duan H, et al. "(68)Ga-RM2 PET-MRI versus MRI alone for evaluation of patients with biochemical recurrence of prostate cancer: a single-centre, single-arm, phase 2/3 imaging trial." Lancet Oncol, 2024;25(4):501-508. PMID: 38423030.
- [pubmed] Hoberück S, et al. "68Ga-RM2 PET in PSMA- positive and -negative prostate cancer patients." Nuklearmedizin, 2019;58(5):352-362. PMID: 31443113.
- [clinical-trial] Ghezzo S, et al. "Diagnostic accuracy of fully hybrid [(68)Ga]Ga-PSMA-11 PET/MRI and [(68)Ga]Ga-RM2 PET/MRI in patients with biochemically recurrent prostate cancer: a prospective single-center phase II clinical trial." Eur J Nucl Med Mol Imaging, 2024;51(3):907-918. PMID: 37897615.
- [clinical-trial] Touijer KA, et al. "Prospective Study of the Radiolabeled GRPR Antagonist BAY86-7548 for Positron Emission Tomography/Computed Tomography Imaging of Newly Diagnosed Prostate Cancer." Eur Urol Oncol, 2019;2(2):166-173. PMID: 31017093.
- [pubmed] Duan H, et al. "Correlation of (68)Ga-RM2 PET with Postsurgery Histopathology Findings in Patients with Newly Diagnosed Intermediate- or High-Risk Prostate Cancer." J Nucl Med, 2022;63(12):1829-1835. PMID: 35552245.
- [clinical-trial] Schollhammer R, et al. "Comparison of (68)Ga-PSMA-617 PET/CT and (68)Ga-RM2 PET/CT in Patients with Localized Prostate Cancer Who Are Candidates for Radical Prostatectomy: A Prospective, Single-Arm, Single-Center, Phase II Study." J Nucl Med, 2023;64(3):379-385. PMID: 36215569.
- [pubmed] Baratto L, et al. "Physiological (68)Ga-RM2 uptake in patients with biochemically recurrent prostate cancer: an atlas of semi-quantitative measurements." Eur J Nucl Med Mol Imaging, 2020;47(1):115-122. PMID: 31478089.
- [pubmed] Stoykow C, et al. "Gastrin-releasing Peptide Receptor Imaging in Breast Cancer Using the Receptor Antagonist (68)Ga-RM2 And PET." Theranostics, 2016;6(10):1641-50. PMID: 27446498.
- [review] Al-Ibraheem A, et al. "PET/CT Assessment of Estrogen Receptor positivity for Breast Cancer using [(68)Ga]Ga-RM2 Bombesin Receptor Antagonist: A Systematic Review and Meta-Analysis." Semin Nucl Med, 2024;54(6):896-903. PMID: 39370376.
- [pubmed] Kurth J, et al. "First-in-human dosimetry of gastrin-releasing peptide receptor antagonist [(177)Lu]Lu-RM2: a radiopharmaceutical for the treatment of metastatic castration-resistant prostate cancer." Eur J Nucl Med Mol Imaging, 2020;47(1):123-135. PMID: 31482426.
- [pubmed] Baratto L, et al. "PSMA- and GRPR-Targeted PET: Results from 50 Patients with Biochemically Recurrent Prostate Cancer." J Nucl Med, 2021;62(11):1545-1549. PMID: 33674398.
Sources & Citations
Studies were read from their PubMed abstracts on October 29, 2026; regulatory status from Drugs@FDA (openFDA) and the EMA medicines list. The formula is PubChem's (gallium complex).
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.