Edotreotide

What is Edotreotide?

Edotreotide is a somatostatin analog built for one purpose: delivering a radioactive metal atom to cells that display somatostatin receptor subtype 2. It is not a therapeutic peptide in the usual sense — nobody takes edotreotide for its own pharmacology. It is a targeting vehicle. Chemically it is octreotide with two changes. The phenylalanine at position 3 is replaced by tyrosine, and the macrocyclic chelator DOTA is attached to the N-terminal D-phenylalanine through an amide bond formed from one of DOTA's four acetic-acid arms. The remaining three arms cage a radiometal — gallium-68 for imaging, lutetium-177 or yttrium-90 for therapy. Because the chelator sits at the N-terminus, the pharmacophore that actually binds the receptor (D-Trp-Lys-Thr, held in a disulfide-constrained ring) is untouched. Molecular formula C65H92N14O18S2, molecular weight 1421.6, CAS 204318-14-9. The distinction people most often get wrong is edotreotide versus dotatate. Both are DOTA-conjugated, Tyr3-substituted octreotide derivatives, and they differ at exactly one position: edotreotide ends in threoninol, a reduced amino-alcohol, while dotatate ends in threonine with a free carboxylic acid. The formula difference is minus two hydrogens, plus one oxygen. That single oxidation raises SSTR2 affinity roughly twelve-fold when gallium-labelled — Ga-DOTATATE has an sst2 IC50 around 0.2 nM against Ga-DOTATOC's 2.5 nM. Edotreotide compensates with broader subtype coverage, retaining measurable sst3 and sst5 affinity where Ga-DOTATATE is near-exclusively sst2-selective, and intrapatient imaging comparisons have found no clinically significant difference between the two tracers. As a diagnostic, Ga 68 DOTATOC Injection was FDA-approved on 21 August 2019 for localising somatostatin-receptor-positive neuroendocrine tumours by PET in adults and children — unusually, under an academic NDA held by the University of Iowa's PET Imaging Center rather than by a pharmaceutical company. As a therapeutic, 177Lu-edotreotide (ITM-11, from ITM Isotope Technologies Munich) met its primary endpoint in the Phase 3 COMPETE trial, published in the Lancet in July 2026, but the FDA issued a complete response letter on 7 August 2026 citing chemistry, manufacturing, and controls plus third-party facility items — explicitly not clinical or safety concerns.

What Edotreotide Is Investigated For

Edotreotide's clinical value comes in two forms that share a targeting peptide and differ in what is attached to it. The diagnostic form, 68Ga-DOTATOC, has been FDA-approved since 21 August 2019 for PET localisation of somatostatin-receptor-positive neuroendocrine tumours in adults and children, at 4 mCi intravenously in adults or 0.043 mCi/kg in children. Its approval history is a genuine curiosity: the NDA was held by the University of Iowa Health Care PET Imaging Center rather than a company, one of very few academic NDAs, and the product has no proprietary name — it is labelled simply Ga 68 DOTATOC Injection. In Europe the same active substance is marketed as SomaKit TOC, authorised December 2016. The therapeutic form is 177Lu-edotreotide, developed as ITM-11. The pivotal evidence is COMPETE (NCT03049189), published by Walter and colleagues in the Lancet in July 2026: a prospective, randomised, open-label, multicentre superiority trial that randomised 309 patients with unresectable or metastatic, progressive, grade 1 or 2 somatostatin-receptor-positive gastroenteropancreatic neuroendocrine tumours 2:1 to 177Lu-edotreotide at 7.5 GBq every three months for up to four cycles, or oral everolimus 10 mg daily for up to 30 months, across 49 centres in 14 countries. Median progression-free survival by blinded independent central review was 23.9 months versus 14.1 months, with a stratified hazard ratio of 0.67 (95% CI 0.48–0.95, p=0.022) and objective response rates of 22% versus 4%. The tolerability comparison favoured the radiopharmaceutical: grade 3–4 treatment-related adverse events occurred in 18% on 177Lu-edotreotide against 40% on everolimus, with no treatment-related deaths in either arm. Overall survival data are immature. A companion Phase 3, COMPOSE (NCT04919226, 259 patients enrolled), is testing 177Lu-edotreotide against best standard of care — physician's choice of CAPTEM, FOLFOX, or everolimus — in aggressive well-differentiated grade 2 and grade 3 disease, with estimated completion in late 2027. The honest caveats are regulatory and comparative rather than clinical. The FDA accepted the NDA with a PDUFA date of 28 August 2026 but issued a complete response letter on 7 August 2026, citing chemistry, manufacturing, and controls and third-party commercial facility items while stating explicitly that it identified no concerns with the clinical or nonclinical data package or the safety profile. ITM intends to resubmit, and as of this writing has not announced doing so. Comparatively, Novartis's Lutathera (177Lu-dotatate) has been approved since January 2018 and has both NETTER-1 and the first-line NETTER-2 trial behind it, so 177Lu-edotreotide would enter a market with an established incumbent and no head-to-head data against it.

History & Discovery

The idea behind edotreotide is older than the molecule and simpler than it sounds: if tumour cells display an unusual number of a particular receptor, a ligand for that receptor becomes a delivery address. Somatostatin was characterised in the 1970s and its receptors were found to be heavily overexpressed on well-differentiated neuroendocrine tumours. Native somatostatin was useless as a targeting agent — cleared within minutes — but octreotide, developed at Sandoz and approved in 1988, was a stable cyclic octapeptide analog with sst2 preference. Through the late 1980s and 1990s, radiolabelled octreotide derivatives were developed for imaging, beginning with 111In-pentetreotide (OctreoScan). The therapeutic ambition followed naturally: if a peptide could carry a gamma emitter for imaging, it could carry a beta emitter for treatment. DOTA-TOC emerged from this effort as octreotide with Tyr3 substituted for Phe3 and the macrocyclic chelator DOTA conjugated to the N-terminus, giving a molecule that could stably hold trivalent radiometals — 111In, 90Y, 177Lu, or 68Ga — without disturbing receptor binding. Reubi and colleagues published the definitive comparative affinity panel in 2000, quantifying DOTA-TOC against DOTA-TATE and establishing the trade-off between DOTA-TATE's roughly twelve-fold higher sst2 affinity and DOTA-TOC's broader subtype coverage. The renal-toxicity problem that limited early dosing was solved in parallel: Bernard and colleagues showed in 1997 that D-lysine blocked renal reabsorption, and Rolleman and colleagues refined this into the lysine-plus-arginine co-infusion that remains standard. The diagnostic application reached approval by an unusual route. Ga 68 DOTATOC Injection was FDA-approved on 21 August 2019 under NDA 210828 — held not by a pharmaceutical company but by the University of Iowa Health Care PET Imaging Center, one of very few academic NDAs, described by Sunderland and Graham in J Nucl Med the following year. The product has no proprietary name. In Europe the same active substance had already been authorised as SomaKit TOC in December 2016. On the therapeutic side, Novartis got there first with a different peptide. Lutathera (177Lu-dotatate) was FDA-approved on 26 January 2018 on the strength of NETTER-1, becoming the first approved peptide receptor radionuclide therapy, with the indication later expanded to patients 12 and older in April 2024 and the first-line NETTER-2 trial reported in 2024. ITM Isotope Technologies Munich pursued the edotreotide route, differentiating on non-carrier-added lutetium-177 manufacturing. Its COMPETE trial (NCT03049189) enrolled from April 2017 to June 2022 and made a deliberately harder comparison than NETTER-1 had: rather than testing against high-dose octreotide, it randomised patients against everolimus, an active targeted agent. Topline results were presented at ENETS in Kraków in March 2025 and published in the Lancet in July 2026 — median progression-free survival 23.9 versus 14.1 months, hazard ratio 0.67, with markedly better tolerability than everolimus. A companion trial, COMPOSE, took the agent into aggressive grade 2 and grade 3 disease against physician's-choice standard of care, and the LEVEL study extended the everolimus comparison into lung and thymic neuroendocrine tumours. The regulatory endgame has been the frustrating part. The FDA accepted ITM's NDA with a PDUFA goal date of 28 August 2026, announced in November 2025. Then on 7 August 2026 — three weeks before that date — the agency issued a complete response letter citing chemistry, manufacturing, and controls items and third-party commercial facility items, while stating explicitly that it had identified no concerns with the clinical or nonclinical data package or the safety profile. ITM's chief executive said the company's confidence in the therapeutic potential had not wavered and that it intends to resubmit. For a drug with a positive Phase 3 and a favourable safety comparison against the incumbent alternative, being held up by manufacturing paperwork is an unusually clean kind of setback — but as of this writing 177Lu-edotreotide remains unapproved, and no resubmission has been announced.

How It Works

Neuroendocrine tumours tend to cover themselves in receptors for a hormone called somatostatin — far more of them than normal tissue carries. That makes those receptors a handle. Edotreotide is a lab-modified copy of octreotide, a somatostatin lookalike, with a molecular cage welded onto one end. The cage grips a radioactive metal atom. Inject the whole assembly and it circulates until the peptide half finds a somatostatin receptor on a tumour cell, latches on, and gets pulled inside — carrying the radioactive atom with it. Load the cage with gallium-68, which gives off signal a PET scanner can see, and you get a picture of every tumour deposit in the body. Load it with lutetium-177, which emits tissue-damaging radiation over a short range, and the same delivery system becomes a treatment that irradiates tumour cells from the inside while largely sparing everything else.

Edotreotide is DOTA-TOC: DOTA-D-Phe1-Cys2-Tyr3-D-Trp4-Lys5-Thr6-Cys7-threoninol8, cyclised through a Cys2–Cys7 disulfide bridge. It derives from octreotide by two modifications. First, Phe3 is replaced by Tyr3, which increases hydrophilicity and alters receptor subtype affinity. Second, the macrocyclic chelator DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) is conjugated to the free alpha-amino group of the N-terminal D-phenylalanine via an amide bond formed from one of DOTA's four carboxymethyl arms. The remaining three arms coordinate a trivalent radiometal — 68Ga3+, 177Lu3+, 90Y3+, or 111In3+. Because conjugation occurs at the N-terminus and the chelator is remote from the disulfide-constrained pharmacophore (D-Trp4-Lys5-Thr6), receptor binding is preserved. The target is somatostatin receptor subtype 2 (SSTR2), a Gi-coupled class A GPCR overexpressed on well-differentiated neuroendocrine tumour cells, often at densities far above surrounding tissue. Native somatostatin binds all five subtypes with roughly comparable affinity and is cleared within minutes; octreotide and its analogs were engineered for sst2 preference and proteolytic stability. Reubi and colleagues established the canonical affinity panel in 2000: Ga-DOTA-TOC has an sst2 IC50 of 2.5 nM, Ga-DOTA-TATE 0.2 nM, Y-DOTA-TATE 1.6 nM. DOTA-TOC retains measurable sst3 and sst5 affinity, while Ga-DOTA-TATE is near-exclusively sst2-selective — the practical trade-off between the two agents. Note that affinity is metal-dependent: the coordination geometry of the metal-DOTA complex measurably shifts binding even though it sits away from the pharmacophore, which is why the same peptide labelled with different radiometals is not pharmacologically interchangeable. On binding, the receptor-ligand complex is internalised by endocytosis and the radiometal is retained intracellularly, largely in lysosomes, because the chelated metal cannot readily diffuse back out. This trapping is what produces the tumour-to-background ratio that makes the approach work. For imaging, 68Ga (half-life 68 minutes, positron emitter) provides PET signal. For therapy, 177Lu (half-life 6.6 days) emits beta particles with a mean tissue range of roughly 0.7 mm plus imageable gamma photons, delivering cytotoxic radiation across a few cell diameters — enough to kill the target cell and its immediate neighbours through DNA double-strand breaks while limiting damage further afield. 90Y emits higher-energy beta particles with a longer range, useful for bulkier lesions but with a wider damage radius. The dose-limiting organ is the kidney, and for a mechanistic reason. Radiolabelled somatostatin analogs are freely filtered at the glomerulus and then reabsorbed by the proximal tubule via megalin- and cubilin-mediated endocytosis, concentrating the radiometal in the renal cortex. Co-infusion of cationic amino acids — L-lysine and L-arginine — competitively inhibits that reabsorption, an approach established by Bernard and colleagues with D-lysine in 1997 and refined into the lysine-plus-arginine combination by Rolleman and colleagues in 2003. Bone marrow is the second dose-limited compartment, which underlies both the acute myelosuppression and the long-latency risk of secondary myelodysplastic syndrome and acute leukemia arising from radiation damage to haematopoietic stem cells.

Evidence Snapshot

Research Gaps & Open Questions

What the current literature has not yet settled about Edotreotide:

• 01Overall survival from COMPETE — immature at publication, with ITM stating patients will be followed up to five years post-study. Progression-free survival is a meaningful endpoint but the survival question is what will determine positioning against everolimus in practice.
• 02Whether the August 2026 complete response letter is quickly remediable. The FDA identified no clinical or safety concerns, but the specifics of the CMC and third-party facility findings have not been disclosed and no resubmission has been announced.
• 03Head-to-head comparison against 177Lu-dotatate (Lutathera) — none exists and none is planned. COMPETE used everolimus as its comparator while NETTER-1 used high-dose octreotide, so the two agents have never been tested against each other and cross-trial ranking is not legitimate.
• 04COMPOSE results — the Phase 3 in aggressive well-differentiated grade 2 and grade 3 disease against physician's-choice standard of care (CAPTEM, FOLFOX, or everolimus), with estimated completion in late 2027, is where 177Lu-edotreotide would meet NETTER-2's first-line indication most directly.
• 05Whether DOTA-TOC's broader sst3 and sst5 coverage confers any clinical advantage over DOTA-TATE's higher sst2 selectivity. The receptor-binding difference is well characterised; a corresponding clinical difference has never been demonstrated, and intrapatient imaging comparisons found none.
• 06Optimal sequencing and retreatment — where peptide receptor radionuclide therapy belongs relative to somatostatin analogs, everolimus, chemotherapy, and surgical options, and whether retreatment after progression is safe and effective, remain unsettled across the whole class rather than for edotreotide specifically.
• 07Long-term secondary-malignancy risk for 177Lu-edotreotide specifically. The 2.3% myelodysplastic syndrome rate comes from NETTER-1's 177Lu-dotatate arm; given identical radionuclide and comparable dosimetry the class risk almost certainly applies, but it has not been separately quantified.
• 08Lung and thymic neuroendocrine tumours — the LEVEL trial extends the everolimus comparison to this population but has not reported.
• 09Alpha-emitter alternatives — whether targeted alpha therapy using the same peptide scaffolds improves the therapeutic index over beta emitters is an active question that could reshape the field.

Forms & Administration

Edotreotide is never given unlabelled — it is always administered as a radiometal complex prepared in a radiopharmacy shortly before use, and the two clinical forms are entirely different procedures. For imaging, Ga 68 DOTATOC Injection is given as a single intravenous bolus, 4 mCi (148 MBq) in adults and 0.043 mCi/kg (1.59 MBq/kg) in paediatric patients, with PET acquisition beginning after an uptake interval; the EU equivalent is SomaKit TOC. For therapy, the COMPETE trial administered 177Lu-edotreotide at 7.5 GBq (± 0.7) every three months for a maximum of four cycles, always with concomitant amino acid co-infusion for renal protection. By comparison, the approved 177Lu-dotatate regimen (Lutathera) is 7.4 GBq every eight weeks for four doses, with long-acting octreotide 30 mg intramuscularly given 4 to 24 hours after each dose. Therapeutic administration requires a licensed nuclear medicine facility with radiation-safety infrastructure, dosimetry capability, and the ability to run a multi-hour amino acid infusion beginning 30 minutes before the radiopharmaceutical and continuing at least three hours after. Patients remain radioactive after treatment, with radiation detectable in urine for up to 30 days, and require radiation-precaution counselling. There is no oral, subcutaneous, or outpatient self-administered form, and no context in which edotreotide belongs in a wellness or research-chemical setting.

Common Questions

Who Edotreotide Is NOT For

Drug & Supplement Interactions

Edotreotide's interaction profile is unusual because the clinically important interactions concern the targeting step and the protection regimen rather than metabolism. The peptide is not appreciably metabolised by hepatic cytochrome P450 enzymes, so conventional CYP-mediated interactions are not a consideration. The interaction that most affects efficacy is with unlabelled somatostatin analogs. Long-acting octreotide and lanreotide occupy the same receptor the radiopharmaceutical needs to bind, so concurrent administration can competitively reduce tumour uptake. Clinical protocols therefore time long-acting somatostatin analog dosing around radiopharmaceutical administration — the Lutathera label, for instance, specifies giving long-acting octreotide 30 mg intramuscularly 4 to 24 hours after each therapeutic dose rather than before it, and short-acting octreotide is typically withheld for around 24 hours beforehand. Getting this sequence wrong can compromise the treatment. The amino acid co-infusion interacts with the therapy by design: L-lysine and L-arginine competitively inhibit proximal tubular reabsorption of the radiopeptide, reducing renal radiation dose. The critical operational point from the label is that the amino acid dose must not be reduced when the radiopharmaceutical dose is reduced, because renal protection is not proportional to therapeutic dose. Nephrotoxic agents compound the principal organ risk. Concurrent or recent aminoglycosides, amphotericin B, cisplatin, high-dose NSAIDs, or iodinated contrast raise the stakes on a therapy whose dose-limiting organ is the kidney. Myelosuppressive chemotherapy and prior extensive external-beam radiotherapy similarly compound haematological toxicity and, plausibly, secondary-malignancy risk. Corticosteroids deserve specific mention because they can downregulate somatostatin receptor expression, potentially reducing tumour uptake — relevant since corticosteroids are also used to manage hormonal crisis and infusion reactions. And because these tumours are hormonally active, agents that provoke mediator release should be used cautiously around treatment given the risk of neuroendocrine hormonal crisis. All concomitant medication should be reviewed by the nuclear medicine and oncology teams before each cycle.

Safety Profile

Legal Status

Regulatory status changes over time. Verify current local rules with a qualified professional.

Myths & Misconceptions