Dalargin

A synthetic hexapeptide analog of Leu-enkephalin (Tyr-D-Ala-Gly-Phe-Leu-Arg) registered as an injectable anti-ulcer and pancreatitis drug in Russia, acting as a peripherally restricted opioid agonist that does not meaningfully cross the blood-brain barrier.

Also referenced as: Dalargine, Tyr-D-Ala-Gly-Phe-Leu-Arg, (D-Ala2)-Leu-Enkephalin-Arg, D-Ala2-Leu5-Arg6-enkephalin, Tageflar

Also appears in: Other

What is Dalargin?

Dalargin is a synthetic hexapeptide with the sequence Tyr-D-Ala-Gly-Phe-Leu-Arg, built from the natural pentapeptide Leu-enkephalin by two deliberate changes: the glycine at position 2 is replaced with D-alanine, and an arginine is appended at the C-terminus. The name encodes those two edits — D-Ala plus Arg. Both changes are functional rather than cosmetic: the D-configuration at position 2 confers resistance to peptidases and fixes the active folding of the molecule, and the C-terminal arginine turns out to be required for the tissue effects the compound is actually sold on.

It was developed in the Soviet Union in the 1980s and registered in Russia as a prescription injectable, classified for the treatment of peptic ulcer disease and pancreatitis. That is an unusual position for a research-market peptide: dalargin is not a compound that stalled in preclinical work, and it is not a compound that failed a Western trial. It is an approved drug in its home market — still supplied there by several manufacturers under their own brand names — that has never entered the United States regulatory system at all: no FDA approval, no DailyMed entry, and no US-based trial on record.

That gap is most of why it appears in research catalogs. The marketing story attached to it — cytoprotection, ulcer and pancreatic tissue repair, “stress protection” — comes from a clinical tradition written almost entirely in Russian, and the compound reaches Western buyers with the credential of foreign approval but none of the documentation that credential would normally carry here.

How it works

• Nonselective mu- and delta-opioid receptor agonism. In a systematic bioassay series across guinea-pig myenteric plexus and the vasa deferentia of four species — hamster, mouse, rat, and rabbit — dalargin behaved as a mu-preferring agonist with meaningful delta activity, and the study established which structural features carry that profile: an [L-Ala2] analog was 19 times less potent than dalargin and, unlike dalargin, was peptidase-sensitive (Pencheva et al., British Journal of Pharmacology, 1999;128(3):569–576). Take “nonselective” literally, because the corpus does not agree with itself on which receptor does the work: one group titles its cardiovascular paper around peripheral mu activation (Maslov et al., Eksperimental’naia i Klinicheskaia Farmakologiia, 2008;71(2):21–28, Russian), the isolated-heart work hypothesizes cardiac delta receptors (Lasukova et al., 2004), the chronotropic work points at peripheral kappa (Maslov et al., 2005), and the nephroprotection paper simply labels dalargin a δ-opioid agonist in its title (Plotnikov et al., 2013).
• Peripheral restriction — it is designed not to reach the brain. The 1998 nanoparticle paper states the situation plainly: dalargin does not normally penetrate the blood-brain barrier when given intravenously (Schroeder et al., Peptides, 1998;19(4):777–780). The landmark demonstration of the opposite case proves the rule — dalargin produced central analgesia in mice only when adsorbed onto polysorbate-80-coated poly(butyl cyanoacrylate) nanoparticles, with every control including a simple unbound mixture of the same three components showing no effect, and the analgesia prevented by naloxone pretreatment (Kreuter et al., Brain Research, 1995;674(1):171–174). A peripherally acting opioid is the entire design premise, not a limitation discovered later.
• Gastric mucosal effects run through nitric oxide and require the C-terminal arginine. In rat gastric mucosa, dalargin stimulated epithelial DNA synthesis and raised antiradical buffering capacity; the NO synthase inhibitor L-NAME abolished the DNA-synthesis effect, and the analog lacking arginine — [D-Ala2]-Leu-enkephalin — had little effect on either parameter (Zivotova et al., Bulletin of Experimental Biology and Medicine, 2007;144(3):314–316). The same group reproduced the split in an injury model: dalargin reduced erosive and ulcerative lesion area, normalized epithelial proliferation, and lowered oxidative stress in indomethacin-treated animals, while [D-Ala2]-Leu-enkephalin did not improve the mucosa at all (Zhivotova et al., Bulletin of Experimental Biology and Medicine, 2009;147(4):441–443). PubMed indexes this group under both “Zivotova” and “Zhivotova,” which matters when checking the two papers against each other.
• Antioxidant and kinase-signaling tissue protection. Against gentamicin nephrotoxicity, dalargin reduced renal tubular cell death and enhanced phosphorylation of glycogen synthase kinase 3β — the same nephroprotective pathway engaged by lithium ions in the comparator arm (Plotnikov et al., Toxicology Letters, 2013;220(3):303–308). In a separate stress model, dalargin blunted lipid peroxidation in plasma and erythrocytes during moderate hypothermia by reducing reactive oxygen species generation and maintaining low-molecular-weight antioxidants (Tadzhibova et al., Bulletin of Experimental Biology and Medicine, 2011;150(3):304–306).

Research status

Dalargin has roughly 380 PubMed records, which substantially overstates the therapeutic evidence behind it. The corpus splits into three groups that should be read very differently.

The Russian clinical tradition (1980s–2000s). The original clinical work on peptic ulcer was reported by the developing group in 1986 (Smagin et al., Bulletin of the All-Union Cardiology Research Center of the USSR Academy of Medical Sciences, 1986;9(2):63–65), followed by a gastroenterology review positioning it as the first enkephalin analog used in the field (Vinogradov & Polonskii, Terapevticheskii Arkhiv, 1988;60(8):147–153). The pancreatitis literature is similar in character — around 28 PubMed records for dalargin and pancreatitis, nearly all Russian- or Ukrainian-language clinical reports, such as dalargin in exacerbations of chronic pancreatitis (Geller et al., Terapevticheskii Arkhiv, 1992;64(8):80–82). Most of these records carry no English abstract, predate modern trial reporting standards, and have no Western replication. Rat pharmacokinetics were characterized in the same era, with the kinetic curve described as a three-exponential function following intravenous dosing (Kalenikova et al., Voprosy Meditsinskoi Khimii, 1988;34(1):75–83).

The drug-delivery methodology literature. A large share of dalargin’s English-language footprint is not about dalargin as a therapy at all — it is about dalargin as a convenient model cargo for blood-brain barrier delivery research, chosen precisely because it does not cross on its own and produces an easily measured analgesic readout when it does. That lineage runs from Kreuter et al. (1995) and Schroeder et al. (1998) through peptide-vector conjugation (Rousselle et al., Journal of Pharmacology and Experimental Therapeutics, 2003;306(1):371–376), self-emulsifying oral systems (Zupančič et al., Drug Development and Industrial Pharmacy, 2017;43(10):1694–1702), and chitosan-cyclodextrin nanoparticles (Migone et al., Pharmaceutics, 2020;13(1)). Counting these papers as evidence for dalargin’s clinical effects is a category error.

The negative cardiac results. The cardioprotection framing that often accompanies dalargin is the part the animal literature least supports. In isolated perfused rat heart, dalargin decreased contractility of the intact heart but had no effect on pump function of the ischemic myocardium — and des-Tyr-dalargin, which does not bind opioid receptors, decreased contractility as well, which the authors read as a non-opioid mechanism operating alongside dalargin’s own, hypothesized to run through cardiac delta receptors (Lasukova et al., Bulletin of Experimental Biology and Medicine, 2004;137(1):27–30). Chronic intraperitoneal administration at 1 mg/kg for 20 days had no effect on the incidence of ischemic ventricular arrhythmias or the size of the necrotic zone after coronary occlusion and reperfusion in rats — and neither did the selective kappa agonist, the nonselective antagonist, or naltrexone tested alongside it (Lishmanov et al., Bulletin of Experimental Biology and Medicine, 2008;145(6):696–699). Rate effects are real but mixed: intravenous dalargin produced bradycardia in anesthetized rats, abolished by naloxone, naloxone methiodide, and norbinaltorphimine alike and therefore attributed to cardiac kappa receptors, while some animals showed tachycardia instead — a reaction that disappeared under ganglionic blockade (Maslov et al., Bulletin of Experimental Biology and Medicine, 2005;140(6):682–686).

Registered trials. Two studies appear on ClinicalTrials.gov, both Phase 3, both conducted in Russia, and neither has posted results. NCT04346693 was an open, randomized, factorial study of Leitragin — a dalargin-based product — added to Russian Ministry of Health standard therapy either intramuscularly, by inhalation, or both, for prevention and treatment of pulmonary complications in severe and critical COVID-19; it was sponsored by the Burnasyan Federal Medical Biophysical Center, enrolled 320 participants, completed in November 2020, and has no results posted and no corresponding indexed publication. NCT07404358 is a randomized, quadruple-masked, placebo-controlled trial of perioperative intravenous dalargin — a 72-hour continuous infusion begun after induction of anesthesia — for prevention of postoperative organ dysfunction in high-risk abdominal surgery, sponsored by Botkin Hospital, with 200 participants enrolled; it is listed as active, not recruiting, with estimated completion in December 2026. This is the first well-controlled test of the compound’s core tissue-protection hypothesis, and its outcome is not yet known.

No regulatory authority outside Russia and neighboring post-Soviet registries has approved dalargin for any indication.

Common dosage forms

• Ampoules of lyophilized powder for injection, 1 mg per ampoule, in the Russian pharmaceutical presentation — reconstituted in 1 mL of sterile saline immediately before intravenous or intramuscular administration. Ready-made 1 mg/mL solution ampoules are also listed in Russian drug references. This is the unit dose the older clinical literature was built around, but it is not the only clinical format: the active Botkin Hospital trial uses a 30 mg lyophilized vial reconstituted into 300 mL of saline and delivered by infusion pump.
• Lyophilized powder in vials, most commonly 10 mg, in the research-compound market. The higher per-vial mass reflects research-market packaging conventions rather than the clinical unit dose.
• Electrophoresis, which appears repeatedly in the Russian clinical literature as a delivery route for gastric and duodenal ulcer work — endonasally in one series of giant and multiple duodenal ulcers (Buglak et al., Likars’ka Sprava, 2003;(8):102–103), and over the epigastric region for secondary ulcer prophylaxis (Lukash, Vrachebnoe Delo, 1991;(1):72–73). Do not collapse the two: they are different application sites in different papers. A nasal route has some early pharmacokinetic support — absolute bioavailability was put at 8% intranasally against 15% intramuscularly (Vinogradov et al., Biulleten’ Eksperimental’noi Biologii i Meditsiny, 1988;106(7):48–50) — but none of this has a counterpart in Western practice or an equivalent in the research market.
• Topical and local preparations, described in the Russian wound-healing and surgical literature, generally as compounded or investigational applications rather than a registered product form.
• Oral formats have no supporting basis. Dalargin is a hexapeptide degraded by gastric and intestinal proteases, and the entire oral-delivery research program — self-emulsifying systems, lipidized derivatives such as dalargin palmitate, hydrophobic ion pairing — exists because unaided oral administration does not work (Zupančič et al., 2017).

This section describes formats only and is not dosing guidance.

Key considerations

• Approved in one country is not approved here, and the paperwork does not travel. Dalargin is a registered prescription injectable in Russia, but it has no FDA approval, no DailyMed label, and no US clinical trial on record — queries against the FDA drug label and NDC endpoints and against DailyMed return nothing. The foreign approval is often used as a shorthand credential in the research market without the accompanying prescribing information, contraindications, or pharmacovigilance data that make an approval meaningful.
• The evidence base is language-siloed, old, and largely unverifiable from outside. The clinical core dates from the 1980s through the early 2000s, is written in Russian and Ukrainian, frequently carries no English abstract, and predates CONSORT-era reporting. Neither of the two registered Phase 3 trials has posted results: the COVID-19 study completed in 2020 with nothing published in the indexed literature, and the surgical study is not due to finish until December 2026. As of now, there is no modern, well-controlled, independently reported efficacy result for this compound in any indication.
• The cardioprotection claim runs against the cardiac data. Two independent results found dalargin ineffective where it would matter most — no effect on pump function of ischemic myocardium in isolated heart, and no reduction in arrhythmia incidence or necrotic zone size after chronic dosing in vivo. Tissue-protection marketing that generalizes from the gastric and renal models into cardiac protection is extending past what the literature shows.
• It is a real opioid agonist with a documented hemodynamic signal. The Russian prescribing information lists reduced blood pressure and allergic reactions among adverse effects and names arterial hypotension as a contraindication, alongside acute infectious processes, pregnancy, breastfeeding, and use under 18. Animal work shows bradycardia in anesthetized rats, with tachycardia in some animals, and reduced contractility of the intact heart. Peripheral restriction limits central opioid effects but is a design property, not a safety guarantee, and no Western pharmacovigilance dataset exists for this compound.
• Several near-neighbors are routinely confused with it. [D-Ala2]-Leu-enkephalin — dalargin minus the C-terminal arginine — is not interchangeable, and failed to reproduce dalargin’s gastric effects in both of the studies that tested them side by side. Note that the abbreviation “DALA” in the opioid literature refers to a different compound again, [D-Ala2]-Met-enkephalinamide, and should not be attached to either. DADLE ([D-Ala2, D-Leu5]-enkephalin) is a different, more widely studied delta-selective peptide. des-Tyr-dalargin does not bind opioid receptors at all. Chemical databases index dalargin under dynorphin and beta-neoendorphin fragment names as well — the Tyr-Gly-Gly-Phe-Leu-Arg backbone is the 1–6 stretch of both — and it is marketed in Russia under multiple manufacturer-specific names, so identity should be confirmed by sequence rather than by label.