Cognitive & Neuroprotection

Met-Enkephalin

Met-enkephalin leads a double life. It is one of the body's two enkephalins, a five-amino-acid opioid released to damp pain — and under a second name, opioid growth factor, it binds a receptor inside the cell nucleus and raises p16 and p21, slowing cell division. That second identity is where the research has gone: it has been trialled as an immune and anti-tumour agent rather than as an analgesic, reaching Phase 2 in pancreatic cancer and in human immunodeficiency virus (HIV) infection, and a randomised COVID-19 trial under the brand name Enkorten. No regulator on file has approved it, and every trial it has been through was in serious illness.

Last updated 12 August 2026

Studied forImmune modulation research · Cell proliferation research · Analgesia and mood signalling

Evidence on file2 animal studies · 1 citation not yet graded

Strongest sourcePrimary structure of the human Met- and Leu-enkephalin precursor and its mRNA (Nature 1982, cited 554x) (animal study)

Mechanism

Binds delta-opioid receptors, and as opioid growth factor engages nuclear OGFr to raise p16 and p21, slowing cell-cycle progression.

Reported effects

What sources associate with this compound. Reported categories, not outcomes we have graded — each would need its own citation and rung.

Immune modulation research
Cell proliferation research
Analgesia and mood signalling

Dosing on file unverified

FK 33-824 analogue: 2 mg IM daily for 7 days (schizophrenia study); Phase 2 for pancreatic cancer, HIV; No standard dose

Carried from a source that labels it unverified, and reproduced with that label attached. A record of what is reported, not a recommendation. No citation on this page establishes it.

Literature on file 3

animal in vivo
Primary structure of the human Met- and Leu-enkephalin precursor and its mRNA (Nature 1982, cited 554x) graded on: an animal model — read from the indexed abstract — “cattle”
animal in vivo
Immunohistochemical localization of enkephalin in rat brain and spinal cord (Journal of Comparative Neurology 1978, cited 684x) graded on: an animal model — “rat”

Not graded

1 citation whose study design could not be read from the title. Left ungraded rather than guessed at.

not graded
NCT04374032: An Open-label, Prospective, Randomized, Comparative Clinical Trial to Evaluate the Efficacy and Safety of ENKORTEN® as an Immunomodulatory Therapy graded on: NCT04374032 is completed and has posted no results - a registration, not a reported outcome — “NCT04374032”

Identity

Space-filling 3D model of Met-Enkephalin, carbon grey, nitrogen blue, oxygen red — Built from the SMILES on this record — the atoms and bonds are exact. The shape is **one computed low-energy pose**, not a measured structure: a flexible peptide in solution has no single conformation, and where the SMILES leaves a stereocentre undefined the pose commits to one arbitrarily. The skeletal formula below claims connectivity and nothing more, which is what we actually know.

2D chemical structure of Met-Enkephalin — Built from the SMILES on this record — the atoms and bonds are exact. The shape is **one computed low-energy pose**, not a measured structure: a flexible peptide in solution has no single conformation, and where the SMILES leaves a stereocentre undefined the pose commits to one arbitrarily. The skeletal formula below claims connectivity and nothing more, which is what we actually know.

Molecular weight: 573.7
Molecular formula: C27H35N5O7S
CAS number: 58569-55-4
PubChem CID: 443363
UniProt: P01210 (precursor)
InChI key: YFGBQHOOROIVKG-FKBYEOEOSA-N
SMILES: CSCC[C@@H](C(=O)O)NC(=O)[C@H](CC1=CC=CC=C1)NC(=O)CNC(=O)CNC(=O)[C@H](CC2=CC=C(C=C2)O)N
InChI: InChI=1S/C27H35N5O7S/c1-40-12-11-21(27(38)39)32-26(37)22(14-17-5-3-2-4-6-17)31-24(35)16-29-23(34)15-30-25(36)20(28)13-18-7-9-19(33)10-8-18/h2-10,20-22,33H,11-16,28H2,1H3,(H,29,34)(H,30,36)(H,31,35)(H,32,37)(H,38,39)/t20-,21-,22-/m0/s1

Notes unverified prose

Phase 2 for pancreatic cancer, HIV; Phase 2/3 for COVID-19 (NCT04374032); FK 33-824 2 mg IM daily in schizophrenia crossover study; Phase 2 (pancreatic cancer, HIV); NCT04374032 (COVID-19)

Not on file 2

1 of the 8 fields we track hold nothing on this record, and each says why. 1 further absence is named below. A blank field is a bug; a named absence is a finding.

amino-acid sequencenothing we hold supplies it
half-lifenothing we hold supplies it

Each field links to every other record missing the same thing. The full ledger holds 765 gaps across 163 records.