PainResearch Phase

Leu-Enkephalin

Overview

Leu-enkephalin is a pentapeptide (Tyr-Gly-Gly-Phe-Leu) that functions as an endogenous opioid agonist with preferential activity at delta-opioid receptors and moderate affinity for mu receptors. It is derived from the precursor proenkephalin and is widely distributed in the central and peripheral nervous systems. The peptide modulates nociceptive transmission and contributes to endogenous analgesia. Leu-enkephalin is rapidly degraded by peptidases, limiting its duration of action.

Key Research Findings

Preclinical studies have demonstrated analgesic effects of leu-enkephalin in rodent pain models when administered centrally or when protected from enzymatic degradation. Clinical use of native leu-enkephalin has been precluded by its rapid metabolism and poor bioavailability. Research has focused on developing stabilized analogs and peptidase-resistant derivatives, though none have reached approval.

Route of Administration

Endogenous peptide

Regulatory Status

Research Phase

Interested in Leu-Enkephalin?

Find a verified provider experienced with Leu-Enkephalin protocols in your area. All providers are credentialed and use compliant sourcing.

Find a Leu-Enkephalin Provider

Related Peptides

Ziconotide (Prialt)

FDA Approved

A synthetic 25-amino acid peptide identical to omega-conotoxin MVIIA, a neurotoxin found in the venom of the marine cone snail Conus magus. Ziconotide selectively and reversibly blocks N-type voltage-gated calcium channels (Cav2.2) in the dorsal horn of the spinal cord, inhibiting neurotransmitter release from primary afferent nociceptive neurons. It provides analgesia without opioid receptor activation, tolerance development, or respiratory depression.

Difelikefalin (Korsuva)

FDA Approved

A selective kappa-opioid receptor (KOR) agonist peptide that does not cross the blood-brain barrier, providing peripheral analgesia and anti-pruritic effects without central opioid side effects such as euphoria, dysphoria, sedation, or addiction. Difelikefalin activates kappa receptors on peripheral sensory neurons and immune cells to reduce itch signaling and inflammation. Its restricted CNS penetration is a deliberate design feature to avoid abuse potential.

ARA-290

In Clinical Trials

A synthetic 11-amino acid peptide derived from the structure of erythropoietin (EPO) that selectively activates the innate repair receptor (IRR), a heteromer of the EPO receptor and the beta common receptor (CD131). Unlike EPO, ARA-290 does not stimulate erythropoiesis or promote thrombosis. It produces cytoprotective, anti-inflammatory, and tissue-reparative effects by activating the IRR on neurons, immune cells, and endothelial cells.

Palmitoylethanolamide (PEA)

Research Phase

An endogenous fatty acid amide belonging to the N-acylethanolamine family, naturally produced by cells in response to tissue damage and inflammation. PEA acts primarily through peroxisome proliferator-activated receptor alpha (PPAR-alpha), downregulating mast cell activation and pro-inflammatory mediator release. It also modulates the endocannabinoid system via the entourage effect, enhancing anandamide activity at CB1/CB2 receptors and TRPV1 channels without directly binding cannabinoid receptors.