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Protein / target

Delta-type opioid receptor

Encoded byOPRD1P41143Homo sapiensSwiss-Prot
Clinically validated
Therapeutic maturity
20
Approved medicines
Open Targets target-level
View by indication →
30
Clinical trials
Small-molecule tractable
Druggability
Approved Drug

Protein at a glance

Biological role

G protein-coupled enkephalin receptor

Strongest disease association

Alcoholism

Via encoding gene OPRD1 · Clinical evidence · score 0.60

Therapeutic position

Established drug target

Small molecules

Derived from structured UniProt, Open Targets and literature data on this page.

Protein profile

UniProt 2026_02

Canonical identity and biological annotation from UniProt.

Function overview

G protein-coupled receptor that functions as a receptor for endogenous enkephalins and for a subset of other opioids.

View complete UniProt function annotation

G protein-coupled receptor that functions as a receptor for endogenous enkephalins and for a subset of other opioids. Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors, such as adenylate cyclase. Signaling leads to the inhibition of adenylate cyclase activity. Inhibits neurotransmitter release by reducing calcium ion currents and increasing potassium ion conductance. Plays a role in the perception of pain and in opiate-mediated analgesia. Plays a role in developing analgesic tolerance to morphine

Subcellular location

Cell membrane
Domains and Gene Ontology detail (29)

Gene Ontology

  • Caxon terminus
  • Cdendrite membrane
  • Cneuron projection
  • Cneuronal dense core vesicle
  • Cplasma membrane
  • Cpostsynaptic density membrane
  • Cpresynaptic membrane
  • Cspine apparatus
  • Csynaptic vesicle membrane
  • FG protein-coupled enkephalin receptor activity
  • FG protein-coupled opioid receptor activity
  • Fneuropeptide binding

372 aa · 40 kDa

Biological roles

Reactome v97

What this protein does, drawn together from its UniProt function, Gene Ontology terms and Reactome pathways.

G protein-coupled signallingUniProt · GOImmune signallingGO · Reactome
View supporting evidence

G protein-coupled signalling

  • ·G protein-coupled receptor that functions as a receptor for endogenous enkephalins and f…
  • ·G protein-coupled enkephalin receptor activity
  • ·G protein-coupled opioid receptor activity
  • ·G protein-coupled opioid receptor signaling pathway

Immune signalling

  • ·immune response
  • ·Interleukin-4 and Interleukin-13 signaling
View underlying pathways (3)

Concepts derived from UniProt GO Reactome — each badge above shows which sources supported that role.

Interaction neighbourhood

STRING v12.0

Proteins with the strongest functional or physical association. Node size and line weight reflect STRING confidence; hover or select a partner to inspect one association.

GNAI1PENKPDYNOPRM1POMCKNG1GNAI2GNAI3PNOCGPRASP1OPRD1

10 strongest partners — larger node and heavier line mean higher confidence

Functional and physical associations from STRING v12.0. Only associations with this protein are drawn — partner-to-partner links are not part of this evidence.

Approved medicines with mapped indications

1 medicine · 1 area

Approved therapies targeting this protein, grouped by what they are approved to treat — the disease-first view of the medicines below. Relationships come from the canonical approved-indication graph (ChEMBL phase-4), the same source as the drug cards.

Alcoholism1 medicine

20 medicines meet Open Targets' target-level approved-medicine definition; the 1 shown here are those on this page with a canonical approved disease indication in the graph. Approved indications from ChEMBL (phase-4), via the canonical drug→disease graph.

Drugs targeting this protein

1

How approved and investigational drugs engage this protein — mechanism and action type, direct vs complex targeting, and how broadly each acts across other targets. A drug-first view (the section above groups the approved ones disease-first); direct binders with few recorded targets are listed first.

Naltrexone
ApprovedAntagonist

Opioid receptors; mu/kappa/delta antagonist

Indicated for Alcoholism

Acts on a complex — shared with OPRK1, OPRM1 · 1 of 3 recorded protein targets — narrow recorded profile

ChEMBL mechanism, action type, target identity and approved indications. Open Targets clinical status.

Translational evidence

Open Targets 26

Why this target matters therapeutically, strongest evidence first. Disease associations are gene-level (via the gene that encodes this protein) and open into the full confidence synthesis; the development universe, tractability and safety annotations are target-level, from Open Targets.

Strongest disease associations · via encoding gene OPRD1

Gene-level evidence surfaced through the gene OPRD1 that encodes this protein — not a direct protein–disease relationship. Ranked by Forefront's causal-directness weighting, so genetically- and clinically-evidenced diseases lead over ones that merely share the literature.

Alcoholism
0.74Moderately supported

Clinical evidence dominant · Open Targets 0.60

Migraine Disorders
0.74Moderately supported

Clinical evidence dominant · Open Targets 0.60

Opioid-Related Disorders
0.74Moderately supported

Clinical evidence dominant · Open Targets 0.60

Major depressive disorder
0.69Moderately supported

Clinical evidence dominant · Open Targets 0.56

Schizophrenia
0.63Moderately supported

Clinical evidence dominant · Open Targets 0.51

View evidence synthesis (5)
AlcoholismModerately supported
0.74
agreement 0.590.90
Clinical98%Literature2%

Open Targets aggregate 0.60 · 2 independent evidence families

Migraine DisordersModerately supported
0.74
agreement 0.580.89
Clinical97%Literature3%

Open Targets aggregate 0.60 · 2 independent evidence families

Opioid-Related DisordersModerately supported
0.74
agreement 0.580.89
Clinical97%Literature3%

Open Targets aggregate 0.60 · 2 independent evidence families

Major depressive disorderModerately supported
0.69
agreement 0.540.84
Clinical98%Literature2%

Open Targets aggregate 0.56 · 2 independent evidence families

SchizophreniaModerately supported
0.63
agreement 0.480.79
Clinical98%Literature2%

Open Targets aggregate 0.51 · 2 independent evidence families

The evidence agreement range shows how closely the independent evidence families agree — it is not a statistical confidence interval, and nothing here is fitted to outcome data. Derived from Open Targets evidence types under Forefront weighting; the per-type scores above show the calculation.

Show all associations
Alcoholism0.60
Migraine Disorders0.60
Opioid-Related Disorders0.60
Major depressive disorder0.56
Schizophrenia0.51

Drug development

26 compounds recorded · 20 approved · 6 in clinical development

Open Targets' development universe — every compound recorded against the target at any stage, not all approved medicines. Distinct from the 1 drug that targets this protein in Forefront's canonical graph (1 with a mapped approved indication, shown above): these count different sets and are not a subset relation.

View all recorded compounds (10)
NALOXONE HYDROCHLORIDEApproval
NALMEFENE HYDROCHLORIDE DIHYDRATEApproval
NALBUPHINEApproval
SAMIDORPHAN L-MALATEApproval
DEXTROMORAMIDEApproval
HYDROCODONE BITARTRATEApproval
ONDELOPRANApproval
OXYMORPHONE HYDROCHLORIDEApproval
AXOMADOLPhase 2
CODEINE SULFATEApproval

Open Targets known-drugs universe. Drug name and highest clinical stage only — the disease relationship is NOT read from this slice (it carries trial-context noise); approved indications come from the canonical graph above.

Tractability

Small moleculesStrong

Approved Drug and Structure with Ligand support this modality.

AntibodiesEmerging

Feasibility evidence (uniprot loc high conf and go cc high conf) — no clinical-stage drug of this modality recorded.

Protein degradersEmerging

Feasibility evidence (uniprot ubiquitination and small molecule binder) — no clinical-stage drug of this modality recorded.

View underlying tractability evidence (9)
SM · Approved DrugSM · Structure with LigandSM · High-Quality LigandSM · Druggable FamilyAB · UniProt loc high confAB · GO CC high confAB · UniProt SigP or TMHMMPR · UniProt UbiquitinationPR · Small Molecule Binder

Raw Open Targets tractability assessment buckets, by modality.

Safety-related annotations

heroin dependenceClinPGxseizureUrban et al. (2012)increased cardiac outputUrban et al. (2012)cardiovascular effectsUrban et al. (2012)euphoriaLynch et al. (2017)increased contractilityUrban et al. (2012)cardiovascular effectsBowes et al. (2012)increased blood pressureUrban et al. (2012)dysphoriaBowes et al. (2012)convulsionsLynch et al. (2017)increased cardiac contractilityBowes et al. (2012)convulsionUrban et al. (2012)

Terms indexed against this target in Open Targets' safety data, with their datasource. These are annotations, not causal claims: the direction of effect (whether activation or inhibition is implicated), species and evidence strength are not captured here, so an entry does not mean that modulating this target is known to cause that condition.

Clinical trials

30

Trials of drugs that target this protein — reached indirectly through those drugs, so a trial listed here studies the drug, not the protein. Ranked by active status, then clinical phase and recency, and spread across the targeting drugs.

View all trials (26)

RECRUITING · via Naltrexone · NCT05827159

ENROLLING_BY_INVITATION · via Naltrexone · NCT07221565

COMPLETED · via Naltrexone · NCT04276259

COMPLETED · via Naltrexone · NCT01993108

ClinicalTrials.gov via the drug-target graph.

What's happening now

8

Recent therapeutic activity around this target — regulatory actions, clinical trials and safety signals for a drug that targets this protein, plus publications where such a drug is a genuine subject. Every item is reached indirectly through the drug, not the protein itself; incidental mentions (a paper that merely measures a drug) and press items are excluded.

  1. New publication2023-09-26
    Naltrexone/bupropion for binge-eating disorder: A randomized, double-blind, placebo-controlled trial.

    Obesity (Silver Spring, Md.) · 2023 · 40 citations · Europe PMC · via Naltrexone

  2. New publication2016-10-01
    Randomized, proof-of-concept trial of low dose naltrexone for patients with breakthrough symptoms of major depressive disorder on antidepressants.

    Journal of affective disorders · 2017 · 41 citations · Europe PMC · via Naltrexone

  3. New publication2015-05-01
    Naltrexone vs Placebo for the Treatment of Alcohol Dependence: A Randomized Clinical Trial.

    JAMA psychiatry · 2015 · 87 citations · Europe PMC · via Naltrexone

  4. New publication2014-07-18
    Naltrexone for impulse control disorders in Parkinson disease: a placebo-controlled study.

    Neurology · 2014 · 78 citations · Europe PMC · via Naltrexone

  5. New publication2013-04-01
    Safety and tolerability of low-dose naltrexone therapy in children with moderate to severe Crohn's disease: a pilot study.

    Journal of clinical gastroenterology · 2013 · 38 citations · Europe PMC · via Naltrexone

  6. New publication2011-03-31
    Gabapentin combined with naltrexone for the treatment of alcohol dependence.

    The American journal of psychiatry · 2011 · 95 citations · Europe PMC · via Naltrexone

  7. New publication2010-06-12
    Low-dose naltrexone augmentation of nicotine replacement for smoking cessation with reduced weight gain: a randomized trial.

    Drug and alcohol dependence · 2010 · 35 citations · Europe PMC · via Naltrexone

  8. New publication2006-09-08
    Association of OPRM1 A118G variant with the relative reinforcing value of nicotine.

    Psychopharmacology · 2006 · 95 citations · Europe PMC · via Naltrexone

Objective event titles are shown unmodified; the event kind and significance line are derived from structured fields. Forefront AttentionEvent stream aggregating Europe PMC Regulatory filings ClinicalTrials.gov.