Expressive

rs4680 - COMT

What the research says

The rs4680 G>A variant in the COMT gene (Val158Met) substitutes methionine for valine at position 158, reducing catechol-O-methyltransferase enzyme activity roughly three- to four-fold in Met (A) allele carriers relative to Val (G) homozygotes - an effect that most sharply impacts dopamine clearance in the prefrontal cortex, where COMT is the dominant inactivating enzyme [Study 4]. In a 234-patient Parkinson's disease cohort, the AA genotype independently predicted levodopa-induced dyskinesia with a 2.8-fold higher risk compared to AG and GG carriers, placing rs4680 among the genetic contributors to motor complications alongside ANKK1/DRD2 variants [Study 1]. Among advanced cancer patients receiving opioids, A allele carriers required significantly lower doses (median 130 vs. 180 mg) but experienced a 7.1-fold adjusted odds of sickness-response adverse effects, suggesting that reduced dopaminergic clearance simultaneously heightens analgesic sensitivity and adverse-effect burden [Study 7].

Reported associations

  • Levodopa-induced dyskinesia (Parkinson's disease): AA genotype independently predicted 2.8-fold higher risk; motor fluctuation haplotypes also identified [Study 1]
  • Opioid dosing and adverse effects in advanced cancer: A allele carriers used lower doses but had higher rates of sickness response (aOR 7.1, p=0.01) [Study 7]
  • Anti-CGRP migraine preventive response: rs4680-A allele associated with non-responder status (OR 0.6) to subcutaneous anti-CGRP biologics [Study 6]
  • Tardive dyskinesia severity in schizophrenia: AA genotype carriers had higher involuntary movement scores than AG/GG carriers in a Chinese cohort (p=0.006-0.01) [Study 8]
  • Methylphenidate adverse effects in ADHD: Both AA and GG genotypes - a non-monotonic pattern - were overrepresented in the adverse-effect group compared to responders [Study 5]
  • Subjective alcohol response: Higher-COMT-activity (GG) individuals showed greater tolcapone-mediated reduction in alcohol-induced stimulation (p=0.008) and sedation (p=0.053), with stimulation mediating self-administration effects [Study 4]
  • O-methylascorbate levels: A allele associated with higher circulating levels (p=5×10^-¹^78, n=7,788) [GWAS 1]
  • 3-Methoxytyrosine levels: A allele associated with elevated levels (p=6×10^-¹¹, n=8,258), mechanistically consistent with reduced catecholamine methylation [GWAS 13]
  • Body mass index: G allele modestly associated with higher BMI (beta=0.009, p=1×10^-¹¹, n=1.1M) [GWAS 12]
  • Internet addiction disorder: Reported association (OR=1.8, p=5×10^-9, n=34,520); preliminary, single study [GWAS 14]
  • ABHD14B/COMT protein level ratio: Associated across 43,509 participants (p=1×10^-³^0) [GWAS 5]
  • Piperine glucuronide metabolite levels: G allele associated with higher levels (p=1×10^-²^9, n=8,809) [GWAS 7]

Evidence quality

Across all curated sources, rs4680 has 58 GWAS Catalog associations drawn from 130 distinct studies, a best p-value of 2.0×10^-¹^85, and 4,988 PharmGKB clinical annotations - placing it among the most extensively characterized functional SNPs in human genetics. The strongest signals are metabolomic and directly reflect the enzymatic phenotype: circulating O-methylascorbate reaches p=5×10^-¹^78 (n=7,788) [GWAS 1] and a serum metabolite panel p=1×10^-48 (n=1,678) [GWAS 3]. Clinical intervention studies are considerably smaller and mostly underpowered: the Parkinson's dyskinesia cohort enrolled 234 patients [Study 1], the cancer opioid study recruited 54 participants [Study 7], the ADHD pharmacogenomics study included 102 children [Study 5], and the NICU morphine study covered 55 infants without reaching statistical significance [Study 2]. A 380-patient sufentanil labor analgesia study found no significant effect of COMT genotype on maternal or neonatal outcomes [Study 3]. The migraine anti-CGRP study genotyped 198 patients and found a nominally significant non-responder association (OR 0.6, p=0.041) for the A allele, but reported no multiple-testing correction [Study 6]. A key conflict: Study 5 found both AA and GG - not just one extreme of the activity gradient - overrepresented in the methylphenidate adverse-effect group, a non-monotonic pattern inconsistent with a simple dose-response model and at odds with PharmGKB's Level 4 "no significant association" designation for methylphenidate [PharmGKB 28]. Most PharmGKB opioid annotations carry Level 3 evidence (single study or limited replication), and CPIC has issued "no recommendation" for the majority of opioid-COMT pairs, citing insufficient evidence for clinical action.

Clinical classifications

  • Schizophrenia / Tramadol response: Benign for the A allele [ClinVar 1]. This Benign classification reflects the absence of a Mendelian causal disease relationship, not the absence of functional or pharmacogenomic effects - the A allele is simultaneously covered by 58 GWAS associations and nearly 5,000 PharmGKB annotations. The tension between ClinVar's disease-framework Benign call and the breadth of published associations is essential context: they answer different questions.

Drug response by genotype

All annotations are Level 3 (limited replication) unless noted; CPIC has issued "no recommendation" for most opioid-COMT pairs. Entries below are capped at 1-2 representative drugs per clinical category.

  • AA: Pain - opioids / morphine (increased analgesic response, decreased dose requirements; conflicting across studies) [PharmGKB 9, 37, 41]; Migraine - erenumab (increased response vs GG) [PharmGKB 27]; +2 other anti-CGRP biologics (fremanezumab [PharmGKB 13], galcanezumab [PharmGKB 29]); Psychiatric - clozapine (poorer response vs GG) [PharmGKB 5]; antipsychotics (decreased tardive dyskinesia risk vs GG) [PharmGKB 21]; Smoking - nicotine replacement therapy (increased cessation likelihood; conflicting) [PharmGKB 12]; Parkinson's - entacapone (decreased response vs GG) [PharmGKB 40]; Antidepressants - paroxetine and fluvoxamine (increased response in major depression) [PharmGKB 16, 43]; ADHD - methylphenidate (no significant association, Level 4, DPWG no recommendation; conflicting) [PharmGKB 28]
  • AG: Pain - opioids / morphine (increased analgesic response vs GG; conflicting) [PharmGKB 80, 60]; Migraine - erenumab and fremanezumab (increased response vs GG) [PharmGKB 54, 45]; Psychiatric - antipsychotics (decreased tardive dyskinesia risk vs GG) [PharmGKB 70]; Smoking - NRT (decreased cessation likelihood vs AA; conflicting) [PharmGKB 67]
  • GG: Pain - opioids / morphine (decreased analgesic response, increased dose requirements; conflicting) [PharmGKB 101, 90]; Migraine - erenumab and fremanezumab (decreased response vs AA/AG) [PharmGKB 88, 96]; +1 other anti-CGRP (galcanezumab [PharmGKB 120]); Psychiatric - clozapine (better response vs AA/AG) [PharmGKB 106]; antipsychotics (increased tardive dyskinesia risk vs AA/AG) [PharmGKB 117]; Parkinson's - entacapone (increased response vs AA) [PharmGKB 111]; Smoking - NRT (decreased cessation likelihood vs AA; conflicting) [PharmGKB 128]

Tissue-specific expression effects

  • COMT: The A allele associates with increased COMT transcript levels in esophageal mucosa, small intestinal mucosa (terminal ileum), and unexposed skin [GTEx]. This is a notable dissociation: the A allele simultaneously lowers enzyme activity (the Val158Met amino-acid change) while raising expression in peripheral tissues through a separate regulatory mechanism - these two effects do not cancel each other.
  • ARVCF: The A allele reduces ARVCF expression in aorta but increases it in thyroid, unexposed skin, and esophageal mucosa [GTEx]. ARVCF encodes an armadillo-repeat scaffolding protein encoded adjacently to COMT on chromosome 22q11; these tissue-specific expression changes most likely reflect linkage with nearby regulatory variants rather than a direct consequence of the Val158Met substitution itself.
  • ENSG00000289946: The A allele associates with increased expression of this currently uncharacterized gene in testicular tissue [GTEx].

Study sources

  1. Radojević B et al., Neurological research, 2026 - levodopa-induced motor complications in Parkinson's disease
  2. Mankouski A et al., Clinica chimica acta, 2026 - morphine dosing in the neonatal intensive care unit
  3. Huang H et al., Journal of visualized experiments (JoVE), 2025 - CYP3A4, COMT, and OPRM1 effects on sufentanil in labor analgesia
  4. Schacht JP et al., Alcohol, clinical & experimental research, 2025 - COMT inhibition and subjective response to alcohol
  5. Suzer Gamli I et al., American journal of medical genetics (Part B), 2025 - pharmacogenetics of methylphenidate in childhood ADHD
  6. Chase BA et al., Headache, 2024 - clinical and genetic predictors of anti-CGRP migraine preventive response
  7. Wong AK et al., Journal of palliative medicine, 2024 - COMT and OPRM1 variants, opioid dose, and adverse effects in advanced cancer
  8. Chi J et al., Brain research, 2024 - COMT polymorphisms and tardive dyskinesia in schizophrenia