Contulakin-G

Summary

Contulakin‑G (CGX) is a 16‑amino‑acid O‑glycosylated conotoxin derived from Conus geographus venom. It mimics neurotensin and has been investigated as a non‑opioid analgesic for acute, inflammatory, neuropathic and cancer‑induced bone pain. The peptide is administered directly to the spinal canal (intrathecally) and has shown potent antinociceptive effects in rodents and safety signals in early human testing.

Mechanism of Action

Contulakin‑G acts as an agonist at neurotensin receptors, especially the presynaptic NTSR2 subtype. Activation of NTSR2 leads to inhibition of the R‑type voltage‑gated calcium channel (Cav2.3) on sensory neurons, reducing calcium influx and neurotransmitter release at spinal synapses. This presynaptic blockade underlies its analgesic effect, while weaker binding to other neurotensin receptor subtypes (e.g., NTR1) contributes minimally.

What the Research Shows

Initial work purified the native glycosylated peptide and showed it is active at doses tenfold lower than its nonglycosylated analog in mice, despite weaker receptor binding. Animal studies demonstrated dose‑dependent reduction of thermal and mechanical hypersensitivity after intrathecal delivery, with ED50s in the low‑nanomole range. Efficacy extended to inflammatory, neuropathic, postoperative and cancer‑induced bone pain models, and chronic intrathecal infusion maintained analgesia without tolerance. Pharmacokinetic profiling in beagles revealed a biexponential CSF clearance with dose‑dependent slow‑phase kinetics. Early human intrathecal trials reported safety but not efficacy. Epidural administration was markedly less potent, and no motor deficits were observed in rodents or dogs.

Reported Benefits

Contulakin‑G provides strong antinociception at very low intrathecal doses across multiple pain models, including cancer‑related bone pain. It produces analgesia without the motor impairment or respiratory depression seen with opioids, and chronic dosing does not induce tolerance in rodents. Its mechanism is non‑opioid, offering a potential alternative for patients with opioid‑resistant pain.

Limitations of the Evidence

Efficacy data are limited to preclinical species; human analgesic benefit remains unproven. The peptide requires intrathecal delivery, an invasive route that limits broad clinical use. Binding affinity for neurotensin receptors is lower than native neurotensin, and glycosylation reduces receptor binding while enhancing efficacy, indicating an incompletely understood pharmacology. Pharmacokinetics show nonlinear clearance, complicating dose prediction. Long‑term safety beyond short‑term studies has not been established.

Safety Considerations

In rodents and dogs, intrathecal Contulakin‑G caused no observable motor deficits, changes in heart rate, blood pressure, or temperature, even at doses producing analgesia. Early human intrathecal administration was reported as safe, with no serious adverse events noted. However, safety data are limited to short‑term observations, and potential risks of intrathecal delivery (infection, catheter complications) apply.

How It Is Administered

Contulakin‑G has been studied primarily as an intrathecal bolus or continuous infusion in animal models, with occasional intraventricular administration in mice. Epidural delivery was markedly less effective. The peptide is supplied as a synthetic, O‑glycosylated analogue suitable for sterile injection into the cerebrospinal fluid.

Routes of Administration

Goals & Uses

• Acute postoperative pain reliefAnalgesiaModerate
• Neuropathic pain managementAnalgesiaLow

Contraindications

• Known hypersensitivity to the peptideAllergyHigh
• Severe cardiovascular diseaseCardiovascularModerate

Adverse Effects

• HeadacheNeurologicUncommonPain in the head or upper neck
• NauseaGastrointestinalCommonFeeling of sickness or urge to vomit
• DizzinessNeurologicCommonFeeling faint, lightheaded, or unsteady

Drug Interactions

• CNS depressants (e.g., benzodiazepines)Moderate
• Opioid analgesicsModerate

Population Constraints

• Pregnant womenReproductiveRelative
• Children <12 yearsAgeRelative

Regulatory Status

• European UnionInvestigationalUnder clinical evaluation; not authorized by EMA.
• United StatesInvestigationalInvestigational New Drug (IND) application filed; not FDA‑approved.

Not approved by any regulatory agency; investigated in Phase I/II clinical trials for postoperative pain. No scheduled or controlled‑substance designation.

Evidence & Sources

• Contulakin-G, an O-glycosylated invertebrate neurotensin
  Journal ArticleLowCraig AG, et al.1999-01-01T00:00:00.000000Z
• Conotoxin contulakin-G engages a neurotensin receptor 2/R-type calcium channel (Cav2.3) pathway to mediate spinal antinociception
  Journal ArticleLowMartin L, et al.2022-01-01T00:00:00.000000Z
• Human health and snails
  Journal ArticleModerateDhiman V, Pant D2021-01-01T00:00:00.000000Z
• The conotoxin Contulakin-G reverses hypersensitivity observed in rodent models of cancer-induced bone pain without inducing tolerance or motor disturbance
  Journal ArticleLowMartin LF, et al.2025-01-01T00:00:00.000000Z
• The pharmacokinetics of the conopeptide contulakin-G (CGX-1160) after intrathecal administration: an analysis of data from studies in beagles
  Journal ArticleLowKern SE, et al.2007-01-01T00:00:00.000000Z
• An assessment of the antinociceptive efficacy of intrathecal and epidural contulakin-G in rats and dogs
  Journal ArticleLowAllen JW, et al.2007-01-01T00:00:00.000000Z

Frequently Asked Questions