G17DT Immunogen
Also known as: Anti-gastrin vaccine, G17DT, Gastrimmune, Gastrin‑17 diphtheria toxoid, Gastrin‑17 vaccine, PAS (polyclonal antibody stimulator)
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Summary
G17DT immunogen is a synthetic peptide vaccine that couples gastrin‑17 to diphtheria toxoid, prompting the body to generate high‑affinity antibodies against gastrin‑17. It is being investigated as an adjunct treatment for gastrointestinal malignancies, including metastatic colorectal cancer and gastric type I carcinoid, where gastrin‑driven growth may contribute to tumor progression.
Mechanism of Action
Vaccination with G17DT induces an active immune response that produces neutralising anti‑gastrin‑17 antibodies. These antibodies bind circulating gastrin‑17, preventing it from stimulating the cholecystokinin‑2 (CCK‑2) receptor on enterochromaffin‑like cells and certain tumor cells. By blocking this trophic signal, the vaccine reduces gastric acid secretion and interferes with gastrin‑mediated proliferative pathways that support growth of gastrointestinal cancers.
What the Research Shows
Preclinical work demonstrated that G17DT‑induced antibodies lower gastrin‑stimulated acid output and block gastrin‑CCK‑2 receptor interaction. Early clinical studies reported high seroconversion rates (>80%) with minimal systemic toxicity. In a phase II trial of 161 irinotecan‑refractory colorectal cancer patients, G17DT (500 µg IM at weeks 1, 5, 9, 26) yielded a 3 % partial response rate, 32 % disease stabilization, and a median survival of 217 days; anti‑G17 responders survived longer (9.0 vs 5.6 months). A pilot of three patients with type I gastric carcinoid showed tumor regression in two and disappearance of enterochromaffin‑like hyperplasia in one, accompanied by reduced chromogranin A levels. Phase I/II GI cancer trials noted no systemic autoimmune events and suggested additive effects when combined with 5‑FU/leucovorin in animal models.
Reported Benefits
Evidence to date suggests G17DT can generate robust anti‑gastrin antibodies that correlate with improved survival in a subset of colorectal cancer patients and may induce regression of gastric type I carcinoids. Preclinical data indicate potential synergy with standard chemotherapies, and early trials report a favorable safety profile aside from local injection reactions. The vaccine targets a biologically relevant growth pathway rather than cytotoxic mechanisms alone.
Limitations of the Evidence
Findings are limited to early‑phase, small‑sample studies; no large randomized controlled or Phase III trials have been published. The colorectal trial lacked a control arm, making efficacy conclusions tentative. Carcinoid data derive from only three patients, and long‑term outcomes remain unknown. Injection‑site adverse events are common, and the overall impact on overall survival across tumor types has not been definitively established.
Safety Considerations
The most frequent adverse events are local reactions at the injection site, including pain (≈42 %), induration, edema, erythema, and occasional abscess formation, reported in about half of participants. Systemic toxicities mirrored those of concurrent chemotherapy (diarrhea, nausea, neutropenia, fatigue). Early phase studies did not observe systemic autoimmune phenomena, but monitoring for hypersensitivity and infection at injection sites is recommended.
How It Is Administered
G17DT is administered by intramuscular (or subcutaneous) injection, typically 500 µg per dose on a schedule such as weeks 1, 5, 9, and 26. The vaccine is supplied as a sterile peptide‑toxoid conjugate and may be combined with standard chemotherapy regimens in clinical protocols.
Routes of Administration
Goals & Uses
- Inhibition of tumor angiogenesisOncology / MechanisticLow
- Treatment of colorectal cancerOncologyLow
- Prevention of gastric cancer recurrenceOncologyModerate
- Treatment of pancreatic cancerOncologyModerate
- Treatment of gastric adenocarcinomaOncologyModerate
- Post-surgical adjuvant therapyOncologyLow
- Treatment of gastric cancerOncologyModerate
Contraindications
- Hypersensitivity to diphtheria toxoidAllergyHigh
- Known hypersensitivity to diphtheria toxoidAllergy / ImmunologyHigh
- Active autoimmune disordersImmunologyModerate
- Severe immunodeficiencyImmunologyModerate
- PregnancyPopulationModeratePotential fetal risk or insufficient safety data
- Severe immunosuppressionImmunologyModerate
Adverse Effects
- Flu-like symptomsSystemic/ImmunologicalCommon
- Hypersensitivity / allergic reactionsImmunologicRare
- Injection site reactionsLocalCommon
- Gastrointestinal disturbancesGastrointestinalUncommon
- Hypersensitivity reactionImmunologicRare
- Reduced gastric acid secretionGastrointestinal / PharmacodynamicUncommon
- Injection site erythemaLocalCommonRedness at the injection site
- Flu‑like systemic symptomsSystemicCommon
Drug Interactions
- Chemotherapy agentsModerate
- Proton pump inhibitors / H2 blockersLow
- Immunosuppressive agents (e.g., corticosteroids, biologics)Moderate
- Immunosuppressive agents (e.g., corticosteroids, methotrexate)Moderate
Population Constraints
- PregnancyReproductive SafetyRelative
- Patients with active severe infectionsInfectious DiseaseRelative
- Pediatric patientsAgeRelative
- Pediatrics (<18 y)AgeAbsolute
- Elderly patients with poor immune functionAge / ImmunologicRelative
Regulatory Status
- European UnionInvestigationalClinical trial sponsor; not authorized by EMA.
- United StatesInvestigationalInvestigational New Drug (IND) application filed; no FDA approval.
- United KingdomInvestigationalUnder clinical investigation; not licensed by MHRA.
Investigational vaccine; has undergone Phase II/III clinical trials for gastric cancer but has not received regulatory approval in major jurisdictions.
Evidence & Sources
- Journal ArticleModerateRocha-Lima CM, et al.2014-01-01T00:00:00.000000Z
- Journal ArticleModerateWatson SA, Gilliam AD2001-01-01T00:00:00.000000Z
- Journal ArticleLowTieppo C, et al.2011-01-01T00:00:00.000000Z
Frequently Asked Questions
What type of cancer is G17DT being tested for?
Clinical investigations have focused on gastrointestinal malignancies, especially metastatic colorectal cancer that has progressed on irinotecan and gastric type I carcinoid tumors that arise in the setting of autoimmune gastritis.
How does the vaccine work without causing general immune suppression?
G17DT specifically induces antibodies that bind gastrin‑17, a hormone that drives growth in certain GI tumors. The response is targeted, and early studies reported no systemic autoimmune reactions or broad immunosuppression.
Are there any serious side effects to be aware of?
The main safety concern is local injection‑site inflammation, which occurred in roughly half of participants and occasionally led to abscesses. Systemic side effects were generally those of accompanying chemotherapy rather than the vaccine itself.
Is G17DT approved for clinical use?
No. G17DT remains investigational and is only available within clinical research protocols; it has not received regulatory approval for any therapeutic indication.
Can G17DT be used alone, or must it be combined with chemotherapy?
Studies have examined both monotherapy (e.g., in gastric carcinoid patients) and combination regimens (e.g., with irinotecan in colorectal cancer). The optimal context is still under investigation.
What is G17DT Immunogen?
G17DT immunogen is a synthetic peptide vaccine that couples gastrin‑17 to diphtheria toxoid, prompting the body to generate high‑affinity antibodies against gastrin‑17. It is being investigated as an adjunct treatment for gastrointestinal malignancies, including metastatic colorectal cancer and gastric type I carcinoid, where gastrin‑driven growth may contribute to tumor progression.
What is G17DT Immunogen used for?
G17DT Immunogen is educationally associated with: Inhibition of tumor angiogenesis, Treatment of colorectal cancer, Prevention of gastric cancer recurrence, Treatment of pancreatic cancer, Treatment of gastric adenocarcinoma, Post-surgical adjuvant therapy, Treatment of gastric cancer. Educational only — not medical advice.
How is G17DT Immunogen administered?
Recorded routes of administration: Intramuscular, Subcutaneous.
What are the potential side effects of G17DT Immunogen?
Reported adverse effects include: Flu-like symptoms, Hypersensitivity / allergic reactions, Injection site reactions, Gastrointestinal disturbances, Hypersensitivity reaction, Reduced gastric acid secretion, Injection site erythema, Flu‑like systemic symptoms. This list is not exhaustive — consult a qualified clinician.
Who should avoid G17DT Immunogen?
Recorded contraindications: Hypersensitivity to diphtheria toxoid, Known hypersensitivity to diphtheria toxoid, Active autoimmune disorders, Severe immunodeficiency, Pregnancy, Severe immunosuppression. Consult a qualified clinician before use.