This Phase 2 study was an open label, single-center 18-week study to compare basal and meal stimulated plasma gastrin levels before and after treatment with 3 intramuscular injections of 250 µg G17DT, with and without the concomitant administration of Omeprazole.

Inclusion Criteria:

• Male or female subjects aged 18 to 70 years, inclusive
• Written informed consent was provided
• Histologically confirmed Stage II/III colorectal cancer after radical surgery
• A minimum of 3 months elapsed since completion of the chemotherapy for subjects who had received adjuvant chemotherapy
• Subject had recovered from any toxic effects of chemotherapy

Exclusion Criteria:

• Had a known local recurrence of colorectal cancer or presence of metastatic colorectal cancer lesions
• Was using an inadequate method of contraception (determined at the discretion of the investigator), only for women of childbearing potential who were sexually active
• Was unable to comply with the protocol
• Was unable to abstain from H2 receptor antagonists, PPIs or anticholinergics medications for 2 weeks
• Required H. pylori eradication therapy during the study
• Had prior vaccination with G17DT or any other product with a similar mechanism of action
• Had a history of gastric or vagus nerve surgery
• Had any clinically significant laboratory abnormalities and medical conditions which were unexplained, or, in the opinion of the investigator, did not allow for safe entry of the subject into the study
• Had contraindications to intramuscular injections (e.g., bleeding disorders or treatment with anticoagulants [except for aspirin])
• Had serious and unstable cardiovascular or respiratory disease, other malignancy or any other condition that would have jeopardized subject safety or confounded the results
• Had a known hypersensitivity to diphtheria toxoid, G17DT, any of its components or any similar compound
• Had any other condition that might have influenced the plasma gastrin level (e.g., achlorhydria, Zollinger-Ellison syndrome)
• Had used of an investigational drug within the previous month
• Had taken treatments that alter the immune response such as radiotherapy, corticosteroids, and antineoplastic drugs (Inhaled corticosteroids were permitted.)
• Had conditions that impaired the immune response (e.g., acquired immune deficiency syndrome)
• Had a history of drug or alcohol abuse within the past year
• Was unable to accept a standard breakfast for dietary reasons