A Phase II Randomised Trial of Three Regimens of GX301 Vaccination in Castration-resistant Prostate Cancer

Inclusion Criteria:

Documented patient history

* Histologically confirmed diagnosis of prostate cancer, with an available Gleason score.
* Diagnosis of progressive, castration-resistant prostate cancer (CRPC), leading to inception of first-line chemotherapy with a docetaxel-based regimen.
* Completion of chemotherapy with a cumulative delivered dose of 300 to 825 mg/m2 docetaxel.

Note: Pre-chemotherapy exposure to abiraterone and prednisone does not preclude eligibility, provided that both agents have been discontinued prior to initiation of docetaxel.

Current patient status

* Ability to understand study-related patient information and provision of written informed consent for participation in the study.
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
* Life expectancy of at least 6 months.
* An interval ≥4 weeks elapsed from the last docetaxel administration.
* Documented achievement of response or disease stability with docetaxel chemotherapy.
* Absence of cancer-related symptoms suggesting clinical disease progression.
* Current castrate testosterone level (≤50 ng/dL) due to current gonadotropin-releasing hormone (GnRH) agonist or antagonist therapy or past orchiectomy.
* Haematology and blood chemistry tests within specified limits.
* Successful recovery from acute toxicities from prior chemotherapy.
* Confirmation from the immunology laboratory that the blood sample provided for baseline immunological tests is technically adequate.

Exclusion Criteria:

* Known intolerance to Montanide or imiquimod.
* Known presence of brain metastatic disease or spinal cord compression.
* Radiotherapy within the past 4 weeks.
* Concomitant presence of other primary malignancy
* Major surgery within 4 weeks prior to randomisation.
* Cardiovascular illness or complication which, in Investigator's judgment, compromises prognosis at 6 months or prevents the patient from following study procedures.
* Serious uncontrolled infection.
* Known presence of active autoimmune disease.
* Known presence of acquired, hereditary, or congenital immunodeficiency.
* HIV infection.
* Current need for immunosuppressive drug therapy, including systemic corticosteroids.
* Current need for denosumab therapy. (Patients under bisphosphonate treatment are eligible).
* Skin disease interfering with evaluation of local tolerance of GX301 injections.
* Participation in any interventional drug or medical device study within 30 days prior to treatment start.