An orally bioavailable, immunotherapeutic vaccine composed of hydrolyzed and formulated glioblastoma multiforme (GBM) antigens and alloantigens derived from a pool of patients' cancer cells in the blood and samples of tumor tissues, with potential immunomodulating and antineoplastic activities. Upon oral administration of the GBM antigens and alloantigens immunotherapeutic vaccine, the GBM antigens and alloantigens may stimulate the host immune system via antigen-presenting cells (APCs) lining the gut to mount an immune response against tumor cells expressing these antigens. This may lead to tumor cell death.