This study is designed to evaluate the clinical activity of CDX-110 vaccination when given with standard of care treatment (maintenance temozolomide therapy). Study treatment will be given until disease progression and patients will be followed for long-term survival information. Efficacy will be measured by the progression-free survival status at 5.5 months from the date of first dose.

Inclusion Criteria:

• Newly diagnosed de novo GBM with documented EGFRvIII expression in tumor tissue.
• Gross total resection followed by conventional chemoradiation therapy without progression of disease.

Exclusion Criteria:

• Presence of diffuse leptomeningeal disease or gliomatosis cerebri.
• Systemic corticosteroid therapy > 2 mg of dexamethasone or equivalent (as defined by the investigator) per day at study enrollment.
• Patients who have undergone stereotactic radiosurgery prior to or following surgical resection, or the placement of Gliadel® Wafers.
• Known allergy or hypersensitivity to KLH, GM-CSF or yeast derived products, or a history of anaphylactic reactions to shellfish proteins.