Inclusion Criteria:

          -  Written informed consent to participate in this study

          -  Histological or radiological confirmation of glioblastoma with PSMA positivity

          -  Recurrent or progressive GBM following at least one (1), but no more than two (2)
             prior regimens; one of the prior regimens must have included surgery and/or
             radiotherapy

          -  Age >/= 18 years

          -  Karnofsky Performance Status (KPS) ≥ 60%

          -  Life expectancy > 2 months

          -  Adequate hematologic, renal and hepatic function

          -  Adequate coagulation profile

          -  Not pregnant, nursing or planning to become pregnant; willing to use contraception

        Exclusion Criteria:

          -  Deteriorating neurological symptoms, or need for increasing doses of corticosteroids
             or new onset of seizures

          -  Surgical resection or major surgery within 4 weeks or stereotactic biopsy within 1
             week of first G-202 treatment

          -  Toxicity from prior therapy (excluding alopecia) that has not resolved to ≤ Grade 1
             unless otherwise specified

          -  Investigational or cytotoxic therapy within 28 days or nitrosoureas within 42 days of
             the first treatment with G-202

          -  Currently requiring any type of full-dose anti-coagulation treatment, systemic
             administration of antibiotics or chronic administration of anti-viral agents.

          -  History or evidence of cardiac risk, including QTc interval on screening ECG >470
             msec, left ventricular ejection fraction (LVEF) < 50%, clinically significant
             uncontrolled arrhythmias or arrhythmia requiring treatment with the exceptions of
             atrial fibrillation and paroxysmal supraventricular tachycardia, history of acute
             coronary syndromes within 6 months prior to the first dose of study therapy (including
             myocardial infarction and unstable angina, coronary artery bypass graft, angioplasty,
             or stenting)

          -  Uncontrolled cardiac or coronary artery disease

          -  Uncontrolled hypertension (mean systolic BP ≥ 160 mm Hg and/or mean diastolic BP ≥ 100
             mm Hg on 3 determinations 5 minutes apart while on 2 anti-hypertensive agents) or
             hypertension requiring treatment with more than 2 anti-hypertensive agents

          -  Severe or uncontrolled medical disease, including uncontrolled diabetes, congestive
             heart failure, chronic renal disease or chronic pulmonary disease

          -  Severe GI bleeding within 12 weeks of treatment with G-202

          -  Known history of HIV, hepatitis B or hepatitis C

          -  Documentation of keratosis follicularis (also known as Darier or Darier-White disease)

          -  Requirement for chronic use of strong inhibitors or inducers of cytochrome (CYP3A4)
             iso-enzymes

          -  Known hypersensitivity to any study drug component including thapsigargin derivatives,
             polysorbate 20, or propylene glycol

          -  Any other condition, including concurrent medical condition, social circumstance or
             drug dependency, which in the opinion of the investigator could compromise patient
             safety and/or compliance with study requirements

          -  Another primary malignancy that has not been in remission for at least 2 years;
             non-melanoma skin cancer, intraepithelial carcinoma of the cervix, or prostate cancer
             with a current PSA ≤ 0.1 ng/mL is allowed-