A Ph 2 Study of Fosbretabulin in Subjects w Pancreatic or Gastrointestinal Neuroendocrine Tumors w Elevated Biomarkers

Inclusion Criteria: * Ability to read, understand and provide written consent to participate in the study * Age ≥ 18 years * Biopsy-proven well-differentiated, low-to-intermediate-grade PNET or GI-NET with elevated (\> ULN) biomarkers (serotonin, 5-hydroxyindoleacetic acid (5-HIAA), chromogranin A (CgA), neurokinin A, and neuron-specific enolase (NSE)) * Life expectancy \> 12 weeks * Must have received or may still be receiving one or more therapies including octreotide or serotonin synthesis inhibitor (SSI) or other somatostatin analogues * Confirmed progressive disease within 18 months of enrollment on study * Recovered from prior radiation therapy or surgery * Eastern Cooperative Oncology Group (ECOG) performance score 0-2 * Absolute neutrophil count (ANC) ≥ 1,500/µL (without growth factors) * Platelet count ≥ 100,000/µL * Adequate renal function as evidenced by serum creatinine ≤ 2.0 mg/dL (177 µmol/L) * Adequate hepatic function: serum total bilirubin ≤ 2X greater than the upper limit of normal (ULN) (≤ 3X ULN in subjects with liver metastases), aspartate aminotransferase) AST) / alanine aminotransferase (AST) ≤ 2X the ULN for the local reference lab (≤ 5X the ULN for subjects with liver metastases) * Disease that can be assessed (evaluable) with imaging (CT, MRI, PET, radionuclide imaging or other imaging modality) * Women of childbearing potential as well as fertile men and their partners must use an effective method of birth control Exclusion Criteria: * Inadequately controlled hypertension defined as BP \> 150/100 mm Hg despite medication * Prior history of hypertensive crisis or hypertensive encephalopathy * Recent history (within 6 months of start of screening) of unstable angina pectoris pattern, myocardial infarction (including non-Q wave MI), or NYHA (New York Heart Association) Class III and IV Congestive Heart Failure (CHF) * Subjects who have clinical evidence of carcinoid-induced heart disease * History of prior cerebrovascular accident (CVA), including transient ischemic attach (TIA) * Known central nervous system (CNS) disease except for treated brain metastasis * History of torsade de pointes, ventricular tachycardia or fibrillation, pathologic sinus bradycardia (\<60 bpm), heart block (excluding 1st degree block, being PR interval prolongation only), congenital long QT syndrome or new ST segment elevation or depression or new Q wave on ECG * Corrected QT interval (QTc) \> 480 msec * Ongoing treatment with any drugs known to prolong the QTc interval, including anti-arrhythmic medications (stable regimen of antidepressants of the selective serotonin reuptake inhibitor (SSRI) class is allowed)) * Evidence of bleeding diathesis or significant coagulopathy (in the absence of therapeutic anticoagulation) * Significant vascular disease or recent peripheral arterial thrombosis * Known intolerance of or hypersensitivity to fosbretabulin * History of solid organ transplant or bone marrow transplant * Any other intercurrent medical condition, including mental illness or substance abuse, deemed by the Investigator to be likely to interfere with a subject's ability to sign informed consent, cooperate and participate in the study, or interfere with the interpretation of the results * High grade or poorly differentiated NET * NET tumor other than PNET or GI-NET * No elevated biomarker (\>ULN) that can be followed * Received regional hepatic infusion therapy within 6 months of enrollment (RFA allowed \>6 months prior to enrollment)