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)