This is a phase II, multi-center, open-label study of the safety and efficacy of atiprimod treatment in patients with low to intermediate grade neuroendocrine carcinoma who have metastatic or unresectable local-regional cancer and who have either symptoms (diarrhea, flushing and/or wheezing) despite standard therapy (octreotide) or progression of neuroendocrine tumor(s) (defined as the appearance of one or more new lesions or a 20% increase in the sum of the longest diameter of target lesions during the 6 months prior to enrollment). A maximum of 40 evaluable patients will be enrolled in this study. Atiprimod will be administered orally as a single daily dose of 120 mg/day for 14 days, followed by a 14-day treatment-free period (i.e., 1 treatment cycle = 28 days).