KPT-330 to Treat Poorly Differentiated Lung and Gastroenteropancreatic Tumors

Inclusion Criteria: * Written informed consent in accordance with federal, local, and institutional guidelines * Age ≥18 years * Patients must have a tissue diagnosis of any of the following: * Small cell lung cancer (SCLC) or poorly differentiated gastroenteropancreatic neuroendocrine tumor (GEP-NET) * Poorly differentiated metastatic neuroendocrine tumors of unknown primary origin * Measurable disease: Any primary and/or metastatic mass reproducibly measurable in one or two diameters by RECIST 1.1 parameters by cat scan (CT) scan. * Objective evidence of tumor progression within 4 months prior to study entry, as defined by serial cat scan (CT) per RECIST 1.1 criteria. (At least a 20% increase in the sum of diameters of target lesions. In addition, the sum must also demonstrate an absolute increase of at least 5 mm. The appearance of one or more new lesions is also considered progression). * Patients must have received at least one prior line of chemotherapy and must have exhausted any other standard-of-care treatment option. * Prior radiation and surgery is allowed. At least 3 weeks should have elapsed from surgery, chemotherapy, hepatic embolization/ chemoembolization or radioactive isotopes (i.e. Yttrium 90). In any case, disease progression must be documented after treatment. * Eastern Cooperative Oncology Group (ECOG) performance status of 0-1 * Concomitant octreotide treatment for carcinoid syndrome is allowed for patients whose tumor has progressed while on octreotide. Patients must have been on a stable dose of octreotide two weeks prior to enrollment and must remain on a stable dose during the study. * Hematological function: * Total white blood cell count (WBC) \> 2,000/mm³ * Absolute neutrophil (ANC) \> 1,000/mm³ * Platelet \>100,000mm³ * Adequate hepatic function within 14 days prior to C1D1: total direct bilirubin \<2 times the upper limit of normal (ULN; 1.0 mg/dL) and alanine aminotransferase (ALT) \<2.5 times ULN (30 U/L). In the case of known (radiological and/or biopsy documented) liver metastasis, ALT \<5.0 times ULN is acceptable. * Adequate renal function within 7 days prior to C1D1: estimated creatinine clearance of ≥ 30 mL/min, calculated using the formula of Cockcroft and Gault: (140-Age) • Mass (kg)/(72 • creatinine mg/dL); multiply by 0.85 if female. * Blood electrolytes should be within the following normal limits: Bicarbonate (total) 18-30 mEq/L Sodium 135-147 mEq/L Potassium 3.5-5.5 mEq/L Phosphorus 1.8-2.3 mEq/L Magnesium 1.5-3.0 mEq/L Chloride 98-106 mEq/L Calcium (total) 4.5-5.5 mEq/L * Female patients of child-bearing potential must agree to use dual methods of contraception and have a negative serum pregnancy test at screening, and male patients must use an effective barrier method of contraception if sexually active with a female of child-bearing potential. Acceptable methods of contraception are condoms with contraceptive foam, oral, implantable or injectable contraceptives, contraceptive patch, intrauterine device, diaphragm with spermicidal gel, or a sexual partner who is surgically sterilized or post-menopausal. For both male and female patients, effective methods of contraception must be used throughout the study and for three months following the last dose. Exclusion Criteria: * Patients who are pregnant or lactating * Patients with the following tumor types: lung carcinoid, pheochromocytomas, paragangliomas, medullary thyroid carcinomas, any other tumors with neuroendocrine features not listed in the inclusion criteria * Radiation, chemotherapy, or immunotherapy or any other anticancer therapy ≤3 weeks prior to C1D1 * Major surgery ≤3 weeks prior to C1D1 * Unstable cardiovascular function: * Congestive heart failure (CHF) of NYHA Class ≥3 OR * Myocardial infarction (MI) within 3 months * Uncontrolled infection requiring parenteral antibiotics, antivirals, or antifungals within one week prior to first dose; patients with controlled infection or on prophylactic antibiotics are permitted in the study * Known to be human immunodeficiency virus (HIV) seropositive * Known active hepatitis A, B, or C infection; or known to be positive for hepatitis C virus (HCV RNA) or HBsAg (HBV surface antigen) * Any underlying condition that would significantly interfere with the absorption of an oral medication * Patients who have active central nervous system (CNS) malignancy. Asymptomatic small lesions are not considered active. Treated lesions may be considered inactive if they are stable for at least 3 months. Patient with malignant cells in their cerebrospinal fluid (CSF) without CNS symptom may be included. * Serious psychiatric or medical conditions that could interfere with treatment * Patients with coagulation problems and active bleeding in the last month (peptic ulcer, epistaxis, spontaneous bleeding) * Patients with signs of gastrointestinal obstruction or uncontrolled vomiting or diarrhea (\>3 episodes/week) with electrolyte abnormalities * Concurrent therapy with approved or investigational anticancer therapeutic agents other than glucocorticoids * Participation in an investigational anti-cancer study within 3 weeks prior to cycle 1 day 1