Patient description: A 34 year old man comes to the clinic complaining of dizziness and severe diarrhea since yesterday. He has returned from an international trip few days ago and was living in a camp in Sudan for a month. He developed abdominal pain followed by bloating and nausea as well as loose bowel movements. Soon he was having profuse watery diarrhea without odor. The stool is watery and white but the patient has no fever. Blood pressure is 95/62 lying down and drops to 75/40 standing. The skin turgor has reduced. HR is 110 and he looks ill with dry mucosa. V. cholerae was seen in dark-field microscopy of a fresh stool specimen. The lab study is as bellow: Sodium 137 meq/L Potassium 2 meq/L Chloride 94meq/L CO2 15 meq/L Fecal leukocytes None seen Fecal occult blood Negative

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Advanced Digestive System Neuroendocrine Neoplasm Digestive System Neuroendocrine Tumor Foregut Carcinoid Tumor Hindgut Carcinoid Tumor Locally Advanced Unresectable Digestive System Neuroendocrine Neoplasm Metastatic Digestive System Neuroendocrine Neoplasm Midgut Neuroendocrine Tumor G1 Pancreatic Neuroendocrine Tumor Refractory Digestive System Neuroendocrine Neoplasm Histologically confirmed GEP NET, radiographically progressed on at least one line of standard therapy within the past 12 months Primary tumors may be in: pancreas, foregut (esophagus, stomach, duodenum), midgut (small intestine, appendix), hindgut (large intestine, rectum), or unknown origin Tumors may be functional (associated with clinical symptoms of hormone secretion) or non-functional Well-differentiated low grade (Ki67 index < 3% or mitotic index < 2 mitoses/10 high power fields [HPF]), or intermediate grade (Ki67 index 3-20% or mitotic index 2-20 mitoses/10 HPF) NETs Metastatic or locally advanced unresectable disease Measurable disease by computed tomography (CT) or magnetic resonance imaging (MRI) as per Response Evaluation in Solid Tumors (RECIST) version (v) 1.1 Prior or concurrent therapy with somatostatin analogs (SSAs) is allowed. If concurrent therapy, dose must be stable for at least 2 months Patients with carcinoid syndrome must have symptoms controlled with stable doses of SSAs for at least 2 months * Telotristat is not allowed Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2 Able to swallow oral medications  Poorly differentiated or high-grade GEP NETs (Ki67 index > 20% or mitotic index > 20 mitoses/10 HPF) Prior treatment with abemaciclib or other CDK4/6 inhibitors Known hypersensitivity to abemaciclib or its components Receipt of any therapy or investigational agent within 4 weeks prior to study registration, except SSAs Any surgery, radiation, or embolization within 4 weeks Peptide receptor radionuclide therapy (PRRT) within 6 weeks Patients receiving other investigational agents Patients who have not recovered from adverse events of prior therapy to =< grade 1 (National Cancer Institute [NCI] Common Terminology for Adverse Events [CTCAE] version [v] 5), except for alopecia or grade =< 2 peripheral neuropathy prior to study treatment initiation. Subjects must have fully recovered from the acute effects of any prior radiotherapy Patients with untreated or symptomatic brain metastases (must be off corticosteroids for >= 4 weeks) Uncontrolled or untreated intercurrent illness including, but not limited to, active bacterial or fungal infection, congestive heart failure, severe/unstable angina, syncope of cardiac etiology, ventricular arrythmia (including but not limited to ventricular tachycardia, ventricular fibrillation), history of cardiac arrest, interstitial lung disease, severe dyspnea at rest or requiring oxygen supplementation, arterial or venous thrombotic event, pre-existing chronic condition resulting in baseline grade >= 2 diarrhea, or psychiatric illness/social situations that would limit compliance with study requirements