A Study of Abemaciclib (LY2835219) Alone or in Combination With Other Agents in Participants With Previously Treated Pancreatic Ductal Adenocarcinoma

Inclusion Criteria:

* Histological or cytological diagnosis of ductal adenocarcinoma of the pancreas.
* Metastatic disease with documented disease progression following previous treatment with at least one, but no more than 2 prior therapies, with one of the prior therapies having been either gemcitabine-based or fluoropyrimidine-based therapy. Neoadjuvant and/or adjuvant therapies for localized resectable or unresectable PDAC each count as a line of therapy if multiagent chemotherapy regimens were administered (and neoadjuvant regimen was different than adjuvant regimen) and if the participant progressed with metastatic disease while taking or within 6 months of completion of (neo)adjuvant therapy.
* Measurable disease per Response Evaluation Criteria in Solid Tumors (RECIST) 1.1.
* Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
* Participant for whom treatment with monotherapy chemotherapy such as gemcitabine or capecitabine is a reasonable choice.
* Discontinued all prior treatment for cancer at least 14 days prior to initial dose of study treatment.
* Adequate organ function.

  * allow alanine aminotransferase (ALT) or aspartate aminotransferase (AST) up to 5x upper limit of normal (ULN) if liver metastases.
  * allow bilirubin up to 2.5 times ULN if elevation is not associated with other signs of liver toxicity or can be explained by mechanical obstruction - requires clinical research physician approval.

Exclusion Criteria:

* Have a personal history of any of the following conditions: syncope of either unexplained or cardiovascular etiology, ventricular arrhythmia (including but not limited to ventricular tachycardia and ventricular fibrillation), or sudden cardiac arrest. Exception: Participants with controlled atrial fibrillation for \>30 days prior to study treatment initiation are eligible.
* Have insulin-dependent diabetes mellitus. Participants with type 2 diabetes mellitus are eligible if adequate control of blood glucose level is obtained by oral anti-diabetics as documented by hemoglobin A1c (HbA1c) \<7%.
* Have symptomatic central nervous system metastasis. Screening of asymptomatic participants is not required for enrollment.
* Have had major surgery within 7 days prior to initiation of study drug to allow for postoperative healing of the surgical wound and site(s).
* Have previously received treatment with any cyclin-dependent kinase (CDK) 4 and 6 inhibitor or phosphatidylinositol 3-kinase (PI3K) and/or mammalian target of rapamycin (mTOR) inhibitor or have a known hypersensitivity to any component of the investigational products in this study.
* Have a known hypersensitivity to investigator's choice of standard of care (gemcitabine or capecitabine).