Inclusion Criteria:

- Cytologically or histologically confirmed pancreatic adenocarcinoma (excluding islet
cell or ampullary tumors) that is metastatic or unresectable

- Measurable disease as defined by Response Evaluation Criteria in Solid Tumors
(RECIST) 1.1

- Patients may have received prior chemotherapy for advanced disease as long as it did
not include gemcitabine; if patients received prior adjuvant therapy including
gemcitabine, patients must be > 6 months from the last dose of gemcitabine; patients
must have recovered from side effects of prior therapy to grade =< 1 as measured by
National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events
(CTCAE) version (v) 4.0

- Patients may have received prior radiation presuming > 4 weeks since last dose and
measurable disease outside the radiation field

- Eastern Cooperative Oncology Group (ECOG) performance status =< 1

- Anticipated life expectancy of greater than 3 months

- Leukocytes >= 3,000/mcL

- Absolute neutrophil count >= 1,500/mcL

- Platelets >= 100,000/mcL

- Total bilirubin < 2.5 x institutional upper limit of normal (ULN)

- Aspartate aminotransferase (AST) (serum glutamic pyruvate transaminase
[SGOT])/alanine aminotransferase (ALT) (serum glutamic pyruvate transaminase [SGPT])
=< 2.5 X institutional upper limit of normal OR =< 5 X institutional upper limit of
normal when liver metastases are present

- Creatinine within normal institutional limits OR creatinine clearance >= 60
mL/min/1.73 m^2 for patients with creatinine levels above institutional normal

- Women of child-bearing potential and men must agree to use adequate contraception
(hormonal or barrier method of birth control; abstinence) prior to study entry and
for the duration of study participation; should a woman become pregnant or suspect
she is pregnant while participating in this study, she should inform her treating
physician immediately

- Ability to understand and the willingness to sign a written informed consent document

- Patients must be able to swallow pills

Exclusion Criteria:

- Patients who have had chemotherapy or radiotherapy within 4 weeks (6 weeks for
nitrosoureas or mitomycin C) prior to entering the study or those who have not
recovered from adverse events due to agents administered more than 4 weeks earlier
(with the exception of alopecia and neuropathy); no radiation is allowed on study

- Patients who are receiving any other investigational agents

- Major surgical procedure within 4 weeks of treatment

- Patients with known brain metastases

- History of allergic reactions attributed to compounds of similar chemical or biologic
composition to dasatinib, erlotinib or gemcitabine

- Uncontrolled intercurrent illness including, but not limited to, ongoing or active
infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
arrhythmia, or psychiatric illness/social situations that would limit compliance with
study requirements

- Pregnant women are excluded from this study because of the potential for teratogenic
or abortifacient effects; because there is an unknown but potential risk for adverse
events in nursing infants secondary to treatment of the mother with erlotinib or
dasatinib, breastfeeding should be discontinued if the mother is treated with
erlotinib or dasatinib

- Patients with immune deficiency are at increased risk of lethal infections when
treated with marrow-suppressive therapy and are thus excluded

- Patients on potent cytochrome P450 3A4 (CYP3A4) inducers and inhibitors

- Malabsorption syndrome or other condition that would interfere with intestinal
absorption

- Other active malignancy (with the exception of locally treated non-melanoma skin
cancers)

- Human immunodeficiency virus (HIV) positive patients who are on combination
antiretroviral therapy

- Myocardial infarction or ventricular tachyarrhythmia within 6 months

- Prolonged corrected QT interval (QTc) > 480 msec (Fridericia correction)

- Known ejection faction less than institutional normal

- Major conduction abnormality (unless a cardiac pacemaker is present)