Inclusion Criteria:

- Histologically or cytologically confirmed pancreatic adenocarcinoma

- Clinical stage IV disease

- No known brain metastases

- ECOG performance status 0-2

- Life expectancy ≥ 12 weeks

- ANC ≥ 1,500/mm³

- Platelet count ≥ 100,000/mm³

- Total bilirubin normal

- AST ≤ 2.5 times upper limit of normal (ULN)

- Alkaline phosphatase ≤ 2 times ULN (5 times ULN if liver metastases are present)

- Creatinine normal

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- Ejection fraction > 40% by echocardiogram

- Patients who received prior anthracyclines must have a normal ejection fraction
by echocardiogram

- QTc < 500 msec

- Pulse oximetry > 88% on room air at rest and after gentle exercise (according to
Group 1Medicare Guidelines)

- No history of allergic reactions attributed to compounds of similar chemical or
biologic composition to tanespimycin (17-AAG) or gemcitabine hydrochloride

- No known allergy to eggs

- No concurrent uncontrolled illness including, but not limited to, any of the
following:

- Ongoing or active infection

- Symptomatic congestive heart failure

- Unstable angina pectoris

- Cardiac arrhythmia

- Psychiatric illness/social situations that would limit compliance with study
requirements

- No active ischemic heart disease within the past 12 months

- No history of uncontrolled dysrhythmias

- No congenital long QT syndrome

- No left bundle branch block

- No other significant cardiac disease, including any of the following:

- New York Heart Association class III or IV heart failure

- Myocardial infarction within the past year

- Poorly controlled angina

- Uncontrolled dysrhythmias

- History of serious ventricular arrhythmia (ventricular tachycardia or
ventricular fibrillation ≥ 3 beats in a row)

- No clinically significant interstitial lung disease

- No symptomatic pulmonary disease requiring medication, including any of the
following:

- Dyspnea

- Dyspnea on exertion

- Paroxysmal nocturnal dyspnea

- Significant pulmonary disease requiring oxygen*, including chronic
obstructive/restrictive pulmonary disease

- No pulmonary or cardiac symptoms ≥ grade 2

- No history of cardiac or pulmonary toxicity after receiving anthracyclines (e.g.,
doxorubicin hydrochloride, daunorubicin hydrochloride, mitoxantrone hydrochloride,
bleomycin, or vincristine)

- No prior chemotherapy for metastatic disease

- No prior radiotherapy to the chest

- No prior radiotherapy that potentially included the heart in the field (e.g.,mantle
radiotherapy)

- More than 3 months since prior adjuvant chemotherapy or chemotherapy for locally
advanced disease

- More than 3 weeks since prior radiotherapy

- No concurrent medications that prolong or may prolong QTc

- No concurrent antiarrhythmic drugs

- No concurrent prophylactic colony-stimulating factors

- No other concurrent investigational agents

- No other concurrent anticancer therapy