This study is designed to assess the effect of food and antacid use on the pharmacokinetic properties of BIIB021.

This study has 2 phases (the Food Phase and the Antacid Phase), each consisting of a 2-period, 2-sequence, 2-treatment crossover design. The Food Phase will assess the effect of a high fat meal on the pharmacokinetics of 100 mg BIIB021, and the Antacid Phase will assess the effect of an antacid (ranitidine) on the pharmacokinetics of 450 mg BIIB021 in the same subjects. Ranitidine 150 mg will be taken the evening before and the morning of the antacid dosing day.

Inclusion Criteria:

• Subjects with histologically or cytologically confirmed solid tumors who have failed or are not candidates for standard therapies or for whom no approved therapy is available.
• Eastern Cooperative Oncology Group (ECOG) performance status of greater or equal to 2.
• Medically able to tolerate a high fat meal and to fast as per protocol.
• Expected survival time of at least 3 months in the opinion of the Investigator.
• Ability to take ranitidine as per protocol.
• Must be able to swallow and retain oral medication.
• Lab values consistent with adequate renal, hepatic, and bone marrow functions.
• Electrocardiogram (ECG) with QTc of ≤450 msec for men or ≤470 msec for women and no clinically significant findings.

Exclusion Criteria:

• Pregnant (positive pregnancy test) or nursing women.
• Previous treatment with an Hsp90 inhibitor.
• Use of antacids within 7 days of Study Day 1.
• Prior antitumor therapies, including prior experimental agents or approved antitumor therapies within 28 days of the first dose of BIIB021.
• Major surgery or radiation within 28 days of the first dose of BIIB021.
• Uncontrolled, severe medical illness, which in the opinion of the Investigator and/or Sponsor could compromise protocol objectives.
• History of gastrectomy or major surgery to small intestine.
• History of exocrine pancreatic insufficiency.
• Chronic diarrhea (excess of 2 to 3 stools/day above normal frequency).
• Active bacterial or viral infection requiring concurrent treatment.
• History of hepatitis B or C or human immunodeficiency virus.
• History of central nervous system metastasis.
• Any thrombotic event occurred <3 months prior to Day 1.
• Conditions that may predispose subjects to seizures: History of seizure, previous significant head trauma
• Drug or alcohol abuse.