 2. History or clinical evidence of central nervous system CNS metastases or leptomeningeal carcinomatosis, except for patients with previously-treated CNS metastases, who are asymptomatic and have had no requirement for steroids or anti-seizure medication for 6 months prior to first dose of study drug. CNS screening with computed tomography CT or magnetic resonance imaging MRI is required only if clinically indicated or if the subject has a history of CNS metastases. 