The purpose of this study is to assess the safety and tolerability of KRN951 administered to patients with solid tumors. In the single dose period, patients in each cohort will receive one oral dose of KRN951 in the first day, followed by a 6-day rest period during which no treatment is received. After that, patients in each cohort will receive one oral dose of KRN951 daily over a 21-day treatment period, followed by a 7-day rest period during which no treatment is received. Treatment will be continued in the absence of disease progression or unacceptable adverse events.

Inclusion Criteria:

• Signed written informed consent
• Solid tumors to be unresponsive to, or untreatable by standard therapies
• ≥ three-month life expectancy
• Eastern Cooperative Oncology Group Performance Status score of 0, 1 or 2

Exclusion Criteria:

• Hematologic abnormality
• Myocardial infarction or clinically symptomatic left ventricular failure
• Active hypertension or controllable hypertension more than 3 antihypertensive medications
• Symptomatic CNS metastasis
• Unhealed wounds
• Active infections
• Hepatic or renal functional disorder
• Any of the HBs antigen, HCV antibody and HIV antibody positivity
• Prior use of any chemotherapy, radiotherapy, immunotherapy or surgery within four weeks previous to first dose of study drug
• Pregnant or lactating women
• Women of childbearing potential and fertile men, unless willing to use adequate contraceptive protection