Because of the low probability of achieving the primary endpoint.

The purpose of this study is to compare the effects of ICA-17043 to placebo with or without hydroxyurea (an oral drug used for treatment of sickle cell disease) in patients with sickle cell disease who have had 2 or more acute sickle-related painful crises requiring a visit to a medical facility within the past 12 months.

Inclusion Criteria:

• 16 to 65 years of age (inclusive)
• Male or female (not capable of becoming pregnant or using appropriate birth control)
• Medical history of sickle cell disease
• Have a history of at least two or more acute sickle-related painful crises requiring a visit to a medical facility within the preceding 12 months

Exclusion Criteria:

• Hemoglobin <4 or >11 g/dL
• On a chronic transfusion program
• Has significant active and poorly controlled (unstable) cardiovascular, neurologic, endocrine, hepatic, or renal disorders clearly unrelated to sickle cell disease