Patients are randomized in a double-blinded manner, with 12 patients entering the treatment arm and 6 patients entering the control arm. Patients in the treatment arm receive 6 single escalating doses of 1592U89 separated by at least a 6-day washout period. Patients in the control arm receive 6 single oral doses of placebo at least 6 days apart. The second and third doses of 1592U89 are equivalent. During these doses, investigators study the effects of food on the pharmacokinetics of 1592U89 by giving half of the patients the second dose with a standardized, high-fat breakfast and giving the other half the dose in a fasted state. During the third dose, patients are crossed over so that patients who received the second dose with a meal now receive it in a fasted state, and vice versa. Following the sixth dose, investigators break the blind. Patients who received 1592U89 take a seventh dose in solution form and return for follow-up at least 7 days later; patients who received placebo receive no further treatment or follow-up. Serial blood and urine samples are collected before and after each administration of 1592U89 (or placebo) for determination of plasma and urine concentrations of 1592U89, and investigators monitor patients closely for adverse events or abnormal laboratory test findings.