2069 Background: S-CKD602 is a pegylated STEALTH liposomal formulation of CKD-602, a semi-synthetic analogue of camptothecin. Camptothecins are topoisomerase I interactive agents occurring in equilibrium between the active lactone (LAC) and inactive hydroxy acid (HA) forms. STEALTH liposomes prolong the circulation time in plasma, achieve high drug exposure in tumor, and allow for a convenient schedule of administration. The internal acidic pH of S-CKD602 preserves the LAC form. Results from the first human dose-escalation study are presented. Methods: Patients (pts) were treated with S-CKD602 by 1-h IV infusion once every 3 weeks. Modified Fibonacci escalation was used (3–6 pts/cohort), and dose levels were 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.65, and 0.85 mg/m2. For PK analysis, plasma samples were obtained prior to administration, end of infusion, and at 2, 4, 8, 24, 48, 72, and 96 h after administration, and at days 8 and 15 of cycle 1. Plasma samples were processed to measure concentrations of encapsulat...