A phase I study of tasisulam sodium (LY573636 sodium), a novel anticancer compound, administered as a 24-h continuous infusion in patients with advanced solid tumors

Abstract

To determine the recommended/maximum tolerated dose (MTD), pharmacokinetics (PK), and safety profile of tasisulam sodium (hereafter tasisulam), a novel anticancer agent. In this phase I study, tasisulam was administered as a 24-h continuous intravenous infusion on day 1, every 28 days, to patients with advanced solid tumors. A flat-dosing schema was planned for four cohorts of 3-6 patients: 600, 1,200, 2,000, and 2,500 mg. Twenty-six patients were enrolled. No dose-limiting toxicities (DLTs) were observed until cohort 3 (grade 3 hyperbilirubinemia). Interim PK analyses of this and another ongoing phase I study suggested that a lower dose after cycle 1 was necessary for doses ≥2,500 mg because of the long half-life of tasisulam (~14 days). Therefore, a loading dose of 2,500 mg followed by a chronic dose of 1,750 mg was implemented for cohort 4; one patient developed DLT (grade 4 neutropenia), and another developed grade 3 thrombocytopenia in cycles 2 and 3. These findings, together with PK data, which indicated a disproportionate increase in free drug relative to total tasisulam concentrations at doses >2,500 mg, led to the determination of the 2,500-/1,750-mg regimen as the MTD. Eight patients had stable disease, and two patients unconfirmed partial responses. When administered as a flat-dose, 24-h infusion, the MTD of tasisulam was a loading dose of 2,500 mg followed by a chronic dose of 1,750 mg, every 28 days. Consistent with the profile of the 2-h infusion in clinical development, bone marrow suppression was the major DLT.