A phase I study of tasisulam sodium using an albumin-tailored dose in Japanese patients with advanced solid tumors

This phase I study was designed to determine the maximum tolerated dose (MTD) and the dose to be recommended for a future phase II study of tasisulam sodium in Japanese patients with advanced, refractory solid tumors. Safety, pharmacokinetics and preliminary anti-tumor activities were assessed. Due to high-affinity albumin binding, an albumin-tailored dose to reduce the variability in tasisulam exposure was also studied.

A dose escalation scheme of tasisulam was used over 4 dose levels. Dose levels 1-3 targeted the maximum plasma concentration (C max) of 300, 340, and 360 μg/mL. Dose level 4 used an albumin-tailored range of C max-targeted doses to achieve an albumin-corrected exposure (AUCalb) of 1,200-6,400 μg h/mL, the range chosen for global tasisulam studies. Tasisulam was administered intravenously on day 1 of each 21-day (dose levels 1 and 2) or 28-day (dose levels 3 and 4) cycle.

The major adverse events were related to bone marrow suppression, particularly neutropenia and thrombocytopenia. Dose-limiting toxicities (DLTs) were not observed until dose level 4, where 3 out of 6 patients experienced DLT, despite a tendency toward lower AUCalb variability (CV %) in the albumin-tailored dose group (38 %) compared with the targeted C max groups (50-236 %).

Tasisulam in doses up to dose level 3 (target C max 360 μg/mL) was well tolerated. Although albumin-tailored dosing provided less AUCalb variability, a MTD that aligns with other global tasisulam studies was not identified. A lower AUCalb range may be required for the Japan population.