Phase I Study of Zotiraciclib in Combination with Temozolomide for Patients with Recurrent High-grade Astrocytomas.

PURPOSE To investigate the toxicity profile and establish an optimal dosing schedule of zotiraciclib with temozolomide (TMZ) in patients with recurrent high-grade astrocytoma. EXPERIMENTAL DESIGN This two-stage phase 1 trial determined the maximum tolerated dose (MTD) of zotiraciclib combined with either dose-dense (Arm1) or metronomic (Arm2) TMZ using a Bayesian Optimal Interval design; then a randomized cohort-expansion compared the progression-free survival rate at 4 month (PFS4) of the two arms for an efficient determination of a TMZ schedule to combine with zotiraciclib at MTD. Pharmacokinetics (PK) and pharmacogenomic (PG) profiling were included. Patient-reported outcome was evaluated by longitudinal symptom burden. RESULTS Fifty-three patients were enrolled. Dose-limiting toxicities were neutropenia, diarrhea, elevated liver enzymes, and fatigue. MTD of zotiraciclib was 250mg in both arms and thus selected for the cohort expansion. Dose-dense TMZ plus zotiraciclib (PSF4 40%) compared favorably with metronomic TMZ (PFS4 25%). Symptom burden worsened at Cycle 2 but stabilized by Cycle 4 in both arms. A significant decrease in absolute neutrophil count and neutrophil reactive oxygen species production occurred 12-24 hours after an oral dose of zotiraciclib but both recovered by 72 hours. PK/PG analyses revealed that the CYP1A2_5347T>C (rs2470890) polymorphism was associated with higher AUCinf value. CONCLUSIONS Zotiraciclib combined with TMZ is safe in patients with recurrent high-grade astrocytomas. Zotiraciclib-induced neutropenia can be profound but mostly transient, warranting close monitoring rather than treatment discontinuation. Once validated, polymorphisms predicting drug metabolism may allow personalized dosing of zotiraciclib.