Pharmacokinetic analysis and pharmacodynamic evidence of autophagy inhibition in patients with newly diagnosed glioblastoma treated on a phase I trial of hydroxychloroquine in combination with adjuvant temozolomide and radiation (ABTC 0603).

Abstract

3086 Background: Preclinical studies indicate autophagy inhibition by hydroxychloroquine (HCQ) can augment the efficacy of DNA damaging cancer therapy. The primary objective of this trial was to determine the maximum tolerated dose (MTD) of HCQ in combination with adjuvant chemoradiation and temozolomide (TMZ) for glioblastoma (GBM). Methods: A 3+3 phase I trial design was conducted in surgically resected GBM patients (Pts). Pts received HCQ (200 -800 mg po qd) with radiation therapy (RT) and concurrent TMZ (75 mg/m2 po qd) followed by adjuvant TMZ (150-200 mg/m2 po qd ) 5/28 days for up to 6 cycles. Limited pharmacokinetic (PK) sampling and a novel high performance liquid chromatography/tandem mass spectroscopy assay for HCQ and metabolites were used to build a population PK model and blood concentration relationships. Quantitative electron microscopy (EM) and immunoblotting against the autophagy marker LC3 were used to assess therapy-associated changes in autophagic vesicles (AV) in peripheral blood mononuclear cells (PBMC). Results: 17 patients were enrolled at 6 centers with 15 pts evaluable for dose limiting toxicities (DLT). No DLT was observed in cohorts 1 or 2 (200, 400 mg HCQ). In cohort 3 (800 mg HCQ) 3/3 pts experienced Grade 3-4 neutropenia and thrombocytopenia, one with fever and sepsis. Deescalation of HCQ to 400 mg and 600 mg qd resulted in no DLTs and HCQ 600 mg qd was found to be the MTD. PK analysis indicated dose-proportional exposure for HCQ. Concentrations of HCQ which preclinical studies indicate are required for autophagy inhibition were achieved. Significant therapy-associated increases in AV with confirmatory elevations in LC3II were observed in PBMC in 1/5 pts at 400 mg, 2/3 patients at 600 mg and 2/2 patients at 800 mg HCQ. Conclusions: HCQ 600 mg is the MTD in this regimen and population. Dose-dependent myelosuppresion suggests a mechanistic interaction between HCQ and TMZ/RT. A novel PD assay for autophagy inhibition detected HCQ dose-dependent changes in AV in PBMC. Analyses of PK-PD interactions and a phase II study are underway. No significant financial relationships to disclose.