BACKGROUND: Pazopanib, an oral angiogenesis inhibitor targeting vascular endothelial growth factor receptor (VEGFR)/platelet-derived growth factor receptor (PDGFR)/c-Kit, is approved in locally advanced/metastatic renal cell carcinoma (RCC).
METHODS: Data from trials in advanced solid tumours and advanced/metastatic RCC were used to explore the relationships between plasma pazopanib concentrations and biomarker changes, safety, and efficacy. Initially, the relationships between pharmacokinetic parameters and increased blood pressure were investigated, followed by analysis of steady-state trough concentration (Cτ) and sVEGFR2, safety, progression-free survival (PFS), response rate, and tumour shrinkage. Efficacy/safety end points were compared at Cτ decile boundaries.
RESULTS: Strong correlation between increased blood pressure and Cτ was observed (r2=0.91), whereas weak correlation was observed between Cτ and decline from baseline in sVEGFR2 (r2=0.27). Cτ threshold of >20.5 μg ml-1 was associated with improved efficacy (PFS, P<0.004; tumour shrinkage, P< 0.001), but there was no appreciable benefit in absolute PFS or tumour shrinkage from Cτ >20.5 μg ml-1. However, the association of Cτ with certain adverse events, particularly hand-foot syndrome, was continuous over the entire Cτ range.
CONCLUSIONS: The threshold concentration for efficacy overlaps with concentrations at which toxicity occurs, although some toxicities increase over the entire Cτ range. Monitoring Cτ may optimise systemic exposure to improve clinical benefit and decrease the risk of certain adverse events.
Written by:
Suttle AB, Ball HA, Molimard M, Hutson TE, Carpenter C, Rajagopalan D, Lin Y, Swann S, Amado R, Pandite L. Are you the author?
Salix Pharmaceuticals, Inc., 8510 Colonnade Center Drive Raleigh, NC 27615, USA; GlaxoSmithKline, 1250 S. Collegeville Road, Collegeville, PA 19426, USA; Pharmacology Department, Université de Bordeaux INSERM U657, 146 Leo Saignat, Bordeaux 33076, France; GU Oncology Center of Excellence, Baylor University Medical Center, 3410 Worth Street, Dallas, TX 75246, USA; GlaxoSmithKline, 5 Moore Drive, Research Triangle Park, NC 27709, USA.
Reference: Br J Cancer. 2014 Nov 11;111(10):1909-16.
doi: 10.1038/bjc.2014.503
PubMed Abstract
PMID: 25349968