Correlation of sorafenib plasma concentrations and clinical toxicity: A prospective population pharmacodynamic and pharmacokinetic study

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Background: Sorafenib is an angiogenesis inhibitor recently approved for the treatment of metastatic renal cell carcinoma and hepatocarcinoma. This oral multi-targeted kinase inhibitor blocks the VEGF, PDGF receptors, BRAF and c-kit. In clinical trials, severe toxicities included rash, hand-foot syndrome and diarrhea. We investigated the relationship between severe toxicity and sorafenib plasmatic exposure. Patients and methods: From February 2008 to December 2008, 32 patients (pts) were treated with sorafenib (800 mg given daily). Clinical and blood exams were performed at baseline and every 2 weeks. Toxicity events were graded according to National Cancer Institute Common Toxicity Criteria 3.0. The sorafenib area under the plasma concentration-time curve over 12 hours (AUC0–12) was determined every 2 weeks by gradient elution liquid chromatography, data analysis with one-compartment disposition and a population approach using NONMEM software. Grade 3 toxicity free survival was estimated by Kaplan-Meier method. Results: Pts (23 males), ECOG 0–1 (27 pts), median age 62.8 years (range 37–78), with metastatic hepato-carcinoma (11), melanoma (6), thyroid cancer (8), renal cell carcinoma (7), received a median treatment duration of 94 days (range : 7–330). 20 pts experienced grade 3 toxicities with 33 events: hand-foot hyperkeratosis (14), diarrhea (5), cutanous rash (4), asthenia (2), anorexia (2), dyspnea (1), scrotal toxicity (1), post surgical complication (1), hypertension (1), increase creatinine level (1), digestive hemorrhage (1). The median AUC0–12 was 62.4 mg/L.h, ranging from 28.7 to 202.2 mg/L.h. Amongst pts experiencing grade 3 toxicity, two groups of 16 pts were defined with the median AUC0- 12 as cut off: low exposure (Lw) and high exposure (Hi). Six Lw pts experienced grade 3 toxicity versus 14 Hi pts (exact Fisher Test p=0.009). The probability of free grade 3 toxicity survival was higher for Lw (Logrank test p=0.004). Conclusions: These results show that grade 3 toxicity occurrence may be related to high plasma sorafenib exposure. This supports the need for therapeutic drug monitoring to prevent toxicity grade 3 occurrence and therefore optimize the clinical management of patients under sorafenib.

No significant financial relationships to disclose.