Nexavar is currently FDA approved for renal cell carcinoma and hepatocellular carcinoma . Sorafenib (Nexavar) is designed to interfere with growth of new blood vessels and the growth of new cancer cells.Inhibition of KIT signaling provides a direct anti-tumor effect in most GIST tumors and inhibition of VEGF receptors and PDGFR-β provide antiangiogenesis effects (similar to Sutent). Since RAF is downstream of KIT, inhibition of RAF might also contribute an anti-tumor effect. While inhibition of PDGRF-β has been reported, inhibition of PDGFRα, an alternative target in about 5% of GISTs has NOT BEEN reported.
The providers aim to flollow the model of a single-centre, open-label, phase I dose-escalation study that was performed to investigate the safety, pharmacokinetics (PK) and efficacy of sorafenib, a multi-kinase inhibitor, combined with irinotecan, a cytotoxic agent, in patients with advanced, refractory solid tumours. Thirty-four patients were treated: 20 in the dose-escalation phase (common tumour types: CRC [45%], ovarian [5%], pancreatic [5%]) and 14 patients in the CRC extension. Stable disease was achieved in 12/20 (60%) evaluable patients in cohorts 1–3, and 10/13 (77%) evaluable patients in cohort 4. A further patient from cohort 4 had a partial response of >200 days. The increase of SN38 exposure might be due to inhibition of formation of the SN38 glucuronide by sorafenib. In vitro, sorafenib strongly inhibited SN38 glucuronidation in human liver microsomes as indicated by a Ki value of 2.7 μmol/l. The investigators concluded: "Sorafenib 400 mg bid can be combined with irinotecan 125 mg/m2 or 140 mg for the treatment of patients with advanced, refractory solid tumours, although monitoring for toxicity is recommended."