Phase I trial of the oral smoothened inhibitor sonidegib in combination with paclitaxel in patients with advanced solid tumors.

Purpose To establish a recommended phase II dose (RP2D) for the oral smoothened inhibitor sonidegib in combination with paclitaxel; secondary objectives include evaluation of safety, tolerability, markers of Hedgehog (Hh) signaling and preliminary antitumor activity. Methods Patients with advanced solid tumors were enrolled in cohorts of escalating sonidegib dose levels (400mg, 600mg and 800mg orally, once daily on days 1-28) in combination with paclitaxel 80 mg/m2 on days 1, 8 and 15 in 4-weekly cycles. Dose-limiting toxicities (DLTs) were assessed using CTCAE v4. Once the RP2D was defined, patients with advanced ovarian carcinoma were treated at this dose level in an expansion phase. Biomarkers of Hh signaling were assessed by immunohistochemistry in archival tissue and antitumor activity evaluated using RECIST 1.1. Results 18 patients were treated: 3 at 400 mg, 3 at 600 mg and 12 at 800 mg sonidegib. Only one patient treated at 800 mg presented a DLT (prolonged neutropenia resulting in failure to receive 75% of the planned sonidegib dose). However, 4 of 12 patients treated at 800 mg had their sonidegib dose reduced for toxicity after cycle 1. Hh biomarker (SHH, Patched, SMO and GLI1) staining did not correlate with clinical activity. Best response was partial response in 3 patients (2 ovarian, 1 breast cancer) and stable disease >4 cycles in 3 patients (2 ovarian, 1 anal cancer). Conclusions The combination of sonidegib and paclitaxel is tolerable and evidence of antitumor activity was identified. The RP2D of sonidegib was 800 mg in combination with paclitaxel 80mg/m2.

Evidence for the pro-oxidant effect of gamma-glutamyltranspeptidase-related enzyme.

It has been previously reported that the metabolism of reduced glutathione (GSH) by gamma-glutamyltranspeptidase (GGT) in the presence of chelated metals leads to free radical generation and lipid peroxidation (LPO). The present study demonstrates for the first time that an established cell line expressing GGT-rel, a human GGT-related enzyme, metabolizes extracellular GSH to cysteinylglycine (CysGly) in a time-dependent manner when cells were incubated in a medium containing 2.5 mM GSH and 25 mM glycylglycine. Supplementation with 150-165 microM Fe(3+)-EDTA resulted in a reactive oxygen species (ROS) generation process. The resulting data showed a significantly higher level (7.6-fold) of ROS production in the GGT-rel positive cells in comparison with the GGT-rel negative control cells. CysGly and Cys, but not GSH, were responsible for the observed ROS production, as we confirmed by measuring the same process in the presence of Fe(3+)-EDTA and different thiols. A higher iron reduction and an increased LPO level determined by malondialdehyde HPLC measurement were also found in GGT-rel-overexpressing cells compared to GGT-rel negative cells. Our data clearly indicate that in the presence of iron, not only GGT, but also GGT-rel has a pro-oxidant function by generation of a reactive metabolite (CysGly) and must be taken into account as a potential physiopathological oxidation system.

Gamma-glutamyltranspeptidase-dependent glutathione catabolism results in activation of NF-kB.

gamma-glutamyltranspeptidase (GGT) is a key enzyme implicated in the homeostasis of intracellular reduced glutathione (GSH) and hence in the regulation of the cellular redox state. Besides, the extracellular cleavage of GSH by GGT leads to reactive oxygen species (ROS) production, depending on the generation and enhanced reactivity of cysteinylglycine (CysGly). Using a model cell line, the V79 GGT, which highly expresses a human GGT transgene, we examined whether the GGT induced oxidant stress could modulate intracellular transcription factors. For the first time, we show that GGT-dependent ROS production induces the NF-kB-binding and transactivation activities. This induction mimicked the one observed by H(2)O(2) and was inhibited by catalase, suggesting the involvement of H(2)O(2) in the NF-kB activation.