Results of two phase I dose escalation studies of the oral heat shock protein 90 (Hsp90) inhibitor SNX-5422.

Abstract

2617 Background: SNX-5422 is a prodrug of SNX-2112, a highly potent, non-geldanamycin analog, HSP90 inhibitor with preclinical anti-tumor activity in multiple tumor models. These phase 1 studies were designed to evaluate safety and tolerability, determine dose limiting toxicities, maximum tolerated doses (MTDs), and describe pharmacokinetics of SNX-2112 and SNX-5422. Methods: Two phase 1, open-label, 3 + 3 dose-escalation studies evaluated SNX-5422 when given daily (QD) or every-other-day (QOD) during the first 30 days of treatment in patients (pts) with advanced solid tumors or lymphoma. Plasma concentrations of SNX-2112 and SNX-5422 were measured after the first and 11th (steady state) doses. Tumor assessments were performed every 8 weeks. Results: In both studies, pts received SNX-5422 QOD, 3 wks on/1 wk off, with doses ranging from 4 to 133 mg/m2 QOD. In one study, pts also received QD doses from 50 to 89 mg/m2, 3 wks on/1 wk off, and 50 mg/m2 QD continuously. Fifty-six pts (34M/22F; mean age 62 years) were enrolled. Treatment-related adverse events were mainly low grade (G), including diarrhea (64%), nausea (39%), vomiting (29%), fatigue (27%), abdominal pain (14%), and anorexia (14%). Reversible G 1 blurry vision, and G 1-2 blurry vision/vision darkening were reported by 1 pt on 100 mg/m2 QOD, and 4 pts treated with 50 to 89 mg/m2 QD. G 3 diarrhea was dose limiting in 2 of 3 pts (89 mg/m2 QD; 133 mg/m2 QOD). MTDs for the QOD and QD schedules were declared at100 mg/m2 and 67 mg/m2, respectively. The QD schedule was associated with higher incidences of treatment related adverse events. 38 pts were evaluable for response including 1 confirmed durable complete response, 1 unconfirmed partial response, and 17 with stable disease. Activity was seen in adrenal, lung, liver, neuroendocrine, GIST, and prostate. All but 2 were seen with the QOD schedule. Conclusions: SNX-5422 mono-therapy was generally well tolerated and showed promising signs of efficacy in pts with advanced solid tumors. Given the superior benefit-risk profile of QOD dosing over QD dosing based on these preliminary clinical findings, 100 mg/m2 QOD has been selected for further clinical testing. Clinical trial information: NCT00506805 and NCT01611623.