Elevated HSP70 protein necessary plasma levels persisted for at least a week following drug exposure. Additionally, the higher mean maximum increase of HSP70 observed in Cycle 1 suggested that Hsp70 Inhibitors,Modulators,Libraries induction satu rates at dose levels above 180 mgm2, further supporting the selection of the 200 mgm2 dose for Phase 2. There was no statistically significant association between HSP70 induction and DCR at 8 weeks, or with diarrhea incidence. Discussion We report here the first in human phase I study of ganetespib administered once weekly for 3 weeks of a 4 week cycle. This study demonstrated dose proportional pharmacokinetics and tolerability at doses ranging from 7 mgm2 to 216 mgm2 in patients with advanced solid malignancies. There were no DLTs in the 216 mgm2 dose escalation cohort, and therefore, this dose was rounded to 200 mgm2 and selected as the RP2D of ganetespib.
After this phase I study, ganetespib 200 mgm2 has been Inhibitors,Modulators,Libraries studied in several phase II studies as a single agent, and has shown to be well tolerated. The most common toxicities were diarrhea and fatigue. Although there was no correlation with AUC or Cmax, diarrhea incidence appeared to increase with increasing doses of ganetespib, and it may serve as a PD biomarker for ganetespib. Diarrhea has also been observed with other Hsp90 inhibitors, suggesting that it may be a mechanism based toxicity rather than an off target effect. EGFR, a known client protein to Hsp90, is recognized to play a key role in intestinal Inhibitors,Modulators,Libraries epithelial integrity and restitu tion. Consequently, proactive diarrhea manage ment is incorporated in recent ganetespib clinical trials.
Two patients in the current study experienced treatment related visual impairment, which Inhibitors,Modulators,Libraries were mild and transient. Hsp90 plays a key role in the folding of key signaling mole cules required to maintain retinal function. Inhibitors,Modulators,Libraries Visual disor ders, including blurred vision, flashes, delayed lightdark accommodation and photophobia, have been reported with other Hsp90 inhibitors, suggesting retinal injury. It was recently postulated Ixazomib Sigma that high retinal exposure and the slow elimination rate of several Hsp90 inhibitors with hydrophilic properties led to induction of apoptosis in the retinal outer nuclear layer. Over 400 patients have been treated to date with ganetespib in other studies. The inci dence of treatment related visual changes is 3% suggesting that the physicochemical properties of ganetespib molecular structure may provide a favorable safety profile. No formal ophthalmologic examination was required in this study. Clinical activity of ganetespib was demonstrated in heav ily pre treated patients with metastatic cancers. Disease stabilization was generally associated with doses higher than 80 mgm2.