A phase I trial of bortezomib with temozolomide in patients with advanced melanoma: toxicities, antitumor effects, and modulation of therapeutic targets

Abstract

Purpose: Preclinical studies show that bortezomib, a proteasome inhibitor, blocks NF-kappaB activation and, combined with temozolomide, enhances activity against human melanoma xenografts and modulates other critical tumor targets. We initiated a phase I trial of temozolomide plus bortezomib in advanced melanoma. Objectives included defining a maximum tolerated dose for the combination, characterizing biomarker changes reflecting inhibition of both proteasome and NF-kappaB activity in blood (if possible tumor), and characterizing antitumor activity.

Experimental design: Cohorts were enrolled onto escalating dose levels of temozolomide (50-75 mg/m(2)) daily, orally, for 6 of 9 weeks and bortezomib (0.75-1.5 mg/m(2)) by i.v. push on days 1, 4, 8, and 11 every 21 days. Peripheral blood mononuclear cells were assayed at specified time points for proteasome inhibition and NF-kappaB biomarker activity.

Results: Bortezomib (1.3 mg/m(2)) and temozolomide (75 mg/m(2)) proved to be the maximum tolerated dose. Dose-limiting toxicities included neurotoxicity, fatigue, diarrhea, and rash. Nineteen melanoma patients were enrolled onto four dose levels. This melanoma population (17 M1c, 10 elevated lactate dehydrogenase, 12 performance status 1-2) showed only one partial response (8 months) and three with stable disease >or=4 months. A significant reduction in proteasome-specific activity was observed 1 hour after infusion at all bortezomib doses. Changes in NF-kappaB electrophoretic mobility shift assay and circulating chemokines in blood failed to correlate with the schedule/dose of bortezomib, inhibition of proteasome activity, or clinical outcome.

Conclusions: We have defined phase II doses for this schedule of temozolomide with bortezomib. Although proteasome activity was inhibited for a limited time in peripheral blood mononuclear cells, we were unable to show consistent effects on NF-kappaB activation.

Fig. 1

Treatment schema for phase I study. Outline of schedule of drug therapy and all intended correlative studies. *, 20S proteasome inhibition; #, tumor biopsies (p65 and phospho-p65; after day 21, if feasible); +, NF-κB status in blood (serum cytokines-RANTES, VEGF, IL-8, MGSA, MIP-2, nuclear EMSA, nuclear p65, and phospho-IκB).

Fig. 2

Effect of bortezomib on proteasome activity short term (1 h after) and at steady state. The natural logarithm of proteasome activity data points overlay box plots, depicting the interquartile range (bottom line and top line of boxes) and median (thick solid bar). Box whiskers extend to the minimum and maximum data values but no further than 1.5 times the interquartile range. P values across days are from linear regression models with repeated measures comparing pretreatment values from baseline to day 8 and then day 8 to day 32. P values comparing pretreatment and posttreatment values on the same day are from the Wilcoxon signed rank test. The degrees of proteasome inhibition increased from baseline by 14.6% on day 8 before bortezomib (P = 0.006) and 26.8% on day 32 before bortezomib (P = 0.0004). The 1-h postbortezomib values for proteasome inhibition compared with prebortezomib on days 8 and 32 were 56.8% and 63.8%, respectively.

Fig. 3

Nuclear NF-κB DNA binding changes with therapy of bortezomib and temozolomide. The natural logarithm of EMSA data points overlay box plots, depicting the interquartile range (bottom line and top line of boxes) and median (thick solid bar). Box whiskers extend to the minimum and maximum data values but no further than 1.5 times the interquartile range. P values across days are from mixed-models ANOVA for repeated measures comparing pretreatment values from baseline to day 8 and then day 8 to day 29.

Fig. 4

Changes in chemokine levels in peripheral blood with therapy of bortezomib and temozolomide. The natural logarithm of chemokine data points overlay box plots, depicting the interquartile range (bottom line and top line of boxes) and median (thick solid bar). Box whiskers extend to the minimum and maximum data values but no further than 1.5 times the interquartile range. P values across days are from mixed-models ANOVA for repeated measures comparing pretreatment values from baseline to day 8 and then day 8 to day 29.