Final analysis of a phase IB/randomized phase II study of gemcitabine (G) plus placebo (P) or vismodegib (V), a hedgehog (Hh) pathway inhibitor, in patients (pts) with metastatic pancreatic cancer (PC): A University of Chicago phase II consortium study.

Abstract

4012 Background: Sonic Hh (SHh), the ligand for the Hh pathway, is over-expressed in >80% of PC. V had activity in preclinical murine PC models leading to increased tumor perfusion, enhanced tumor delivery of G, and an improvement in survival. Methods: We conducted a placebo-controlled, phase IB/randomized phase II trial of GV or GP. Eligible pts, KPS 80-100, had untreated metastatic PC, or had completed adjuvant therapy > 6 months (mo) prior. Primary endpoint: progression-free survival (PFS). Correlatives: serial SHh serum levels; serial perfusion CT imaging. All pts received G 1000mg/m2over 30 minutes, days (D) 1, 8, 15, Q28D. A lead-in phase IB was performed. Pts, stratified by KPS (80 v 90/100), and disease status (newly diagnosed/recurrent), were randomized to V (150 mg PO daily) or P. For pts on P, cross-over was allowed at progression. Assuming a mPFS of 3.5 months for GP and 5.7 months for GV (HR=0.61), a sample size of 106 subjects (53 per group) provided 85% power to detect this difference, using a one-sided test at the 0.10 significance level. Results: No safety issues were identified in 7 pts enrolled in the phase IB study. The phase II study enrolled 106 evaluable pts (V/P 53/53) at 13 sites 2/10-6/12. Pt characteristics: median age 65/64 (range 52-82/39-83); KPS (% pts) 80: 38/30; 90: 26/38; 100: 36/32; newly diagnosed 91%/91%; recurrent: 9%/9%. Grade 3/4 toxicity (V/P, % pts, >5% in either arm): neutropenia 32/28; lymphopenia 4/15; thrombocytopenia 9/11; anemia 9/23; hyponatremia 4/15; fatigue 13/8; hyperglycemia 23/19; elevated ALT 13/9; hyperbilirubinemia 11/6; nausea 11/11. Response (%): CR 0/2, PR 8/11, SD 51/38. mPFS: 4.0/2.5 mo (95% CI: 2.5-5.3/1.9-3.8; HR 0.81 [0.54-1.21], p=0.30). 22 pts (42%) on GP crossed over to GV at progression. mOS: 6.9/6.1 mo (95% CI:5.8-8.0/5.0-8.0, HR 1.04, [0.69-1.58], p=0.84). Updated laboratory/radiological correlatives will be presented. Conclusions: Toxicity between the groups was similar. The addition of V to G in an unselected cohort does not improve response, PFS, or OS in pts with metastatic PC. Funding NCI N01-CM-62201. Clinical trial information: NCT01064622.