Presentation Abstract

Abstract Number: LB-121
Presentation Title: Randomized phase II study of the efficacy and safety of gemcitabine + TH-302 (G+T) vs gemcitabine (G) alone in previously untreated patients with advanced pancreatic cancer
Presentation Time: Monday, Apr 02, 2012, 10:35 AM -10:50 AM
Location: McCormick Place West (Level 1), Room W192
Author Block: M. J. Borad, S. Reddy, H. Uronis, D. S. Sigal, A. L. Cohn, W. R. Schelman, J. Stephenson, E. G. Chiorean, P. J. Rosen, B. Ulrich, T. Dragovich, S. Del Prete, M. Rarick, C. Eng, S. Kroll, D. Ryan. Mayo Clinic Arizona, Scottsdale, AZ, Louisiana State University Health Sciences Center, Shreveport, LA, Duke University Medical Center, Durham, NC, Scripps Clinical Medical Group, La Jolla, CA, Rocky Mountain Cancer Centers, Denver, CO, University of Wisconsin Hospital and Clinics, Madison, WI, Institute for Translational Oncology Research, Greenville, SC, Indiana University Simon Cancer Center, Indianapolis, IN, Providence Saint Joseph Medical Center, Burbank, CA, Texas Oncology, Wichita Falls, TX, Arizona Cancer Center, Tucson, AZ, Hematology Oncology PC, Stamford, CT, Kaiser Permanente Northwest Region Oncology Hematology, Portland, OR, Threshold Pharmaceuticals, South San Francisco, CA, Massachusetts General Hospital, Boston, MA
Abstract Body: A hypoxic microenvironment is believed to be a characteristic of solid tumors including pancreatic adenocarcinoma (PAC) and is associated with resistance to chemotherapy. The hypoxia-activated prodrug, TH-302, is designed to specifically target the hypoxic microenvironment. Combining G with TH-302 may enable the targeting of both the normoxic and hypoxic regions of PAC. TH-302 was investigated with full-dose G as part of a Phase 1/2 study with a 21% response, median PFS and OS of 5.9 and 8.5 months, respectively, and one-year survival of >40%. Based upon these data, a randomized Phase 2B study (NCT01144455) was conducted to assess the benefit of G+T to standard dose G for first-line therapy of PAC.
An open-label multi-center study of two dose levels of TH-302 (240 mg/m2 or 340 mg/m2) in combination with G versus G alone (randomized 1:1:1) was initiated in June 2010. G (1000 mg/m2) and T were administered IV over 30-60 minutes on Days 1, 8 and 15 of a 28-day cycle. Patients on the G arm could crossover after progression and be randomized to a G+T arm. The primary efficacy endpoint is a comparison of progression-free survival (PFS) between the combination arms and G alone (80% power to detect 50% improvement in PFS with one-sided alpha of 10%).
214 pts (69 G: 71 G+T240: 74 G+T340) with advanced PAC including 77% distant metastases,62% involving liver and 11% with prior adjuvant tx; median age: 65 (range 29-86); 126 M/88 F; 79/128 ECOG 0/1. Median cycles received: G - 4, G+T240 - 5, G+T340 - 6. Median PFS was 3.6 mo in G vs 5.6 mo in G+T arms with HR of 0.61 (95% CI: 0.43 - 0.87) and logrank p-value of 0.005. Median PFS in G + T340 was 6.0 mo. RECIST best response was 12% in G, 17% in G+T 240 and 27% in G+T340. 153 (71%) patients had elevated CA19-9 and follow-up. CA19-9 decreases were significantly greater in the G+T groups and greatest in the G+T340 arm which had 37 of 53 (70%) pts with a greater than 50% CA19-9 decrease. One death (suicide) was considered possibly related to study drug. Adverse events leading to discontinuation were: 16% G, 15% G+T240 and 11% G+T340. Serious adverse events were balanced across the treatment arms. The most common non-laboratory events, fatigue (49%), nausea (43%), constipation (34%) and peripheral edema (38%), were similar across groups. Rash (14% G, 39% G+T240 and 45% G+T340) and stomatitis (6% G, 17% G+T240 and 36% G+T340) were significantly greater with G+T combination but no Grd 4 (4 pts with Grade 3). Grd 3/4 thrombocytopenia (11% G, 39% G+T240 and 59% G+T340) and Grd 3/4 neutropenia (28% G, 56% G+T240 and 59% G+T340) were higher with G+T. G+T combination with full dose G improved the efficacy of G with significantly longer PFS, higher response rate and greater CA19-9 declines. The G+T combination was well tolerated. Skin and mucosal toxicity and myelosuppression were the most common related adverse events with no increase in treatment discontinuation.