Abstract LB-121: 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

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL

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][1]) 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.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-121. doi:1538-7445.AM2012-LB-121

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