A phase Ib trial of IPI-926, a hedgehog pathway inhibitor, plus gemcitabine in patients with metastatic pancreatic cancer.

Abstract

213 Background: IPI-926 is a novel, natural product-derived small molecule that targets the Hedgehog (Hh) pathway by inhibiting smoothened. In preclinical models of pancreatic cancer, repressing activation of the Hh pathway diminishes tumor-associated desmoplasia and improves chemotherapy delivery. Methods: This is the final report of the Phase 1b portion of a Phase 1b/2 trial evaluating the safety and efficacy of IPI-926 plus gemcitabine. Eligible patients (pts) with untreated metastatic pancreatic cancer and ECOG status 0-1 were administered oral IPI-926 daily (QD) for 28-day cycles, in 3 to 6 pt dose cohorts. Gemcitabine (1,000 mg/m2) was administered IV weekly for 3 weeks with 1 week off. DLTs were evaluated during Cycle 1. Results: 16 pts (median age 69 years; range 58-86) were enrolled at IPI-926 doses of 110, 130 or 160 mg QD (single agent MTD). Pts received a median of 5 cycles (1-13). Two pts remain on trial. No IPI-926-related serious AEs have been observed. One DLT of Grade 3 AST increase was observed (130 mg dose cohort) and was asymptomatic; it resolved with dose interruption, and did not recur with dose reduction. The most common AEs occurring were fatigue (75% total, 6% ≥ Grade 3), thrombocytopenia (63%, 25%), anemia (56%, 13%), nausea (50%, 0%), diarrhea (44%, 0%), vomiting (44%, 0%), peripheral edema (44%, 0%), pyrexia (44%, 0%), and AST increase (44%, 13%). Dose reductions of IPI-926 occurred in 3 (19%) pts. Dose reductions of gemcitabine occurred in 11 (69%) pts, primarily for thrombocytopenia (9 pts). One pt (6%) discontinued due to an AE (microangiopathic hemolytic anemia). Five (31%) radiographic partial responses were observed (1/3 at 110 mg, 2/6 at 130 mg, 2/7 at 160 mg). Median progression-free survival is > 7 months. 74% of pts were alive 6 months after study entry. Conclusions: IPI-926 plus gemcitabine is well tolerated in pts with untreated metastatic pancreatic cancer, with evidence of activity and no unexpected toxicity. Complete Phase 1b data, including final overall survival, will be presented. Clinical evaluation of this combination continues in the randomized, double-blind, placebo-controlled Phase 2 portion of the trial.