Final results of phase Ib of anticancer stem cell antibody tarextumab (OMP-59R5, TRXT, anti-Notch 2/3) in combination with nab-paclitaxel and gemcitabine (Nab-P+Gem) in patients (pts) with untreated metastatic pancreatic cancer (mPC).

Abstract

278 Background: Tarextumab (TRXT), fully human IgG2 antibody, inhibits signaling Notch 2, 3 receptors. Tumor regression seen in Notch 3 patient-derived PC xenografts when TRXT added to Nab-P+Gem. The maximum tolerated dose (MTD) of single agent TRXT was 7.5mg/kg every other week (Smith, EORTC 2012); the main dose limiting toxicity (DLT) was Grade 3 diarrhea. This study evaluates MTD, pharmacokinetics (PK), pharmacodynamics (PD) and early efficacy of TRXT + Nab-P+Gem in mPC. Methods: Cohorts of 3-6 pts treated at 6 dose levels of TRXT. TRXT IV Days 1 + 15 with GEM 1000mg/m2 alone (first two cohorts) or nab-P 125 mg/m2 and GEM 1000mg/m2on Days 1, 8, 15 of every 28-day cycle. Biomarker analysis of surrogate tissue and tumor undertaken. Results: By 08/22/14, N= 40 treated. TRXT 15 mg/kg selected as Phase 2 dose. 1 DLT Grade 3 diarrhea in 15 mg/kg cohort. Frequently reported (≥15%) TRXT adverse events(AEs) were: diarrhea(60%), fatigue(43%), anemia(28%), decreased appetite (18%) and nausea(15%); most grade 1 or 2 and managed supportively. Other AEs (≥ 30%) were: cytopenia, alopecia, vomitng and peripheral edema. GEM or Nab-P+Gem did not alter PK of TRXT. Notch pathway-related genes, HEYL, HES2, NOTCH2 and cancer stem cell markers were altered in hair follicles at TRXT > 7.5 mg/kg combined with Nab-P+Gem. Plasma, blood RNA biomarkers were also modulated by TRXT + Nab-P+Gem. Conclusions: TRXT + Nab-P+ Gem is well tolerated. 15 mg/kg is the selected Phase 2 dose of TRXT. Encouraging anti-tumor activity was observed. Final safety, efficacy, PK and PD results in surrogate and serial tumor tissues will be presented. The Phase 2 randomized, placebo-controlled ALPINE study is underway. Clinical trial information: NCT01647828. [Table: see text]