Comparative benefits of nab-paclitaxel over gemcitabine or polysorbate-based docetaxel in experimental pancreatic cancer.

Abstract

192 Background: Gemcitabine (Gem), a standard cytotoxic therapy for pancreatic cancer, has shown limited clinical benefits. Nanoparticle albumin-bound (nab) paclitaxel (NPT), an approved treatment for breast cancer, has shown efficacy as mono- and combination therapy in multiple tumor types including pancreatic, lung and ovarian cancer. We evaluated the NPT treatment benefits compared with Gem or solvent-based taxane docetaxel (DT) in experimental pancreatic cancer. Methods: In vitro cell proliferation and protein expression were measured by WST-1 assay and immunoblotting. Tumor growth and animal survival studies were performed in murine xenografts. Intratumoral proliferative activity was measured using Ki67 nuclear antigen staining. Results: For AsPC-1, BxPC-3, MIA PaCa-2 and Panc-1 cells in vitro, Gem IC50 levels were 23.9 mM, 506 nM, 332 nM and 14.5 nM; DT IC50 levels were 30 nM, 4.6 nM, 37.5 nM and 27 nM; and NPT IC50 levels were 7.6 mM, 208 nM, 519 nM and 526 nM. NPT addition decreased Gem IC50 to 1.7 mM, 189 nM, 123 nM and 913 nM; DT addition decreased Gem IC50 to 436 nM, 470 nM, 124 nM and 0.2 nM in AsPC-1, BxPC-3, MIA PaCa-2 and Panc-1 cells, respectively. NPT and DT treatment increased stathmin phosphorylation and decreased tubulin expression in vitro. In a heterotopic in vivo model, net tumor growth inhibition after Gem, DT and NPT was 67, 31 and 72 percent, while intratumoral proliferative index inhibition was 41, 53 and 68 percent, respectively. In an intraperitoneal model, median animal survival was significantly longer in the NPT treatment group (41 days, p<0.002 vs. control and Gem) compared to Gem (32 days, p=0.005 vs. control), DT (32 days, p=0.005 vs. control) and controls (20 days). Animal survival in NPT-Gem and DT-Gem sequential treatment groups was 43 and 40 days, and thus not superior to NPT alone. Conclusions: Nab-paclitaxel has significantly superior antitumor activity as a single agent in experimental pancreatic cancer compared with gemcitabine or docetaxel. These findings provide a strong rationale for considering nab-paclitaxel as first-line monotherapy in patients with pancreatic cancer.