Phase I Trial of LCL161 and Gemcitabine Plus Nab-Paclitaxel in Metastatic Pancreatic Cancer

Improved therapeutic options for advanced pancreatic adenocarcinoma treatment need to continue to be investigated. Since 1997, gemcitabine has been the agent of choice for first-line therapy in advanced pancreatic cancer, with a median survival of 5.7 months, and a 20% 1-year survival (Eli Lilly 1996). Combination therapies using gemcitabine as a backbone have been investigated, but none are superior to gemcitabine monotherapy, except for a modest increase in overall survival (OS) with erlotinib and gemcitabine (Moore et al 2007). In a study of FOLFIRINOX compared with gemcitabine as first-line therapy in 342 metastatic pancreatic cancer patients, median OS was 11.1 months in the FOLFIRINOX group and 6.8 months in the gemcitabine group; however, the FOLFIRINOX group experienced more adverse events particularly febrile neutropenia (Conroy et al 2011). LCL161 is a biostable, cell-permeable, small molecular weight Smac-mimetic compound. It is an orally bioavailable pan-IAP inhibitor that demonstrates anti-tumor efficacy as a single agent in a small subset of cell lines, and in many more cell lines and xenograft models when given in combination with paclitaxel. Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is a formulation that is readily soluble in saline, eliminating the need for lipid-based solvents (ie, Cremophor EL) and corticosteroid and antihistamine premedications for hypersensitivity reactions required for traditional unbound paclitaxel. nab-paclitaxel has also been shown to actively bind to secreted protein acidic and rich in cysteine (SPARC) in the tumor stroma, which is highly expressed in pancreatic cancer and actively binds to the albumin in nab-paclitaxel and further concentrates the drug into the tumor. SPARC expression in the stroma of tumor cells has been associated with poor survival. In a Phase I/II trial (Von Hoff et al 2011) involving 67 patients with metastatic pancreatic adenocarcinoma, the regimen of nab-paclitaxel plus gemcitabine had tolerable adverse effects with substantial antitumor activity, warranting Phase III evaluation. The Phase III study (MPACT) was a large, international study that determined that survival with nab-paclitaxel plus gemcitabine is superior to gemcitabine alone. nab-paclitaxel plus gemcitabine is a new standard for treatment of patients with metastatic pancreatic cancer (Von Hoff et al 2013). However, although this study shows promise for substantially improving OS in patients with pancreatic adenocarcinoma, insensitivity to these agents is likely to occur due to resistance to apoptosis, which has been observed in laboratory studies to occur for most of the cytotoxic agents used to treat pancreatic cancer in the past (Westphal and Kaltoff 2003). Exploitation of the apoptosis pathway may ultimately provide more effective, less toxic anticancer therapy that selectively circumvents treatment-resistant pathways. Based on the above, there is a high likelihood that LCL161 in combination with nab-paclitaxel and gemcitabine will be determined to be safe and well tolerated, and will show substantial antitumor activity, warranting Phase II evaluation. Up to 24 patients will be enrolled in Part A - Phase I Safety study. If the combination therapy is determined to be safe and well tolerated and shows substantial antitumor activity, a safety expansion cohort of 12 additional patients will be enrolled in Part B - Efficacy study to further confirm the tolerability and efficacy of LCL161 with an endpoint of complete response (CR).