The evolution of our regimen, consisting of Gemzar, Taxotere and Xeloda (oral 5FU) (GTX), was carefully developed over the past three years from laboratory and clinical work. Initially, in collaboration with Dr. William Sherman of the Division of Medical Oncology we assessed the clinical effects of two agents, Gemzar and Taxotere in pancreatic cancer patients. In our in vitro studies we found that as single agents these drugs (Gemzar and Taxotere) were minimally effective against pancreatic carcinoma lines, which expressed mutant p53 and activated mutated ras. Activated or mutant ras is found in approximately 95% of all pancreatic carcinomas. However, when the agents were added together in tissue culture experiments we found that their activity was additive. The clinical study performed at Columbia Presbyterian Medical Center demonstrated a 27% objective response rate by CT scan including one complete response with intent to treat analysis of all 15 patients within the study. The majority of these patients had metastatic liver disease and a minority had inoperable pancreatic carcinoma without liver metastases. Though this was a small single arm, single institution study it did suggest a trend towards improved responses in patients with this disease when these two agents were combined. In addition, valuable lessons were learned from the in vitro work with Gemzar and Taxotere. Importantly, we found that this combination was equally toxic to mutant and wild type p53 pancreatic cancer cells, as well as to cells with mutant ras. Also, docetaxel pharmacokinetics are more favorable and have distinct advantages over the use of the other taxane known as paclitaxel. They are the following: 1) Taxotere enters tumor cells more efficiently than paclitaxel because it is more lipophilic; 2) Taxotere is not pumped out by the cell by P-glycoprotein as efficiently as paclitaxel; 3) Taxotere' half life was significantly longer than that of paclitaxel such that a 60 minute infusion of Taxotere gives you approximate pharmacokinetics as paclitaxel when administered as a 24 hour continuous infusion. These laboratory studies from the literature formed the rationale for our use of Taxotere (docetaxel) instead of paclitaxel.

After our initial clinical and laboratory study we went back to the laboratory to investigate further some of the properties of Gemcitabine, Taxotere added to Xeloda (5-DFUR) in vitro to maximize biochemical synergy and to minimize toxicity. We found important characteristics of these drug combinations against pancreatic cancer cells that have been synthesized into the current protocol. We found that there was sequence specificity for these drugs in that 5-DFUR should precede Gemzar by 72 to 96 hours and Gemzar should be added before Taxotere to achieve maximum synergy. Taxotere cytotoxicity was dose dependent up to 20 nM but then no further cell kill was obtained past that point. This would mean that one would not need to use high dose Taxotere in a regimen because it would be doubtful whether increased doses would obtain further cell kill in a linear scale.

We investigated many different combinations of these 3 agents in the laboratory to determine the best combination to achieve biochemical synergy while decreasing the concentration of each drug and not lose anti-tumor effect so as to decrease toxicity to patients.