Adherex Technologies Inc. announced that the company has completed patient enrollment in the Company's Phase 2 clinical trial for Metastatic Breast Cancer comparing the oral regimen of eniluracil + 5-fluorouracil (5-FU) and leucovorin (Treatment Arm 1) versus capecitabine (Xeloda®)(Treatment Arm 2). Patients who have disease progression in Arm 2 may crossover to take eniluracil plus 5-FU and leucovorin (Treatment Arm X). Enrollment in the study exceeded initial recruitment expectations.

The Company expanded the initial enrollment target from 140 patients to 153 patients and enrolled 21 patients in Arm X. Final efficacy and safety data is expected to be available during the second or third quarter of 2013. Eniluracil: Eniluracil is a mechanism-based inactivator of DPD, the enzyme that rapidly breaks down 5-FU. Accordingly, Eniluracil increases the 5-FU elimination half-life from about 15 minutes to 5 hours and enables 5-FU to be administered orally, making it 100% orally bioavailable.

In addition, Eniluracil prevents the formation of -fluoro--alanine (F-Bal), the 5-FU-breakdown product. F-Bal appears to cause hand-foot syndrome and neurotoxicity. It also decreases the antitumor activity of 5-FU in laboratory animals.

Furthermore, because DPD is present in variable levels, the highly variable and nonlinear pharmacokinetics of 5-FU become predictable and linear when DPD is inactivated by Eniluracil in cancer patients. The weekly regimen used in the current Phase 2 trial is based on a Phase 1 Eniluracil/5-FU/Leucovorin trial that produced durable tumor responses and no hand-foot syndrome in advanced colorectal cancer patients who were refractory to intravenous 5-FU/Leucovorin. In a similar Phase 2 study with capecitabine, no tumor responses occurred and 87% of the patients experienced hand-foot syndrome, a painful condition that may require dosing interruptions and dose reductions.

The regimen was modified according to the methods described in the Adherex patent applications.