SillaJen Inc. has announced that the company has reached agreement with the U.S. Food and Drug Administration (FDA) on a Special Protocol Assessment (SPA) for the global Phase 3 clinical trial of its oncolytic immunotherapy, Pexa-Vec. The pivotal trial will evaluate the use of Pexa-Vec to treat patients with advanced liver cancer, also known as hepatocellular carcinoma (HCC), who have not received sorafenib (Nexavar®) therapy, and is expected to begin enrollment later this year. The Phase 3 clinical trial is designed to enroll 600 patients with advanced liver cancer who are eligible to receive sorafenib therapy.

The randomized study will be conducted at approximately 120 sites worldwide including North America, Asia, and Europe. The primary objective of the trial is to determine the overall survival benefit for patients receiving Pexa-Vec followed by sorafenib, compared to sorafenib alone in patients with advanced liver cancer. Pexa-Vec is the most advanced product candidate from SillaJen's proprietary SOLVE (Selective Oncolytic Vaccinia Engineering) platform.

The vaccinia poxvirus strain backbone of Pexa-Vec has been used safely in millions of people as part of a worldwide vaccination program. This strain naturally targets cancer cells due to common genetic defects in cancer cells; Pexa-Vec was engineered to enhance this by deleting its thymidine kinase (TK) gene, thus making it dependent on the cellular TK expressed at persistently high levels in cancer cells. Pexa-Vec is also engineered to express the immunogenic GM-CSF protein.

GM-CSF complements the cancer cell lysis of the product candidate, to a cascade of events resulting in tumor necrosis, tumor vasculature shutdown and sustained anti-tumoral immune attack.