Geron Corporation announced the presentation of final data from its Phase 2 clinical trial of GRNVAC1 vaccine in patients with acute myelogenous leukemia (AML). The multi-center, open label trial was designed to evaluate the safety and tolerability of the GRNVAC1 vaccination regimen in patients with AML who were in complete clinical remission. Additional objectives of the study evaluated the immune responses to GRNVAC1 and explored the effects of vaccination on minimal residual disease and relapse rates in this patient population stratified by risk groups.

Twenty-one patients received GRNVAC1 in the study, including 19 in clinical remission (CR; 16 in CR1 and three in CR2) and two in early relapse. Of the 19 patients in CR, eight were considered intermediate risk for relapse and eleven were at high risk for relapse as predicted by their cytogenetics, FAB type, or because they were in second CR.

Thirteen out of 21 patients in the trial remain in CR. Median duration of follow-up from first vaccination is 13.2 months. At 12 months after vaccination with GRNVAC1, estimated disease-free survival is 81% for patients at high-risk of relapse (95% CI: 42-95%). Previously published data on this patient population suggests that approximately 45% of patients would normally remain free from relapse at this stage.

Expression of WT-1, a marker of minimal residual disease, was sequentially analyzed by qPCR in 21 patients. The 13 patients who remain in CR are negative for WT-1, while six of seven with clinical relapse were WT-1 positive. One patient was positive for WT-1 prior to vaccination with GRNVAC1 and became WT-1 negative during the course of vaccination. This patient relapsed after 30 months. Positive immune responses to telomerase after vaccination with GRNVAC1 were detected in 55% of patients using the ELISPOT assay.

GRNVAC1 is an autologous dendritic cell vaccine designed to induce an immune cell mediated response targeted against tumor cells expressing telomerase antigen on their surface.

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