Geron says interim data shows cancer vaccine meets goals

MENLO PARK, Calif. — Geron Corp. announced Dec. 8 the presentation of interim data from its phase II trial of GRNVAC1, an autologous dendritic cell vaccine, in patients with acute myelogenous leukemia at the 51st Annual Meeting of the American Society of Hematology in New Orleans.

The vaccine is designed to induce an immune response to tumor cells, which express telomerase on their surface. Telomerase is an enzyme found in many malignant tumors.

The trial is designed to evaluate the feasibility of GRNVAC1 manufacture and the safety and tolerability of the vaccination regimen in patients with AML who are in complete clinical remission.

Additional objectives of the study are to evaluate the immune responses to GRNVAC1 and to explore the effects of vaccination on minimal residual disease and relapse rates in this patient population.

"First, we are pleased to have met our endpoints of safety and tolerability," said Stephen M. Kelsey, Geron's executive vice president and chief medical officer, oncology. "At this point in the study a number of high-risk patients have entered the extended boost phase of the vaccination regimen. These patients have been in remission for a period ranging from four months to nearly two years. Our analyses of minimal residual disease by qPCR of WT-1 are also very encouraging with one patient whose WT-1 levels became undetectable following vaccination."

Twenty patients have received GRNVAC1 product in the study. One patient relapsed prior to vaccination. GRNVAC1 was found to be safe and generally well tolerated over multiple vaccinations, including one patient who had 28 serial vaccinations to date. Idiopathic thrombocytopenic purpura (grade 4) was reported in one patient. Other toxicities were mild to moderate, including rash or headache in 15 percent to 20 percent of patients.

Fourteen out of 20 patients in the study remain in complete clinical remission (CR). Median duration of CR, including the patients who have relapsed, is 12 months.

Six of the patients in CR are in the extended boost phase of vaccination and the duration of their remission since the start of vaccination ranges from four to 20 months. Four of these six patients are at a high risk of relapse as predicted by their cytogenetics or because they are in the second CR.

Follow-up of the patients for approximately one additional year is required in order to estimate the impact of vaccination on disease-free survival.

Enrollment of additional patients will end this month.