Positive results reported for telomerase cancer vaccine clinical trial.

2004 JUL 7 - (NewsRx.com & NewsRx.net) -- Geron Corp. (GERN) announced the presentation of new positive results from a phase I/II clinical trial of its telomerase therapeutic vaccine in metastatic prostate cancer.

The presentation was given at the American Society of Clinical Oncology (ASCO) annual meeting in New Orleans, Louisiana, by the principal investigator of the trial, Johannes Vieweg, MD, associate professor of urology and associate professor of immunology at Duke University Medical Center in Durham, North Carolina.

Vieweg's presentation summarized the laboratory and clinical findings from the 20 patients who have been enrolled in the trial. Nineteen of the 20 patients responded to the vaccine by generating telomerase-specific cytotoxic T-cells. None of the patients experienced any treatment-related side effects.

Patients in the high dose group (those receiving 6 weekly injections) responded with a dramatic telomerase-specific T-cell response that increased over the treatment course and peaked 2-4 weeks after the final dose. Peak levels of their telomerase-specific T-cells were remarkably high, ranging from 0.9-1.8% of the total circulating cytotoxic T-cell pool. Telomerase-specific T-cells were detected for at least 16 weeks after vaccination.

Although designed primarily as a safety study, it was observed that patients in the high dose group experienced a statistically significant increase in their PSA (prostate specific antigen) doubling time during the postvaccination period when telomerase-specific T-cells were present. PSA doubling time (the rate of increase in PSA levels, expressed as the time it would take for a patient's PSA levels to double) is a clinically used surrogate marker of disease progression.

The median PSA doubling time in the high dose group before vaccination was 2.9 months. After vaccination, the median PSA doubling time improved to 100 months. Moreover, of the 10 patients who were found to have elevated levels of circulating prostate cancer cells at the onset of the study, nine exhibited substantial reduction or complete clearance of their circulating tumor cells during the period in which telomerase-specific T-cells were detected in their blood.

"These results are important," said Vieweg. "First, we are confident in the reliability of the ex vivo cell processing protocol. Second, the effectiveness of the vaccine is very high, with 19 of 20 subjects responding appropriately with the generation of telomerase-specific cytotoxic T-cells in their blood.