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The Journal of New England Technology |
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www.masshightech.com May 22 - 28, 2000 Volume 18, Issue 21 |
By Judy Stringer associate editor
Therion Biologics Corp. of Cambridge is celebrating an encouraging first report regarding its therapeutic prostate vaccine.
In an article published in Clinical Cancer Care earlier this month, cancer researchers from Dana-Farber Cancer Institute and the National Cancer Institute said that Therion's Prostvac vaccine stabilized the progression of prostate cancer in nearly half of patients treated.
The slowdown or even freezing of rising levels of Prostate Specific Antigen (PSA), a common gauge of prostate cancer progression, was used to measure disease stabilization in the Phase I trial. Stabilized PSA levels were observed for at least six months in 14 of the 33 patients with advanced prostate cancer. Nine patients remained stable for 11 to 25 months.
The data is encouraging, Therion President and Chief Executive Officer Dennis Panicali said, because there is a lack of effective treatments for recurrent prostate cancer, although the disease is currently the second-leading cause of death in American men. There are roughly 180,000 cases diagnosed in the United States every year; annual death rates top 32,000.
Patients are initially treated with radiation, surgical removal of the prostate, or both. A high likelihood of recurrence remains, at which time patients may undergo hormonal therapy. Panicali said the hormone therapy often results in impotence, weight gain and other unfavorable side effects. Therion's vaccine was used as an alternative to hormone therapy in the recent trial.
"Vaccines are very benign," he said, "and do not carry all of these quality-of-life issues."
The Phase I study included 33 patients who had been previously diagnosed with rising PSA levels after undergoing prostate removal and/or radiation therapy. The patients were given three doses of Prostvac at one-month intervals.
Results demonstrate that the vaccine is safe and well-tolerated among cancer patients. And besides PSA stabilization, clinicians measured an increase in the number of T-cells in five of seven patients assayed. These are immune cells specifically sent by the body to fight rising PSA levels.
Since Phase I trials are typically designed to prove a new drug's safety, the data coming out of Prostvac's first human study is a good indication that oncology researchers should follow the vaccine path, said Dr. Howard Kaufmann. Kaufmann, based at Albert Einstein College of Medicine, is the lead investigator for a Phase II, multi-center trial that will administer Therion's vaccine to about 60 advanced prostate cancer patients.
The follow-up trial will measure PSA levels at six months, as well as T-cell response across the patient group. Kaufmann said the T-cell measure tells researchers whether they are activating the immune system against PSA. As a secondary end-point, the investigators will also look at tumor progression.
Kaufmann said the early Phase I data may also justify beginning Prostvac trials earlier in disease treatment, where vaccines typically have the most benefit.
"If you are vaccinated against the measles before being exposed, you are nearly 100 percent protected, but vaccines used after the disease has presented itself are not nearly as effective," he said. "In much the same way, I see these cancer vaccines as more promising as they move to early stages of the disease."
Prostvac is Therion's lead cancer product, but it is still years away from market. The company is also developing a therapeutic colorectal vaccine in partnership with Aventis Pastuer, which is in Phase II trials, and has an early-stage HIV vaccine in the works.
Reprinted with permission. All rights reserved. Mass High Tech 2000.