Dendritic Cell Immunotherapy - The Provenge Prostate Cancer Vaccine

Dendritic Cell Immunotherapy  - The Provenge Prostate Cancer Vaccine
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A Milestone for Dendritic Cell Immunotherapy

The prostate cancer vaccine, sipuleucel-T (Provenge) has taken 15 years of research. It is designed to stimulate T cells (white blood cells) to kill tumor cells and its approval by the FDA is considered by many as a milestone for cancer immunotherapy.

In a phase III clinical trial, patients on Provenge showed extended median survival of 4 months. This is a modest effect, but provides evidence that the immune system can be stimulated to control cancer. Questions remain about what stage of disease vaccines should be used, and how they can best be combined with other treatments. The company that produces the vaccine (Dendreon) and others are continuing to develop dendritic cell immunotherapy approaches for cancer.

Provenge: How it Works

  • Provenge is an autologous vaccine, meaning that it is individually made for each patient using their own immune cells.
  • Antigen-presenting cells (dendritic cells) are obtained from the patient and then incubated with a tumor antigen called PAP (prostatic acid phosphatase) in vitro in the laboratory for 2 days. These antigen exposed cells are then fused to a substance called GM-CSF (granulocyte–macrophage colony-stimulating factor).
  • Patients receive an infusion on day 3 or 4 which is repeated 2 and 4 weeks later.

Compared with some forms of chemotherapy, Provenge’s side effects are mild. Clinical trials showed that 83.4% of those treated were fully active and could perform normal activities. Half the participants had fever, chills and backache, which resolved within 2 days. Only 3% had more severe side-effects. One concern however was a slightly higher incidence of cerebral hemorrhage among those taking the vaccine. Therefore patients are being monitored for this over the next year.

The Future for Cancer Immunotherapy

  • Dendritic cell immunotherapy for bladder, breast, and gastric cancers based on the same principle as Provenge, are being developed.
  • Some predict that immunotherapeutic vaccines will be more effective in nonmetastatic disease (before it has spread), when the tumor burden is relatively low and the patient’s immune system is still healthy.
  • It may be that Immune therapy can be effective when given after surgery and radiation but not post chemotherapy. This is because chemotherapy can be highly suppressive to the immune system.
  • Researchers are looking at strategies to improve the effects of immunotherapy, such as combining cancer vaccines with other agents.

Provenge: How Much Will it Cost?

Treatment with Provenge is not cheap, presently costing around $90,000 for three infusions. In contrast, Docetaxel, a standard chemotherapy treatment for prostate cancer, costs $18,000, but that does not include the cost of treating the considerable side effects. Medicare policies will usually pay for FDA approved drugs, however there is some uncertainty at present whether Provenge will be covered.

References

Approval of Provenge Seen As First Step for Cancer Treatment Vaccines by Vicki Brower. Journal of the National Cancer Institute P1108-1110

Immunotherapy for prostate cancer using antigen-loaded antigen presenting cells: APC8015 (Provenge) by A.Harzstark & E.Small. Expert Opinion on Biological Therapy 2007, Vol 7, P1275-1280.