Saturday, 6 October 2012

Cancer vaccine, cancer medication, cancer vaccination

The term cancer vaccine refers to a vaccine that either prevents infections with cancer-causing viruses, treats existing cancer or prevents the development of cancer in certain high risk individuals. (The ones that treat existing cancer are known as therapeutic cancer vaccines.)
Some types of cancer, such as cervical cancer and some liver cancers, are caused by viruses, and traditional vaccines against those viruses, such as HPV vaccine and Hepatitis B vaccine, will prevent those cancers. (These anti-viral vaccines are not further discussed in the rest of this article) Other cancers are to some extent caused by bacterial infections (e.g. stomach cancer and Helicobacter pylori) and traditional vaccines against cancer causing bacteria are also not currently discussed in this article.
Scientists have also been trying to develop vaccines against existing cancers. Some researchers believe that cancer cells routinely arise and are destroyed by the healthy immune system; cancer forms when the immune system fails to destroy them.

Recommendations for success

In January 2009, a review article was published in Expert Reviews in Anticancer Therapy (Vol 9, #1, pages 67–74) which highlighted past program failures and made recommendations for success as follows:
1. Target settings with a low or very low burden of disease; it is clear that vaccines will not work in patients with advanced metastatic disease.
2. Conduct randomized Phase II trials so that the Phase III program is sufficiently powered – resist the temptation to leap into Phase III prematurely.
3. Do not randomize antigen plus adjuvant versus adjuvant alone. The goal is to establish clinical benefit of the immunotherapy (i.e.,adjuvanted vaccine) over the standard of care, not over standard of care plus adjuvant. The adjuvant may have a low-level clinical effect that would skew the statistical powering of the trial, increasing the chances of a false negative.
4. Base development decisions on clinical data, not just immune responses. Time-to-event end points are more valuable and clinically relevant. To date, immune responses have not been predictive of clinical benefit. It is possible that the ability to mount an immune response is merely a prognostic factor that identifies patients with pretreatment characteristics that favor longer survival.
5. Regulatory compliance needs to be designed into the program from inception; invest in the manufacturing process and product assays early. It is much more difficult to retrofit.

No comments:

Post a Comment