- Allogeneic vaccines use cells of a particular cancer type that originally came from someone other than the patient who will receive them. The cells are often grown in a lab.
Although the FDA has not yet approved any tumor cell vaccines for general use, they are being studied in clinical trials against many types of cancer, including:
- melanoma
- kidney cancer
- ovarian cancer
- breast cancer
- colorectal cancer
- lung cancer
- prostate cancer
- non-Hodgkin's lymphoma
- leukemia
Antigen Vaccines
Antigen vaccines boost the immune system by using only one antigen (or a few), rather than whole tumor cells that contain many thousands of antigens. The antigens are usually proteins or pieces of proteins called peptides. Antigen vaccines may be specific for a certain type of cancer, but they are not made for a unique patient as autologous cell vaccines are.
The challenge has been to find better antigens, as well as to package the antigen in such a way so that they enhance the patient's immune system helping to fight cancer cells that contain the antigen.
Antigen vaccines are being studied for use against these cancer types:
- breast cancer
- prostate cancer
- colorectal cancer
- ovarian cancer
- melanoma
- kidney cancer
- pancreatic cancer
- multiple myeloma
Most clinical trials that investigated a cancer vaccine have resulted in failure (the vaccine didn't work). The precise reasons for this failure are unknown, but possible explanations include:
- The stage of the disease being treated was too advanced: it is difficult to get the immune system to fight bulky tumor deposits
- Cancer vaccines that target just one tumor antigen are likely to be less effective. Tumors are highly heterogeneous and antigen expression differs markedly between types of cancer cells in tumors.
- Prior treatments - numerous clinical trials in the past have treated patients who have received numerous cycles of chemotherapy. Chemotherapy is often myelosuppressive and destroys the immune system.
- Some tumors progress very rapidly and/or unpredictably; their growth can literally outpace the response of the immune system.
Monoclonal antibodies
Monoclonal antibody therapy uses monoclonal antibodies (or mAb) to bind specifically to target cells. This can then stimulate the patient's immune system to attack those cells.
The idea of a "magic bullet" against cancer was first proposed by Paul Ehrlich who at the beginning of the 20th century postulated that if a compound could be made that selectively targeted a disease-causing organism, a toxin for that organism could be delivered along with the selective agent.
Monoclonal antibodies were first produced in the 1970's, further developed in the 1980's, and approved for specific types of cancer in the 1990's.
Antibodies are proteins that are normally part of the immune system and bind to antigens in the body. Researchers manufacture antibodies outside of the human body that adhere to specific targets in cancer cells.
Targeted immunotherapy drugs are essentially a collection of monoclonal antibodies that have different cellular targets. Targeted therapies provide specific antigens for specific types of cancer in order to generate an immune response. Cancer cells have substances on their outer surfaces that can act as antigens and mark the cells as abnormal.
