Over the past few years, many biological agents and many approaches to biological therapy have been investigated. Most clinical trials originally concentrated on one or another of the strategies outlined above, trying to understand and exploit individual approaches to improving the immune response of cancer patients.
With the data from these trials in hand, it is now becoming possible to design useful combinations of strategies and agents. At the moment, a range of biological agents is being researched. These include biological response modifiers that have no direct antitumor effect but are able to trigger or stimulate the immune system and so indirectly affect tumors.
The Interferons (IFN) There are several interferons. One of them—interferon-alpha—was the first of the cytokines shown to have an antitumor effect, both a direct effect and indirect effects through a more active immune system.
So far, studies have shown that interferon-alpha causes tumors to shrink 15 to 20 percent of the time in patients with kidney cancer (renal cell carcinoma) and melanoma. Other studies have shown it to have a major effect in 90 percent of patients with the rare hairy cell leukemia and with the more common chronic myelocytic (myelogenous) leukemia. Interferon-alpha is also occasionally effective in people with indolent non-Hodgkin's lymphoma and in some people with AIDS who develop Kaposi's sarcoma .
