Immunotherapy has been referred to as the “most exciting development in cancer treatment in years” (Guardian, 2015). When treatments such as chemotherapy seem to have hit the proverbial wall in terms of progressive effectiveness, immunotherapy sets out on an entirely different path. Instead of just focusing on killing the offending organism, scientists are focused on working with the body’s own natural defensive system.
The concept has been around since the 1970s. In recent years, it is seeing a renewed public interest. According to the Wall Street Journal, immunotherapy these days focuses on a number of different methods:
- Checkpoint inhibitors: these “inhibitors” target body’s natural “brakes” on the immune system to prevent it going into overdrive. The breaks are necessary to prevent attacks on healthy tissue. Some tumors, however, can trigger the brakes to evade the immune system. The breaks are referred to as “checkpoints” and immunoterapy that inhibits these checkpoints allow the immune system to fight the cancer cells. (E.g., Yervoy, by Bristol-Myers Squibb BMY, disables CTLA-4 which halts the activation of T-cells. Approved as a treatment for metastatic melanoma in 2011.)
- TNF receptor agonists: TNF receptor agonists stimulate the immune response. The two TNF receptors being targeted by drug maker are known as OX40 and CD40. Research is at an earlier stage. (E.g., clinical trial by Novartis on a CD40 agonist.)
- Cell therapy: Some tumors send out chemical signals covering them fro T-cells. One strategy is to engineer a patient’s T-cells to recognize and attack certain molecules found on the surface of tumors. One way to do this is to graft a new, tumor targeted receptor known as a “chimeric antigen receptor”, or CAR, onto the T-cell. The other, T-cell receptor (TCR) gene therapy, genetically modifies an existing T-cell receptor to make it more effective at recognizing tumors.
- Cancer vaccines: Like other vaccines, it works by training the immune system to respond to tumors by introducing a harmless version of a tumor cell to the body. This stimulates an immune response directed at the tumor. But these have consistently failed late-stage clinical trials. The first approved cancer immunotherapy was a vaccine known as Provenge for prostate cancer (2010).
Despite the excitement, scientific understanding and ethical concerns on biologically engineered solutions are still in their very beginning. The Guardian warns that over excitement is a “dangerous thing.”
“There have been melanoma drugs before that were greeted as miracle cures. The “targeted drugs”, the BRAF inhibitors, caused tumours to vanish completely. There was euphoria at cancer conferences. But within a few months, the disease came back with a vengeance and killed.”