Keytruda (Pembrolizumab) – a new anti-cancer drug approved as state-subsidized in Israel, 2015

Our immune system is made up of several types of cells. The purpose of these cells is to protect the body and its biological systems (e.g. the urinary system, the respiratory system, the digestive system etc.) from any danger and to permit normal function.

This can be carried out due to the ability of the immune system to recognize and attack different types of pathogens (such as bacteria, viruses and parasites from outside the body that can cause different types of diseases) and to overwhelm these pathogens in order to prevent any damage they may cause.

Not less important is the ability of the immune system to recognize pathological processes that initiate in the body itself and to fight them. One of the most prominent examples is the immune system’s ability to recognize normal cells that for unknown reasons undergo inner changes. These changes subsequently cause the normal cells to be transformed into cancer cells which are destroyed by the immune system before they can grow into a malignant tumor. However, in order to survive and keep growing, cancer cells develop sophisticated mechanisms by which they attach themselves to the cells of the immune system and neutralize them: a specific protein called PDL-1 which is located on the cancer cell surface, attaches itself to another protein called PD-1 located on the immune cell surface that is trying to attack it. The connection between these two proteins neutralizes the ability of the immune cell to destroy the cancer cell, thus enabling the continuation of the cancerous process without any disruption.

The new drug, Keytruda, blocks the interaction between the PDL-1 protein (existing on the cancer cell surface) and the PD-1 protein (existing on the immune cell surface). Once this interaction is blocked, the ability of the immune system to fight and destroy cancer cells is not harmed.  

This unique mechanism of blocking the interaction between PD-1 and PDL-1 is a breakthrough in cancer treatment. All over the world a great deal of effort is devoted to the development of new drugs with such mechanisms that will enhance the immune response against the malignant process and change the whole approach of cancer treatment.  

Keytruda has proved successful in treating melanoma - an aggressive skin cancer - that has progressed after treatment. Patients receiving Keytruda in a clinical trial experienced shrinking of their tumors and in some patients this effect has lasted for a long time. 

Based on these exciting, although preliminary results, the FDA recently approved Keytruda for the treatment of patients with advanced melanoma who no longer respond to other drugs. 

In Israel, Keytruda and Opdivo (another drug with the same mechanism) were both approved by the Israeli drug panel as state-subsidized for the treatment of advanced melanoma.

*Keytruda is defined as a drug that prolongs life and delays the progression of cancer. However, there is still no proof that it can cure cancer!

*There are more than 200 different types of cancer. Not all anti-cancer drugs are effective in treating all the different types of cancer. There are many anti-cancer drugs that may be effective for the treatment of one type of cancer but not for another type. The effectiveness of each anti-cancer drug must be proved separately, via clinical trials, for each type of cancer.

As of today, the efficacy of Keytruda has been established in advanced melanoma only.

*Keytruda is also being studied, via clinical trials, for the treatment of other cancer types. In some of them (lung cancer, bladder cancer, gastric cancer, head and neck cancer, renal-cell cancer, ovarian cancer), there are hints of promising early results.  Nevertheless, except in the case of melanoma, any potential effectiveness of Keytruda has not yet been established. 

In Israel, Keytruda is  indicated for the treatment of advanced melanoma only, while patients with other types of cancer may be able to obtain it via clinical trials