The Names of Targeted Therapies Give Clues to How They Work
by Deborah Christensen RN, BSN, HNB-BC
I was reading through the program of my granddaughter's dance recital and noticed that there was not a single common name in the first three groups of young dancers. It was as if their parents purposefully decided to come up with the most unique names possible. There may have been some family significance in the names, but it was hard to tell without knowing the family. This is not the case with the family names of targeted cancer drugs. Each generic name gives information on the what, how, and where of each particular drug.
In contrast to traditional chemotherapeutic agents that affect rapidly dividing cells, targeted agents are more precise in the way they fight cancer. Presently, two main families of targeted therapies exist—monoclonal antibodies and small molecule inhibitors. The ending letters (stem) of the generic names are like surnames that tell what family the drug is from and how the drug works to kill cancer cells. Monoclonal antibodies end with the stem “-mab” and small molecule inhibitors end with the stem “-ib”. The “-mab” family of targeted therapies has three distinct methods for interfering with cancer cell growth.
- Attach to receptors on the outside of cells to prevent the receptors from interacting with signaling molecules (e.g., growth factor receptors and growth factor interaction)
- Deliver radioactive molecules or toxins to the inside of the cells through attachment to cellular receptors
- Activate the body’s natural immune response
The “-mab” family is used when receptor targets are overexpressed on the outside of cancer cells. Conversly, the “-ib” family targets processes within the cell and therefore must be small enough in molecular weight to enter the cell and interfere with proteins on both the inside and outside of the cell. Proteins that code for growth or inhibit growth are some of the targets of this small but powerful family of drugs.
The sub stem of the generic names of the “-mabs” identifies the source where the antibodies were generated or cloned. The three most common sources are:
- Chimeric human-mouse—drugs ending in “-ximab” (i.e., rituximab)
- Humanized mouse—drugs ending in “-zumab” (i.e., bevicizumab)
- Fully human—drugs ending in “-mumab” (i.e., ipilimumab)
Finally, both “-mabs” and “-ibs” contain an additional stem to describe the targeted therapies bullseye. For example, the “tu” in rituximab indicates the target is the tumor, the “ci” in bevicizumab designates the circulatory system, and the “li” in ipilimumab identifies the immune system target. Some of the intracellular targets for the “-ibs” include:
- Tyrosine kinase inhibition—sub stem “-tinib” (i.e., imatinib)
- Proteasome inhibition—“-zomib” (i.e., bortezomib)
- Clyclin-dependent kinase inhibition—“-ciclib” (i.e., seliciclib)
The prefix of the generic names and the drug market names are where researchers and pharmaceutical companies—like the parents of the young dancers—take creative liberty.
The development of targeted therapies is expected to accelerate as new targets are identified; as a result, oncology nurses will need to stay up to date on the new medications so they can educate their patients on the way these therapies work as well as the possible side effects of the medications. Unfortunately, many people may have the idea that there are few if any side effects associated with targeted therapy. Although side effects can be less than those of standard chemotherapy, targeted therapies also affect normal cells to some degree.
So how do nurses keep up on the new therapies? Recently, ONS merged two key special interest groups (SIGs) the Targeted and Biologic Therapies SIG and the Chemotherapy SIG. The new SIG is now called the Chemotherapy and Biotherapy SIG. Another resource I found especially helpful was an animated video titled Understanding Targeted Cancer Therapies presented by the National Institute of Health.
Identifying the source, target, and mechanism of action by uncoding the generic names of targeted therapies is fun. It is a whole lot easier than trying to figure out how parents come up with clever names for their children.