This page has been fact checked by a Doctor of Pharmacy who specializes in Oncology. Sources of information are listed at the bottom of the article.
We make every attempt to keep our information accurate and up-to-date.
Please Contact Us with any questions or comments.
Immunotherapy is a popular research target for cancer treatment. It is a relative newcomer to cancer treatment, especially compared to traditional therapies like chemotherapy and radiation. Immunotherapy uses the body’s immune system to kill cancer cells or slow the spread of tumors.
One immunotherapy strategy uses immunotoxins, and is currently being tested in clinical trials for patients with mesothelioma and other cancers. Several ongoing trials are evaluating whether or not these immune-modulating drugs can kill cancer cells selectively, halting progression of the disease. Some reported results are promising and are beginning to combine immunotoxins with other types of treatment.
What is an Immunotoxin?
Immunotoxins are targeted compounds that use designed molecules to attach to cancer cells. As a targeted treatment, the goal of the medication is to seek out the specific cancer cells and deliver a toxic payload directly into the cancer while leaving normal cells relatively unharmed. An immunotoxin is a combination of a designed antibody and a toxin. The antibody is designed to find and attach to proteins called an antigen on the surface of cancer cells. The cell then absorbs the toxin and dies.
While toxins have long been used to treat cancer through chemotherapy, this treatment is generally not specific. Chemotherapy drugs circulate the entire body, killing cancer cells and healthy cells. The immunotoxin strategy specifically targets and kills cancer cells, which should reduce the side effects while increasing the amount of drug that can reach the cancer.
Clinical Trials Using SS1P Immunotoxin
Researchers have been studying immunotoxins in many cancer types for years. Some are using these therapies to target mesothelioma cancer cells. A clinical trial that began in 2011 showed promise for patients with mesothelioma. Supported by the National Cancer Institute, this phase I trial used an immunotoxin known as SS1P, which combines an anti-mesothelin targeting antibody with a toxin derived from a bacteria called Pseudomonas aeruginosa.
In one trial with SS1P, 60 percent of patients showed at least stable disease when the drug was combined with other drugs. One patient had a stunning response, seeing 74 percent reduction in tumor size. In this trial, the drugs combined SS1P with immune-suppressants.
Results were even more positive than those seen with the chemotherapy drugs. In previous trials, patients’ immune systems recognized and began developing antibodies that destroyed the immunotoxin treatment used to target the cancer cells. Combining the treatment with immune-suppressant drugs, reduced this activity and the immunotoxin worked more effectively.
Immunotoxin Trial Recruitment Halted
While there have been promising results with immunotoxin drugs for mesothelioma, there have also been some unexpected results. A phase I trial tested the combination of immunotoxin known as LMB-100 with an immune-suppressant called SEL-110. Both pleural and peritoneal mesothelioma patients participated in the trial.
Although this combined therapy has great opportunity for treating mesothelioma, the recruitment was halted due to adverse reactions. Several patients developed a severe type of pneumonitis, an inflammation of the tissue around the lungs. Pneumonitis can cause difficulty breathing, coughing, fatigue, and loss of appetite. While recruitment for this trial was stopped, no results for effectiveness in original participants have been reported.
Clinical Trial Currently Recruiting
One trial using the LMB-100 immunotoxin is currently recruiting pleural and peritoneal mesothelioma patients. LMB-100 targets mesothelin, a protein heavily expressed by mesothelioma cells. The study is using LMB-100 along with pembrolizumab, a different kind of immunotherapy drug.
Pembrolizumab works by interfering with an interaction between cancer cells and immune system cells that protects the cancer cells. This drug allows immune system T-cells to recognize cancer cells as harmful, boosting the immune system’s effectiveness. The theory is that the immunotoxin can mark the cancer cells as foreign to the body, allowing the immune system to recognize and clean them up more effectively.
Qualified patients must have peritoneal or pleural mesothelioma that cannot be treated by surgery. Patients must also meet several health and medical markers to be accepted. There are also many health factors that could exclude a patient. Your oncologist or medical team can help you determine if you qualify for this trial.
Potential Adverse Events
Immunotoxin therapy is still very new. Therefore, all potential side effects are not yet known. However, one potential risk is hepatotoxicity, or liver damage. Liver function may decline in patients receiving immunotoxin therapy.
Other recorded side effects include vascular leak syndrome (which causes swelling and edema), pleuritic syndrome (an inflammation of the pleural tissue), and hemolytic uremic syndrome (which can cause anemia and kidney damage).
Immunotoxin therapy is an emerging approach to cancer treatment that is being tested for a wide variety of cancers. There is great hope for patients with difficult-to-treat cancers like mesothelioma. These clinical trials may someday show that combinations of immunotoxins with other drugs could extend patient lives. If you are interested in trying these therapies, talk to your medical team about finding and enrolling in an appropriate immunotoxin clinical trial.
Page Medically Reviewed and Edited by Kyle J. Becker, PharmD, MBA, BCOP
Kyle J. Becker, PharmD is certified by the Board of Pharmacy Specialties in Oncology Pharmacy. Dr. Becker earned his pharmacy degree from Shenandoah University and he currently serves as an oncology pharmacist at Parkview Cancer Institute.