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Clinical trials are important for testing the effectiveness and the safety of experimental drugs and therapies. They also provide additional options for patients with advanced cancer, like late-stage mesothelioma. For some it may be a last chance to try to manage this terrible disease.
Several trials are currently testing a new targeted therapy called anetumab ravtansine, which is made by Bayer. There have been some setbacks, but there is still great opportunity for this new therapy, which selectively targets certain types of cancer cells to deliver a cytotoxic drug directly to them.
Anetumab Ravtansine and ADCs
Anetumab ravtansine is an experimental targeted therapy made by German pharmaceutical company Bayer and biotech companies ImmunoGen and MorphoSys. 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. The title of this particular medication’s mechanism is antibody-drug conjugate (ADC).
An ADC is a drug that combines an antibody with a cytotoxic drug. An antibody is a protein that recognizes chemical signals on the targeted cells and binds to the abnormal cells preferentially over the normal cells. Antibodies have been developed by researchers to target cancer cells.
How Anetumab Ravtansine Works
ADCs work by using the antibody to find and recognize cancer cells and deliver the cytotoxic drug to them. In chemotherapy, patients are given systemic non-specific drugs that are cytotoxic. This means they circulate the body and kill any fast growing cells, including both cancer and healthy cells. The delivery system of ADCs like anetumab ravtansine ensures that the drug only goes to and acts upon cancer cells.
The drug is made up of three parts: the antibody, the cytotoxic drug, and a linker molecule that holds them together. When given to the patient the antibody recognizes and attaches to a specific protein, known as an antigen, present on the surface of the cancer cells. The cancer cell absorbs the entire three-part drug. In the cell the linker dissolves and the cytotoxic drug is free to take action and kill the cell.
This ADC (anetumab) has been linked (conjugated) to a highly toxic cytotoxic drug, in this case called DM4 (ravtansine). Anetumab finds mesothelin and brings the toxic payload directly to the cancer, where the toxin is delivered into the cell and destroys it.The targeted nature of ADCs means that, if effective, they should produce fewer side effects than traditional therapy.
Anetumab Ravtansine and Mesothelioma
For an ADC to work it must have an antibody that targets an antigen on the surface of cancer cells. Researchers created anetumab ravtansine to target an antigen known as mesothelin. Mesothelin is not only prevalent on the surface of many mesothelioma cancer cells, but it is also found on the cells that make up many pancreatic and ovarian tumors. Healthy cells may have some mesothelin, but not nearly as much as these cancer cells, so they are not targeted to any significant degree by the drug.
Once anetumab ravtansine is absorbed into a mesothelioma, pancreatic, or ovarian cancer cell, the cytotoxic drug disrupts its ability to thrive. The cell is unable to grow, develop, and divide. This disruption stops cells from dividing, and they simply die.
Clinical Trials with Anetumab Ravtansine
Anetumab ravtansine is a drug giving hope for more treatment options to patients with mesothelioma. However, it is still in clinical trials and is not yet an approved treatment. There are currently two trials associated with the National Institutes of Health and the National Cancer Institute using this drug to treat mesothelioma. We are awaiting results from both of these trials that have recently ended enrollment.
One study that is currently active is evaluating the safety and potential side effects of anetumab ravtansine both in combination with and without another immunotherapy drug called pembrolizumab (Keytruda). Patients involved in this phase I and II trial have pleural mesothelioma and have already undergone chemotherapy.
Another clinical trial has been ongoing since 2015 and involves patients with advanced pleural mesothelioma or non-small lung cell cancer. Still in phase I, this study is looking at the safety and effectiveness of combining anetumab ravtansine with the standard chemotherapy drugs pemetrexed and cisplatin.
A Disappointing Failure
One early trial of anetumab ravtansine conducted by Bayer has already failed to meet its target with mesothelioma patients. Participants were either given the trial drug, anetumab ravtansine, or the chemotherapy drug vinorelbine. The study results have so far been disappointing with no evidence that the drug was any more effective than chemotherapy in the participants.
While the results have been disappointing for this trial, researchers have not given up on anetumab ravtansine. The trials that are ongoing or about to start will continue, and there is hope that the results of these trials, including combinations of drugs, will be better. It is a setback but not the end of anetumab ravtansine.
If you are interested in clinical trials or think you may qualify for a trial with anetumab ravtansine, talk to your oncologist or other members of your medical team. There are requirements you must meet, and it is also important to consider the risks of joining clinical trials. Immunotherapy drugs like anetumab ravtansine are showing great promise as a new line of treatment for difficult cancers and patients can help make them better by participating.
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.