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Keytruda® is a brand name for the drug pembrolizumab. This cancer drug was developed, manufactured, and sold by Merck. In 2014, Keytruda was approved by the U.S. Food and Drug Administration (FDA) to treat metastatic melanoma and other cancers, including non-small cell lung cancer in patients with certain biomarkers. This is the first time the FDA has approved a cancer drug based on genetics rather than disease location.
For people affected by asbestos exposure, Keytruda is exciting because early studies suggest it may be a useful chemotherapy drug for mesothelioma. While more research is necessary, results are promising. This could lead to an additional therapy for mesothelioma patients with limited options for treatment.
Pembrolizumab and Immunotherapy
Keytruda is an immunotherapy drug designed to help the immune system identify and attack cancer cells. The immune system’s duty is to recognize and attack foreign invaders in the body. Immune system cells recognize some pathogens because of receptors called antigens on their surfaces.
Healthy cells in the body have receptors on their surfaces that signal immune cells to leave them alone. Some cancer cells express these same receptors, called PD-1 proteins. This causes immune cells to mistake cancer cells for healthy cells and leave them alone to grow and thrive. Pembrolizumab acts on these cancer cell receptors, helping the immune system to recognize them as foreign and attack them. This strategy is sometimes referred to as the immune checkpoint blockade.
Indications and Side Effects
The FDA approved Keytruda for specific types of cancers, for cancers in certain stages or with certain characteristics, and for cancer patients with certain biomarkers. For example, it is approved for melanoma, but only melanoma that has spread and cannot be treated surgically. For other cancers, like non-small cell lung cancer, Keytruda is approved only in cases where the patient’s cancer worsened after treatment with standard chemotherapy drugs.
The side effects associated with pembrolizumab can be serious. Contact your doctor immediately if you have unusual cough or diarrhea. Otherwise, the most common side effects include fatigue, rash, diarrhea or constipation, nausea, decreased appetite, shortness of breath, coughing, and itching. More serious side effects are less common but may include bruising, anemia, numbness, dizziness, hot flashes, flu-like symptoms, hair loss, edema, irregular heartbeat, pain, kidney failure, infections, insomnia, diabetes and jaundice. Chest pains, shortness of breath, and a cough may indicate a serious reaction that should be addressed immediately.
Keytruda for Mesothelioma
Right now, indications for Keytruda do not include mesothelioma, but research is underway to determine if it could be an effective and safe treatment for this cancer. Most recently, a study published in The Lancet Oncology showed promising results. This study shows that while other chemotherapy drugs are failing mesothelioma patients, immune checkpoint drugs may be a better alternative.
The clinical trial is called KEYNOTE-028 and involved 13 research teams in six different countries. The trial included 25 patients with pleural mesothelioma who had already received at least one chemotherapy treatment prior to the trial. Patients received a larger than normal dose of pembrolizumab every two weeks. As a result, 20% of the patients saw reductions in tumor size, and and additional 52% had stable disease. Patients who responded had an average of 12 months of response. Considering how aggressive mesothelioma can be, helping patients extend their life after initial treatments failed is impressive. Also notable is that while there were common side effects, including fatigue and nausea, no patients had to stop taking the drug.
Keytruda for Asbestos Lung Cancer
Pembrolizumab is promising for mesothelioma patients. However, the drug is already approved for non-small cell lung cancer (NSCLC), another cancer that can be triggered by asbestos exposure. Approval for treating this kind of cancer came after clinical trial results showed it to be safe and effective. More recent studies suggest it may be more effective than standard chemotherapy drugs like cisplatin and carboplatin.
The KEYNOTE-024 clinical trial of pembrolizumab in non-small cell lung cancer patients whose tumors express PD-L1 at 50% or higher. Data showed pembrolizumab has several advantages over traditional chemotherapy. Patients given this drug experienced better overall survival rates, fewer side effects that were less severe, and improved quality of life. While some side effects were worse with pembrolizumab, overall adverse effects were lower and less severe. The benefits of pembrolizumab were seen in its use as a first-line treatment. This trial means patients with lung cancer may be prescribed pembrolizumab in place of cisplatin or carboplatin, avoiding chemotherapy side effects and possibly achieving better results.
The promise of immunotherapy drugs for cancer treatment is overwhelmingly positive. Keytruda is paving the way to a new strategy for better treatment of mesothelioma. There are now more than 90 ongoing clinical trials using Keytruda to treat various types of cancers.
Approval for Keytruda Expands, Hope for Mesothelioma Patients
In June of 2019 the FDA announced a new indication for Keytruda. It is now approved for the first-line treatment of metastatic, unresectable, or recurrent head and neck squamous cell carcinoma (HNSCC). The FDA has approved the immunotherapy drug as part of a combination treatment with chemotherapy and also as a stand-alone treatment for HNSCC patients with PD-L1 expression on the tumor cells. This is important news, not just for the HNSCC patients who may now benefit from Keytruda, but also for mesothelioma patients. HNSCC is a rare cancer that is difficult to treat, just like mesothelioma. The approval for pembrolizumab is an important step in giving these patients more hope of improved survival. It is also a step in the direction of getting drugs like this approved for other rare cancers.The approval came after the clinical trial KEYNOTE-048 showed the drug could significantly prolong patient survival.
Two new mesothelioma trials are expected to start soon. If you are struggling with mesothelioma, pembrolizumab is not currently approved for treatment. However, you may be able to participate in a clinical trial. Talk to your doctor about how to get involved if you qualify for this revolutionary treatment for this difficult type of cancer.
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.