A trial of immunotherapy drug pembrolizumab in patients with mesothelioma has had promising results. The trial shows that the benefits of the therapy equal those of standard chemotherapy, which can cause a lot of uncomfortable side effects. Researchers hope that the study will also shed light on why some patients respond better to immunotherapy than others, advancing this important type of treatment.
Pembrolizumab and Immunotherapy
Pembrolizumab is an immunotherapy drug used under the brand name Keytruda. It is currently approved to treat several types of cancer, including lung cancer, gastric cancer, cervical cancer, and esophageal cancer, often along with chemotherapy. It is used for mesothelioma in trials, where researchers hope it will prove useful for these patients.
This drug is known as a checkpoint inhibitor. It is a humanized antibody that binds to a receptor known as PD-1 on T-cells. The T-cells are cells in the immune system that attack and eliminate invading, harmful cells in the body. Cancer cells have developed to evade T-cells by expressing a protein on their surfaces called PD-L1.
PD-L1 on cancer cells binds to PD-1 on immune system T-cells. This causes the T-cells to recognize the cancer cells as harmless. Pembrolizumab binds to PD-1 so that cancer cells cannot bind there and fool the T-cells into thinking they are harmless. In some patients this has the effect of increasing immune system action against cancer cells. In other words the immunotherapy drug boosts the immune system to attack tumors.
The PROMISE-Meso Trial
The current trial, known as PROMISE-Meso, is testing the use of pembrolizumab in patients with mesothelioma. Results so far show that about four times as many patients responded to the immunotherapy than standard chemotherapy.
The bad news about these results is that the positive response to immunotherapy did not extend patients’ lives. However, the results are promising in that they demonstrate that many more patients can benefit from pembrolizumab than previously believed.
A difficulty with immunotherapy is that some patients respond to it and others do not. Why this is the case is not well understood, but studies like the PROMISE-Meso trial are helping to answer the question. And, with similar benefits to chemotherapy but with fewer side effects, pembrolizumab may be a better option for some patients.
Moving Forward with Immunotherapy
The PROMISE-Meso trial is providing important information about immunotherapy and mesothelioma. Moving forward researchers hope to get even better results by combining pembrolizumab with other types of chemotherapy drugs and trying it in patients with earlier-stage mesothelioma, which is considered much more treatable.
Researchers also hope that ongoing studies with this drug and with mesothelioma patients will give them a better understanding of who benefits. This will help oncologists provide more targeted, effective treatments for individuals.
Treatment options for patients with mesothelioma, especially in the later stages, are currently limited. Studies like this one are important for developing better, more individualized treatment that will provide patients with more hopeful results and fewer damaging side effects.
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