Key takeaways: Vaccines are currently being developed as treatment for mesothelioma. These vaccines
utilize and manipulate the body’s existing immune defenses in different ways: DNA
manipulation, the introduction of helpful bacteria or viruses, or the introduction of certain
immune proteins. There are promising clinical trials for treating mesothelioma with vaccines.
Vaccines as Immunotherapy
Vaccines to treat cancer–beyond mesothelioma–are a form of immunotherapy. Immunotherapy
refers to the external manipulation of the body’s immune system to target, destroy, or isolate
cancerous cells.
In terms of mesothelioma vaccines, doctors will extract a sample of the tumor(s) in order to
formulate a patient-specific vaccine. Depending on the tumor burden, or the amount of mutations
present in the cancerous cells, the vaccine would likely be used in conjunction with other
therapies, like radiotherapy or chemotherapy. A high tumor burden, or a relatively high amount
of mutations present in the tumor, lends itself to a combination of therapies. A low tumor burden
might be successfully targeted by a vaccine alone. Another “prerequisite” for vaccine-based care
is the holistic health of the patient: they need to have working cell-mediated immunity, or
working T cells and cytokines. T cells and cytokines are responsible for identifying antigens, or
any foreign substance that elicits an immune response.
Vaccines work by invoking the natural immune response: by introducing a small amount of an
antigen, cell-mediated immunity recognizes, kills, and remembers the antigen for future
encounters. Vaccine-based mesothelioma care works the same way: the tumor’s DNA or proteins
are artificially fabricated to be an antigen recognized by the cell-mediated immunity system.
Because antigens present as bacteria or viruses, the tumor’s DNA/proteins need to be introduced
to the body in the same way. Oftentimes, these proteins or DNA molecules are put into bacteria
or viruses so the body easily recognizes them. Once the body recognizes the tumor’s DNA as an
antigen, the cascading immune response ensues. The immune system mobilizes an attack against
the tumors, which helps in effective treatment.
Treatment for Mesothelioma: Clinical Trials
Galinpepimut-S (GPS) is a protein-based mesothelioma vaccine that uses a different medium to
target tumors. While we’ve covered bacterial and viral introduction, GPS targets antigens that
mesothelioma cells release. So, instead of utilizing the natural immune response, GPS attacks
secretions of tumor cells directly. This approach is more widely applicable, as the vaccine
doesn’t have to be tailored to each patient’s immune system. Instead, it leverages a protein that
doctors know mesothelioma tumors produce.
In one clinical trial, patients received the GPS vaccine after pemetrexed-based chemotherapy
treatments. Their survival rate–compared to patients initially treated with the same
pemetrexed-based chemotherapy but with a different secondary treatment–was 35% higher. This
is important for doctors and researchers hoping to effectively pair different techniques for
mesothelioma treatment.
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Sources:
Nowak, A. K., Lake, R. A., Kindler, H. L., & Robinson, B. W. S. (2002). New approaches for
mesothelioma: Biologics, vaccines, gene therapy, and other novel agents. Seminars in Oncology,
29(1), 82–96. https://doi.org/10.1053/sonc.2002.30234
SELLAS Life Sciences Reports Encouraging Updated Clinical Data Indicating Increased
Survival from Ongoing Phase 1 Mesothelioma Study of Galinpepimut-S Combined with Opdivo.
(n.d.). Retrieved February 12, 2024, from
https://www.sellaslifesciences.com/investors/news/News-Details/2022/SELLAS-Life-Sciences-R
eports-Encouraging-Updated-Clinical-Data-Indicating-Increased-Survival-from-Ongoing-Phase1-Mesothelioma-Study-of-Galinpepimut-S-Combined-with-Opdivo/default.aspx
What Is Tumor Mutational Burden? | Cancer Today. (n.d.). Retrieved February 12, 2024, from
https://www.cancertodaymag.org/cancer-talk/What-Is-Tumor-Mutational-Burden/
