A bacteria-based immunotherapy vaccine for mesothelioma may improve the odds of surviving the disease by boosting the effects of chemotherapy.
That is the word from the latest clinical trial of CRS-207 headed by researchers at the National Cancer Institute.
Thirty-five inoperable patients received the immunotherapy vaccine for mesothelioma along with standard mesothelioma chemotherapy. Eighty-nine percent of them experienced either a full or partial response to the treatment combination.
CRS-207 Immunotherapy Vaccine for Mesothelioma
CRS-207 is based on a modified version of Listeria monocytogenes. The bacterium is best known for causing the food borne illness Listeriosis. In CRS-207, the bacteria has been changed so it cannot make patients sick.
The immunotherapy vaccine for mesothelioma uses the bacteria to trigger a powerful immune response against cells that produce mesothelin. Mesothelioma cells and some other types of cancer express a lot of mesothelin but it is rare in normal cells.
In the newly-published trial, 35 patients with tumors that could not be removed received two doses of CRS-207, two weeks apart. Then they had up to six cycles of chemotherapy with pemetrexed (Alimta) and cisplatin.
After chemotherapy, patients had two more doses of the immunotherapy vaccine for mesothelioma. If things seemed to be going well, the patient continued to receive a “maintenance dose” of CRS-207 every eight weeks.
Results Show Vaccine Boosts Chemotherapy Response
Eight-nine percent of the mesothelioma patients on the combination treatment responded to it.
In 20 cases, the mesothelioma tumors actually shrunk in size. In the other 10 cases, the mesothelioma tumors at least stopped growing. These patients lived for a median of 7.5 months before their tumors began to progress again.
Overall, patients who received the immunotherapy vaccine for mesothelioma along with chemotherapy lived for a median of 14.7 months. There were no deaths or serious side effects from the treatment.
Biopsy samples taken before and after the CRS-207 combination treatment help explain why it works. They show that the immunotherapy vaccine for mesothelioma attracts lots of cancer-fighting immune system cells to the tumor site.
Researchers found extra CD8+ T cells, dendritic cells, and natural killer cells all around the mesothelioma tumors. These immune system cells work along with the chemotherapy drugs to kill mesothelioma cells.
The researchers conclude that the new mesothelioma treatment “induced significant changes in the local tumor microenvironment” for most of the patients.
Hassan, R, et al, “Live-Attenuated, Listeria monocytogenes Expressing Mesothelin (CRS-207) with Chemotherapy for Treatment of Malignant Pleural Mesothelioma”, July 1, 2019, Clinical Cancer Research, Epub ahead of print, http://clincancerres.aacrjournals.org/content/early/2019/06/29/1078-0432.CCR-19-0070