Of the 10 chemotherapy-resistant mesothelioma patients ...3 experienced 'major tumor regressions'.
Raleigh, NC (PRWEB) October 31, 2013
In a report published in the journal Science Translational Medicine and detailed by Surviving Mesothelioma, Dr. Raffit Hassan and his colleagues at the National Institute of Health (NIH) explain how they successfully used an immunotoxin to find and attack mesothelioma cells.
The treatment is based on an immunotoxin called SS1P, which targets cells that overproduce a protein called mesothelin. SS1P is designed to work by inhibiting protein synthesis inside mesothelioma cells, triggering cell death. While the immunotoxin approach has worked well in cancer patients with weakened immune systems, such as those with leukemia, previous studies have found that the immune systems of people with mesothelioma tend to attack immunotoxins and render them ineffective.
To counter this effect, Dr. Hassan and his NIH colleagues elected to deliver SS1P along with two immune-suppressing drugs – pentostatin and cyclophosphamide. These two drugs worked to reduce the numbers of T- and B-cells, allowing more SS1P to circulate through the body, finding and killing mesothelioma cells.
Of the 10 chemotherapy-resistant mesothelioma patients who received the combination treatment, 3 experienced “major tumor regressions”, 2 of which were still ongoing after 15 months of follow-up. In addition, 2 other mesothelioma patients in whom SS1P did directly impact their tumors became responsive to chemotherapy treatment after discontinuing the immunotoxin treatment.
While pentostatin and cyclophosphamide “markedly delayed” the formation of antibodies, allowing more cycles of SS1P to be delivered, the researchers say this alone cannot account for the antitumor activity. They will try to determine the exact mechanism of the treatment’s success in future trials.
A combination of delayed symptom onset, late diagnosis, and treatment resistance make mesothelioma an especially deadly cancer for many people. If a planned larger study of the immunotoxin mesothelioma treatment produces similar results, it could offer new hope for thousands of patients with this rare but aggressive cancer.
The original immunotoxin study was published in Science Translational Medicine. (Hassan, Raffit, et al, “Major Cancer Regression in Mesothelioma After Treatment with an Anti-Mesothelin Immunotoxin and Immune Suppression”, October 23, 2013, Science Translational Medicine, Vol. 5, Issue, 208, p. 208. http://stm.sciencemag.org/content/5/208/208ra147)
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