University of South Carolina
Eric Bartee, PhD Photo from the Medical
Myxoma virus (MYXV), a nonhuman oncolytic agent, has demonstrated efficacy in mouse models of multiple myeloma (MM), according to research published in Molecular Therapy—Oncolytics.
MYXV significantly improved overall survival in mice with MM, providing a modest delay in disease progression for about two-thirds of the mice and completely eradicating the disease in a quarter of them.
“[W]e could actually get rid of disease, and it didn’t appear to ever come back,” said study author Eric C. Bartee, PhD, of the Medical University of South Carolina in Charleston.
For the past several years, Dr Bartee has been using MYXV to treat MM in cell culture. He and his colleagues previously showed that MYXV was able to kill human MM cells.
The team found that treatment with MYXV could eradicate MM cells in patient stem cell samples prior to transplant, thereby preventing relapse of MM.
In the current study, Dr Bartee and his colleagues took this one step further by assessing whether treatment with MYXV also has a benefit on disease outside the context of transplantation.
Using a mouse model of MM, the researchers showed that systemic treatment with MYXV reduced tumor burden and led to a modest decrease in disease progression (about 6 days) in 66% of mice.
In 25% of mice, there was complete eradication of disease with no evidence of relapse.
Since MYXV does not replicate in MM cells, the researchers postulated that eradication was caused by the host’s immune system. Investigation of the bone marrow showed that it was unaffected by treatment with MYXV.
This suggested that the immune system remained functional and could combat MM. Indeed, treatment with MYXV led to an increase in CD8+ T cells in the bone marrow, indicating a strong antitumor response.
The researchers noted that, although these results are promising, there are hurdles that must be overcome before this treatment can be brought to the clinic. One hurdle is large-scale production of clinical-grade virus. Another is demonstrating a high response rate.
“I think the major next question is ‘How do you get that response rate from 25% to 50% to 80% to 100%?’” Dr Bartee said. “How do you define the patients in which it works?”
