You’ve probably heard by now that a team at the University of Pennsylvania built a virus in the lab which inserted a gene into the T cells of three patients with chronic lymphocytic leukemia who had no treatment options left. All three patients had over two pounds of tumors which were affecting B cells in the blood. The gene therapy altered the T cells to target B cells and destroy them. All three patients have been in remission for the past year. The change was enormous. 85% of one patient’s bone marrow was comprised of cancerous cells; after treatment only 2% of cells in that patient’s bone marrow were found to be cancerous. (Full text of the study here.)
Don’t start injecting cigarettes directly into your veins to celebrate, however, because this treatment (besides only being tested on three people so far) has some downsides brought up by Veronique Greenwood of 80beats:
- Cancer patients are routinely exposed to treatments much worse, at least in the short term, than the disease: killing cancer cells means killing a lot of healthy cells. With this treatment, nearly all of the patients’ B cells, healthy and otherwise, were destroyed, and even months afterwards the B cells had not recovered. Since this is the class of immune cells that produces antibodies, this loss could be quite serious in the long term, though all the rest of the patients’ cells were unharmed.
- The team also notes that the mass murder of cancer cells provoked a serious response: the patients’ bodies were flooded with detritus from the bursting cells and inflammatory molecules produced by the immune system, some at 160 times the normal levels. Their kidneys were in acute distress, and at least one had to be hospitalized because of it. The researchers note that they are really going to have to pay attention to this when they’re designing larger studies. Maybe the injections will be spread out more, or maybe not as many altered immune cells are required.
- Additionally, one of the most exciting things about this study—that the T cells stay in circulation and may keep destroying any cancer that crops up for years—makes it quite different from, and possibly riskier than, most cancer treatments, which usually are purged from your body in a matter of weeks. That means that the follow-up work to figure out what the T cells are doing, and whether they might be somehow dangerous in the long term, will be substantial. What, for instance, will the indefinite lack of B cells mean? The FDA will need serious reassurance on these points, especially since gene therapy carries a risk of causing mutations in modified cells that might eventually turn them cancerous over the patient’s lifetime.
So . . . don’t try to get leukemia, I guess? There go my plans for the weekend.