It seems like every other day, my Google News alert regarding melanoma research lights up with another advance using immunotherapy. This one comes from a team at UCLA who combined immunotherapy with an experimental sequence of nucleic acids that mimics a bacterial infection.
The researchers provided 22 people who had inoperable or advanced metastasized melanoma an immunotherapy drug called pembrolizumab and SD-101 (that stuff that acts like a bacterial infection). Pembrolizumab is a PD-1 blocker (as mentioned quite a few times in this blog the past month or so, PD-1 is a protein that inhibits the response of T cells). So what is the function of SD-101? Researchers found that it not only directs T cells to the cancer cells, but it also makes the microenvironment more hospitable for the T cells, so that they can better kill the cancer cells.
Some of those people had previously tried immunotherapy while the rest had not. What was really interesting about the results of the trial was that the people who responded best to this combination were newbies to immunotherapy. Of those 9 people, 7 of them had a positive response (78% overall response rate) with 2 of them seeing their tumors completely disappear. According to the research team, the estimated 12 month progression-free survival (PFS) rate was 88%, and overall survival (OS) rate was 89%. Those are some interesting results. Less exciting was the outcome for those who had previously tried some type of immunotherapy – out of 13 people, only 7 saw any reduction in their tumors and none were completely cleared.
This is an early-stage trial though. Perhaps the reasons why the previous immunotherapy patients saw limited benefit may be something to do with why immunotherapy didn’t work prior. It could be something as esoteric as what their digestive bacteria are.