Adam Snook, PhD, Assistant Professor, Sidney Kimmel Cancer Center – Jefferson Health at Jefferson University talks about a cancer vaccine.
Interview conducted by Ivanhoe Broadcast News in August 2019.
You thought about this 17 years ago. What was the motivation?
SNOOK: Immunotherapy has been an idea for cancer for decades really. But it’s a problem that’s been difficult to solve. We had this molecule that we identified in our lab as a biomarker in colon cancer. It was good at detecting cancer that spread from the colon into other places and we thought that maybe it could be a target for therapies too, whether that was immunotherapies or other kinds of therapies. It fit a big need in colon cancer where patients are treated by surgery and then chemotherapy and then they kind of go into this waiting period where hopefully the cancer is gone, but in a lot of cases it’s not. We thought that targeting the molecule in that period could be really effective to eliminate those cancer cells by the immune system and prevent the disease from coming back.
How’s it going to find where to target?
SNOOK: Our immune cells are really amazing. Their job is to travel throughout the body at all times and survey different tissues. We can administer a vaccine in the arm for example and then those immune cells will spread out from there and seek out cancer cells in different places, like the lungs or the liver where they may have spread to in the same way that the immune cells would seek out a viral or bacterial infection that’s in different tissues in the body. It’s really the same process. We are just taking advantage of the same mechanisms to target cancer as opposed to an infection.
So these are really difficult cancers to treat, many of them. But this particular point in the insertion process is after chemotherapy. People traditionally think of a vaccine as coming before. Why did you decide to place it there?
SNOOK: It’s partly because of the current management for all cancers. We have to fit whatever our new therapy is into the standard therapy. It’s going to be difficult to replace something like chemotherapy, which is already fairly effective. In a disease like colon cancer, it’s actually going to be easier. The standard practice for approving new cancer therapy today is to combine them with or test them in the context of the established therapy. That might be combining them with therapies that are already out there or using them sequentially after those therapies that are out there rather than replacing the current therapies, which already work. Standard therapies are just not that effective. We call it a vaccine, which you think of as being given before you have the disease, because the molecular mechanisms and cellular mechanisms that we’re using are all the same. That’s why we call it a vaccine even though it’s given as a therapeutic vaccine as opposed to a prophylactic or preventative vaccine.
Walk us through the process of when the vaccine is administered. Is it a shot? Or is it drunk?
SNOOK: The vaccine is administered in the muscle in the arm almost like a flu vaccine would be given. The vaccine is actually composed of a virus that expresses this tumor antigen that we’re targeting. The virus infects cells and that antigen is made and presented to the immune system to say “here’s something dangerous. Create an immune response to go out and find more cells expressing this protein.” That’s what they’ll do. Those cells will leave that injection site where they’ve been activated and go out and find other cells making our protein and kill them.
Odd question, but in your head as the developer here, how do you picture this? Is it soldiers fighting or what’s your picture that you see here?
SNOOK: Picturing it as little soldiers is a good way to think about it. The T cells are the ones that we’re specifically focused on – they’re like soldiers and they really do go out and find those cancer cells and kill them. They have these cytotoxic molecules that they secrete that bind to the cancer cell and actually poke little holes in the cancer cell, deliver cell killing molecules to the inside of the cancer cells, killing them one cell at a time. Each of those T cells can find hundreds or thousands of cancer cells and sequentially kill them one by one by one until, hopefully, the cancer is all gone.
We interviewed a pancreatic cancer patient. She was stage two when they took it out. In a perfect world, what would you hope to see happen with someone like that?
SNOOK: Our goal is that for patients with pancreatic cancer or colon cancer, that they receive the standard therapies and they, instead of hoping that their disease is gone after they’ve received their chemotherapy, that they now know that their immune system is working for those weeks or months or years afterwards to help prevent it from coming back.
Great job.
END OF INTERVIEW
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