What an mRNA melanoma vaccine may mean for cancer treatment

[THEME MUSIC] IRA FLATOW: Hey, it’s Ira, and you’re listening to Science Friday.

A new mRNA vaccine for melanoma is making headlines. Moderna and Merck recently announced results from their clinical trial, which suggests that this new vaccine, in combination with another drug, significantly reduced recurrence rates of the skin cancer in patients. The companies have not yet released full data from the trial.

So, how does the vaccine work, and does this mark the beginning of a new era of cancer treatments using mRNA vaccine technology? Here to explain is a physician, whose patients were part of the drug trial. Dr. Michael Postow, Chief of the Melanoma Service at Memorial Sloan-Kettering Cancer Center here in New York. Welcome to Science Friday.

MICHAEL POSTOW: Thank you very much for having me. It’s a pleasure.

IRA FLATOW: You’re welcome. All right, Dr. Postow, can you put this news in context for us? Just how big a deal is this new vaccine?

MICHAEL POSTOW: We, in the melanoma field and an MSK, are extremely excited about these new results. I think the most important aspect of a trial like this is the scientific principle that established, in that this is the first time a cancer vaccine has been made on a personalized basis, meaning each individual patient has their own tumor serve as the source of the vaccine creation. So this is the ultimate personalized medicine for each of these patients. And the fact that the top line results from the phase III study showed that this actually worked in combination with Keytruda, to decrease the risk of melanoma recurrence is quite phenomenal.

IRA FLATOW: OK, let’s talk a bit more about the science. Take us into the weeds, how this is personalized vaccine, and how it’s made.

MICHAEL POSTOW: Each of our tumors is very unique. And the goal of a treatment like this, in broad brushstrokes, is to boost our own body’s immune response against the specific aspects of the tumor that are unique to an individual, such that our own immune systems can seek and destroy anything that looks like that tumor in our bodies. And so what happens is that the tumor is removed from a patient, the DNA is sequenced, and there is a complicated computer algorithm, essentially, that determines what among the mutations that are present in the tumor are immunologically relevant, in that not all the mutations in the tumor are relevant for an immune response.

But by seeing what genes are mutated in a tumor and what genes might be relevant to a productive immune response, an mRNA construct is made for that individual patient based upon characteristics of that individual patient’s tumor. And then the patient’s received this therapeutic vaccination. And the theory is that this bootstrap patient’s immune response only against the aspects of the tumor that are within that patient’s individual tumor, and by having that enhanced immunity, that has been shown to protect that patient from future melanomas coming back.

IRA FLATOW: So to use this vaccine, it’s a personalized therapy. Each individual would have to be looked at individually, not just in mass as a vaccine.

MICHAEL POSTOW: That’s correct. Each patient has to have their own vaccine made for them. One vaccine wouldn’t work for another patient because each patient’s melanoma tumor is different. So there is a personalization to this that’s really special in a trial like this. It does make it difficult as well, because it takes some time to manufacture a vaccine like this. And each of these treatments is a bespoke treatment for an individual patient. Many times when people think about vaccines, they think about treatments that are intended to prevent a disease from ever happening in the first place, when we think about tetanus vaccination or polio vaccination and that type of a way. This personalized therapeutic cancer vaccination is not a prevention for melanoma in the first place.

IRA FLATOW: So it sounds like it’s an expensive and time-consuming process. We don’t yet know what the price tag is, right? Is it the cost of a new treatment something you consider when treating patients?

MICHAEL POSTOW: Absolutely. Cost is always important when we think about our treatments. We don’t yet know what the cost of something like this could be. But recurrent melanoma, in and of itself, can be quite costly. Patients and families lose time away from work. More treatments that are often expensive are needed in the setting of recurrent melanoma. So when we ultimately see what the cost of an approach like this would be, it would be important to think about how many patients are able to have their melanomas prevented from recurring with this type of approach, and what could be the downstream cost savings with that type of a therapeutic vaccination.

IRA FLATOW: Could this approach be used to treat other cancers, too?

MICHAEL POSTOW: We think that ultimately this could have implications for other cancers, too. We haven’t yet demonstrated the efficacy in other cancers to the extent that we have in melanoma at this juncture, meaning that melanoma, we finished the phase III study that showed that benefit here. However, there’s really nothing specific about melanoma that this would only be expected to work in melanoma. And in many clinical trials at our institution, Memorial Sloan-Kettering Cancer Center, and otherwise are testing this type of a vaccination approach in patients with other cancers like lung cancer, bladder cancer, kidney cancer, and I know, now that this result is positive melanoma, likely more cancers to come.

IRA FLATOW: Well, that being the case, what is it about melanoma that made it a prime candidate to be the first type of cancer to try and treat with this new mRNA platform?

MICHAEL POSTOW: I think there are two reasons why melanoma was the most exciting tumor type to start these types of studies. Number one, melanoma has long been believed to be one of the more immunogenic types of cancers, and that other immune therapy strategies, related, but somewhat different than this vaccination approach, have demonstrated significant successes in melanoma, and therefore, a new immune therapy approach like this personalized cancer vaccine had at a welcome home in the melanoma field to explore something like this.

And melanoma, because it’s induced by ultraviolet light in many situations, is associated with many different mutations. And so the success or anticipated success of vaccine creation, production, and execution is high in the melanoma field because there are a lot of mutations in melanoma. And so when we think about other cancers where this may be relevant, the number of mutations, that could be relevant for success of the vaccine creation.

IRA FLATOW: As we’ve talked about, patients in the trial were on the drug Keytruda, in addition to this new mRNA vaccine. Are the vaccines intended as a complementary treatment to existing ones, or could a vaccine therapy replace other types of drugs entirely?

MICHAEL POSTOW: In melanoma, this vaccine was tested with Keytruda because Keytruda is a current standard of care for this patient population that has had melanoma surgically removed and is at risk of recurrence. So the trial that we’ve conducted so far is testing the vaccine, plus Keytruda versus Keytruda alone as the current standard by itself. Keytruda plus the vaccine makes sense as a combination because Keytruda is an immune enhancer, as well. And so the idea is Keytruda globally enhances the immune response, and then the vaccine drives that immune response to the specific neoantigens and parts of the tumor that are relevant for that one individual patient. So it’s a very welcome combination that makes scientific sense to combine them.

In the future, one could think about different trials where Keytruda plus this therapeutic vaccination could be tested against other standard treatments to see how much better, or if it’s better, to use this type of a vaccine with Keytruda against other standard treatments, potentially even including chemotherapy in certain malignancies.

IRA FLATOW: You’ve said that not all the data has been released, yet. What will you be looking for once that final data comes out?

MICHAEL POSTOW: What we know so far is there’s a statistically significant improvement in what’s called recurrence-free survival, meaning how many patients will never have the melanoma ever come back whatsoever. We know there’s a significant improvement on a statistical level in what’s called distant metastasis-free survival, meaning how many patients have melanoma spread to a distant part of their body, like inside lungs, liver, bone, brain, for example.

What we don’t know yet is the degree of that improvement. But the main question that we all are waiting on is how much was the reduction in risk of recurrence, and what type of patient characteristics were associated with the greatest benefit in this type of an approach in this trial? And we are hoping in the coming months to have more information on that topic.

IRA FLATOW: Whenever we talk about a drug, we talk about possible side effects or drawbacks to this approach. Are there any here?

MICHAEL POSTOW: Remarkably, this therapeutic vaccination approach is very well tolerated. It does not increase the rate of immune therapy toxicities otherwise that one might see with Keytruda by itself. Most of this knowledge is based on the earlier phases of this type of an approach. We’re still waiting on the phase III results, but in general, with the earlier experience with this and with treating patients myself in this particular trial, anytime you inject somebody with a shot, there’s some redness or soreness where the vaccine has been injected, that blunt side effect. But most patients tolerated that pretty well. And then the other side effect some people had was a little bit of fatigue and some chills or mild fever after the injection for a couple of days.

IRA FLATOW: Of course, when people hear about this story, they listen to us talking about it, they’re going to wonder how long it is before patients might be able to access this therapy.

MICHAEL POSTOW: We still need to see the results of the phase III trial. And the FDA has not approved this at this juncture. So we are still in this time period where we need more information, and we need to see how the regulatory agencies react to this type of an approach, and ideally, hopefully, approve it with appropriate considerations in mind. So I would expect it would probably be at least several months, but it’s hard for me to be more specific on when this might be available. I think, at the moment, the need for patients to keep in mind is this may be something to talk to your doctor and see if a clinical trial might be appropriate for you. But at the moment, this is not something that can be routinely administered.

IRA FLATOW: Now, I know you see what melanoma patients go through in your practice. I mean, this must really be an uplift, potentially having a new therapy to offer them.

MICHAEL POSTOW: For sure. I think this is very exciting because when patients get diagnosed with melanoma and they have it surgically removed, I think, the main issue, it’s a very scary time for patients, and one thinks about the future. And no one ever wants to deal with the recurrence of melanoma inside the body because that can be a life-threatening situation in certain situations. So the idea that you can take a treatment to help reduce the risk that melanoma will ever be a problem, again, is a remarkable advance, and I think one that we can celebrate, and we can tell our patients more confidently that the odds of surgery and treatment being curative for them in the long run have now been shown to be increased. And we’re delighted with that information.

IRA FLATOW: Dr. Postow, thank you for taking time to be with us today. Very interesting stuff.

MICHAEL POSTOW: Thank you very much for having me. It’s a pleasure.

IRA FLATOW: Dr. Michael Postow, Chief of the Melanoma Service at Memorial Sloan-Kettering Cancer Center in New York.

This episode was produced by Shoshannah Buxbaum. Did you enjoy this conversation? Do you want to give us some feedback or suggest a topic we should cover? Give us a call, 877-4-SCI-FRI. That’s 877, the number 4, SCI-FRI. Our listener line is always open. I’m Ira Flatow. We’ll catch you next time.

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