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promise. In two separate Phase I trials treating a small number of patients at slightly different stages of prostate cancer, the lead vaccine showed the ability to trigger an immune response in some patients, without any major side effects. The planned 106-patient Phase II trial will attempt to show the vaccine delays metastases.
The company’s pipeline also includes a DNA vaccine that codes for part of the androgen receptor, which is often produced in higher volumes by prostate cancer cells as the disease progresses. That vaccine could enter a 40-patient Phase I trial by the end of the year. MVI is also developing a pre-clinical companion diagnostic test intended to help identify the patients that are most likely to respond to the company’s vaccines.
One of the challenges the company faces, though, is that prostate cancer often takes at least a year or two to reappear in patients after surgery, even in men with fast-rising PSA levels like those targeted by MVI. As a result, the trials also will take years to prove that the treatment delays the spread of cancer. The Phase II trial, for example, is planned to last for at least two years. That’s different from a typical cancer drug that may be approved because of its ability to shrink a tumor in a matter of a few months, Lesniewski says.
“We’re trying to prevent the appearance of this disease, rather than measure if we can shrink it,” he says. “For some investors, it’s too long.”
Investors may also worry that using just one antigen in the vaccine increases the risk of tumors learning to defend against the vaccine. “I do believe that targeting just one antigen is not as good as targeting more than one antigen,” Johnson warns.
And even if the company’s lead drug hits the market, there are no guarantees it will gain traction with doctors and patients.
“This is potentially a step above Provenge from a logistical standpoint” because it’s an off-the-shelf vaccine, Cooperberg says. “But how it stacks up against Prostvac or others” remains to be seen.
Prostvac is Bavarian Nordic’s immunotherapy drug candidate that is in a Phase III trial. Like MVI, it’s designed as an off-the-shelf vaccine, but it’s intended to treat patients at a later stage of the disease—after the cancer has metastasized and doesn’t respond to castration therapy, but before the patients show pervasive symptoms.
Still, there may be room for a number of approaches, Cooperberg adds, because the answer to successfully attacking cancer will almost certainly involve combinations of treatments. In fact, McNeel is already conducting a small Phase I study exploring synergies between MVI’s lead vaccine and Provenge, Lesniewski says.
“It’s not to say that we couldn’t be surprised and the vaccine by itself could be efficacious in preventing and delaying bone” metastases, Lesniewski says. “That would be a wonderful outcome. But history teaches us that many, if not most, of the agents that are successful end up being used in some type of combination therapy.”
That adds yet another set of challenges for companies like MVI. “The problem is there’s probably an infinite number of combinations that could be done, so how do we intelligently do this in the most efficient way?” says O’Donnell-Tormey of the Cancer Research Institute. “Combinations are the future, but what those combinations are is still the question.”