Like stem cells and gene therapy, cancer vaccines have been long on hope but short on results. Gene therapies have had a couple of recent breakthroughs, but where are we with vaccines?
Jacksonville, Florida-based TapImmune released some interesting results this week from a Phase I trial conducted at the Mayo Clinic that will add some spice to that discussion. Published in Clinical Cancer Research, the study assessed 22 women with breast and ovarian cancer and found their T-cell vaccine, TPIV200, was safe and induced an immune response against the antigens being targeted. The study also hinted at efficacy, though the sample is tiny.
President and CEO Peter Hoang recently took over at TapImmune because he believes cancer vaccines have immense potential. He feels previous trials failed to meet their endpoints because the vaccines simply did not have enough firepower.
“Fighting cancer is a competitive proliferation battle,” said Hoang in a phone interview. “Tumor cells not only don’t die, but they tend to proliferate fast. To get the body to fight cancer, you need to get those killer T-cells proliferating faster than the tumor.”
Another problem may have been vaccinating for killer (CD8) T-cells alone, which by themselves may not win the arms race against fast-growing tumors. The company is banking that adding helper (CD4) T-cells into the mix will make all the difference.
“CD8 T-cells don’t kill well on their own because they don’t survive long, and they don’t see the tumor,” said Hoang. “You have to generate memory against a certain antigen in the immune system, and helper T-cells generate that memory. They also generate cytokines, interferon gamma, IL2 and TNF? that drive survival and proliferation of killer T-cells to help them outcompete the tumor.”
TapImmune’s vaccine targets folate receptor alpha (FR?), which is overexpressed in some cancers. In addition, it hits multiple antigens to broaden the immune response to more patients.
While the study results speak more to safety, TapImmune found a glimmer of efficacy buried in the numbers. The ten ovarian cancer patients who started the trial in their first remission after standard treatments were still alive after two years.
In addition, their progress free survival averaged 528 days compared to 313 days, the historical average for the standard of care. But again, small sample size. In a white paper released with the results, the company acknowledges “the uncertainty around our results, which could have reasonably been expected to be between 110 and 548 days.”
Still, these are good Phase I numbers and TapImmune has already begun two randomized, double-blind phase II trials to really explore the vaccine’s efficacy against breast and ovarian cancer. The company has also built an interim analysis into the ovarian trial, which might allow them to circle back with the FDA to expand the phase II and possibly seek approval based on those results.
“That study has FDA Fast Track status as well as Orphan Drug designation,” said Hoang. “We really have every advantage in the world to push that through approvals as quickly as anyone can.”
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