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will it have to do to win FDA approval? In November, after early data from this study, Celldex officials said they may talk to the agency about the possibility of “accelerated approval”—on a thinner body of evidence than the FDA usually requires—if the data were to hold up as time went on. The FDA gave Celldex a breakthrough therapy designation in February, which speeds up the process. Davis says those talks “have not come to a conclusion at this point,” and Celldex is treading carefully about its prospects for an early nod.
“I think we’ve been careful to say that this is not a stereotypical approval data set,” he says. “We’re not predicting that this would, based on any precedents, lead to accelerated approval. But at the very least it gives us greater confidence that [the Phase 3 study Celldex is running in newly-diagnosed glioblastoma patients] will be positive.”
There’s good reason to tiptoe here. This trial is an exploratory study in a small number of patients. Success isn’t as clear-cut as it would be in a large Phase 3 trial where the statistical reads are more definitive. In a recent research note, for instance, Leerink Partners analyst Howard Liang cited an expert in the field as being “somewhat cautious” about a speedier approval because of the size and structure of the study.
Davis acknowledged that this “isn’t the standard that the FDA usually likes for approval,” but then again, Celldex will produce the first results from the aforementioned Phase 3 trial in the next few months. The hope is that even modestly extending patients’ lives will help Celldex build its case. (Bevacizumab, by comparison, was approved for these patients because of tumor responses on MRI scans, not a survival benefit.)
“There’s no precedent for approving a drug based on a randomized survival endpoint with this number of patients, but the numbers are very strong, and the patients are very, very needy,” Davis says. “This is a situation where the breakthrough designation should be appropriate to allow some flexibility in approval.”
Rindo is a cancer vaccine that stimulates an immune response against EGFRvIII, a mutated molecule found on tumor cells in about 30 percent of patients with glioblastoma. Because this molecule is only present on tumor cells, the treatment can theoretically kill tumor cells while sparing healthy ones. Celldex estimates that about 3,000 patients in the U.S., and 6,000 in Europe, have glioblastoma with an EGFRvIII mutation. The cancer recurs for most of them.