She was speaking about the study design and what they were appearing to see in patient survival. Although the study is blinded you're going to notice very much if everyone in the study is living longer than expected.
In this P3 study there are 2 groups of patients in a 2 to 1 random distribution; for every 2 patients put into the treatment group with DCVax 1 patient is selected to receive placebo. The main premise to receive approval from FDA is that people on DCVax will progress more slowly than those on placebo, by more than 4 months. If this shows to be true NWBO, and most investors, feels they'll be approved.
The second endpoint is Overall Survival; it's believed that a longer time to progression on DCVax will also correlate with longer Overall Survival. This is because after progression there is no viable treatment for patients with GBM and so if PFS is longer so would be survival.
In most Treatment vs. Placebo trials the patients on Placebo stay on Placebo for the entire trial. In the NWBO trial all patients have surgery and have vaccine made for them, but only the treatment group actually receives it. Because a patient who progresses on Placebo will most likely die rather quickly after this progression the FDA told NWBO they should "cross over" the Placebo patients upon progression of their tumor and start to give them their vaccine that had been made at the beginning.
What Dr. Liau was referring to was this crossover. She stated that ALL the patients were living longer than expected. This would imply that even the patients who had progressed on Placebo were not dying as quickly as expected because the vaccine, even though given "LATE" in the trial was even benefitting those who's tumor had returned. If this is the case it could be blockbuster results.
The caveat to all of this is that it's making it harder to sort out the survival data; if the Placebo patients simply stayed on Placebo after progression they would likely die much sooner than those on DCVax and the Overall Survival benefit would be easy see. In the case of the crossover it's now necessary to look at how long people are living who got "Early" vaccine (DCVax from the start) and compare those to the ones who progressed and got vaccine "Late", after their tumor returned.
So, you can see what she meant:
1. EVERYONE is living longer (Good for the patients)
2. They now might have to compare early vaccine to late vaccine to see the survival benefit. This is where it's 'not good for our trial (most of us feel she means it makes it difficult and more work, NOT that the trial will fail as some pessimists claim. Remember also the primary end point is a longer PFS, not OS.)
3. If Placebo patients had stayed on Placebo instead of receiving DCVax upon progression they might have died earlier as expected and the survival difference between placebo and DCVax might have been greater. ('If they hadn't been given anything')
Does this help?
