I will also be curious to hear more from E'man when he gets a chance, but a couple things that it might be useful to know about p2 --> p3 trials.
A p2 trial is not really about achieving statistically significant effiacy data. Generally, p2 studies are smaller (to save money) and stat sig is largely about having a large enough sample size to rule out luck. What you are really looking for in a p2 is a sign that there is efficacy (of a sort that would be worth developing a new drug for) and safety.
The FDA does not require that a p2 be statistically significant in order to run a p3. While I haven't done massive reviews of study numbers, I would bet that most p2 studies that go to p3 did not have statistically significant results.
For those who don't know, when a study is reported with a p-value of <.025 that is saying that there is less than a 2.5% chance that vgx-3100 is a placebo and its apparent efficacy was the result of luck alone. If the p-value had come in at .06 (6% chance results were due to luck) it would not have met the standard for statistical significance but it would still be a pretty safe bet that the results would not mere chance. In a p3, the FDA requires that you meet the stat sig threshold in order to approve the drug, but you are way more likely to meet the standard when you work with a larger trial size.
Keeping that in mind, I have absolutely no doubt that INO is takign vgx-3100 to phase 3. There has been some speculation that in conversations with the FDA they will be permitted to add an adjuvant (IL-12 or IL-33) in the phase 3 which should further improve the results. I don't know for sure whether they will end up doing that, and I have no idea whether they will partner for the phase 3 or not, or whether they end up with even better data in a predetermined subset and so narrow the inclusion criteria for p3, but they will be going to p3 and it looks like it won't have to be a huge trial in order to be reasonably sure of hitting stat sig.
