Upfront disclaimer that this analysis is very rubbery! But as there have been quite a few posts discussing the positive signal from the blinded data - with the underlying pivot being behaviour of the VF001 control arm versus the VenUS data, I thought it would be useful to get an idea of how large the placebo effect can be over VenUS M1 in order to maintain a 10% seperation of the active cohort(*) given the wound curves published by FTT in the last update.
* Obviously, given limitations of what we know, this is the average across both active arms.
To cut a long story short: According to the way I cut the analysis (with underlying caveats), the limit to improvement in control arm compared to the VenUS M01 subset that would leave a 10% improvemnt bettwen the AVERAGE of all active patients and the contol is 17.5% (obviously this does not mean that one of the active arms might exceed +10% under the condition of a 17.5% improvement of the control over VenUS M01).
For those that are interested, here is the method: I digitised the average wound size plot for VF001 and the VenUS M03 plot (from the last FTT data update). Fitted a polynomial through both cuves. Then, starting from the assumption that 1/3 of the patients followed the VenUS polynomial I backed out the implied curve for the remaining 2/3. Finally, I just made incemental adjutments to the assumed VenUS curve until the implied curve converged to +10% at 12 weeks.
Very rubbery, but sheds some light on how much of a placebo effect we can tolorate given the observatitons made to date.
Here are the curves:-
1) Assuming the control follows VenUS M1
2) Assuming a 17.5% up-shift in the control over VenUS M1
