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“Fluid convection within
the brain” is important because if the fluid moves, it can penetrate
much larger distances than the diffusion of a large protein molecule
would and consequently can be used to reach and saturate a
biologically-interesting part of the brain.
Let me show you what this
so-called convection looks like in agar. (video)

When it
works like we would like it to work, as the first and the second from
the left, we get a spherical distribution of the agent. When the flow
conditions are not right, the fluid clings to the outside of the cannula
and creeps up. This is known as a backflow.
With that
as a background, the surgeon involved in the open-label trial and the
surgeons involved in the multi-site control trial thought that they were
doing convection enhanced delivery. The first clinical results in the
open-label trial look pretty good.


The Phase
II trial does not look as good. The first thing you notice is that the
results are scattered, like a bunch of peas thrown against a wall.
Unfortunately, the way the investigators looked at it, they compared the average
of the left side to the average of the right side and the results were
something like a 20 percent improvement – but less than the completely
arbitrarily-picked target of 30 percent. And consequently it was a
failure, trial halted, let's go home.
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