Fampridine-SR's long trek to approval

Where are the patient's clamoring for Fampridine-SR?

We know that Acorda Therapeutics' (ACOR) Fampridine-SR works for MS patients by hy affecting the potassium channels (and hence the action potentials), so why is it taking so long to get approved by the FDA?

The FDA posted the following question for the October 14th, 2009 meeting of the

Peripheral and Central Nervous System Drugs Advisory Committee, and my responses are below them (bold).

Let's address the FDA comments each separately, my comments (which can be quoted are in red).

1) Has the sponsor demonstrated substantial evidence of effectiveness of fampridine as a treatment to improve walking in patients with MS?


This depends who you a the FDA itself said that they met their primary endpoints.The question is, are these significant clinically?

From using compounded 4-Aminopyridine extensively, there is no question that the answer is, a resounding yes.

2) If so, has the sponsor demonstrated that this effect is clinically meaningful, either in the group of fampridine-treated patients as a whole, or in a specific subset?

Have the makers of the beta interferons or gatiramer acetate done this either?

3) If so, should the sponsor be required to evaluate the effects of doses lower than 10 mg BID?

There is a strong possibility that the FDA will require this (ala the FTY720 studies).

4) If so, should this be required prior to approval?

In my opinion, no. This is because they have met their primary endpoint and not every drug has to do this. The FDA may take another track, though.

5) If substantial evidence of a clinically meaningful effect has been demonstrated, do you conclude that there are conditions under which fampridine SR could be considered safe in use for this indication?

Yes. It is unclear what this question is getting at, or is it simply repeating the question of approval?

6) If so, what are those conditions (e.g., specific enrollment criteria, specific monitoring, etc.)?

This attempt at limiting its use is, in my opinion, dangerous (and a slippery slope) as we do not do this with every drug. Does compazine (prochlorperaine), which lowers the seizure threshold, have to do this as well?

What does this mean for Sanofi-Aventis' development of Nerispirdine (affecting both the potassium and sodium channels but possibly without the seizure risk).

MS patients demanded Biogen Idec (BIIB) and Elan's (ELAN) Tysabri (natalizumab) be re-released by the FDA, despite the PML (progressive multifocal leukoencephalopathy), so where are they now?

What do we do in the meantime?

Well, there is always compounded 4-aminopyridine.

- Dr. Daniel Kantor, MD BSE
Medical Director
Neurologique

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