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To: scaram(o)uche who wrote (363)	12/28/2008 9:46:50 PM
From: Biomaven	Read Replies (4) \| Respond to of 411

Well I can't translate (need Biotech Jim for that), but this hints to me that ranolazine might be worth trying in migraine with aura and maybe in some neurological and chronic pain conditions too. I had been kind of wondering about this, but had assumed ranolazine only was effective in the cardiac (1.5V) sodium channels - this abstract indicates it might have broader efficacy. Tetrodotoxin blocks cortical spreading depression in some animal models of migraine, indicating that the 1.7V Na channels might be involved. (That's one suggested mode of action for Topamax). For chronic pain, again BJ can speak to this much better than I, but 1.8v and 1.9v sodium channels appear to be implicated. The abstract you cited doesn't discuss the 1.9v channels - wonder if they just didn't try or it doesn't work there. I have no idea if the potencies they show here are adequate or not. Here's a typical neuropathic pain abstract (from Vertex - didn't even know they were working on this stuff): 1: Curr Opin Investig Drugs. 2008 Jan;9(1):83-9.Links The role of tetrodotoxin-resistant sodium channels in pain states: are they the next target for analgesic drugs? Silos-Santiago I. Vertex Pharmaceuticals Inc, San Diego, CA 92121, USA. ada_silos@sd.vrtx.com Neuropathic pain, a persistent chronic pain resulting from damage to the central or peripheral nervous system, is a condition that severely affects the quality-of-life of millions of individuals worldwide. The treatment of neuropathic pain is still an unmet medical need; however, recent advances in our understanding of mechanisms underlying the perception and transmission of painful stimuli offer significant potential for improvement of therapies directed to neuropathic pain. Ectopic activity in damaged and dysfunctional sensory afferents is believed to have a role in the generation and maintenance of neuropathic pain. One of the mechanisms underlying this ectopic firing involves abnormal modulation of voltage-gated sodium channels (NaVs) in the soma and axonal membranes of dorsal root ganglion (DRG) sensory neurons. In fact, NaV blockers have been clinically validated as treatments for neuropathic pain. However, current drugs are weak, non-selective inhibitors of NaVs with dose-limiting CNS and cardiovascular side effects that prevent their use in long-term therapy. Selective NaV tetrodotoxin-resistant channels (NaV 1.8 and NaV 1.9) are expressed exclusively in nociceptive neurons in the DRGs where they play a key role in normal and/or pathological pain sensation, providing an opportunity for the development of novel peripheral analgesics with a better safety profile.

To: scaram(o)uche who wrote (363)	12/30/2008 1:07:36 PM
From: idos	Respond to of 411

Not really my area of expertise but I guess that the big deal is that it shows higher effect in active neurons (high firing frequencies) and more efficient in blocking pain(?). They also slow down the recovery of the Na channel from inactivated (following an action potential) to activated (ready for the next action potential).

To: scaram(o)uche who wrote (363)	1/2/2009 2:42:31 PM
From: Biotech Jim	Respond to of 411

Hello Rick and a happy and healthy new year to you! I have played around with sodium channels a bit so I can provide some comments on this work. These channels are complex in that they are large highly homologous proteins and they have regulatory subunits as well. Be careful when investigators evaluate activity of compounds in recombinant systems, as they might not have the same regulatory apparati as in the native neurons or cells. Note that it is quite difficult to evaluate selectivity against all voltage gated sodium channels, so investigators often use the major brain, cardiac and muscle forms for such studies. Note also that there are different firing rates for different neurons, and pain neurons have relatively slow firing rates (0.5 to 4 Hz). These channels have open, closed and inactive states as well. Having said this, the work is of interest and in these biophysical they primarily focus on 1.8 and 1.7. The activity of ranolazine seems to be somewhat weak in this non-protein loaded cell system, and compounds can bind to sites in serum proteins. How about activity against the cardiac, brain and muscle forms? How about activity in the 3 major commonly used pain models? Sorry that I do not have many answers here, but the work described is only a good start. BJ