Flex Pharma Inc (NASDAQ:FLKS) just kicked off a phase II in its lead multiple sclerosis candidate, FLX-787. The drug is a muscle cramp target (MS here is the underlying condition that causes the indication, rather than the indication itself) and has the potential to target a huge range of patients if it can pick up this first marketing authorization. With this in mind, and ahead of any interim release on the phase II ongoing, here’s a look at what the drug involves (it’s an interesting one, this one, so stick with us) and what to look out for as far as any releases are concerned from the current study.

So, the drug. As mentioned, its called FLX-787, and it’s part of a family of drugs called TRP ion channel activators. The mechanism of action of these drugs is pretty complicated, but here’s a go at an explanation. Scientists found out about two decades ago that muscle cramps (in the vast majority of instances) come about as a result of neural stimulation, rather than coming from the muscles themselves. Basically, the nervous system fires erratically, and this erratic firing translates to muscle spasm and tightening, which in turn causes the cramps. This is where the interesting bit comes in. On the outside of the cells that line our mouth, tongue, throat and esophagus, there are receptors that associate with the above mentioned TRP ion channels. FLX-787 targets these receptors, activates them, and sends a signal through the nerve cells directly to the nervous system in a patient’s spine. This signal mutes the erratic nervous system, and in doing so, eases the cramps. That’s the theory, at least.

The current phase II trials are targeting the cramps associated with MS – a condition for which there are very few effective treatment options currently available. For those not familiar with MS, the cramps and other tightening of muscles that present themselves as what we might refer to as one of the classic symptoms of the condition are called spasticity. It’s this spasticity that the drug is targeting in the phase II.

So what’s the potential market if the drug is shown to be effective and safe, and clears the commercialization hurdle come PDUFA? Well, there are up to 350,000 individuals in the US that suffer from MS, and of these 350,000, around 84% require treatment for some degree of spasticity. The current treatment options, as mentioned, are pretty limited. Primary SOC is physiotherapy, and there are a few active compounds on the market that target the support of this physiotherapy. If Flex can get its TRP activator to market, therefore, it could go after a large portion of the 84% subpopulation. A conservative estimate on target population comes in at around 250,000. We don’t yet have a price point on the drug (it’s far too early given the company hasn’t even established a mass production capability) but with a quarter of a million potential patients in the US alone, it won’t require too high a cost to command a multi billion-dollar market.

Further, this is only the beginning. Think of the ongoing phase II (while it’s labeled as an efficacy trial in the MS spasticity indication) as more of a proof of concept for the cramp and muscle tightening space as whole. An FDA approval would open the gate for a flurry of sNDAs and expanded indications. Initially, and as supported by Flex management statements, these indications include athletes (in game, in training cramp indications) and other neurological motor conditions such as ALS, or Lou Gehrig’s disease. That’s where the real money is, and that’s where the potential sentiment driven upside lies if the drug can make it through the current trial with an efficacy showing.

So what are we looking for going forward? Well, it’s an MS indication, but since it’s targeting the spasticity element of the disease specifically, chances are we will see some level of interim data across the coming couple of quarters. We don’t yet have an end date for the trial, but topline will likely hit somewhere around the beginning of 2017. Near term milestones, therefore, come in the form of interim analysis, and any hint at efficacy as well as safety) for the drug in question.

It’s still early days, but with such a wide potential population on proof-of-efficacy, Flex is worth keeping an eye on as we head into the second half of 2016.