The Problem With Somaxon's Silenor

The next time you buy an over-the-counter sleep medication, look carefully at the active ingredient. Turn the bottle over in your hands a couple times, read your way through the fine print, and then, after you’ve struggled to pronounce the name of what seems to be such a foreign molecule – diphenhydramine, which is usually the stuff of over-the-counter sweet dreams – stroll on over to the allergy medication aisle, pick up a bottle of Benadryl, and do the same.

If you are overcome by a feeling of déjà vu while perusing the label for a hay fever remedy, don’t be shaken: the active ingredient in Benadryl, long used for sniffles and itchy eyes, is also diphenhydramine. Unisom, the once popular OTC medication for those who cannot settle down at night, is yet another incarnation of diphenhydramine. And so is Tylenol PM, at least in part: it is acetaminophen (the active ingredient in Tylenol), but mixed in with – you guessed it – diphenhydramine.

If it all sounds like marketing, it is: Take one drug, market it for its intended effect, and call it one name (Benadryl). Take the exact same drug, market it for its unintended side effect, and call it another (Unisom). It is one of the most disingenuous – and, in my opinion, unsavory – aspects of pharmaceuticals.

And yet it is a ploy, used over and over and over again, by dozens of biotechnology start-ups, in an effort to make new money on old ideas: Take an old, off-patent anti-depressant, combine it with an old, off-patent seizure medication, and call it a new drug for obesity. Take an old drug, off-patent drug for acute-onset chemotherapy-induced vomiting, put it in a delayed release formulation, and call it a new drug for delayed-onset chemotherapy-induced vomiting. Take an old anti-depressant that can’t compete for a significant market share, call it a new name, and sell people on the idea that it might be the cure for decreased female libido.

One of the more active players in this kind of pharmaceutical ploy is Somaxon (NASDAQ:SOMX), a company that has a single product, SILENOR, which is indicated for sleep maintenance. SOMX falls into what I consider to be an undesirable category within the biotech world: a company that takes an old, off-patent drug, packages the drug in a new dose, and then tries to convince the world that it has on its hands a new drug for a new indication.

In the case of SOMX and SILENOR, the molecule in question is doxepin, which is among the oldest, off-patent anti-depressants still on the market. Doxepin is widely available as a generic medication, used principally for its initial indication (depression).

But it is also available in some branded formulations, including a version by Pfizer (NYSE:PFE) called SINEQUAN. In fact, PFE’s drug is available for an indication similar to SOMX’s offering: the SINEQUAN version of doxepin is indicated for insomnia, while SOMX’s version of doxepin is indicated for sleep maintenance (in other words, people who fall asleep but cannot stay asleep).

And what brings SOMX and SILENOR all the way back to the Benadryl example I started out with is that sleep promotion – whether it be for the treatment of insomnia at the beginning of the night or sleep maintenance in the middle – is not even the intended effect of doxepin. Sleepiness, somnolence, whatever you want to call it – it is all the unintended side effect of a tricyclic antidepressant like doxepin. And so what you have here is not all that different from an allergy medication that makes you drowsy (diphenhydramine when you call it Benadryl) being suddenly transformed into a pharmaceutical sleep aid (diphenhydramine when you call it Unisom).

This, of course, is only one of the problems that SOMX is going to have with the marketing of SILENOR – the biggest one being that it is available as a generic just about everywhere else. Analysts who have put on a buy rating will probably note that SOMX has the only doxepin product that is available in 3 mg or 6 mg. I have two responses to that:

One, if I were a prescription benefits manager, I would just tell a patient who has been prescribed SILENOR to take half of a 10 mg generic doxepin, and deem it close enough. Two, it would be my best guess that it will take Indian generics manufacturers (many of whom who already produce doxepin and, in fact, have made it available for sleep issues on on-line pharmacies) about 5 minutes to come out with a 3 mg or 6 mg tablet if they thought there was any market there -- and they'll do it for a tenth the price.

In the end, all that SOMX really has is the biotech version of “re-purposing” a Carvel ice cream cake: Look at SILENOR one way, and it is Fudgie the Whale. Turn it upside down, and you’ve got Cookie Puss.

Disclosure: No positions

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