Merck is developing a new pharmaceutical drug, suvorexant, for the treatment of insomnia. It is currently in Phase III clinical trials. In fact, it was already submitted to the FDA for approval last year. The FDA rejected the submission, essentially recommending that Merck come back with data to support the use of a lower dose instead.
Suvorexant has a novel mechanism of action for insomnia drugs. It is often described as being unique in that instead of promoting sleepiness, it inhibits wakefulness. Suvorexant blocks the effect of the neurotransmitter orexin which functions to keep the brain awake.
With any drug with a novel mechanism of action, there is uncertainty in the regulatory path. And that’s certainly what Merck is experiencing. A few weeks ago the Drug Enforcement Administration made a recommendation that suvorexant be classified and regulated as a Schedule IV drug. This means that it is a little more difficult for patients to get prescriptions and refill them. The DEA is concerned that there is a potential risk of abuse, so its availability is controlled. However, Schedule IV is the least restrictive form of scheduling.
I’ve seen different responses to the DEA announcement. On the face of it, it would seem like this is bad news because anything that makes the drug less available is going to cut into the drug’s market success to some extent. But it doesn’t seem like it should be too bad for suvorexant to be classified as Schedule IV because other drugs that it is expected to compete with, such as zolpidem (Ambien), are also listed under Schedule IV.
But some see the DEA decision as good news, because at least Merck has response from the DEA before approval of the drug. That’s not always the case. For example, the DEA spent nearly a year after the approval of the weight loss drug lorcaserin reviewing it. Without the DEA’s classification, Arena Pharmaceuticals couldn’t market the drug for that year even though it had the FDA’s approval. So at least Merck has a DEA response, even if it isn’t an ideal one.
Once Merck completes the clinical study needed to support a lower dose, it is anticipated the FDA will approve it and patients who suffer from insomnia and don’t respond well to current therapy will have a new drug with a unique mode of action to seek relief from.
Update: The FDA approved suvorexant on August 13, 2014. The brand name will be Belsomra.