Another look at esreboxetine: 4th Rx alternative for fibromyalgia?

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A paper published in the July 2012 issue of Arthritis & Rheumatism
Suggests a renewed investment interest by Pfizer Inc. in trials of its investigational drug esreboxetine as an FM therapy. (See “Safety and efficacy of esreboxetine in patients with Fibromyalgia: A 14-week, randomized, double-blind, placebo-controlled, multicenter clinical trial,” by University of Cincinnati fibromyalgia researcher Lesley M Arnold, MD, and a team at the UK-based Pfizer Global Research and Development organization.) 

For specifics not offered in the abstract of this fee-based paper
See MedPageToday’s physician CME report (“Novel Drug Helped in Fibromyalgia”).

By way of background, in Feb 2009…
Pfizer announced that they were discontinuing phase 3 trials of esreboxetine after their review of existing phase 2 trial data indicated the drug was unlikely to “provide meaningful benefit to patients beyond” other fibromyalgia Rx therapies that were already FDA approved (including Pfizer’s Lyrica, aka pregabalin). The average pain score improvement in trials of the drugs had been in the neighborhood of 30% or more, about what the new Arnold, et al. paper reports.

Now, however, at least two factors have entered the mix:

• The big three FDA approved fibromyalgia drugs will be coming off patent starting Oct 2013 with Lyrica, opening this huge multi-billion-dollar market to competition from generally lower price generics. For example, on July 5, the FDA approved marketing of a generic pregabalin product by Lupin Pharmaceuticals. At the same time, industry analysts predict “huge market opportunities” for pharmaceutical companies owing to increased FM awareness, diagnosis rates, and market penetration. 

• And second, it is suggested that the new research reflects physician/patient experience over the past few years demonstrating that responses to/side effects of the approved drugs – and to different combinations of those drugs – differ, sometimes significantly, from patient to patient. A factor that may overcome regulatory preference for a focus on drugs to treat unmet needs.

Currently, for example, a trial at the University of Utah is recruiting fibro patients to determine if differences in blood biomarkers can be linked to different responses to Lyrica (pregabalin) therapy.

Each of the approved drugs – and reboxetine – involves a different mechanism of action (albeit sometimes not entirely understood).
 
• Unlike the three currently approved drugs, esreboxetine is “a highly-selective norepinephrine reuptake inhibitor”: that is, it concentrates only norepinephrine in the brain.

• Savella (milnacipran) and Cymbalta (duloxetine) concentrate both serotonin and norepinephrine, though by different means.

• Lyrica (pregabalin) is said to decrease the release of the neurotransmitters substance P and glutamate, and “restore” release of norepinephrine.

So overall it seems fibromyalgia and neuropathic pain patients and their physicians can expect to see continued FM drug research, by Dr. Arnold at the University of Cincinnati and others.

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