Rare medical conditions rarely receive the treatment they deserve.

That’s because drug manufacturers often focus on products that will yield the highest financial rewards.

Such is the case with inherited erythromelalgia (IEM), a rare and painful condition that involves recurrent attacks, redness, warmth, and swelling of the feet and occasionally the hands.

No current treatment has been consistently effective, a common complaint among sufferers of most chronic pain-related conditions.

With an estimated 100 million adults in the U.S. experiencing chronic pain, the need for effective treatments continues to grow. A major challenge, however, is finding treatments that relieve pain and allow a person to function normally.

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Utilizing Stem Cells

A new potential approach to pain management includes using stem cells to tailor treatments to the individual person, even if they have a rare condition that’s difficult to treat.

In 2014, researchers in Australia successfully used mesenchymal stem cells — those that can grow into bone, cartilage, muscle, or fat cells — to treat pain in 10 women with neuropathic pain symptoms. At six months, their pain intensity was reduced and the treatment was considered safe and well-tolerated.

While stem cells may hold the key to many future treatments, they’re also being investigated as a way to help patients find treatments to treat pain and other symptoms.

Researchers with Pfizer Inc. and different universities in the U.K. published the findings of their new research Wednesday in the journal Science Translational Medicine. This study was entirely funded by Pfizer.

They used a type of stem cell, specifically induced pluripotent stem cells (iPSC), to target the mutated pathways of people with IEM.

The pluripotent cells are adult cells that have been genetically reprogrammed to an embryonic stem cell–like state.

For roughly a decade, these cells have been the focus of potential ways to develop new treatments, such as using cancer cell lines to develop antitumor drugs.

The research team focused specifically on Nav1.7, a sodium ion channel that is especially high in neurons associated with pain.

In patients with IEM, the channel is slightly mutated. This is one possible explanation for how the condition develops in some people and not others.

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Testing Novel Pain Drugs

Researchers are currently developing new drugs that would selectively block the Nav1.7 channel.

One Nav1.7 blocker, Raxatrigine, in development from Convergence Pharmaceuticals, received orphan drug status from the U.S. Food and Drug Administration (FDA) in 2013 for the treatment of lumbosacral radiculopathy and sciatica, according to the company.

Last year, Pfizer completed a phase II trial on its own Nav1.7 blocker for the treatment of painful nerve damage related to diabetes. The results of that trial have not been posted.

Lishuang Cao, Ph.D., an ion channel expert at Pfizer Neusentis, and his team used iPSC technology and blood samples from four people with IEM, each with their own specific genetic mutation along their sodium channels. Using the iPSC technology and blood samples, the team created sensory neurons in a lab.

The researchers noted these neurons showed “abnormally high excitability and sensitivity to heat,” resembling features of IEM.

Researchers then tested the novel selective Nav1.7 blocker, finding the drug reduced the spontaneous firing of these neurons.

Researchers then gave a single dose to patients, which helped reduced heat-induced pain attacks in most of the subjects.

Modeling these types of scenarios using iPSC, researchers say, can offer more personalized approaches to finding effective treatments in patients with IEM and other pain disorders.

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