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Gene Therapy Relieves Pain of Diabetic Neuropathy

Positive effects of treatment last for months in mid-stage trial

A new study from Northwestern University has found that patients with peripheral diabetic neuropathy (DPN) who received two low-dose rounds of a nonviral gene therapy called VM202 experienced significant improvement of their pain that lasted for months.

The results of this phase II, double-blind, placebo-controlled study were published March 5 in the Annals of Clinical and Translational Neurology.

Currently there is no effective treatment for reversing DPN, which affects 20% to 25% of diabetics. Patients with the most extreme form of the disease feel intense pain with a slight graze or touch. The pain can interfere with daily activities, sleep, and mood, and can diminish quality of life.

"Those who received the therapy reported more than a 50% reduction in their symptoms and virtually no side effects," said lead author Dr. Jack Kessler. "Not only did it improve their pain, it also improved their ability to perceive a very, very light touch."

VM202 contains the human hepatocyte growth factor (HGF) gene. Growth factor is a naturally occurring protein in the body that acts on cells — in this case nerve cells — to keep them alive, healthy, and functioning. Future studies are needed to investigate whether the therapy can regenerate damaged nerves, thereby reversing the neuropathy.

Patients with PDN have abnormally high levels of glucose in their blood. These high levels of glucose can be toxic, according to the authors.

In DPN, damaged nerve cells send out abnormal signals, causing the patients to feel pain, usually in their lower limbs and fingertips. The condition can lead to injuries, chronic foot ulcers, and even amputations.

Painkillers and other medications can alleviate the symptoms of the disorder, but those drugs often come with undesirable side effects.

Eighty-four subjects with PDN completed the new study. They went to a clinic twice in a two-week period for a series of injections into the back of their calf muscles and lower legs. Some received injections of a saline placebo, others a low dose of the gene therapy, and others a higher dose.

"We found that the patients who received the low dose had a better reduction in pain than the people who received the high dose or the placebo," said co-author Dr. Senda Ajroud-Driss. "Side effects were limited to injection-site reactions."

The subjects reported their pain symptoms to the researchers over the next 9 months. At 3 months, patients in the low-dose group experienced a significant reduction in pain compared with the placebo group. The effect persisted at 6 and 9 months in the low-dose group, the scientists said.

A larger phase III study will soon be under way.

"Right now there is no medication that can reverse neuropathy," Kessler said. "Our goal is to develop a treatment. If we can show with more patients that this is a very real phenomenon, then we can show we have not only improved the symptoms of the disease, namely the pain, but we have actually improved function."

Source: Medical Xpress; March 5, 2015.


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