Pain Patch for Neuropathy Fails in Study

The San Mateo-based pharmaceutical company, NeurogesX, reported in a press release February 27, 2008 early results from their recent study of their experimental pain patch NGX-4010 to treat HIV-related neuropathy. The results from their second Phase 3 study showed that NGX-4010 failed to perform better than placebo.

Given the current lack of treatments for neuropathy, failure of this skin patch to control pain caused by distal sensory polyneuropathy (DSP) is a disappointment to people with HIV looking for a new option for relieving their foot and hand pain. These results differ from two earlier studies that suggested NGX-4010 did reduce pain.

The patch is placed on the skin of the affected area with pain where the experimental drug gets absorbed into the skin with little absorption into the bloodstream. The patch contains capsaicin, the compound that makes chili peppers "spicy". Earlier studies have shown capsaicin patches control pain in some patients with certain forms of neuropathy. In this study, NGX-4010 seemed to be well tolerated with few side effects.

The C119 study compared 494 people, some who used the NGX-4010 skin patch to those who used placebo. Two applications were studied in both groups: one for 30 minutes and one for 60 minutes. Participants were followed from 2-12 weeks. Overall, those who took the NGX-4010 patch reached a 29.5% reduction in pain while the placebo groups reached a 24.6% reduction. Although the 60-minute application showed better control of pain, neither application showed any clinical difference between NGX-4010 and placebo.

In spite of these results, the company is still moving forward with their application to the Food and Drug Administration (FDA) to use the drug in treating post-herpetic neuralgia (PHN) and perhaps other forms of neuropathy. Early acceptance in Europe has already occurred.

The company explained that NGX-4010 performed similarly in this study as in others, despite the results in the placebo groups. They hope that further analysis of data from the several studies of 1,600 volunteers will favor the drug as a broader treatment for neuropathy and not just PHN. However, the data from this study suggest that NGX-4010 does not show benefit over using placebo for HIV-associated peripheral neuropathy.

What these results means for people with HIV is unclear. An earlier study of NGX-4010 in HIV-positive people with neuropathy actually showed improvement in pain. More study may be needed before the FDA considers approving this experimental drug for the conditions the company hopes will be covered.

For more information on peripheral neuropathy, read Project Inform's publication, Peripheral Neuropathy.