Gene therapy for chronic pain.

The dorsal horn of the spinal cord represents an attractive site for interventions designed to treat chronic pain, but it has been difficult to identify small molecules that act selectively on pain transmission at the spinal level. One approach is the use of viral vector-mediated gene transfer to achieve focal production and release of short-lived analgesic peptides. Herpes simplex virusbased vectors, expressing proenkephalin delivered by subcutaneous inoculation, transduce neurons of the dorsal root ganglion, leading to release of enkephalin from nerve terminals in dorsal horn to produce an analgesic effect in several models of chronic pain. A clinical trial is set to commence.