Novel Gene Therapy for Cancer Pain Proves Successful in Small Trial

Researchers from the University of Michigan Department of Neurology recently reported that injections of a novel gene therapy treatment successfully reduced pain symptoms in patients with persistent, severe cancer pain.

According to results published in Annals of Neurology, researchers administered intradermal injections of NP2, “a replication defective HSV-based vector expressing human preproenkephalin (PENK),” in 10 patients with moderate to severe cancer pain that was intractable to previous treatment that included up to 200 mg/day of morphine. They reported that the treatment was well tolerated, with no reported serious adverse events. Patients who received higher doses of treatment reported pain relief as assessed by a numeric rating scale (NRS) and the Short Form McGill Pain Questionnaire (SF-MPQ). Patients who received a low dose of NP2 “reported no substantive change in pain.”

In their discussion of these results, the authors of the study noted that although the study did not feature the use of placebo controls, in their opinion “the dose-responsive analgesic effects suggest that NP2 may be effective in reducing pain and warrants further clinical investigation.”

A news release from the University of Michigan Health System accompanying publication of these results noted that NP2 is “a gene transfer vector that expresses the naturally-occurring opioid peptide enkephalin,” and that preclinical work by lead author David Fink, MD, and colleagues demonstrated that NP2 injections reduced pain “in models of pain caused by nerve damage, inflammation, or cancer.”

Fink said “the concept underlying this therapeutic approach is that injection of NP2 into the skin results in uptake into the nervous system and the production and release of a pain-relieving chemical in a controlled site in the pain pathway.”

The patients who received higher doses of NP2 reported up to an 80% reduction in their pain symptoms over four weeks following treatment.

Diamyd Inc, maker of the NP2 vector, is sponsoring a phase II, placebo-controlled trial that will “examine the impact of intradermal delivery of NP2 on pain scores and pain medication usage in subjects with intractable pain due to malignant disease.”