University of Michigan scientists are beginning a phase 1 clinical trial for the treatment of cancer-related pain, using a novel gene transfer vector injected into the skin to deliver a pain-relieving gene to the nervous system.
A gene transfer vector is an agent used to carry genes into cells. In this groundbreaking clinical trial, the investigators will use a vector created from herpes simplex virus (HSV) – the virus that causes cold sores – to deliver the gene for enkephalin, one of the body's own natural pain relievers.
"In pre-clinical studies, we have found that HSV-mediated transfer of enkephalin can reduce chronic pain," says David Fink, M.D., Robert Brear Professor and chair of the department of neurology at the U-M Medical School. Fink developed the vector with collaborators and will direct the study.
"After almost two decades of development and more than eight years of studies in animal models of pain, we have reached the point where we are ready to find out whether this approach will be effective in treating patients," Fink says. The investigators are recruiting 12 patients with intractable pain from cancer to examine whether the vector can be used safely to deliver its cargo to sensory nerves.
The trial represents two firsts, says Fink: It is the first human trial of gene therapy for pain, and the first study to test a nonreplicating HSV-based vector to deliver a therapeutic gene to humans. Fink says the technique may hold promise for treating other types of chronic pain, including pain from nerve damage that occurs in many people with diabetes.
The HSV vector, genetically altered so it cannot reproduce, has a distinct advantage, Fink says: "Because HSV naturally travels to nerve cells from the skin, the HSV-based vector can be injected in the skin to target pain pathways in the nervous system."