Therapeutic Diabetes Vaccine Advances
Following promising results of earlier studies, phase 3 trials of a therapeutic vaccine for diabetes mellitus are moving in the United States and Europe. Each trial will enroll about 300 patients.
In a phase 2 study, just two injections of the vaccine given 30 days apart to patients with type 1 diabetes significantly preserved endogenous insulin production compared with placebo. The active compound in the vaccine, which is being developed by Diamyd Medical AB, is GAD65, a major auto-antigen in autoimmune diabetes. GAD65 is an enzyme that converts the excitatory neurotransmitter glutamate to the inhibitory transmitter γ-aminobutyric acid (GABA).
The most recent results from that study were presented in September at the European Association for the Study of Diabetes annual meeting in Rome by investigator Carl-David Agardh, MD, of the University Hospital Malmo in Malmo, Sweden. “We saw a steep improvement in beta-cell function already at six months after vaccination in patients treated with 20 µg of Diamyd,” Dr. Agardh said. “This improvement was largely maintained over the five years of study.”
No treatment-related serious adverse events have been reported, according to Diamyd Medical.
In the phase 3 trials, all subjects will receive the vaccine within three months of diagnosis. The primary end point will be the levels of meal-stimulated C-peptide, a direct marker of endogenous insulin production. Evidence of benefit in terms of insulin requirements and glycemic end points will also be evaluated.
Meal-stimulated C-peptide levels are believed to be the most accurate parameter for clinical trials to show whether a drug can maintain function of pancreatic beta cells in type 1 diabetes patients, according to Jerry P. Palmer, MD, director of the Diabetes Endocrinology Research Center at the University of Washington in Seattle and the principal investigator for the phase 3 trial in the United States.
If this approach is successful in maintaining pancreatic beta-cell function, it could be a major leap forward in the treatment of type 1 diabetes, Dr. Palmer said. Saving insulin-producing cells from being destroyed by the autoimmune process could be of great clinical value. It could help simplify patient treatment regimens and ultimately help reduce the acute and late complications associated with the disease.