TB vaccine may help reverse diabetes

A vaccine that prevents tuberculosis and is used to treat bladder cancer has been approved for clinical trials in the US to tests its ability to reverse advanced type 1 diabetes.

The US Food and Drug Administration (FDA) approved a phase II clinical trial testing the ability of the generic vaccine bacillus Calmette-Guerin (BCG) to reverse advanced type 1 diabetes.

Over a course of five years, the trial will investigate whether repeat BCG vaccination can clinically improve type 1 diabetes in adults between 18 and 60 years of age who have small but still detectable levels of insulin secretion from the pancreas.

Denise Faustman director of the Massachusetts General Hospital (MGH) and his research team was the first group to document reversal of advanced type 1 diabetes in mice and subsequently completed a successful phase I human clinical trial of BCG vaccination.

"We have learned a lot since the early studies in mice - not just about how BCG works but also about its potential therapeutic benefits, similar to what is being seen in trials against other autoimmune diseases," said Faustman.

"Our goal is to complete enrolment and also to raise the remaining funds needed for the trial by the end of this year," she said.

A generic drug with over 90 years of clinical use and safety data, BCG is currently approved by the FDA for vaccination against tuberculosis and for the treatment of bladder cancer.

The vaccine is known to elevate levels of the immune modulator tumour necrosis factor (TNF), which Faustman's team previously showed can temporarily eliminate in both humans and mice the abnormal white blood cells responsible for autoimmune type 1 diabetes.

Increased TNF levels also stimulated the production of protective regulatory T cells.

In the phase I clinical trial, two injections of BCG spaced four weeks apart led to the temporary elimination of diabetes-causing T cells and provided evidence of a small, transient return of insulin secretion.

The phase II clinical study will include more frequent dosing over a longer time period to determine the potential of repeat BCG vaccination to ameliorate the autoimmune state and improve clinical parameters such as HbA1c, a marker of average blood sugar control.

About 150 adults with long-term type 1 diabetes will be randomly assigned to receive two injections four weeks apart of either BCG or placebo and then a single injection annually for the next four years.

Patients will be closely monitored over the five-year trial period. The primary outcome measure will be improved results on the HbA1c blood test, which have been shown to prevent complications.

"In the phase I clinical trial we demonstrated a statistically significant response to BCG, but our goal in phase II is to create a lasting therapeutic response," said Faustman, an associate professor at Harvard Medical School in the US.

"We will be working again with people who have had type 1 diabetes for many years. This is not a prevention trial; instead, we are trying to create a regimen that will treat even advanced disease," she said.